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                                                                     Exhibit 4.2


                     SERIES B CONVERTIBLE PREFERRED STOCK
                              PURCHASE AGREEMENT

                                    BETWEEN

                         ENERGY BIOSYSTEMS CORPORATION

                                      AND

                      THE PURCHASER LISTED ON SCHEDULE I

                         DATED AS OF FEBRUARY 21, 1997
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                           STOCK PURCHASE AGREEMENT


          STOCK PURCHASE AGREEMENT dated as of February 21, 1997 by and between
Energy BioSystems Corporation, a Delaware corporation (the "Company"), and the
Purchaser listed on Schedule I of this Agreement (the "Purchaser").

                             W I T N E S S E T H :
                             - - - - - - - - - -

          WHEREAS, the Company desires to sell to the Purchaser and the
Purchaser desires to purchase from the Company shares of the authorized but
unissued Series B Convertible Preferred Stock, par value $0.01 per share, of the
Company (the "Series B Preferred Stock"), upon the terms and provisions
hereinafter set forth.

          WHEREAS, concurrently with this offering, the Company has made an
exchange offer whereby holders of Series A Preferred Stock will exchange shares
of Series A Preferred Stock for shares of the authorized but unissued Series B
Preferred Stock, par value $0.01 per share, of the Company (the "Exchange
Offer") to exchanging parties who will be executing Stock Exchange Agreements
substantially similar to this Agreement, containing similar representations and
warranties by the Company, covenants of the Company, registration rights,
conditions and other terms.

          NOW, THEREFORE, in consideration of the mutual covenants and
agreements set forth herein and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties agree as
follows:

     SECTION 1.  SALE AND PURCHASE OF THE PREFERRED SHARES

          (a) The Company agrees to sell to the Purchaser and, subject to the
terms and conditions hereof and in reliance upon the representations and
warranties of the Company contained herein or made pursuant hereto, the
Purchaser agrees to purchase from the Company on the Closing Date specified in
Section 2 hereof, the number of shares of Series B Preferred Stock set forth
opposite the Purchaser's name on Schedule I hereto.  The shares of Series B
Preferred Stock being acquired under this Agreement and by the other Purchasers
under the other Stock Purchase Agreements (as hereinafter defined) are
collectively herein referred to as the "Shares", containing rights and
privileges as more fully set forth in the Certificate of Designations for the
Series B Preferred Stock of the Board of Directors of the Company which shall be
substantially in the form attached hereto as Exhibit A (the "Series B
Certificate of Designations").
<PAGE>

          (b) The aggregate purchase price to be paid to the Company by the
Purchaser for the Shares to be purchased by the Purchaser pursuant to this
Agreement shall be the amount set forth opposite the Purchaser's name on
Schedule I hereto.  No further payment shall be required from the Purchaser for
the Shares.

          (c) The Shares are being sold to the Purchaser listed on Schedule I
hereto and to other Purchasers under substantially identical agreements
(collectively, the "Purchasers") pursuant to this Agreement and other
substantially identical agreements dated as of the date hereof (all such
agreements collectively, as from time to time assigned, supplemented or amended
or as the terms thereof may be waived, the "Stock Purchase Agreements").  All
Stock Purchase Agreements shall be dated the date hereof and shall be identical
except as to the identities of the respective Purchasers.  The sale of Shares to
each Purchaser under each Stock Purchase Agreement is to be a separate sale, and
no Purchaser shall have any liability under any Stock Purchase Agreement other
than the Stock Purchase Agreement to which it is a party.

          (d) The Company will use the proceeds from the sale of the Shares as
described in the section of the Memorandum entitled "Use of Proceeds."

          (e) If an aggregate of fewer than 280,000 Shares are sold at the
Closing under the Stock Purchase Agreements, the Company shall have the right,
from time to time thereafter, but not later than March 31, 1997, to sell
additional Shares up to an overall aggregate of 400,000 Shares pursuant to Stock
Purchase Agreements substantially identical to this Stock Purchase Agreement.
Upon completion of any such sale, such additional Shares shall be "Shares"
hereunder, the purchasers of such additional Shares shall be "Purchasers"
hereunder and such additional Stock Purchase Agreements shall be "Stock Purchase
Agreements" hereunder.

     SECTION 2.  THE CLOSING

          (a) Subject to the terms and conditions hereof, the closing of the
purchase and sale of the Shares to be purchased by the Purchaser (the "Closing")
will take place at the offices of Andrews & Kurth L.L.P., 4200 Texas Commerce
Tower, Houston, Texas at 10:00 A.M., Houston, Texas time, on February 26, 1997,
or such other location, time and date as shall be determined by the Company and
the Agent.  Such time and date are herein referred to as the "Closing Date."

          (b) Subject to the terms and conditions hereof, on the Closing Date
(i) the Company will deliver to the Purchaser a certificate registered in the
Purchaser's name (or the name of its nominee, if any, as specified on Schedule I
hereto) evidencing the number of Shares equal to that number of Shares set forth
opposite the Purchaser's name on Schedule I, and (ii) upon the Purchaser's
receipt thereof, the escrow agent (the "Escrow Agent") for the Purchaser's funds

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previously deposited in an escrow account will release from such escrow account
and deliver to the Company a certified or official bank check (or wire transfer)
in an amount equal to the purchase price (as specified in Section l(b) hereof)
for the Shares to be purchased by the Purchaser payable to the order of the
Company in next day funds.

SECTION 3.  DEFINITIONS

          (a) For purposes of this Agreement, the following definitions shall
apply (such definitions to be equally applicable to both the singular and plural
forms of the terms defined):

          "Affiliate", when used with respect to any Person, means (i) if such
     Person is a corporation, any executive officer or director thereof (other
     than a director nominated pursuant to the Series B Certificate of
     Designations) and any Person which is, directly or indirectly, the
     beneficial owner (by itself or as part of any group) of more than five
     percent (5%) of any class of any equity security (within the meaning of the
     Securities Exchange Act) thereof, and, if such beneficial owner is a
     partnership, any general partner thereof, or if such beneficial owner is a
     corporation, any Person controlling, controlled by or under common control
     with such beneficial owner, or any executive officer or director of such
     beneficial owner or of any corporation occupying any such control
     relationship, (ii) if such Person is a partnership, any general partner
     thereof, and (iii) any other Person which, directly or indirectly, controls
     or is controlled by or is under common control with such Person.  For
     purposes of this definition, "control" (including the correlative terms
     "controlling", "controlled by" and "under common control with"), with
     respect to any Person, shall mean possession, directly or indirectly, of
     the power to direct or cause the direction of the management and policies
     of such Person, whether through the ownership of voting securities or by
     contract or otherwise.  Except as provided above, the holding of Shares (or
     Conversion Shares obtained upon conversion of Shares), and the rights under
     any Stock Purchase Agreement or under the Series B Certificate of
     Designations (or the exercise of any such rights, including, without
     limitation, nominating a director to the Board of the Company or sending an
     observer to Board meetings of the Company or any of the Subsidiaries),
     shall not, by themselves, cause a Purchaser to be deemed to be an
     "Affiliate" of the Company or of any Subsidiary.

          "Agreement" means this Stock Purchase Agreement (together with
     exhibits and schedules) as from time to time assigned, supplemented or
     amended or as the terms hereof may be waived.

          "Board" or "Board of Directors" means with respect to any Person which
     is a corporation, a business trust or other entity, the board of directors
     or other group, however

                                      -3-
<PAGE>

     designated, which is charged with legal responsibility for the management
     of such Person, or any committee of such board of directors or group,
     however designated, which is authorized to exercise the power of such board
     or group in respect of the matter in question.

          "Business Day" means any day other than a Saturday, Sunday or a day on
     which banking institutions in the State of New York or the State of Texas
     are authorized or obligated by law or executive order to close.

          "Capitalized Leases" means any lease to which the Company or a
     Subsidiary is a party as lessee, or by which it is bound, under which it
     leases any property (real, personal or mixed) from any lessor other than
     the Company or a Subsidiary, and which is required to be capitalized in
     accordance with generally accepted accounting principles consistently
     applied.

          "Closing" has the meaning set forth in Section 2(a) hereof.

          "Closing Date" has the meaning set forth in Section 2(a) hereof.

          "Code" means the Internal Revenue Code of 1986, as amended from time
     to time, and the regulations and interpretations thereunder.

          "Commission" means the Securities and Exchange Commission and any
     other similar or successor agency of the federal government administering
     the Securities Act or the Securities Exchange Act.

          "Common Stock" of the Company or of a Subsidiary (as the case may be)
     shall mean the Company's or a Subsidiary's (as the case may be) present
     authorized common stock and any stock into which such Common Stock may
     hereafter be changed or for which such Common Stock may be exchanged after
     giving effect to the terms of such change or exchange (by way of
     reorganization, recapitalization, merger, consolidation or otherwise) and
     shall also include any common stock of the Company or of a Subsidiary (as
     the case may be) hereafter authorized and any capital stock of the Company
     or of a Subsidiary (as the case may be) of any other class hereafter
     authorized which is not preferred as to dividends or assets over any other
     class of capital stock of the Company or of a Subsidiary (as the case may
     be) or which has ordinary voting power for the election of directors of the
     Company or of a Subsidiary (as the case may be); provided that preferred
     stock of the Company or a Subsidiary with the right to vote together with
     the common stock of such entity on various matters shall not be treated as
     "Common Stock" hereunder.

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          "Company" means Energy BioSystems Corporation, a Delaware corporation,
     its successors and assigns.

          "Consent and Exchange Agreement" is the agreement by which holders of
     Series A Preferred Stock elect to exchange shares of Series A Preferred
     Stock for shares of Series B Preferred Stock on a one-for-one basis.

          "Conversion Price" has the meaning specified in Section 2 of the
     Series B Certificate of Designations.

          "Conversion Share" or "Conversion Shares" means the shares of the
     Company's Common Stock, par value $0.01 per share, obtained or obtainable
     upon conversion of the Shares and shall also include any capital stock or
     other securities into which Conversion Shares are changed and any capital
     stock or other securities resulting from or comprising a reclassification,
     combination or subdivision of, or a stock dividend on, any Conversion
     Shares.  In the event that any Conversion Shares are sold either in a
     public offering pursuant to a registration statement under Section 6 of the
     Securities Act or pursuant to a Rule 144 Transaction, then the transferees
     of such Conversion Shares shall not be entitled to any benefits under this
     Agreement with respect to such Conversion Shares and such Conversion Shares
     shall no longer be considered to be "Conversion Shares" for purposes of
     Section 8 hereof, for purposes of the definition of Majority Shareholders
     or for purposes of any consent or waiver provision or any other provision
     of this Agreement.

          "Eligible Holder" means any holder (or group of affiliated holders)
     which is a Purchaser (or transferee of a Purchaser approved by the Company,
     such approval not to be unreasonably withheld) or a purchaser of Series A
     Preferred Stock that has elected to exchange its shares of Series A
     Preferred Stock for Shares (or a transferee of such exchanging party
     approved by the Company, such approval not to be unreasonably withheld) and
     which holds 100,000 or more Shares, or Conversion Shares issued on
     conversion of 100,000 or more Shares, or an equivalent combination of the
     foregoing.

          "Environmental Lien" has the meaning set forth in Section 7.7 hereof.

          "ERISA" means, collectively, the Employee Retirement Income Security
     Act of 1974, as amended, and the regulations and interpretations
     thereunder.

          "Exchange Agreement" means the Series B Convertible Preferred Stock
     Exchange Agreement, dated the date hereof, by which holders of Series A
     Preferred Stock agree to exchange shares of Series A Preferred Stock for
     shares of Series B Preferred Stock on a one-

                                      -5-
<PAGE>

     for-one basis consistent with their election reflected in the Consent and
     Exchange Agreement. The Exchange Agreement is substantially similar to this
     Agreement, containing similar representations and warranties by the
     Company, covenants of the Company, registration rights, conditions and
     other terms.

          "Guaranty" means (i) any guaranty or endorsement of the payment or
     performance of, or any contingent obligation in respect of, any
     indebtedness or other obligation of any other Person, (ii) any other
     arrangement whereby credit is extended to one obligor (directly or
     indirectly) on the basis of any promise or undertaking of another Person
     (a) to pay the indebtedness of such obligor, (b) to purchase an obligation
     owed by such obligor, (c) to purchase or lease assets (or to provide funds,
     goods or services) under circumstances that would enable such obligor to
     discharge one or more of its obligations or (d) to maintain the capital,
     working capital, solvency or general financial condition of such obligor,
     in each case whether or not such arrangement is disclosed in the balance
     sheet of such other Person or is referred to in a footnote thereto and
     (iii) any liability as a general partner of a partnership in respect of
     indebtedness or other obligations of such partnership; provided, however,
     that the term "Guaranty" shall not include (1) endorsements for collection
     or deposit in the ordinary course of business or (2) obligations of the
     Company or its Subsidiaries which would constitute Guaranties solely by
     virtue of the continuing liability of a Person which has sold assets
     subject to liabilities for the liabilities which were assumed by the Person
     acquiring the assets, unless such liability is required to be carried on
     the consolidated balance sheet of the Company.  The amount of any Guaranty
     and the amount of indebtedness resulting from such Guaranty shall be the
     maximum amount of the guarantor's potential obligation in respect of such
     Guaranty.

          "Hazardous Materials" means any pollutant, toxic substance, petroleum
     or petroleum by-products, hazardous waste, or any material, compound,
     element or chemical identified as a pollutant, toxic substance or hazardous
     waste or determined to be hazardous or toxic by a governmental agency under
     the Comprehensive Environmental Response Compensation and Liability Act
     (CERCLA), 42 U.S.C. 9601 et seq., the Resource Conservation and Recovery
     Act (RCRA), 42 U.S.C. 6901 et seq., the Toxic Substances Control Act
     (TSCA), 15 U.S.C. 2601 et seq., the Water Pollution Control Act (CWA), 33
     U.S.C. 1251 et seq., the Clean Air Act (CAA), 42 U.S.C. 7501 et seq., the
     Occupational Safety and Health Act (OSHA), 29 U.S.C. 655 and any other
     federal, state, local or municipal laws, statutes, ordinances, codes, rules
     or regulations imposing liability or establishing standards of conduct for
     environmental protection.  The term "Hazardous Materials" shall also
     include: raw materials used or stored by the Company that contain Hazardous
     Materials; building components (including but not limited to asbestos-
     containing materials) that contain Hazardous Materials and manufactured
     products containing Hazardous Materials.

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          "Indebtedness" of any Person means, without duplication, as of any
     date as of which the amount thereof is to be determined, (i) all
     obligations of such Person to repay money borrowed (including, without
     limitation, all notes payable and drafts accepted representing extensions
     of credit, all obligations under letters of credit, all obligations
     evidenced by bonds, debentures, notes or other similar instruments and all
     obligations upon which interest charges are customarily paid), (ii) all
     Capitalized Leases in respect of which such Person is liable as lessee or
     as the guarantor of the lessee, (iii) all monetary obligations which are
     secured by any Lien existing on property owned by such Person whether or
     not the obligations secured thereby have been incurred or assumed by such
     Person, (iv) all conditional sales contracts and similar title retention
     debt instruments under which such Person is obligated to make payments, (v)
     all Guaranties by such Person and (vi) all contractual obligations (whether
     absolute or contingent) of such Person to repurchase goods sold or
     distributed.  "Indebtedness" shall not include, however, Indebtedness of
     the Company to any of its wholly-owned Subsidiaries or Indebtedness of any
     wholly-owned Subsidiary to the Company or to another wholly-owned
     Subsidiary.

          "Lien" means any mortgage, pledge, hypothecation, assignment, deposit
     arrangement, encumbrance, lien (statutory or other), or preference,
     priority or other security interest of any kind or nature whatsoever
     (including, without limitation, any conditional sale or other title
     retention agreement, any financing lease having substantially the same
     effect as any of the foregoing, any assignment or other conveyance of any
     right to receive income and any assignment of receivables with recourse
     against the assignor), any filing of a financing statement as debtor under
     the Uniform Commercial Code or any similar statute and any agreement to
     give or make any of the foregoing.

          "Majority Shareholders" means the holder or holders, at the time, of
     at least a majority of the Conversion Shares, including the Conversion
     Shares then outstanding and the Conversion Shares then obtainable under
     outstanding Shares; provided that such majority must in any event include
     each Eligible Holder.

          "Material Adverse Effect" means any material and adverse effect on the
     assets, properties, liabilities, business affairs, results of operations,
     condition (financial or otherwise) or prospects of the Company.

          "Memorandum" means that certain Confidential Offering Memorandum dated
     February 14, 1997 relating to the Shares.

          "Outstanding" or "outstanding" means (a) when used with reference to
     the Shares or the Conversion Shares as of a particular time, all Shares or
     Conversion Shares theretofore

                                      -7-
<PAGE>

     duly issued except (i) Shares and Conversion Shares theretofore reported as
     lost, stolen, mutilated or destroyed or surrendered for transfer, exchange
     or replacement, in respect of which new or replacement Shares or Conversion
     Shares have been issued by the Company, (ii) Shares and Conversion Shares
     theretofore canceled by the Company and (iii) Shares and Conversion Shares
     registered in the name of, as well as Shares and Conversion Shares owned
     beneficially by, the Company, any Subsidiary or any of their Affiliates and
     (b) when used with reference to the number of shares of Common Stock of the
     Company as of a particular time, the then issued and outstanding shares of
     Common Stock of the Company (not including treasury shares or any other
     shares registered in the name of the Company, any Subsidiary or any of
     their Affiliates), together with shares of Common Stock of the Company
     issuable pursuant to any then outstanding warrants, options, convertible
     securities or other rights to acquire shares of Common Stock of the
     Company. For purposes of the preceding sentence, in no event shall
     "Affiliates" include (x) the persons which are identified as "Purchasers"
     on Schedule I hereto or (y) any Affiliates of any such persons, except if
     such persons would otherwise fall within the definition of "Affiliate"
     described above.

          "Person" or "person" means an individual, corporation, partnership,
     firm, association, joint venture, trust, unincorporated organization,
     government, governmental body, agency, political subdivision or other
     entity.

          "Preferred Stock" means any class of the capital stock of a
     corporation (whether or not convertible into any other class of such
     capital stock) which has any right, whether absolute or contingent, to
     receive dividends or other distributions of the assets of such corporation
     (including, without limitation, amounts payable in the event of the
     voluntary or involuntary liquidation, dissolution or winding-up of such
     corporation), which right is superior to the rights of another class of the
     capital stock of such corporation. "Preferred Stock" includes without
     limitation the Series B Preferred Stock.

          "Purchaser" means the person who accepts and agrees to the terms
     hereof as indicated by such person's signature (as "the undersigned
     Purchaser") on the execution page of this Agreement, together with such
     person's successors and assigns.

          "Purchasers" has the meaning set forth in Section l(c) hereof,
     together with their respective successors and assigns.

          "Registered Securities" means the Conversion Shares, any Common Stock
     issued in payment of dividends on, or in connection with the redemption or
     repurchase of, the Shares and any Shares included herein pursuant to
     Section 8.1(g) hereof.

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<PAGE>

          "Restricted Payment" means (i) every dividend or other distribution
     paid, made or declared by the Company or any Subsidiary on or in respect of
     any class of its capital stock (as defined below), and (ii) every payment
     in connection with the redemption, purchase, retirement or other
     acquisition by or on behalf of the Company or any Subsidiary of any shares
     of the Company's or a Subsidiary's capital stock (as defined below),
     whether or not owned by the Company or any Subsidiary; provided, however,
     that the restrictions of the foregoing clauses (i) and (ii) shall not apply
     to (a) any dividend, distribution or other payment on or in respect of
     capital stock of the Company to the extent payable in shares of Common
     Stock of the Company, (b) any payments from the Company to a wholly-owned
     Subsidiary, from a Subsidiary to the Company or from a Subsidiary to a
     wholly-owned Subsidiary, (c) any repurchase of Common Stock under stock
     purchase or option agreements from employees, advisors, consultants or
     directors of the Company or otherwise upon termination of such relationship
     with the Company (provided, that the aggregate amount paid pursuant to such
     repurchases after the Closing Date shall not exceed $300,000 without the
     consent of the Majority Shareholders), (d) any payments, dividends,
     distributions or other transfers or actions (I) on or with respect to the
     Company's Series A Preferred Stock or the shares of Common Stock issuable
     upon conversion thereof pursuant to the terms of the Stock Purchase
     Agreements or the Certificate of Designations relating to the Series A
     Preferred Stock or (II) on or with respect to the Shares or the Conversion
     Shares pursuant to terms of the Stock Purchase Agreements, Stock Exchange
     Agreements or the Series B Certificate of Designations and (e) any payments
     or distributions in respect of the liquidation and dissolution, or winding
     up of the business and affairs, of the Company.  For purposes of this
     definition, "capital stock" shall also include warrants and other rights
     and options to acquire shares of capital stock (whether upon exercise,
     conversion, exchange or otherwise).

          "Rights Expiration Date" means, with respect to any Eligible Holder,
     the earlier of (a) the date on which such Eligible Holder owns neither (i)
     100,000 or more Shares nor (ii) Conversion Shares issued on conversion of a
     number of Shares at least equal to 100,000 less the number of any Shares
     remaining owned by such Eligible Holder, and (b) the third anniversary of
     the Closing Date, unless such Eligible Holder then owns 100,000 or more
     Shares.

          "Rule 144" means (i) Rule 144 under the Securities Act as such Rule is
     in effect from time to time and (ii) any successor rule, regulation or law,
     as in effect from time to time.

          "Rule 144A" means (i) Rule 144A under the Securities Act as such Rule
     is in effect from time to time and (ii) any successor rule, regulation or
     law, as in effect from time to time.

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          "Rule 144 Transaction" means a transfer of Shares or Conversion Shares
     (A) complying with Rule 144 as such Rule is in effect on the date of such
     transfer (but not including a sale other than pursuant to (i) "brokers'
     transactions" as defined in clauses (1) and (2) of paragraph (g) or (ii)
     paragraph (k) of such Rule as in effect on the date hereof) and (B)
     occurring at a time when Shares (in the case of a transfer of Shares) or
     Conversion Shares (in the case of a transfer of Conversion Shares) are
     registered pursuant to Section 12 of the Securities Exchange Act.

          "Securities Act" means the Securities Act of 1933, as amended, and the
     rules, regulations and interpretations thereunder.

          "Securities Exchange Act" means the Securities Exchange Act of 1934,
     as amended, and the rules, regulations and interpretations thereunder.

          "Series A Certificate of Designations" has the meaning set forth in
     Section 4.2(d) hereof.

          "Series A Preferred Stock" has the meaning set forth in Section 4.2(a)
     hereof.

          "Series B Certificate of Designations" has the meaning set forth in
     Section l(a) hereof.

          "Series B Preferred Stock" means the Company's Series B Convertible
     Preferred Stock, par value $0.01 per share, which will be duly authorized
     on the Closing Date and which will have the rights, powers and privileges
     on the Closing Date as more fully set forth in the Series B Certificate of
     Designations.

          "Shares" has the meaning set forth in Section l(a) hereof, except that
     for purposes of Section 7 and Section 8 hereof and the definition of
     "Conversion Shares," the term "Shares" shall include the shares of Series B
     Preferred Stock issued upon the exercise of the warrant, dated the date
     hereof, granting Alex. Brown & Sons Incorporated (the "Agent") the right to
     purchase a specified number of shares of Series B Preferred Stock and the
     shares of Series B Preferred Stock issued upon the exchange of the Series A
     Preferred Stock pursuant to the Exchange Agreement.  In the event that any
     Shares are sold either in a public offering pursuant to a registration
     statement under Section 6 of the Securities Act or pursuant to a Rule 144
     Transaction, then the transferees of such Shares shall not be entitled to
     any benefits under this Agreement with respect to such Shares and such
     Shares shall no longer be considered to be ''Shares" for purposes of
     Section 8 hereof or any consent or waiver provision or any other provision
     of this Agreement.

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          "Stock Purchase Agreements" has the meaning set forth in Section l(c)
     hereof.

          "Subsidiary", with respect to any Person, means any corporation,
     association or other entity of which more than 50% of the total voting
     power of shares of stock or other equity interests (without regard to the
     occurrence of any contingency) entitled to vote in the election of
     directors, managers or trustees thereof is, at the time as of which any
     determination is being made, owned or controlled, directly or indirectly,
     by such Person or one or more of its Subsidiaries, or both.  The term
     "Subsidiary" or "Subsidiaries" when used herein without reference to any
     particular Person, means a Subsidiary or Subsidiaries of the Company.

          (b) For all purposes of this Agreement, except as otherwise expressly
          provided or unless the context otherwise requires:

               (i) the words "herein", "hereof" and "hereunder" and other words
               of similar import refer to this Agreement as a whole and not to
               any particular Section or other subdivision;

               (ii) all accounting terms not otherwise defined herein have the
               meanings assigned to them in accordance with generally accepted
               accounting principles consistently applied (except as otherwise
               provided herein);

               (iii)  all computations provided for herein, if any, shall be
               made in accordance with generally accepted accounting principles
               consistently applied (except as otherwise expressly provided
               herein);

               (iv) any uses of the masculine, feminine or neuter gender shall
               also be deemed to include any other gender, as appropriate;

               (v) all references herein to actions by the Company or any
               Subsidiary, such as "create", "sell", "transfer", "dispose of",
               etc., mean such action whether voluntary or involuntary, by
               operation of law or otherwise;

               (vi) the exhibits and schedules to this Agreement shall be deemed
               a part of this Agreement;

               (vii)  each of the representations of the Company contained in
               Section 4 hereof is separate and is not limited, qualified or
               modified by the existence, wording or satisfaction of any other
               representation of the Company in Section 4 or otherwise;

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               (viii)  each of the covenants of the Company contained in Section
               7 hereof or otherwise contained in any Stock Purchase Agreement
               or the Series B Certificate of Designations is separate and is
               not limited or satisfied by the existence, wording or
               satisfaction of any other covenant of the Company in Section 7 or
               otherwise; and

               (ix) all references herein (in covenants or otherwise) to any
               action(s) which are to be taken (or which are prohibited from
               being taken) by any Person, the Company or any Subsidiary shall
               apply to such Person, the Company or such Subsidiary, as the case
               may be, whether such action is taken directly or indirectly.

SECTION 4.  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

     The Company represents and warrants to the Purchaser as follows as of the
date hereof and as of the Closing Date:

            4.1.  Corporate Existence, Power and Authority.

            (a) The Company is a corporation duly organized, validly existing
and in good standing under the laws of the State of Delaware. The Company is
duly qualified, licensed and authorized to do business and is in good standing
in each jurisdiction in which it owns or leases any material property or in
which the conduct of its business requires it to so qualify or be so licensed.

            (b) The Company has no Subsidiaries, and does not control, directly
or indirectly, any other entity and does not own of record or beneficially,
directly or indirectly, (i) any shares of capital stock or securities
convertible into capital stock of any other corporation (except for short-term
investments of the Company's cash reserves and publicly-traded mutual funds) or
(ii) any participating interest in any partnership, joint venture or other non-
corporate business enterprise, except for the strategic alliances described in
the Memorandum.

            (c) No proceeding has been commenced looking toward the dissolution
or merger of the Company or the amendment of its certificate of incorporation
(other than the Series B Certificate of Designations). The Company is not in
violation in any respect of its certificate of incorporation or bylaws.

            (d) The Company has all requisite power, authority (corporate and
other) and legal right to own or to hold under lease and to operate the
properties it owns or holds and to conduct

                                      -12-
<PAGE>

its business as now being conducted and as proposed to be conducted, except
where the failure to have such requisite power, authority and legal right would
not result in a Material Adverse Effect.

          (e) The Company has all requisite power, authority (corporate and
other) and legal right to execute, deliver, enter into, consummate and perform
the Stock Purchase Agreements, including, without limitation, the issuance, sale
and delivery by the Company of the Shares and to issue and deliver the
Conversion Shares issuable upon conversion of the Shares as contemplated herein
and therein and in the Series B Certificate of Designations.  The execution,
delivery and performance of the Stock Purchase Agreements by the Company
(including, without limitation, the issuance, sale and delivery by the Company
of the Shares and the issuance and delivery of the Conversion Shares upon
conversion of the Shares as contemplated herein and therein and in the Series B
Certificate of Designations) have been duly authorized by all required corporate
and other actions.  As described in the Memorandum, the Company may not have the
ability to pay dividends on the Shares under certain circumstances.  The Company
has duly executed and delivered the Stock Purchase Agreements.  The Stock
Purchase Agreements constitute the legal, valid and binding obligations of the
Company enforceable in accordance with their respective terms, subject to
bankruptcy, insolvency, reorganization, moratorium and other similar laws
relating to the rights of creditors generally and except that the enforceability
of the indemnification provisions contained in the Stock Purchase Agreements may
be subject to considerations of public policy.

     4.2. Stock.

          (a) The authorized capital stock of the Company consists of (i)
30,000,000 shares of Common Stock, par value $0.01 per share, and (ii) 5,000,000
shares of Preferred Stock, par value $0.01 per share, issuable in one or more
series, of which, after giving effect to the Series B Certificate of
Designations, (w) 508,800 shares have been designated as Series A Convertible
Preferred Stock ("Series A Preferred Stock"), (x) 904,000 shares have been
designated as Series B Preferred Stock, (y) 300,000 shares have been designated
as Series One Junior Participating Preferred Stock and (z) 3,287,200 shares are
Undesignated Preferred Stock.  On the Closing Date and before giving effect to
the exchange of any shares of Series A Preferred Stock into shares of Series B
Preferred Stock:  (A) 11,505,395 shares of the Company's Common Stock, par value
$0.01 per share, will be issued and outstanding (plus any shares of Common Stock
issued after February 13, 1997 pursuant to stock options in effect on such
date), (B) 480,000 shares of Series A Preferred Stock will be issued and
outstanding and (C) up to 280,000 Shares of the Series B Preferred Stock will be
outstanding.  The number of shares of Series A Preferred Stock will be reduced
and the number of shares of Series B Preferred Stock will be increased on a one-
for-one basis to the extent that shares of Series A Preferred Stock are
exchanged for shares of Series B Preferred Stock in the Exchange Offer.  All of
such outstanding shares will be duly authorized, validly issued and outstanding,
fully paid and non-assessable with no personal liability attaching to the
ownership

                                      -13-
<PAGE>

thereof. The Shares issued and delivered pursuant to this Stock Purchase
Agreement will be free and clear of all liens, charges, restrictions, claims and
encumbrances imposed by or through the Company. The Conversion Shares have been
reserved for issuance upon conversion of the Shares and, when issued in
accordance with the terms of the Shares, will be duly authorized, validly
issued, fully paid and non-assessable. None of the shares of the Company's
capital stock outstanding at Closing (including, without limitation, the Shares
issued under the Stock Purchase Agreements) (i) are subject to preemptive rights
or (ii) provide the holders thereof with any preemptive rights with respect to
any issuances of capital stock. Neither the issuance, sale or delivery of the
Shares nor the issuance or delivery of the Conversion Shares is subject to any
preemptive right of stockholders of the Company or to any right of first refusal
or other right in favor of any person.

          (b) The only shares of the Company's Common Stock reserved for
issuance by the Company are as follows (before giving effect to the exchange of
any shares of Series A Preferred Stock into shares of Series B Preferred Stock):
(i) 3,083,636 shares issuable upon conversion of the Series A Preferred Stock
(including the Series A Preferred Stock issuable upon the exercise of warrants
issued to the placement agents in connection with the offering of the Series A
Preferred Stock), (ii) 2,105,862 shares issuable upon conversion of the Series B
Preferred Stock (including the Series B Preferred Stock issuable upon the
exercise of warrants issued to the Agent in connection with the offering of the
Series B Preferred Stock), (iii) 2,030,964 shares issuable upon exercise of
currently outstanding stock options pursuant to the Company's 1992 Stock
Compensation Plan, its Non-Employee Director Stock Option Plan and director and
consultant stock option agreements and (iv) 263,020 shares reserved for issuance
pursuant to the 1992 Stock Compensation Plan, the Non-Employee Director Stock
Option Plan and the Company's 1997 Stock Option Plan with respect to which no
options are presently outstanding.

          (c) Except as referred to in Section 4.2(b) or in the Company's
Amended and Restated Certificate of Incorporation, there are no outstanding
options, warrants, subscriptions, rights, convertible securities or other
agreements or plans under which the Company may become obligated to issue, sell
or transfer shares of its capital stock or other securities.

          (d) The designations, powers, preferences, rights, qualifications,
limitations and restrictions in respect of each class and series of authorized
capital stock of the Company are as set forth in the Amended and Restated
Certificate of Incorporation of the Company and the Certificate of Designations
with respect to the Series A Preferred Stock (the "Series A Certificate of
Designations"), a copy of each of which is attached hereto as Exhibit B and
Exhibit C, respectively, and the Series B Certificate of Designations.

                                      -14-
<PAGE>

          (e) Except as contemplated by Section 8 hereof or as summarized on
Schedule II hereto, there are no outstanding registration rights with respect to
any capital stock of the Company.

          (f) Except as provided in the Series A Certificate of Designations and
the Series B Certificate of Designations, the Company has no obligation
(contingent or other) to purchase, redeem or otherwise acquire any of its
capital stock or any interest therein or to pay any dividend or make any other
distribution in respect thereof.

          (g) The Company has no knowledge of any voting agreements, voting
trusts, stockholders' agreements, proxies or other agreements or understandings
that are currently in effect or that are currently contemplated with respect to
the voting of any capital stock of the Company.

          (h) There are no anti-dilution protections or other adjustment
provisions in existence with respect to any capital stock of the Company or any
capital stock referred to in Section 4.2(b) or 4.2(c) above, except with respect
to the Shares and except as provided in the Amended and Restated Certificate of
Incorporation of the Company, the Series A Certificate of Designations and for
standard provisions in option agreements under the Company's plans for
employees, directors, consultants and advisors and in the warrants and warrant
agreements issued by the Company and described in (b) above.

          (i) All of the outstanding securities of the Company were issued in
compliance with all applicable federal and state securities laws.

          (j) The Series B Certificate of Designations has been duly adopted by
the Company and is fully effective.  The Series B Certificate of Designations
accurately describes all of the rights, priorities and terms of the Shares.

     4.3. Business.

     The Company is engaged in the business of developing and commercializing
innovative biotechnology-based processes for the petroleum refining and
production industries.  The Company does not currently engage in, or have any
intention of engaging in, any other business other than that which is described
in the Memorandum.

     4.4. No Defaults or Conflicts.

          (a) The Company is not in violation or default in any material respect
under any indenture, agreement or instrument to which it is a party or by which
it or its properties may be

                                      -15-
<PAGE>

bound. The Company is not in violation of or default in any material respect
under any law, rule, regulation, order, writ, injunction, judgment, decree,
award or other action of any court or governmental authority or arbitrator(s).
The Company is not in violation of its certificate of incorporation or bylaws.

          (b) The execution, delivery and performance by the Company of the
Stock Purchase Agreements and any of the transactions contemplated hereby or
thereby (including, without limitation, the issuance of the Shares and the
Conversion Shares as contemplated herein and therein and in the Series B
Certificate of Designations and the adoption of the Series B Certificate of
Designations) does not and will not (i) violate or conflict with, with or
without the giving of notice or the passage of time or both, any provision of
(A) the certificate of incorporation or bylaws of the Company or (B) any law,
rule, regulation or order of any federal, state, county, municipal or other
governmental authority, or any judgment, writ, injunction, decree, award or
other action of any court or governmental authority or arbitrator(s), or any
agreement, indenture or other instrument applicable to the Company or any of its
properties, except in the case of this clause (B) for such violations or
conflicts that will not individually or in the aggregate have a Material Adverse
Effect, (ii) result in the creation of any Lien upon any of the Company's
properties, assets or revenues, (iii) require the consent, waiver, approval,
order or authorization of, or declaration, registration, qualification or filing
with, any Person (whether or not a governmental authority and including, without
limitation, any shareholder approval) except for required securities law filings
and board of director approvals, certain approvals of the holders of Series A
Preferred Stock and certain registration rights modifications, which board of
director and Series A Preferred Stockholder approvals and registration rights
modifications have been obtained or (iv) cause anti-dilution clauses of any
outstanding securities to become operative except with respect to the Series A
Preferred Stock pursuant to the Series A Certificate of Designations or give
rise to any preemptive rights.  No provision referred to in the preceding clause
(i) materially adversely affects or reasonably may be expected to materially
adversely affect the continued conduct of the Company's business as described in
the Memorandum or the ability of the Company to perform its obligations under
the Stock Purchase Agreements, the Series B Certificate of Designations or any
of the transactions contemplated hereby or thereby.

     4.5. Disclosure Materials: Other Information.

          (a) The Company has previously furnished to the Purchaser the
Confidential Offering Memorandum dated October 21, 1996 of the Company (Alex.
Brown & Sons Incorporated as exclusive agent), as updated by the Confidential
Offering Memorandum dated January 10, 1997, the Memorandum and the documents
incorporated therein (the "Disclosure Material").  The audited and unaudited
financial statements referred to or contained in the Disclosure Material fairly
present the financial condition of the Company as of the respective dates
thereof and the results of the operations of the Company for such periods and
have been prepared in accordance with generally

                                      -16-
<PAGE>

accepted accounting principles consistently applied, except that any such
unaudited statements may omit notes and may be subject to normal year-end
adjustments.

          (b) Since December 31, 1995, (i) the business of the Company has been
conducted in the ordinary course and (ii) there has been no material adverse
change in the assets, properties, liabilities, business, affairs, results of
operations, condition (financial or otherwise) or prospects of the Company that
has not been described in the Disclosure Material.  As of the Closing Date and
as of the date hereof, there are no material liabilities of the Company which
would be required to be provided for in a balance sheet of the Company as of
either such date prepared in accordance with generally accepted accounting
principles consistently applied, other than liabilities provided for in the
financial statements referred to in Section 4.5(a) above.  Since December 31,
1995, no amount or property has directly or indirectly been declared, ordered,
paid, made or set aside for any Restricted Payment nor has any such action been
agreed to.

          (c) The Company is not aware of any material liabilities, contingent
or otherwise, of the Company that have not been disclosed in the financial
statements (including the notes thereto) referred to in Section 4.5(a) above or
otherwise disclosed in the Disclosure Material.

          (d) Nothing has come to the attention of the Company that would cause
it to believe that any of the Disclosure Material contained or contains a false
or misleading statement of a material fact or omits to state any material fact
necessary in order to make the statements made in such material, in light of the
circumstances under which they were made, not misleading.

          (e) There is no fact known to the Company which is not in the
Disclosure Material and which materially and adversely affects, or would
reasonably be expected to materially and adversely affect, the assets,
properties, liabilities, business, affairs, results of operations, condition
(financial or otherwise) or prospects of the Company.

     4.6. Litigation.

          There is no action, suit, proceeding, investigation or claim pending
against the Company or, to the knowledge of the Company, threatened against the
Company in law, equity or otherwise before any federal, state, municipal or
local court, administrative agency, commission, board, bureau, instrumentality
or arbitrator which either (i) questions the validity of the Stock Purchase
Agreements, the Series B Certificate of Designations, the Shares or the
Conversion Shares or any action taken or to be taken pursuant hereto or thereto,
or (ii) might adversely affect the right, title or interest of any Purchaser to
the Shares or the Conversion Shares or (iii) might result in a material adverse
change in the assets, properties, liabilities, business, affairs, results of
operations, condition (financial or otherwise) or prospects of the Company.  The
Company has not received any

                                      -17-
<PAGE>

opinion or memorandum or legal advice from legal counsel to the effect that it
is exposed, from a legal standpoint, to any liability or disadvantage which may
be material to its assets, properties, liabilities, business, affairs, results
of operations, condition (financial or otherwise) or prospects. There is no
action or suit by the Company pending or threatened against others.

     4.7. Taxes.

          The Company has filed all federal, state, local and other tax returns
and reports (except for foreign returns and reports the failure to file which
will not result in any material liability to the Company), and any other
material returns and reports with any governmental authorities (federal, state
or local), required to be filed by it.  The Company has paid or caused to be
paid all taxes (including interest and penalties) that are due and payable,
except those which are being contested by it in good faith by appropriate
proceedings and in respect of which adequate reserves are being maintained on
its books in accordance with generally accepted accounting principles
consistently applied.  The Company does not have any material liabilities for
taxes other than those incurred in the ordinary course of business and in
respect of which adequate reserves are being maintained by it in accordance with
generally accepted accounting principles consistently applied.  Federal and
state income tax returns for the Company have not been audited by the Internal
Revenue Service or state authorities.  No deficiency assessment with respect to
or proposed adjustment of the Company's federal, state, local or other tax
returns is pending or, to the best of the Company's knowledge, threatened.
There is no tax lien, whether imposed by any federal, state, local or other tax
authority outstanding against the assets, properties or business of the Company.
There are no applicable taxes, fees or other governmental charges payable by the
Company in connection with the execution and delivery of the Stock Purchase
Agreements or the issuance by the Company of the Shares or the Conversion
Shares, except for governmental fees paid in connection with securities law
filings.

     4.8. Employees; ERISA.

          The Company has good relationships with its employees and has not had
and does not expect to have any substantial labor problems.  The Company does
not have any knowledge as to any intentions of any key employee or any group of
employees to leave the employ of the Company.  Each of the officers of the
Company, each key employee and each other employee now employed by the Company
who has access to proprietary business information of the Company has executed a
confidentiality and non-disclosure agreement and such agreements are in full
force and effect.  Other than the Company's Simplified Employee Pension Plan
adopted in April 1992, the Company has not established, sponsored, maintained,
made any contributions to or been obligated by law to establish, maintain,
sponsor or make any contributions to any "employee pension benefit plan" or
"employee welfare benefit plan" (as such terms are defined in ERISA), including,
without

                                      -18-
<PAGE>

limitation, any "multi-employer plan". The Company has complied in all material
respects with all applicable laws relating to the employment of labor, including
provisions relating to wages, hours, equal opportunity, collective bargaining
and the payment of Social Security and other taxes, and with ERISA.

     4.9. Legal Compliance.

          (a) The Company has complied with all applicable laws, rules,
regulations, orders, licenses, judgments, writs, injunctions, decrees or
demands, except to the extent that failure to comply would not materially
adversely affect the assets, properties, liabilities, business, affairs, results
of operations, condition (financial or otherwise) or prospects of the Company.
The Company has all necessary permits, licenses and other authorizations
required to conduct its business as currently conducted, and as proposed to be
conducted, in all material respects.

          (b) There are no adverse orders, judgments, writs, injunctions,
decrees or demands of any court or administrative body, domestic or foreign, or
of any other governmental agency or instrumentality, domestic or foreign,
outstanding against the Company.

          (c) There is no existing law, rule, regulation or order, and the
Company is not aware of any proposed law, rule, regulation or order, which would
prohibit or materially restrict the Company from, or otherwise materially
adversely affect the Company in, conducting its business as now being conducted
and as proposed to be conducted.

     4.10.  Permits, Licenses and Approvals.

            The Company owns or possesses and holds free from restrictions or
conflicts with the rights of others all franchises, licenses, permits, consents,
approvals and other authority (governmental or otherwise), and all rights and
privileges with respect to the foregoing, as are necessary for the conduct of
its business as now being conducted, and as proposed to be conducted,
except where the failure to own or possess and hold such franchises, licenses,
permits, consents, approvals and other authority (governmental or otherwise)
would not have a Material Adverse Effect, and none is in default in any material
respects under any of such franchises, licenses, permits, consents, approvals or
other authority.

     4.11.  Patents, Trademarks and Other Rights.

            The Company has sufficient trademarks, trade names, service marks,
patent rights, copyrights, manufacturing processes, formulae, applications,
trade secrets, know how, licenses, approvals and governmental authorizations (or
rights thereto) (collectively, the "Intellectual

                                      -19-
<PAGE>

Property") to conduct its business as now conducted and the Company believes
that it will be able to obtain such Intellectual Property as will be necessary
to conduct its business as proposed to be conducted except in either case where
the absence of such Intellectual Property would not have a Material Adverse
Effect. No claim is pending or, to the Company's knowledge, threatened to the
effect that any such Intellectual Property owned or licensed by the Company, or
which the Company otherwise has the right to use, is invalid or unenforceable by
the Company, and, to the best of the Company's knowledge, there is no basis for
any such claim (whether or not pending or threatened). To the best of the
Company's knowledge, all proprietary technology developed by or belonging to the
Company and material to its business which has not been patented has been kept
confidential by the Company, its employees and agents. The Company has no
knowledge of any infringement by it of any Intellectual Property or other
similar rights of others, and there is no claim being made or, to the Company's
knowledge, threatened against the Company regarding infringement by the Company
on such Intellectual Property of others which could reasonably be expected to
have a Material Adverse Effect and, to the Company's knowledge, there is no
basis for any such claim (whether or not pending or threatened).

     4.12.  Status Under Certain Statutes.

          The Company is not: (i) a "public utility company" or a "holding
company", or an "affiliate" or a "subsidiary company" of a "holding company", or
an "affiliate" of such a "subsidiary company", as such terms are defined in the
Public Utility Holding Company Act of 1935, as amended, (ii) a "public utility"
as defined in the Federal Power Act, as amended, or (iii) an "investment
company" or an "affiliated person" thereof or an "affiliated person" of any such
"affiliated person", as such terms are defined in the Investment Company Act of
1940, as amended .

     4.13.  Title to Properties; Leasehold Interests.

          The Company has good and marketable title to each of the properties
and assets owned by it.  The Company does not own any real property.  Certain
real property used by the Company in the conduct of its business is held under
lease, and the Company is not aware of any pending or threatened claim or action
by any lessor of any such property to terminate any such lease.  None of the
properties owned or leased by the Company is subject to any Liens which could
reasonably be expected to materially and adversely affect the assets,
properties, liabilities, business, affairs, results of operations, condition
(financial or otherwise) or prospects of the Company.  Each lease or agreement
to which the Company is a party under which it is the lessee of any property,
real or personal, is a valid and subsisting agreement without any material
default of the Company thereunder and, to the best of the Company's knowledge,
without any material default thereunder of any other party thereto.  No event
has occurred and is continuing which, with due notice or lapse of time or both,
would constitute a default or event of default by the Company under any such
lease or

                                      -20-
<PAGE>

agreement or, to the best of the Company's knowledge, by any party thereto,
except for such defaults that would not individually or in the aggregate have a
Material Adverse Effect. The Company's possession of such property has not been
disturbed and, to the best of the Company's knowledge, no claim has been
asserted against it adverse to its rights in such leasehold interests.

     4.14.  Environmental Compliance.

            (a) There is no Hazardous Material about or in, any property, real
or personal, in which the Company has any interest, in violation of law in a
manner which could reasonably be expected to materially and adversely affect the
assets, properties, liabilities, business, affairs, results of operations,
condition (financial or otherwise) or prospects of the Company.

            (b) There is no (and has not been any) off-site disposal or on-site
disposal at any locations currently or formerly owned or occupied by the Company
as a result of which disposal there would exist a reasonably foreseeable risk
that the Company would incur a material liability or obligation under federal,
state or local environmental or other laws, regulations or ordinances.

            (c) Neither the Company nor, to the best of the knowledge of the
Company, any prior or present owner, operator, tenant, subtenant or invitee of
any of the real property (including improvements) currently or formerly owned or
occupied by the Company has (i) used, installed, stored, spilled, released,
transported, disposed of or discharged any Hazardous Material upon, into,
beneath, from or affecting such real property (including improvements) in
violation of law in a manner which could reasonably be expected to materially
and adversely affect the assets, properties, liabilities, business, affairs,
results of operations, condition (financial or otherwise) or prospects of the
Company, or (ii) received any verbal or written notice, citation, subpoena,
summons, complaint or other correspondence or communication from any Person (not
previously satisfactorily resolved) with respect to the presence of Hazardous
Material upon, into, beneath, or emanating from or affecting any of the real
property (including improvements) currently or formerly owned or occupied by the
Company which could materially and adversely affect the assets, properties,
liabilities, business, affairs, results of operations, condition (financial or
otherwise) or prospects of the Company.

            (d) There has been no intentional or unintentional, gradual or
sudden, release, disposal or discharge upon, into or beneath the real property
(including improvements) currently or formerly owned or occupied by the Company
by the Company or, to the best of the knowledge of the Company, by any prior
owner, operator, tenant, subtenant or invitee with respect thereto, that has
caused or is causing soil or ground water contamination which under applicable
environmental laws, regulations or ordinances could require investigation or
remediation or could otherwise create a material liability or obligation on the
part of the Company.

                                      -21-
<PAGE>

     4.15.  Disaster.

            Neither the business nor the properties of the Company is currently
affected (or has been affected at any time since December 31, 1995) by any fire,
explosion, accident, strike, lockout or other dispute, drought, storm, hail,
earthquake, embargo, act of God or of the public enemy or other casualty
(whether or not covered by insurance), of a kind which (individually or in the
aggregate) has materially adversely affected, or could reasonably be expected to
materially adversely affect, the assets, properties, liabilities, business,
affairs, results of operations, condition (financial or otherwise) or prospects
of the Company.

     4.16.  No Burdensome Agreements; Transactions with Affiliates.

            Except as disclosed in the Disclosure Material, the Company is not a
party to, or bound by (nor is any of its properties affected by), any
commitment, contract or agreement, any term of which materially adversely
affects, or which the Company expects in the future to materially adversely
affect, the assets, properties, business, affairs, results of operations,
condition (financial or otherwise) or prospects of the Company.  Except as
disclosed in the Disclosure Material, the Company is not a party to any contract
or agreement with any Affiliate of the Company.  The terms of any contracts or
agreements between the Company and any of its Affiliates are no less favorable
to the Company than those which might have been obtained, at the time such
contract or agreement was entered into, from a person who was not such an
Affiliate.

     4.17.  Other Names.

            The business previously or presently conducted by the Company has
not been conducted under any corporate, trade or fictitious name other than
"Energy BioSystems Corporation" and "Environmental BioScience Corporation",
which was the name of the Company until it was so changed in March 1992.

     4.18.  Offering of the Shares.

            Neither the Company nor, to the knowledge of the Company, any person
authorized or employed by the Company as agent, broker, dealer or otherwise
acting on its behalf, directly or indirectly, (i) offered any of the Shares or
any similar security of the Company (A) by any form of general solicitation or
general advertising (within the meaning of Regulation D under the Securities
Act) or (B) for sale to or solicited offers to buy any thereof from, or
otherwise approached or negotiated with respect thereto with, any person which
the Company did not reasonably believe was an "accredited investor" within the
meaning of Regulation D under the Securities Act or (ii) has done or caused to
be done (or has omitted to do or to cause to be done) any act, which act (or
which

                                      -22-
<PAGE>

omission) would result in bringing the issuance or sale of the Shares within the
provisions of Section 5 of the Securities Act or the filing, notification or
reporting provisions of any state securities laws, except for filings, notices
or reports pursuant to state securities laws which have already been made or
which are contemplated in connection with the offering and sale of the Shares.

     4.19.  No Foreign Assets Control Regulation Violation.

            The transactions contemplated by this Agreement will not result in a
violation of any of the foreign assets control regulations of the United States
Treasury Department, 31 C.F.R., Subtitle B, Chapter V, as amended (including,
without limitation, the Foreign Assets Control Regulations, the Transaction
Control Regulations, the Cuban Assets Control Regulations, the Foreign Funds
Control Regulations, the Iranian Assets Control Regulations, the Nicaraguan
Trade Control Regulations, the South African Transactions Regulations, the
Libyan Sanctions Regulations, the Soviet Gold Coin Regulations, the Panamanian
Transactions Regulations, the Kuwaiti Assets Control Regulations and the Iraqi
Sanctions Regulations contained in said Chapter V), or any ruling issued
thereunder or any enabling legislation or other Presidential Executive Order
granting authority therefor, and the proceeds of the sale of the Shares will not
be used by the Company in a manner which would violate any such regulations.

     4.20.  Indebtedness.

            Schedule II hereto sets forth (i) the amount of all Indebtedness of
the Company outstanding on the Closing Date (excluding Indebtedness in
individual amounts of less than $35,000, but not exceeding an aggregate excluded
amount of $75,000), (ii) any Lien with respect to such Indebtedness and (iii) a
brief description of each instrument or agreement governing such Indebtedness.
The Company has made available to the Purchaser a complete and correct copy of
each such instrument or agreement (including all amendments, supplements or
modifications thereto). No default exists with respect to or under any such
Indebtedness or any instrument or agreement relating thereto.

     4.21.  Proprietary Information of Third Parties.

            No third party has claimed or, to the best of the Company's
knowledge, has reason to claim that any person now or previously employed or
engaged as a consultant by the Company has (a) violated or, to the Company's
knowledge, may be violating any of the terms or conditions of his employment,
non-competition or non-disclosure agreement with such third party, (b) disclosed
or, to the best of the Company's knowledge, may be disclosing or utilized or, to
the best of the Company's knowledge, may be utilizing any trade secret or
proprietary information of documentation of such third party or violated any
confidential relationship which such person may

                                      -23-
<PAGE>

have had with such third party in connection with the business of the Company or
(c) interfered or may be interfering in the employment relationship between such
third party and any of its present or former employees. No third party has
requested information from the Company which reasonably suggests that such a
claim might be contemplated. To the best of the Company's knowledge, none of the
execution or delivery of the Stock Purchase Agreements, or the carrying on the
business of the Company as officers, employees or agents by any officer,
director or key employee of the Company, or the conduct or proposed conduct of
the business of the Company, will conflict with or result in a breach of the
terms, conditions or provisions of or constitute a default under any contract,
covenant or instrument under which any such individual is obligated.

     4.22 Insurance.

          The Company holds valid policies covering insurance in the amounts and
type that the Company reasonably believes is appropriate and customary for
companies in the same or similar businesses to that of the Company or otherwise
required to be maintained by it.

     4.23 Material Contracts and Agreements.

          With respect to all material contracts, agreements, indentures or
instruments not otherwise specifically referred to herein, the Company and, to
the best of the Company's knowledge, each other party thereto have in all
material respects performed all the obligations required to be performed by them
to date, have received no notice of default and are not in default, in any
material respect, (with due notice or lapse of time or both) under any material
contract, agreement, indenture or other instrument now in effect to which the
Company is a party or by which it or its property may be bound.  The Company has
no present expectation or intention of not fully performing all its obligations
under each such material contract, agreement, indenture or other instrument and
the Company has no knowledge of any breach and has received no written notice of
any anticipated breach by the other party to any material contract or commitment
which the Company is a party.

     4.24.  Governmental Approvals.

            Subject to the accuracy of the representations and warranties of the
Purchaser set forth in Section 5 hereof, no registration or filing with, or
consent or approval of or other action by, any federal, state or other
governmental agency or instrumentality is or will be necessary for the valid
execution, delivery and performance by the Company of this Stock Purchase
Agreement, the issuance, sale and delivery of the Shares to the Purchaser or,
upon conversion thereof, the issuance and delivery of the Conversion Shares,
other than filings pursuant to federal and state securities laws (all of which
filings have been or, with respect to those filings which may be duly made after
the Closing will be, made by or on behalf of the Company) in connection with the
sale of the Shares.

                                      -24-
<PAGE>

     4.25.  Brokers.

            Except with respect to Alex. Brown & Sons Incorporated, which acted
as the exclusive agent on behalf of the Company, the Company has no contract,
arrangement or understanding with any broker, finder or similar agent with
respect to the transactions contemplated by this Agreement.

     4.26.  Disclosure.

            The Disclosure Material, as of its date, does not contain an untrue
statement of a material fact or omit a material fact necessary to make the
statements contained therein, in light of the circumstances under which they
were made, not misleading.  All of the statements contained in this Stock
Purchase Agreement, including any Schedule or Exhibit hereto, and contained in
any document, certificate or other items prepared or supplied by the Company
directly to the Purchaser with respect to the transactions contemplated hereby
are accurate in all material respects.  There is no fact which the Company has
not disclosed to the Purchaser in writing and of which the Company is aware
which materially and adversely affects or could reasonably be expected to
materially and adversely affect the assets, properties, liabilities, business,
affairs, results of operations, condition (financial or otherwise) or prospects
of the Company.

SECTION 5.  REPRESENTATIONS OF THE PURCHASER

     The Purchaser hereby makes the representations and warranties to the
Company contained in this Section 5.

            (a) The Purchaser has all requisite power, authority and legal right
to execute, deliver, enter into, consummate and perform this Agreement.  The
execution, delivery and performance of this Agreement by the Purchaser have been
duly authorized by all required corporate, partnership or other actions on the
part of the Purchaser.  The Purchaser has duly executed and delivered this
Agreement, and this Agreement constitutes the legal, valid and binding
obligation of the Purchaser enforceable against the Purchaser in accordance with
its terms, subject to bankruptcy, insolvency, reorganization, moratorium and
other similar laws relating to the rights of creditors generally.

            (b) The Purchaser hereby represents to the Company that it has
substantial knowledge, skill and experience in making investment decisions of
this type, it is capable of evaluating the risk of its investment in the Shares
being purchased by it and is able to bear the economic risk of such investment,
including the risk of losing the entire investment, that (except as the
Purchaser has otherwise advised the Company and the Purchaser's counsel in
writing) it is

                                      -25-
<PAGE>

purchasing the Shares to be purchased by it for its own account, and that the
Shares are being purchased by it for investment and not with a present view to
any distribution thereof in violation of applicable securities laws. It is
understood that the disposition of the Purchaser's property shall at all times
be within the Purchaser's control. If the Purchaser should in the future decide
to dispose of any of its Shares, it is understood that it may do so only in
compliance with the Securities Act, applicable state securities laws and this
Agreement. The Purchaser represents that it is an "accredited investor" as
defined in Rule 501(a) under the Securities Act.

          (c) The Purchaser has received and reviewed the Disclosure Material
and it has had an opportunity to fully discuss the Company's business,
management and financial affairs with the Company's management.

          (d) The Purchaser understands that (i) the Shares and the Conversion
Shares have not been registered under the Securities Act by reason of their
issuance in a transaction exempt from the registration requirements of the
Securities Act pursuant to Section 4(2) or Section 3(b) thereof or Rule 506
promulgated under the Securities Act, (ii) the Shares and, upon conversion
thereof, the Conversion Shares must be held indefinitely unless a subsequent
disposition thereof is registered under the Securities Act or is exempt from
such registration and (iii) the Shares and the Conversion Shares will bear a
legend to such effect.

          (e) The Purchaser represents that at no time was the Purchaser
presented with or solicited by or through any leaflet (other than the
Memorandum), public promotional meeting, advertisement or any other form of
general or public advertising or solicitation.  In addition, the Purchaser
acknowledges that there has never been any representation, guaranty or warranty
made by the Company or any agent or representative of the Company as to the
amount of or type of consideration or profit, if any, to be realized as a result
of any investment by the Purchaser in the Preferred Stock.

          (f) If the Purchaser is a resident of the State of Florida, he
understands that he has the privilege of voiding the purchase within three (3)
days after the first tender of consideration is made by such Purchaser to the
Company or an agent of the Company.

          (g) If the Purchaser is a resident of the Commonwealth of
Pennsylvania, he will not sell his Shares within 12 months from the date of
purchase unless the Shares are registered under the Pennsylvania Securities Act
of 1972 or the Securities Act.

SECTION 6.  RESTRICTIONS ON TRANSFER

                                      -26-
<PAGE>

          (a) The Purchaser agrees that it will not sell or otherwise dispose of
any Shares or Conversion Shares unless (i) such Shares or Conversion Shares have
been registered under the Securities Act and, to the extent required, under any
applicable state securities laws, or (ii) such Shares or Conversion Shares are
sold in accordance with the applicable requirements and limitations of Rule 144
or Rule 144A, or (iii) the Company has been furnished with an opinion or
opinions from counsel to the Purchaser (which counsel and which opinion(s) shall
be reasonably satisfactory to the Company and which counsel may be inside
counsel to the Purchaser) to the effect that registration under the Securities
Act is not required for the transfer as proposed (which opinion may be
conditioned upon the transferee assuming the obligations of a holder of Shares
or Conversion Shares under this Section) or (iv) the Company has been furnished
with a letter from the Division of Corporate Finance of the Commission to the
effect that such Division would not recommend any action to the Commission if
such proposed transfer were effected without a registration statement effective
under the Securities Act.  The Company agrees that within five (5) Business Days
after receipt of any opinion referred to in (iii) above, it will notify the
holder supplying such opinion whether such opinion is satisfactory to the
Company.

          (b) The Company may endorse on all certificates evidencing Shares or
Conversion Shares a legend stating or referring to the transfer restrictions
contained in paragraph (a) above; provided, that no such legend shall be
endorsed on any certificates which, when issued, are no longer subject to the
restrictions of this Section 6; provided, further, that if a transfer is made
pursuant to clause (i), (ii) (other than pursuant to Rule 144A) or (iv) of
paragraph (a) of this Section 6, or if an opinion of counsel provided pursuant
to clause (iii) of paragraph (a) concludes that the legend is no longer
necessary, the Company will deliver upon transfer, certificates without such
legends.

SECTION 7.  COVENANTS OF THE COMPANY

     The Company covenants and agrees, so long as (i) any Shares are outstanding
or (ii) there are any Eligible Holders, whichever is longer (unless such other
period is expressly provided in any subsections of this Section 7, in which case
such specific period will govern) as follows:

     7.1. Use of Proceeds.

          The Company will use the proceeds from the sale of the Shares for
purposes described in the section of the Memorandum entitled "Use of Proceeds."
No portion of such proceeds will be used for the purpose, whether immediate,
incidental or ultimate, of purchasing or carrying, within the meaning of
Regulation U of the Board of Governors of the Federal Reserve System, as amended
from time to time, any "margin stock" as defined in said Regulation U, or any
"margin stock" as defined in Regulation G of the Board of Governors of the
Federal Reserve System, as amended from

                                      -27-
<PAGE>

time to time, or for the purpose of purchasing, carrying or trading in
securities within the meaning of Regulation T of the Board of Governors of the
Federal Reserve System, as amended from time to time, or for the purpose of
reducing or retiring any indebtedness which both (i) was originally incurred to
purchase any such margin stock or other securities and (ii) was directly or
indirectly secured by such margin stock or other securities. None of the assets
of the Company or any Subsidiary includes any such "margin stock", and neither
the Company nor any Subsidiary has any present intention of acquiring any such
"margin stock."

     7.2. Financial Information.

          (a) The Company will maintain a system of accounting established and
administered in accordance with sound business practices to permit preparation
of financial statements in accordance with generally accepted accounting
principles consistently applied.  The Company will deliver the following to each
Eligible Holder during the period through the Rights Expiration Date for such
Eligible Holder (and, in the case of paragraph (v) below, each other holder of
Shares and/or Conversion Shares):

          (i) as soon as practicable but not later than ten (10) Business Days
after their issuance, and in any event within ninety (90) days after the close
of each fiscal year of the Company, (A) a consolidated balance sheet of the
Company and its Subsidiaries as of the end of such fiscal year and (B)
consolidated statements of operations, stockholders' equity and cash flows of
the Company and its Subsidiaries for such fiscal year, in each case setting
forth in comparative form the corresponding figures for the preceding fiscal
year, all such balance sheets and statements to be in reasonable detail and
certified by an independent public accounting firm of recognized national
standing selected by the Company, and such statements shall be accompanied by
management analyses of any material differences between the results for such
fiscal year and the corresponding figures for the preceding fiscal year and
between the budgeted figures (as supplied pursuant to paragraph (ii) below) and
the results for such year and a narrative discussion of the Company's liquidity
and capital resources as of the end of such year materially conforming to the
disclosure requirements contained in Item 303 of Regulation S-K under the
Securities Act.  The Company's Annual Report on Form 10-K filed, or to be filed,
with the Commission will satisfy the requirements of this paragraph, except for
the requirement of the management analyses regarding the comparison of the
Company's results for such fiscal year to the budgeted figures (as supplied
pursuant to paragraph (ii) below);

          (ii) as soon as reasonably practicable, and in any event within thirty
(30) days after the close of the preceding fiscal year of the Company, a budget
for the current fiscal year (or the upcoming fiscal year, as the case may be)
prepared on a quarterly basis regarding the Company's operations and capital
expenditures on a consolidated basis, together with an analysis

                                      -28-
<PAGE>

of such budget prepared in reasonable detail by the Vice President of Finance or
the President of the Company; and (A) any operating budget of the Company
otherwise prepared and submitted to the Board and (B) any revisions or
amendments made by the Company (and submitted to its Board) to any budget
delivered under this paragraph (ii);

         (iii) as soon as reasonably practicable, and in any event within
forty-five (45) days after the close of each of the first three (3) fiscal
quarters of the Company, (A) a consolidated balance sheet of the Company and its
Subsidiaries as of the end of such fiscal quarter and (B) consolidated
statements of operations and cash flows of the Company and its Subsidiaries for
the quarter just ended and for the portion of the fiscal year ended with the end
of such quarter, in each case in reasonable detail, certified by the Vice
President of Finance or the President of the Company and setting forth in
comparative form the corresponding figures for the comparable period one year
prior thereto (subject to normal year-end adjustments) and the comparable
figures included in the budget for such quarter (as delivered or modified
pursuant to paragraph (ii) above), together with management analyses of any
material differences between such results and the corresponding figures for such
prior period and between such results for such quarter and such budgeted
figures.  The Company's Quarterly Report on Form 10-Q filed, or to be filed,
with the Commission will satisfy the requirements of this paragraph, except for
the requirement of the management analyses regarding the comparison of the
Company's results for such quarter to the budgeted figures;

          (iv) as soon as reasonably practicable, copies of summary financial
information prepared on a quarterly basis regarding the Company on a
consolidated basis as presented to the Board and any other summary financial
information otherwise prepared and provided to the Board;

           (v) as soon as reasonably practicable, copies of (A) all financial
statements, proxy material or reports sent by the Company to the Company's or
any Subsidiary's stockholders, (B) any public announcements or press releases
issued by the Company and (C) all reports or registration statements (excluding
registration statements on Form S-8) filed by the Company with the Commission
pursuant to the Securities Act or the Securities Exchange Act;

          (vi) as soon as reasonably practicable and without duplication of any
of the above items, all materials furnished, from time to time, to the Board of
Directors of the Company (including without limitation all communications and
information furnished to the Board of Directors), and copies of minutes of
meetings of the Boards of Directors of the Company;

         (vii) as soon as reasonably practicable and without duplication of
any of the above items, any other materials furnished to holders of the
Company's capital stock or any

                                      -29-
<PAGE>

material information furnished to holders of the Company's indebtedness,
including without limitation any compliance certificates furnished in respect of
such indebtedness; and

        (viii) as soon as reasonably practicable, such other material
information as may reasonably be requested by a holder of Shares (unless
reasonably objected to by the Company), regarding the assets, properties,
liabilities, business, affairs, results of operations, conditions (financial or
otherwise) or prospects of the Company or any Subsidiary.

All such financial statements shall be prepared in accordance with generally
accepted accounting principles consistently applied (except for any change in
accounting principles specified in the accompanying certificate and except that
any interim financial statements may omit notes and may be subject to normal
year-end adjustments).

           (b) Without limiting the foregoing provisions of this Section 7.2,
the Company agrees that, if requested in writing by any Eligible Holder, it will
not deliver to such Eligible Holder (until otherwise instructed by such Eligible
Holder) (x) any non-public information or non-public materials regarding the
Company or any Subsidiary (whether described in this Section 7.2 or otherwise)
and (y) any information (whether or not included in clause (x)) which such
holder specifies that it does not want to receive. The Company shall comply with
any such request with respect to each such Eligible Holder and any subsequent
holders of Shares or Conversion Shares acquired directly or indirectly (through
one or more transfers) from such Eligible Holder, until instructed otherwise in
writing by the then holder of such Shares or Conversion Shares.

     7.3. Tax Matters.

          Unless otherwise required by the Code or applicable state or local
law, the Company agrees that it will not report the accrual of a dividend under
Section 305 of the Code with respect to any redemption premium with which the
Series B Preferred Stock may have been issued, whether on Form 1099 or any other
form, to the Internal Revenue Service or any state or local taxing authority.

     7.4. Inspection.

          At the request of an Eligible Holder, and without out of pocket
expenses to the Company, the Company will permit such Eligible Holder and any
authorized representative of such holder, subject to (if requested by the
Company) execution by such Eligible Holder of a reasonable confidentiality
agreement, to visit and inspect any of the properties of the Company and its
Subsidiaries, and to discuss with their officers the business, results of
operations, condition (financial or otherwise) or prospects of the Company or
any Subsidiary, at mutually acceptable times.

                                      -30-
<PAGE>

     7.5. Maintenance of Existence; Properties and Franchises; Compliance with
          Law; Taxes; Insurance.

          The Company will, and will cause each Subsidiary to:

          (a) maintain their respective corporate existences, rights and other
franchises in full force and effect, except as may be affected by a transaction
permitted by Section 7.11; provided, that the Company may terminate the
corporate existence of any Subsidiary, or permit the termination or abandonment
of rights or other franchises, if in the opinion of the Company it is no longer
in the Company's best interests to maintain such existence, rights or other
franchises and such termination or abandonment will not be prejudicial in any
material respect to the holders of the Shares;

          (b) maintain their respective tangible assets in good repair, working
order and condition so far as necessary or advantageous to the proper carrying
on of their respective businesses;

          (c) comply with all applicable laws and with all applicable orders,
rules, rulings, certificates, licenses, regulations, demands, judgments, writs,
injunctions and decrees, provided, that such compliance shall not be necessary
so long as (i) the applicability or validity of any such law, order, rule,
ruling, certificate, license, regulation, demand, judgment, writ, injunction or
decree shall be contested in good faith by appropriate proceedings and (ii)
failure to comply will not have a Material Adverse Effect on a consolidated
basis;

          (d) pay promptly when due all taxes, fees, assessments and other
government charges imposed upon their respective properties, assets or income
and all claims or indebtedness (including, without limitation, materialmen's,
vendor's, workmen's and like claims) which might become a lien upon such
properties or assets; provided, that payment of any such tax, fee, assessment,
charge, claim or indebtedness shall not be necessary so long as (i) the
applicability or validity thereof shall be contested in good faith by
appropriate proceedings and a reserve, if appropriate, shall have been
established with respect thereto and (ii) failure to make such payment will not
have a Material Adverse Effect on a consolidated basis; and

          (e) keep adequately insured, by financially sound and reputable
insurers of nationally recognized stature, all their respective properties of a
character customarily insured by entities similarly situated, against loss or
damage of the kinds and in amounts customarily insured against by such entities
and with such deductibles or co-insurance as is customary.

     7.6. Office for Payment, Exchange and Registration; Location of Office;
          Notice of Change of Name or Office.

                                      -31-
<PAGE>

          (a) So long as any of the Shares is outstanding, the Company will
maintain an office or agency where Shares may be presented for payment,
exchange, conversion or registration of transfer as provided in this Agreement.
Such office or agency initially shall be the office of the Company's transfer
agent and shall be the following: KeyCorp Shareholder Services, Inc., 700
Louisiana, Suite 2620, Houston, Texas 77002.

          (b) The Company shall give each holder of Shares at least twenty (20)
days' prior written notice of any change in (i) the name of the Company as then
in effect or (ii) the location of the office of the Company required to be
maintained under this Section 7.6.

     7.7. Environmental Matters.

          (a) The Company and each Subsidiary shall keep any property either
owned or occupied by the Company or any Subsidiary free and clear of any
material Liens imposed for failure to comply with any environmental laws,
regulations or ordinances (each, an "Environmental Lien"), and the Company and
each Subsidiary, as the case may be, shall keep all such property in material
compliance with all environmental laws, regulations and ordinances; provided,
however, that the Company or any Subsidiary shall have the right at its cost and
expense, and acting in good faith, to contest, object or appeal by appropriate
legal proceeding the validity of any Environmental Lien.  The contest, objection
or appeal with respect to the validity of an Environmental Lien shall suspend
the Company's obligation to eliminate such Environmental Lien under this
paragraph pending a final determination by appropriate administrative or
judicial authority of the legality, enforceability or status of such
Environmental Lien, provided that the following conditions are satisfied:  (i)
contemporaneously with the commencement of such proceedings, the Company shall
give written notice thereof to each holder of Shares or Conversion Shares; and
(ii) if under applicable law any real property or improvements thereon are
subject to sale or forfeiture for failure to satisfy the Environmental Lien
prior to a final determination of the legal proceedings, the Company or such
Subsidiary must successfully move to stay such sale, forfeiture or foreclosure
pending final determination of the Company's (or Subsidiary's) action; and (iii)
the Company or such Subsidiary must, if requested, furnish to the holders of
Shares or Conversion Shares a good and sufficient bond, surety, letter of credit
or other security satisfactory to such holders equal to the amount (including
any interest and penalty) secured by the Environmental Lien.

          (b) The Company will defend, indemnify and hold harmless each current,
former and future holder of Shares or Conversion Shares, its employees,
officers, directors, stockholders, partners, agents, representatives and
assigns, from and against any liabilities, obligations, losses, damages,
penalties, actions, judgments, suits and claims, joint or several, and any
costs, disbursements and expenses (including attorneys' fees and expenses and
costs of investigation) of whatever kind or nature, known or unknown, contingent
or otherwise, arising out of or in any way

                                      -32-
<PAGE>

related to (i) the presence, disposal, release, removal, discharge, storage or
transportation of any Hazardous Material upon, into, from or affecting any real
property (including improvements) owned or occupied (or formerly owned or
occupied) by the Company or any Subsidiary; and (ii) any judicial or
administrative action, suit or proceeding, actual or threatened, relating to
Hazardous Material upon, in, from or affecting any real property (including
improvements) owned or occupied (or formerly owned or occupied) by the Company
or any Subsidiary; and (iii) any violation of any environmental law, regulation
or ordinance by the Company or any Subsidiary or any of their agents, tenants,
subtenants or invitees; and (iv) the imposition of any Environmental Lien for
the recovery of costs expended in the investigation, study or remediation of any
environmental liability of (or asserted against) the Company or any Subsidiary,
provided, however, that in no case shall such persons be entitled to
indemnification under this Section 7.7(b) for a decrease in the value of the
Shares or the Conversion Shares resulting from or in any way related to items
(i) though (iv) herein, but that the preceding clause shall in no way limit any
indemnification that a Purchaser may otherwise be entitled to under any other
provisions of this Stock Purchase Agreement. This Section 7.7(b) shall survive
any payment, conversion or transfer of Shares and any termination of this
Agreement.

     7.8. No Change in Business.

          Neither the Company nor any of its Subsidiaries will engage in any
business other than business of the general nature described in the Memorandum.

     7.9. Restrictive Agreements Prohibited.

          Neither the Company nor any of its Subsidiaries shall become a party
to any agreement which by its terms restricts the Company's performance of this
Agreement.

     7.10.  Restricted Payments.

          Neither the Company nor any Subsidiary will declare or make or permit
to be declared or made any Restricted Payment.

     7.11.  Consolidation, Merger and Sale.

          Without the consent of the Majority Shareholders, neither the Company
nor any Subsidiary will do any of the following (or agree to do any of the
following) pursuant to a transaction approved by the Board of Directors of the
Company: (a) wind up, liquidate or dissolve its affairs; (b) sell, lease,
transfer or otherwise dispose of all or substantially all of its assets to any
other Person; (c) consolidate with, merge into or enter into a share exchange
with any other Person;

                                      -33-
<PAGE>

or (d) permit any other Person (other than a wholly-owned Subsidiary on the date
hereof) to merge into or sell, lease or transfer all or substantially all of its
property, assets or capital stock to the Company or any Subsidiary, unless:

          (i) in the case of actions under clause (a) or (b) above, a wholly-
owned Subsidiary is wound-up, dissolved and liquidated into another wholly-owned
Subsidiary or into the Company or a wholly-owned Subsidiary sells, leases,
transfers or otherwise disposes of all or substantially all of its assets to
another wholly-owned Subsidiary or to the Company; or

         (ii) in the case of actions under clause (c) or (d) above, each of the
following conditions is satisfied:

          (A) if such action involves the Company and if such surviving Person
is a corporation other than the Company, all liabilities and obligations of the
Company under the Stock Purchase Agreements shall remain in effect and shall
have been expressly assumed by such surviving Person (pursuant to a document in
form and substance reasonably satisfactory to the Majority Shareholders and
their counsel) as if such surviving Person were the "Company" hereunder and
thereunder; and

          (B) either (x) the Common Stock of such transferee Person into which
the Series B Preferred Stock will thereafter be convertible (or American
Depositary Receipts with respect thereto) is listed on a national securities
exchange in the United States or traded on The Nasdaq Stock Market, or (y) all
of the Series B Preferred Stock is concurrently redeemed for cash in accordance
with Section 5 of the Series B Certificate of Designations.

     7.12.  Transactions with Affiliates.

            The Company will not, and will not permit any Subsidiary to,
directly or indirectly, enter into any transaction or agreement (including,
without limitation, the purchase, sale, distribution, lease or exchange of any
property or the rendering of any service) with any Affiliate of the Company or
of any Subsidiary, other than a wholly-owned Subsidiary of the Company, unless
such transaction or agreement (a) is approved by disinterested members of the
Board of Directors of the Company, and (b) is on terms that are no less
favorable to the Company or such Subsidiary, as the case may be, than those
which might be obtained at the time of such transaction from a Person who is not
such an Affiliate; provided, however, that this Section 7.12 shall not limit, or
be applicable to, (i) employment arrangements with any individual who is an
employee of the Company or any Subsidiary if such arrangements are approved by
the Board; and (ii) the payment of reasonable and customary regular fees to
directors who are not employees of the Company.

                                      -34-
<PAGE>

     7.13.  Observer Rights.

            Each of the Eligible Holders shall have the right, during the period
through the Rights Expiration Date for such Eligible Holder, and (if requested
by the Company) subject to execution by such observer of a reasonable
confidentiality agreement, to send one (1) representative to meetings of the
Company's and each Subsidiary's Board of Directors (and the executive committee
if the executive committee has more than five members) of such Boards, such
representatives to act as observers without a vote or other rights as a director
(except the right to receive sufficient notice to enable such attendance and the
right to receive all other communications, information and materials furnished,
from time to time, to directors of the Company and each Subsidiary).  Any
representative acting under this Section 7.13 shall be chosen from the list of
Persons provided to the Company concurrently with execution of this Agreement
(or another individual selected by such holders and reasonably acceptable to the
Company).

     7.14.  No Dilution or Impairment; No Changes in Capital Stock.

            The Company will not, by amendment of its certificate of
incorporation or through any consolidation, merger, reorganization, transfer of
assets, dissolution, issue or sale of securities or any other voluntary action,
avoid or seek to avoid the observance or performance of any of the terms of the
Stock Purchase Agreements or the Series B Certificate of Designations. The
Company will at all times in good faith assist in the carrying out of all such
terms, and in the taking of all such action, as may be necessary or appropriate
in order to protect the rights of the holders of Shares (as such rights are set
forth in the Stock Purchase Agreements and the Series B Certificate of
Designations) against impairment. Without limiting the generality of the
foregoing, the Company (a) will not permit the par value or the determined or
stated value of any shares of the Company's Common Stock receivable upon the
conversion of the Shares to exceed the amount payable therefor upon such
conversion, (b) will take all such action as may be necessary or appropriate in
order that the Company may validly and legally issue fully paid and non-
assessable shares of the Company's Common Stock free from all taxes, Liens and
charges with respect to the issue thereof, upon the conversion of the Shares
from time to time outstanding, (c) will not take any action which results in any
adjustment of the Conversion Price under the Series B Certificate of
Designations if the total number of shares of the Company's Common Stock (or
other securities) issuable after the action upon the conversion of all of the
then outstanding Shares would exceed the total number of shares of the Company's
Common Stock (or other securities) then authorized by the Company's certificate
of incorporation and available for the purpose of issuance upon such conversion,
(d) will not have any authorized Common Stock other than its existing authorized
Common Stock, (e) will not amend its certificate of incorporation to change any
terms of its Common Stock, (f) will not amend its certificate of incorporation
in any manner to alter or change the powers, privileges or preferences of the
holders of the Series B Preferred Stock (including without limitation changing
the Series B

                                      -35-
<PAGE>

Certificate of Designations after any Shares have been called for redemption),
(g) will not create or authorize the creation of any additional class or series
of shares of capital stock unless the same ranks junior to the Series B
Preferred Stock as to the payment of dividends or the distribution of assets on
the liquidation, dissolution or winding up of the Company, or increase the
authorized amount of the Series B Preferred Stock, or increase the authorized
amount of any additional class or series of shares of stock unless the same
ranks junior to the Series B Preferred Stock as to the payment of dividends or
the distribution of assets on the liquidation, dissolution or winding up of the
Company, or create or authorize any obligation or security convertible into
shares of Series B Preferred Stock or into shares of any other class or series
of stock unless the same ranks junior to the Series B Preferred Stock as to the
payment of dividends or the distribution of assets on the liquidation,
dissolution or winding up of the Company, whether any such creation,
authorization or increase shall be by means of amendment to the certificate of
incorporation or by merger, consolidation or otherwise and (h) after the date
hereof, will not create or establish (or make any grants or awards under) any
phantom stock, stock appreciation rights or other equity equivalent plan for
employees, officers, directors, agents or consultants of the Company (unless
such plans in the aggregate relate to the equivalent of less than 5% of the
Common Stock of the Company) whereby the Company or any Subsidiary agrees to pay
any Person a percentage of, or an amount otherwise determined by reference to,
the earnings of the Company or any Subsidiary, the value of their stock or the
proceeds from a sale of their stock or upon their liquidation.

     7.15.  Reservation of Shares.

            There have been reserved, and the Company shall at all times keep
reserved, free from preemptive rights, out of its authorized Common Stock, a
number of shares of Common Stock sufficient to provide for the exercise of the
conversion rights of the Shares provided in the Series B Certificate of
Designations.  If at any time the number of authorized but unissued shares of
Common Stock of the Company shall not be sufficient to effect the conversion of
the Shares or otherwise to comply with the terms of this Agreement, the Company
will forthwith take such corporate action as may be necessary to increase its
authorized but unissued shares of Common Stock to such number of shares as shall
be sufficient for such purpose.  The Company will obtain any authorization,
consent, approval or other action by or make any filing with any court or
administrative body that may be required under applicable state securities laws
in connection with the issuance of the Common Stock upon conversion of the
Shares.

     7.16.  Listing of Shares.

            If any shares of the Company's Common Stock or Series B Preferred
Stock are listed on any national securities exchange (or on The Nasdaq Stock
Market or comparable system), then the Company will take such action as may be
necessary, from time to time, to list the Conversion

                                      -36-
<PAGE>

Shares or the Shares, as the case may be, on such exchange (or system as the
case may be). The Company shall have no obligation to list the Shares if the
Series B Preferred Stock is not so listed.

     7.17.  Securities Exchange Act Registration.

            (a)  The Company will maintain effective a registration statement
(containing such information and documents as the Commission shall specify and
otherwise complying with the Securities Exchange Act) under Section 12(b) or
Section 12(g), whichever is applicable, of the Securities Exchange Act, with
respect to the Company's Common Stock, and will file on time such information,
documents and reports as the Commission may require or prescribe for companies
whose stock has been registered pursuant to such Section 12(b) or Section 12(g),
whichever is applicable.

            (b) The Company will, upon the request of any holder of Shares or
Conversion Shares, make whatever other filings with the Commission, or otherwise
make generally available to the public such financial and other information, as
any such holder may deem reasonably necessary or desirable in order to enable
such holder to be permitted (i) to sell Conversion Shares pursuant to the
provisions of Rule 144 and (ii) after the Company has filed a registration
statement with respect to Series B Preferred Stock under Section 6 of the
Securities Act or Section 12(b) or 12(g) of the Securities Exchange Act, to sell
Shares pursuant to the provisions of Rule 144.

     7.18.  Maintenance of Public Market.

            Except as contemplated by Section 7.11, the Company will not (i)
proceed with a program of acquisition of its own Common Stock or of Series B
Preferred Stock (other than by redemption in accordance with the Series B
Certificate of Designations), (ii) initiate a corporate reorganization or
recapitalization or undertake a consolidation or merger or (iii) authorize,
consent to or take any action without the consent of the Eligible Holders, which
would have the effect of:

               (a) removing the Company from registration with the Commission
under the Securities Exchange Act with respect to the Company's Common Stock,

               (b) requiring the Company to make a filing under Section 13(e) of
the Securities Exchange Act,

          (c) reducing substantially or eliminating the public market for shares
of Common Stock of the Company,

                                      -37-
<PAGE>

          (d) if any shares of the Company's Common Stock or Series B Preferred
Stock are at any time listed on The Nasdaq Stock Market, causing a delisting of
the Company's Common Stock or Series B Preferred Stock, as the case may be, from
such systems (unless such stock is delisted as a result of being listed on a
national securities exchange), or

          (e) if any shares of the Company's Common Stock or Series B Preferred
Stock are at any time listed on a national securities exchange, causing a
delisting of such stock from such exchange.

     7.19.  Private Placement Status.

            Neither the Company nor any agent nor other Person acting on the
Company's behalf will do or cause to be done (or will omit to do or to cause to
be done) any act which act (or which omission) would result in bringing the
issuance or sale of the Shares or the Conversion Shares within the provisions of
Section 5 of the Securities Act or the filing, notification or reporting
requirements of any state securities law (other than in accordance with a
registration and qualification of Conversion Shares pursuant to Section 7.17
hereof), except for filings, notices or reports pursuant to state securities
laws which have already been made or which are contemplated in connection with
the offering and sale of the Shares.

     7.20.  Delivery of Information.

            If a holder of Shares or Conversion Shares proposes to transfer any
such Shares or Conversion Shares pursuant to Rule 144A, the Company agrees to
provide (upon the request of such holder or the prospective transferee) to such
holder and (if requested) to the prospective transferee any information
concerning the Company and its Subsidiaries which is required to be delivered to
any transferee of such Shares or Conversion Shares pursuant to such Rule 144A.

     7.21.  Notices.

            The Company will give to all holders of Shares or Conversion Shares
copies of all notices given by the Company to holders of its Common Stock
concurrently with the giving of such notices to such holders of Common Stock.

     7.22 No Dividends in Common Stock Unless Registered.

          The Company will not declare and cause to be paid dividends on the
Shares in shares of Common Stock until a registration statement covering the
resale of such Common Stock has been filed with the Commission and has been
declared effective thereby.

                                      -38-
<PAGE>

SECTION 8.  REGISTRATION RIGHTS

     8.1. Registration of the Shares.

          (a) The holders of at least an aggregate of 100,000 Shares may request
the Company to register under the Securities Act the resale of all or any
portion of such Shares, but in no event less than 60,000 Shares, held by such
requesting holder or holders for sale in the manner specified in such notice.

          (b) Following receipt of any notice under this Section 8.1, the
Company shall immediately notify all holders of the Shares from whom notice has
not been received and shall commit to register under the Securities Act, for
public sale in accordance with the method of disposition specified in such
notice from requesting holders, the number of Shares specified in such notice
(and in all notices received by the Company from other holders within 30 days
after the giving of such notice by the Company).  All such holders who submit
requests to the Company pursuant to this Section 8.1 shall be referred to
individually as a "Requesting Holder" and collectively as "Requesting Holders."
If the Requesting Holders may elect to have the Shares sold to one or more
persons participating as underwriters ("Underwriters") for an offering of Shares
to the public (an offering of any shares of capital stock of the Company by
means of Underwriters to the public shall be referred to as an "Underwritten
Offering"), the holders of a majority of the Shares to be sold in such offering
may designate the managing Underwriter of such offering, subject to approval of
the Company, which approval will not be unreasonably withheld or delayed.  The
Company shall be obligated to register the Shares pursuant to this Section 8.1
on two occasions only, provided, however, that such obligation shall be deemed
satisfied only when a registration statement covering at least 60% of the total
Shares specified in notices received as aforesaid, for sale in accordance with
the method of disposition specified by the Requesting Holders, shall have become
effective and, if such method of disposition is an Underwritten Offering, all
such shares shall have been sold pursuant thereto.

          (c) Except for registration statements on Form S-4, S-8 or any
successor thereto and except as required under the registration rights
agreements referred to in Schedule II hereto, the Company will not file with the
Commission without the approval of the Requesting Holders any other new
registration statements with respect to its capital stock, whether for its own
account or that of other stockholders, from the date of receipt of a notice from
Requesting Holders pursuant to this Section 8.1 until the earlier of (i) six (6)
months from the date of receipt of such notice and (ii) the completion of the
period of distribution of the registration contemplated thereby.  The
registration statement, together with all amendments and supplements, including
post-effective amendments, in each case including the prospectus contained
therein (including the preliminary prospectus and all amendments and supplements
to the prospectus, including post-effective amendments) (collectively,

                                      -39-
<PAGE>

the "Prospectus"), all exhibits thereto or to the Prospectus and all material
incorporated by reference therein or to the Prospectus, is referred to as the
"Registration Statement".

          (d) If and whenever the Company is required by the provisions of this
Section 8.1 to effect the registration of any Shares under the Securities Act,
the Company will, as expeditiously as possible:

               (i)  prepare and file with the Commission, no later than 60 days
after the receipt of the first notice from the Requesting Holders, a
Registration Statement on Form S-2 (or other appropriate form) with respect to
such securities and use its reasonable best efforts to cause such Registration
Statement to become and remain effective for the period of distribution
contemplated thereby (determined as hereinafter provided);

              (ii)  prepare and file with the Commission such amendments and
supplements to such Registration Statement and the Prospectus used in connection
therewith as may be necessary to keep such Registration Statement effective for
the period contemplated in (i) above and comply with the provisions of the
Securities Act with respect to the disposition of all Shares covered by such
Registration Statement in accordance with the sellers' intended method of
disposition set forth in such Registration Statement for such period;

             (iii)  register or qualify the Shares, by the time the Registration
Statement is declared effective by the Commission, under all applicable state
securities or "Blue Sky" laws of such jurisdictions as each Underwriter, if any,
or the Requesting Holders shall request in writing, provided that the Company
shall not be obligated to qualify as a foreign corporation or as a dealer in
securities in any jurisdiction in which it is not so qualified or to subject
itself to taxation in respect of doing business in any jurisdiction in which it
is not otherwise so subject;

              (iv)  keep each such registration or qualification effective
during the period the Registration Statement is required to be kept effective;

                                      -40-
<PAGE>

               (v)  upon request by the Requesting Holders, do any and all other
acts and things which may be reasonably necessary to enable such Underwriter, if
any, and the Requesting Holders to consummate the disposition of the Shares in
each such jurisdiction;

              (vi)  notify the Requesting Holders when the Registration
Statement has become effective and when any post-effective amendments and
supplements thereto become effective;

             (vii)  in connection with an Underwritten Offering, if any, notify
the Requesting Holders if, between the effective date of the Registration
Statement and the closing of any sale of Shares, the representations and
warranties of the Company contained in the underwriting agreement relating to
any Underwritten Offering cease to be true and correct in all material respects
or if the Company receives any notification with respect to the suspension of
the qualification of the Shares for sale in any jurisdiction or the initiation
of any proceeding for such purpose;

            (viii)  furnish or cause to be furnished forthwith to the Requesting
Holders, a "cold comfort" letter of the Company's independent accountants, as of
the effective date of the Registration Statement, as to such matters as
customarily are covered in accountant's letters delivered to underwriters in
underwritten public offerings of securities;

              (ix)  furnish or cause to be furnished forthwith to the Requesting
Holders, an opinion of counsel to the Company, as of the effective date of the
Registration Statement, in the form customarily provided by issuer's counsel in
underwritten public offerings of securities;

               (x)  furnish such number of Prospectuses and other documents
incident thereto, including any amendment of or supplement to the Prospectus as
the Requesting Holders from time to time may reasonably request during the
period of distribution of the Shares;

              (xi)  provide a transfer agent and registrar for all of the
Shares; and

             (xii)  otherwise use its reasonable best efforts to comply with all
applicable rules and regulations of the Commission with respect to the
disposition of the Shares covered by such Registration Statement, and make
available to its security holders, as soon as reasonably practicable, an
earnings statement covering the period of at least twelve months, but not more
than eighteen months, beginning with the first month after the effective date of
the Registration Statement, which earnings statement shall satisfy the
provisions of Section 11(a) of the Securities Act.

          (e) For purposes of this Section 8.1, the period of distribution of
the Shares in an Underwritten Offering shall be deemed to extend until each
Underwriter has completed the distribution of all securities purchased by it
(but no later than 180 days), and the period of distribution of the Shares in
any other registration shall be deemed to extend until the earlier of the sale
of all Shares covered thereby and 180 days after the effective date thereof.

          (f) In connection with each registration under this Section 8.1, and
as a condition to the inclusion of their shares therein, the Requesting Holders
will furnish to the Company in writing such information with respect to
themselves and the proposed distribution by them as

                                      -41-
<PAGE>

reasonably shall be necessary in order to assure compliance with federal and
applicable state securities laws.

          (g) As soon as the Company is eligible to register the Shares on Form
S-3 (or any successor form thereto under the Securities Act), the Company will,
as expeditiously as possible but in any event no later than 60 days after the
Company is eligible to register the Shares on Form S-3, undertake to amend the
"shelf" Registration Statement on Form S-3 referred to in Section 8.2 to include
any Shares outstanding or to file and to use its reasonable best efforts to have
declared effective a separate registration statement registering the resale of
the Shares.  Any Shares so registered pursuant to the Company's "shelf"
Registration Statement on Form S-3 or such other registration statement shall be
thereinafter included within the definition of "Registered Securities".

          (h) Subject to Section 8.3 below, the Company agrees to supplement or
amend the Registration Statement, if required by the Securities Act.

     8.2  Shelf Registration of the Registered Securities.

     The Company agrees to use its reasonable best efforts to file with the
Commission a "shelf" Registration Statement on Form S-3 (or other appropriate
form under the Securities Act), providing for the resale of all of the
Registered Securities, within sixty (60) days after the Closing Date.  The
Company will use its reasonable best efforts to have the Registration Statement
declared effective by the Commission as soon as practicable after the filing
thereof. Subject to Section 8.3 hereof, the Company will use its reasonable best
efforts to keep the Registration Statement continuously effective until the
earlier of:

          (A) the date upon which all of the outstanding Registered Securities
have been sold pursuant to the Registration Statement or are no longer
outstanding, or

          (B) such date as the Company and each of the Eligible Holders shall be
satisfied that Rule 144(k) of the regulations under the Securities Act is
available for the resale of the Registered Securities held by them, or, in the
case of Eligible Holders for whom Rule 144(k) is unavailable, such Eligible
Holders have consented in writing to permit the Company to discontinue the
effectiveness of the Registration Statement.

Subject to Section 8.3 below, the Company agrees to supplement or amend the
Registration Statement, if required by the Securities Act.

     8.3. Interference with Registration.

                                      -42-
<PAGE>

          (a) For purposes of this Section 8.3, any Registration Statement
pursuant to either Section 8.1 or 8.2 hereof shall collectively be referred to
as the "Registration Statements."  If, after the Registration Statements have
been declared effective, a stop order, injunction or other order or requirement
of the Commission or any other governmental agency or court is issued which
suspends the effectiveness of a Registration Statement, (i) upon receipt of
notice from the Company, the Requesting Holders or Purchaser (as applicable)
will discontinue any disposition of Shares or Registered Securities,
respectively, pursuant to that Registration Statement until receipt of notice
from the Company that the suspension of the effectiveness of the Registration
Statement has been withdrawn and (ii) the Company will use its reasonable best
efforts to obtain the withdrawal of such order or to meet such requirement at
the earliest possible time.

          (b) If, after the Registration Statements have become effective, an
event occurs as a result of which the Company determines that a Registration
Statement or the related Prospectus contains any untrue statement of a material
fact or omits to state any material fact required to be stated therein or
necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading, the Company will notify the Requesting
Holders and any Purchaser (as applicable) thereof and, if applicable, use its
reasonable best efforts to prepare and promptly file a post-effective amendment
or a supplement to the Registration Statement or the related Prospectus or
promptly file any other required document so that, as thereafter delivered to
purchasers of the Shares or Registered Securities, such Prospectus will not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary to make the statements therein,
in light of the circumstances under which they were made, not misleading.

          (c) Without limiting Section 8.3(a) and 8.3(b) hereof, if any
Requesting Holder or Purchaser (as applicable) shall propose to sell any Shares
or Registered Securities, respectively, pursuant to the Registration Statements,
it shall notify the Company of its intent to do so at least three (3) full
Business Days prior to such sale.  At any time within such three (3) Business
Day period, the Company may refuse to permit the Requesting Holder or Purchaser
(as applicable) to resell any Shares or Registered Securities, respectively,
pursuant to the Registration Statements; except that the Company may exercise
this right only once in any one hundred eighty (180) day period, unless the
matter giving rise to the exercise by the Company of this right is beyond the
Company's control; and provided, further, that in order to exercise this right,
the Company must deliver a certificate in writing to the Requesting Holder or
Purchaser (as applicable) to the effect that a delay in such sale is necessary
because a sale pursuant to such Registration Statement in its then-current form
would reasonably be expected to constitute a violation of the federal securities
laws.  Without limiting Section 8.3(b) hereof, in no event shall such delay
exceed ten (10) Business Days; provided, however, that if, prior to the
expiration of such ten (10) Business Day period, the Company delivers a
certificate in writing to the Requesting Holder or Purchaser (as applicable) to
the effect that a further delay in such sale beyond such ten (10) Business Day
trading period is necessary

                                      -43-
<PAGE>

because a sale pursuant to the Registration Statement in its then-current form
would reasonably be expected to constitute a violation of the federal securities
laws, the Company may refuse to permit such Requesting Holder or Purchaser (as
applicable) to resell any Shares or Registered Securities, respectively,
pursuant to the Registration Statement for an additional period not to exceed
five (5) Business Days, but in no event shall any such delay exceed in the
aggregate fifteen (15) Business Days, unless the matter giving rise to the
exercise of such right is beyond the Company's control.

     8.4. Selection of Underwriters for Registered Securities.

          With respect to the registration of Registered Securities pursuant to
Section 8.2 hereof, at any time or from time to time after the Closing, the
Purchaser may elect to have the Registered Securities sold to one or more
persons participating as Underwriters for an Underwritten Offering.  In such
event, the Company shall engage (a) Alex. Brown & Sons Incorporated or (b)
another nationally recognized independent investment banking firm reasonably
acceptable to the holders of a majority of the Registered Securities, as
Underwriters; provided, however, that the Company shall not be required to
engage any Underwriter if such engagement would require the consent or approval
of any governmental authority (including the necessity of obtaining an exemptive
order under the Investment Company Act of 1940, as amended); provided, further,
that after three years after the Closing Date such Underwriters shall be
selected by mutual agreement of the Company and the holders of a majority of the
Registered Securities, each acting reasonably.  In such event, the Company and
each such Purchaser will cooperate with the Underwriter or the managing
Underwriter and take all customary and reasonable actions to facilitate the
disposition of Registered Securities in an Underwritten Offering.

8.5. Other Obligations of the Company with respect to the Registered Securities.

          After the Closing, the Company will:

          (a)  use its reasonable best efforts

               (i) to register or qualify the Registered Securities, by the time
the Registration Statement is declared effective by the Commission, under all
applicable state securities or "Blue Sky" laws of such jurisdictions as each
Underwriter, if any, or the Purchaser shall request in writing, provided that
the Company shall not be obligated to qualify as a foreign corporation or as a
dealer in securities in any jurisdiction in which it is not so qualified or to
subject itself to taxation in respect of doing business in any jurisdiction in
which it is not otherwise so subject;

              (ii) to keep each such registration or qualification effective
during the period the Registration Statement is required to be kept effective;
and

                                      -44-
<PAGE>

             (iii) upon request by the Purchaser, to do any and all other acts
and things which may be reasonably necessary to enable such Underwriter, if any,
and the Purchaser to consummate the disposition of the Registered Securities in
each such jurisdiction;

          (b)  notify the Purchaser

               (i) when the Registration Statement has become effective and when
any post-effective amendments and supplements thereto become effective and

              (ii) in connection with an Underwritten Offering, if any, if,
between the effective date of the Registration Statement and the closing of any
sale of Registered Securities, the representations and warranties of the Company
contained in the underwriting agreement relating to any Underwritten Offering
cease to be true and correct in all material respects or if the Company receives
any notification with respect to the suspension of the qualification of the
Registered Securities for sale in any jurisdiction or the initiation of any
proceeding for such purpose;

          (c) Furnish or cause to be furnished forthwith to the Purchaser,

               (i) a "cold comfort" letter of the Company's independent
accountants, as of the effective date of the Registration Statement, as to such
matters as customarily are covered in accountant's letters delivered to
underwriters in underwritten public offerings of securities and

              (ii) an opinion of counsel to the Company, as of the effective
date of the Registration Statement, in the form customarily provided by issuer's
counsel in underwritten public offerings of securities;

          (d) furnish such number of Prospectuses and other documents incident
thereto, including any amendment of or supplement to the Prospectus as a
Purchaser from time to time may reasonably request;

          (e) cause all such Registered Securities registered as described
herein to be listed on each securities exchange and quoted on each quotation
service on which securities of the same class and series issued by the Company
are then listed or quoted;

          (f) provide a transfer agent and registrar for all Registered
Securities;

          (g) otherwise use its reasonable best efforts to comply with all
applicable rules and regulations of the Commission with respect to the
disposition of the Registered Securities, and make available to its security
holders, as soon as reasonably practicable, an earnings statements

                                      -45-
<PAGE>

covering the period of at least twelve months, but not more than eighteen
months, beginning with the first month after the effective date of the
Registration Statement, which earnings statement shall satisfy the provisions of
Section 11(a) of the Securities Act.

     8.6. Registration Expenses.

          The Company agrees to pay all Registration Expenses in connection with
the registrations pursuant to this Section 8. "Registration Expenses" means any
and all expenses incident to performance of or compliance with the provisions of
this Section 8 by the Company, including without limitation:  (i) all Commission
and National Association of Securities Dealers, Inc. ("NASD") registration and
filing fees, (ii) all fees and expenses incurred in connection with compliance
with state securities or "Blue Sky" laws and compliance with the rules of the
NASD, (iii) all expenses in preparing, printing and distributing the
Registration Statements and other documents relating to the performance of and
compliance with this Agreement by the Company, (iv) the reasonable fees and
disbursements of counsel for the Company and of one counsel selected by the
Eligible Holders and reasonably acceptable to the Company and of the independent
public accountants of the Company, (v) any fees and disbursements of
Underwriters, dealers and agents, if any, customarily paid by issuers of
securities under similar circumstances relating to compliance with applicable
state securities or "Blue Sky" laws and the fees and expenses of any special
experts retained by the Company in connection with the Registration Statements;
but excluding (x) underwriting discounts and commissions and (other than as
provided in clause (v) of this paragraph) fees and disbursements of
Underwriters, dealers and agents in connection with an Underwritten Offering of
Shares or Registered Securities, if any, and (y) transfer taxes, if any,
relating to the sale and disposition of Shares or Registered Securities.

     8.7. Short Sales.

          No Purchaser shall engage in any short-sales of the Company's Common
Stock prior to the effectiveness of the Registration Statement, except to the
extent that any such shortsale is fully covered by freely tradable shares of
Common Stock of the Company.

     8.8. Representations of the Company.

          The Company represents and warrants to, and agrees with, the Purchaser
that:

          (a) The Registration Statements and the Prospectuses contained
therein, when they become effective or are filed with the Commission, as the
case may be, and, in the case of an Underwritten Offering, at the time of the
closing under the underwriting agreement relating thereto, will conform in all
material respects to the requirements of the Securities Act and will not contain

                                      -46-
<PAGE>

an untrue statement of a material fact or omit to state a material fact required
to be stated therein or necessary to make the statements therein not misleading;
and at all times subsequent to the effective date of such Registration
Statements when a Prospectus would be required to be delivered under the
Securities Act, except for the periods provided under Section 8.3 hereof, such
Registration Statements and Prospectuses will conform in all material respects
to the requirements of the Securities Act and will not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein not misleading in
light of the circumstances then existing; provided, however, that this
representation and warranty shall not apply to any statements or omissions made
in reliance upon and in conformity with information furnished in writing to the
Company by the Purchaser or any Underwriter expressly for use therein.

          (b) Any documents incorporated by reference in the Prospectuses, when
they become or became effective or are or were filed with the Commission, as the
case may be, will conform or conformed in all material respects to the
requirements of the Securities Act or the Exchange Act, as applicable, and none
of such documents will contain or contained, as of their respective dates, an
untrue statement of a material fact or will omit or omitted to state a material
fact required to be stated therein or necessary to make the statements therein
not misleading at the time they become or became effective or are or were filed
with the Commission, as the case may be; provided, however, that this
representation and warranty shall not apply to any statements or omissions made
in reliance upon and conformity with information furnished in writing to the
Company by the Purchaser or any Underwriter expressly for use therein.

     8.9. Indemnification.

          (a) The Company will indemnify and hold harmless each holder of Shares
and Registered Securities and any underwriter (as defined in the Securities Act)
for such holder and each person, if any, who controls the holder or underwriter
within the meaning of the Securities Act against any losses, claims, damages or
liabilities, joint or several, and expenses (including reasonable attorneys'
fees and expenses and reasonable costs of investigation) to which the holder or
underwriter or such controlling person may be subject, under the Securities Act
or otherwise, insofar as any thereof arise out of or are based upon (x) any
untrue statement or alleged untrue statement of a material fact contained in a
Registration Statement, a Prospectus or any amendment or supplement thereto, or
(y) the omission or alleged omission to state in any item referred to in the
preceding clause a material fact required to be stated therein or necessary to
make the statements therein not misleading, except insofar as such losses,
claims, damages, liabilities or expenses arise out of or are based upon any
untrue statement or alleged untrue statement or omission or alleged omission
based upon information furnished to the Company in writing by such holder or by
any underwriter for such holder expressly for use therein (with respect to which
information such holder or underwriter shall so indemnify and hold harmless the
Company, any underwriter for the Company and each person,

                                      -47-
<PAGE>

if any, who controls the Company or such underwriter within the meaning of the
Securities Act). The foregoing is subject to the condition that, insofar as the
foregoing indemnities relate to any untrue statement, alleged untrue statement,
omission or alleged omission made in any prospectus which is eliminated or
remedied in any amendment, supplement or final prospectus, the above indemnity
obligations of the Company shall not inure to the benefit of any indemnified
person (or to the benefit of any person who controls such indemnified person
within the meaning of the Securities Act) if a copy of such amendment,
supplement or final prospectus was not sent or given by such indemnified person
at or prior to the time such action is required of such indemnified person by
the Securities Act and if delivery of such amendment, supplement or final
prospectus would have eliminated (or been a sufficient defense to) any liability
of such indemnified person with respect to such statement or omission.

          (b) The Purchaser will indemnify and hold harmless the Company, any
other Purchasers, any underwriter (as defined in the Securities Act) and each
person, if any, who controls the Company, such other Purchasers or any
underwriter within the meaning of the Securities Act, against any losses,
claims, damages or liabilities, joint and several, and expenses (including
reasonable attorneys' fees and expenses and reasonable costs of investigation)
to which the Company, such other Purchaser, underwriter or such controlling
person may be subject, under the Securities Act or otherwise, insofar as any
thereof arise out of or are based upon (x) any untrue statement or alleged
untrue statement of a material fact contained in a Registration Statement, a
Prospectus or any amendment or supplement thereto, (y) the omission or alleged
omission to state in any item referred to in the preceding clause a material
fact required to be stated therein or necessary to make the statements therein
not misleading or (z) any failure of the Purchaser to perform its obligations
hereunder or under law; provided, however, that the Purchaser will be liable
hereunder in any such case if and only to the extent that any such loss, claim,
damage, liability or expense arises out of or is based upon an untrue statement
or alleged untrue statement or omission or alleged omission made in reliance
upon and in strict conformity with information pertaining to the Purchaser, as
such, furnished in writing to the Company by the Purchaser stated to be
specifically for use in such Registration Statement and Prospectus; provided,
further, however, that the liability of the Purchaser hereunder shall be limited
to the proportion of any such loss, claim, damage, liability or expense which is
equal to the proportion that the public offering price of the Shares or
Registered Securities sold by the Purchaser under such Registration Statement
bears to the total public offering price of all securities sold thereunder, but
not in any event to exceed the proceeds received by the Purchaser from the sale
of the Shares or Registered Securities covered by such Registration Statement.
The foregoing is subject to the condition that, insofar as the foregoing
indemnities relate to any untrue statement, alleged untrue statement, omission
or alleged omission made in any prospectus which is eliminated or remedied in
any amendment, supplement or final prospectus, the above indemnity obligations
of the Purchaser shall not inure to the benefit of any indemnified person (or to
the benefit of any person who controls such indemnified person within the

                                      -48-
<PAGE>

meaning of the Securities Act) if a copy of such amendment, supplement or final
prospectus was not sent or given by such indemnified person at or prior to the
time such action is required of such indemnified person by the Securities Act
and if delivery of such amendment, supplement or final prospectus would have
eliminated (or been a sufficient defense to) any liability of such indemnified
person with respect to such statement or omission.

          (c) Promptly after receipt by an indemnified party under Section
8.9(a) or (b) hereof of notice of the commencement of any action, such
indemnified party shall, if a claim in respect thereof is to be made against an
indemnifying party under such subsection, notify the indemnifying party in
writing of the commencement thereof; but the failure to so notify an
indemnifying party shall not relieve the indemnifying party of its obligations
under this Section 8.9 unless such failure to notify materially prejudices the
indemnifying party's defense.  In case any such action shall be brought against
any indemnified party and it shall notify the indemnifying party of the
commencement thereof, the indemnifying party shall be entitled to participate
therein and, to the extent that it shall wish, jointly with any other
indemnifying party similarly notified, to assume the defense thereof, with
counsel reasonably satisfactory to such indemnified party, and, after notice
from the indemnifying party to such indemnified party of its election so to
assume the defense thereof, the indemnifying party shall not be liable to such
indemnified party under this subsection for any legal expenses of other counsel
or any other expenses, in each case subsequently incurred by such indemnified
party, in connection with the defense thereof other than reasonable costs of
investigation.  Notwithstanding the foregoing, the indemnifying party shall pay
as incurred the fees and expenses of separate counsel retained by the
indemnified party in the event (i) the indemnifying party and the indemnified
party shall have mutually agreed to the retention of such counsel or (ii) the
named parties to any such proceeding (including any impleaded parties) include
both the indemnifying party and the indemnified party and representation of both
parties by the same counsel would be inappropriate due to actual or potential
differing interests between them.  It is understood that the indemnifying party
shall not, in connection with any proceeding or related proceedings in the same
jurisdiction, be liable for the reasonable fees and expenses of more than one
separate firm for all such indemnified parties.  In addition, an indemnifying
party shall not be required to indemnify, reimburse, or otherwise make any
contribution to the amount paid or payable by the indemnified party for any
losses, claims, damages, expenses or liabilities incurred by the indemnified
party in settlement of any actions, proceedings or investigations otherwise
covered hereunder, unless such settlement has been previously approved by the
indemnifying party, which approval shall not be unreasonably withheld.

          (d) If the indemnification provided for in this Section 8.9 is
unavailable to or insufficient to hold harmless an indemnified party under
Section 8.9(a) or (b) hereof in respect of any losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) referred to therein,
then each indemnifying party shall contribute to the amount paid or payable by
such

                                      -49-
<PAGE>

indemnified party as a result of such losses, claims, damages or liabilities (or
actions or proceedings in respect thereof) in such proportion as is appropriate
to reflect not only (i) the relative benefits received by the Purchaser on the
one hand and the underwriter on the other from the offering of the Shares or the
Registered Securities but also (ii) the relative fault of the Company, the
Purchaser and the underwriter in connection with the statements or omissions
which resulted in such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof), as well as any other relevant equitable
considerations. The relative benefits received by the Purchaser on the one hand
and the underwriter on the other shall be deemed to be in the same proportion as
the total net proceeds from the offering (before deducting expenses) received by
the Purchaser bear to the total underwriting discounts and commissions received
by the underwriter, in each case as set forth in the table on the cover page of
the Prospectus. The relative fault shall be determined by reference to, among
other things, whether the untrue or alleged untrue statement of a material fact
or the omission or alleged omission to state a material fact related to
information supplied by the Company, the Purchaser or the underwriter and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission.

          (e) The Company and the Purchaser agree that it would not be just and
equitable if contributions pursuant to this Section 8.9 were determined by pro
rata allocation (even if several underwriters were treated as one entity for
such purpose) or by any other method of allocation which does not take account
of the equitable considerations referred to above in this Section 8.9.  The
amount paid or payable by an indemnified party as a result of the losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
referred to above in this Section 8.9 shall be deemed to include any legal or
other expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim. Notwithstanding the
provisions of this Section 8.9, no underwriter, if any, will be required to
contribute any amount in excess of the amount agreed to between the Company and
the underwriter at the time of such offering.  No person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation.  Any underwriters' obligations to contribute will
be several in proportion to their respective underwriting obligations and not
joint.

          (f) In any proceeding relating to a Registration Statement, a
Prospectus or any supplement or amendment thereto, each party against whom
contribution may be sought under this Section 8.9 hereby consents to the
jurisdiction of any court having jurisdiction over any other contributing party,
agrees that process issuing from such court may be served upon him or it by any
other contributing party and consents to the service of such process and agrees
that any other contributing party may join him or it as an additional defendant
in any such proceeding in which such other contributing party is a party.

                                      -50-
<PAGE>

     8.10.  Transferees.

          The right to sell Shares and Registered Securities pursuant to a
Registration Statement described herein will automatically be assigned to each
transferee of Shares or Registered Securities, other than any purchaser of
Shares or Registered Securities sold under a Registration Statement.  In the
event that it is necessary, in order to permit a Purchaser to sell Shares or
Registered Securities pursuant to a Registration Statement, to amend or
supplement the Registration Statement to name such transferee, such transferee
shall, upon written notice to the Company, be entitled to have the Company make
such amendment or supplement as soon as reasonably practicable.

SECTION 9.  CONDITIONS TO PURCHASER'S OBLIGATIONS

     The Purchaser's obligation to purchase Shares hereunder is subject to
satisfaction of the following conditions at the Closing (any of which may be
waived by the Purchaser)

     9.1. Series B Certificate of Designations.

          The Series B Certificate of Designations shall have been filed with
the Delaware Secretary of State in substantially the form attached hereto as
Exhibit A.

     9.2. Certificates for Shares.

          The Purchaser shall concurrently receive the certificates for Shares
contemplated by Section 2(b) hereof.

     9.3. Accuracy of Representations and Warranties.

          The representations and warranties of the Company in the Stock
Purchase Agreements or in any certificate or document delivered pursuant hereto
or thereto shall be correct and complete on and as of the Closing Date with the
same effect as though made on and as of the Closing Date (after giving effect to
transactions contemplated by this Agreement).

     9.4. Compliance with Agreements.

          The Company shall have performed and complied with all agreements,
covenants and conditions contained in the Stock Purchase Agreements and any
other document contemplated hereby or thereby which are required to be performed
or complied with by the Company on or before the Closing Date.

                                      -51-
<PAGE>

     9.5. Officers' Certificates.

          The Purchaser shall have received a certificate dated the Closing Date
and signed by the President and by the Secretary of the Company, to the effect
that the conditions of this Section 9 have been satisfied.

     9.6. Proceedings.

          All corporate and other proceedings in connection with the
transactions contemplated by the Stock Purchase Agreements, and all documents
incident thereto, shall be in form and substance satisfactory to the Purchaser
and its counsel, and the Purchaser shall have received all such originals or
certified or other copies of such documents as the Purchaser or its counsel may
reasonably request.

     9.7. Legality; Governmental and Other Authorization.

          The purchase of and payment for the Shares shall not be prohibited by
any law or governmental order, rule, ruling, regulation, release, interpretation
or opinion applicable to the Purchaser and shall not subject the Purchaser to
any penalty, tax, liability or other onerous condition.  Any necessary consents,
approvals, licenses, permits, orders and authorizations of, and any filings,
registrations or qualifications with, any governmental or administrative agency
or other person with respect to the transactions contemplated by the Stock
Purchase Agreements shall have been obtained or made and shall be in full force
and effect.  The Company shall have delivered to the Purchaser upon its
reasonable request factual certificates or other evidence, in form and substance
satisfactory to the Purchaser and its counsel, setting forth what is required to
enable the Purchaser to establish compliance with this condition.

     9.8. Time of Purchase.

          The Closing shall not be later than 5:00 P.M., New York City time, on
March 31, 1997.

     9.9. No Change in Law, etc.

          No legislation, order, rule, ruling or regulation shall have been
proposed, enacted or made by or on behalf of any governmental body, department
or agency, and no legislation shall have been introduced in either House of
Congress, and no investigation by any governmental authority shall have been
commenced or threatened, and no action, suit or proceeding shall have been
commenced before, and no decision shall have been rendered by, any court, other
governmental

                                      -52-
<PAGE>

body or arbitrator, which, in any such case, in the Purchaser's reasonable
judgment could adversely affect, restrain, prevent or change the transactions
contemplated by the Stock Purchase Agreements (including without limitation the
issuance of the Shares hereunder and thereunder and the issuance of the
Conversion Shares under the Series B Certificate of Designations) or materially
and adversely affect the assets, properties, liabilities, business, affairs,
results of operations, condition (financial or otherwise) or prospects of the
Company.

     9.10.  Opinions of Counsel.

            The Purchaser shall have received an opinion dated the Closing Date
and addressed to the Purchaser of Andrews & Kurth L.L.P., counsel for the
Company, which opinion shall be in form and substance reasonably satisfactory to
the Purchaser.

     9.11.  Other Documents and Opinions.

            The Purchaser shall have received such other documents and opinions,
in form and substance satisfactory to the Purchaser and its counsel, relating to
matters incident to the transactions contemplated hereby as the Purchaser may
reasonably request.

     9.12 Receipt of Consent and Exchange Agreements.

       The Company shall have received a sufficient number of Consent and
Exchange Agreements executed by the holders of Series A Preferred Stock in order
to have the necessary authorization for the parity treatment of the Series B
Preferred Stock and the modification to the registration rights as contemplated
therein.

SECTION 10.  CONDITIONS TO COMPANY'S OBLIGATIONS

     The Company's obligation to sell and issue the Shares at the Closing is, at
the option of the Company, subject to the fulfillment or waiver of the following
conditions:

     10.1.  Representations and Warranties Correct.

            The representations and warranties made by the Purchaser in Section
5 hereof shall be true and correct in all material respects when made, and shall
be true and correct in all material respects on the Closing Date with the same
force and effect as if they had been made on and as of said date.

     10.2.  Covenants.

                                      -53-
<PAGE>

          All covenants, agreements and conditions contained in this Agreement
to be performed by the Purchaser on or prior to the Closing Date shall have been
performed or complied with in all material respects.

     10.3.  Blue Sky.

            The Company shall have obtained all necessary blue sky law permits
and qualifications, or secured exemptions therefrom, required by any state for
the offer and sale of the Shares. No stop order or other order enjoining the
sale of the Shares shall have been issued and no proceedings for such purpose
shall be pending or, to the knowledge of the Company, threatened.

SECTION 11.  BROKERS

     Except for certain fees payable to the Agent (all of which fees will be
paid by the Company), the Company represents and warrants to the Purchaser that
there is no liability for (and the Company will pay and indemnify the Purchaser
against) any fees or expenses (or claims therefor) of any investment banker,
finder or broker retained by the Company or its Affiliates (or that claims it
was retained by the Company or its Affiliates) in connection with any Stock
Purchase Agreement or any of the transactions contemplated hereby or thereby.
The Company will indemnify the Purchaser against all such fees or expenses
payable to the enumerated persons in the preceding sentence and against any
other such fees, expenses or claims of any person, unless such person was
engaged by the Purchaser in connection with this Agreement or any of the
transactions contemplated hereby.

SECTION 12.  BREACH OF REPRESENTATIONS, WARRANTIES AND COVENANTS

          (a) The representations and warranties (as of the date hereof and as
of the Closing Date), covenants and agreements of the Company and the Purchaser
contained in this Agreement or in any document or certificate delivered pursuant
hereto or in connection herewith shall survive, and shall continue in effect
following, the execution and delivery of the Stock Purchase Agreements, the
closings hereunder and thereunder, any investigation at any time made by the
Purchaser or on its behalf or by any other Person, the issuance, sale and
delivery of the Shares, any disposition thereof and any payment, conversion or
cancellation of the Shares provided, that Section 7 (other than Sections 7.1,
7.2, 7.4, 7.5, 7.7, 7.8, 7.9, 7.12, 7.13, 7.16, 7.17, 7.18, 7.20 and 7.21) shall
terminate when no Shares are outstanding.  All statements contained in any
certificate delivered to the Purchaser by or on behalf of the Company pursuant
hereto shall constitute representations and warranties by the Company hereunder.

          (b) The Company agrees to indemnify and hold the Purchaser harmless
from and against and will pay to the Purchaser the full amount of any loss,
damage, liability or expense

                                      -54-
<PAGE>

(including amounts paid in settlement and attorneys' fees and expenses) to the
Purchaser resulting either directly or indirectly from any breach of the
representations, warranties, covenants or agreements of the Company contained in
any Stock Purchase Agreement, or in any certificate delivered to the Purchaser
pursuant hereto or in connection herewith.

SECTION 13.  SPECIFIC PERFORMANCE

     The parties agree that irreparable damage will result in the event that
this Agreement is not specifically enforced, and the parties agree that any
damages available at law for a breach of this Agreement would not be an adequate
remedy.  Therefore, the provisions hereof and the obligations of the parties
hereunder shall be enforceable in a court of equity, or other tribunal with
jurisdiction, by a decree of specific performance, and appropriate injunctive
relief may be applied for and granted in connection therewith.  Such remedies
and all other remedies provided for in this Agreement shall, however, be
cumulative and not exclusive and shall be in addition to any other remedies
which a party may have under this Agreement or otherwise.

SECTION 14.  EXPENSES

          (a) Whether or not the transactions herein contemplated are
consummated, the Company will pay (i) the costs and expenses of the preparation
and production of the Stock Purchase Agreements and the Series B Certificate of
Designations and the issuance of the Shares and the Conversion Shares and the
furnishing of all opinions by counsel for the Company, (ii) the fees and
expenses of Piper & Marbury L.L.P. in connection with the Stock Purchase
Agreements and the Series B Certificate of Designations and the transactions
contemplated hereby and thereby (whether or not a closing occurs hereunder and
if a closing occurs the Company will make such payment on the Closing Date),
(iii) the reasonable fees and expenses of counsel to the Eligible Holders in
connection with any amendments to or modifications or waivers of any provisions
of the Stock Purchase Agreements or the Series B Certificate of Designations or
in connection with any other agreements between the Purchasers and the Company
after the date hereof, any of which are requested by the Company, (iv) the fees
and expenses of any investment banker, broker or finder retained by the Company
or its Affiliates (or that claims it was retained by the Company or its
Affiliates) and involved with the Stock Purchase Agreements or the Series B
Certificate of Designations or any of the transactions contemplated hereby or
thereby, and (v) the fees and expenses (including reasonable attorneys' fees and
expenses) of any holder of Shares or Conversion Shares in enforcing its rights
against the Company if the Company materially defaults in its obligations
hereunder or under the Series B Certificate of Designations.  The obligations of
the Company under this Section 14 shall survive the Closing hereunder and any
termination of the Stock Purchase Agreements.

                                      -55-
<PAGE>

          (b) In addition to all other sums due hereunder or provided for in
this Agreement, the Company shall pay to the Purchaser or its agents,
respectively, an amount sufficient to indemnify such persons (net of any taxes
on any indemnity payments) against all reasonable costs and expenses (including
reasonable attorneys' fees and expenses and reasonable costs of investigation)
and damages and liabilities incurred by the Purchaser or its agents pursuant to
any investigation or proceeding against any or all of the Company, the
Purchasers, or their agents, arising out of or in connection with the Stock
Purchase Agreements, the Shares or the Conversion Shares (or any transaction
contemplated hereby or thereby or any other document or instrument executed
herewith or therewith or pursuant hereto or thereto), whether or not the
transactions contemplated by this Agreement are consummated, which investigation
or proceeding requires the participation of the Purchaser or its agents or is
commenced or filed against the Purchaser or its agents because of the Stock
Purchase Agreements, the Shares or the Conversion Shares or any of the
transactions contemplated hereby or thereby (or any other document or instrument
executed herewith or therewith or pursuant hereto or thereto), other than any
investigation or proceeding in which it is finally determined that there was
gross negligence or willful misconduct on the part of the Purchaser or its
agents which was not taken by them in reliance upon any of the Company's
representations, warranties, covenants or agreements in the Stock Purchase
Agreements or in any other documents or instruments contemplated hereby or
thereby or executed herewith or therewith or pursuant hereto or thereto, except
to the extent that any costs, expenses, damages or liabilities incurred by the
Purchaser is the direct result of its breach of any of its representations,
warranties, covenants or agreements in this Stock Purchase Agreement or in any
other documents or instruments contemplated hereby or thereby or executed in
connection herewith or therewith or pursuant hereto or thereto.  The Company
shall assume the defense, and shall have its counsel represent the Purchaser and
such agents, in connection with investigating, defending or preparing to defend
any such action, suit, claim or proceeding (including any inquiry or
investigation); provided, however, that the Purchaser, or any such agent, shall
have the right (without releasing the Company from any of its obligations
hereunder) to employ its own counsel and either to direct its own defense or to
participate in the Company's defense, but the fees and expenses of such counsel
shall be at the expense of such person unless (i) the employment of such counsel
shall have been authorized in writing by the Company in connection with such
defense or (ii) the Company shall not have provided its counsel to take charge
of such defense or (iii) the Purchaser, or such agent of the Purchaser, shall
have reasonably concluded that there may be defenses available to it or them
which are different from or additional to those available to the Company, then
in any of such events referred to in clauses (i), (ii) or (iii) such reasonable
counsel fees and expenses (but only for one counsel for the Purchasers and their
agents) shall be borne by the Company.  Any settlement of any such action, suit,
claim or proceeding shall require the consent of both the Company and such
indemnified person (neither of which shall unreasonably withhold its consent).

                                      -56-
<PAGE>

          (c) The Company agrees to pay, or to cause to be paid, all
documentary, stamp and other similar taxes levied under the laws of the United
States of America or any state or local taxing authority thereof or therein in
connection with the issuance and sale of the Shares and the execution and
delivery of the Stock Purchase Agreements and any other documents or instruments
contemplated hereby or thereby and any modification of the Series B Certificate
of Designations or the Stock Purchase Agreements or any such other documents or
instruments and will hold the Purchaser harmless without limitation as to time
against any and all liabilities with respect to all such taxes.

          (d) The obligations of the Company under this Section 14 shall survive
the Closing hereunder and any termination of the Stock Purchase Agreements.

SECTION 15.  HOME OFFICE PAYMENTS

     As long as the Purchaser or any institutional holder which is a direct or
indirect transferee (as a result of one or more transfers) from the Purchaser
shall be the holder of record of any Shares, the Company will make all
dividends, redemption payments, repurchase payments, liquidation payments and
other distributions by wire transfer to the Purchaser's or such other holder's
(or its nominee's) account at any bank or trust company in the United States of
America, notwithstanding any contrary provision herein or in the Company's
certificate of incorporation with respect to the place of payment.  The
Purchaser has provided an address on Schedule I hereto for payments by wire
transfer, and such address may be changed for the Purchaser or any subsequent
holder by notice to the Company.  All such payments shall be made in U.S.
dollars and in federal or other immediately available funds.

SECTION 16.  AMENDMENTS AND WAIVERS

          (a) The terms and provisions of this Agreement may be amended, waived,
modified or terminated only with the written consent of the Majority
Shareholders; provided, however, that no such amendment, waiver, modification or
termination shall (i) change the provisions of Section 8 hereof in any material
respect, without the consent of the holders of all Shares or Conversion Shares
affected thereby or (ii) change the definition of Majority Shareholders or this
Section 16(a) without the written consent of the holders of all the Shares and
Conversion Shares then outstanding; and provided further that no such amendment,
waiver, modification or termination shall be effective with respect to a term or
provision of this Agreement unless it is also effective with respect to the
corresponding term or provision, if any, of each other Stock Purchase Agreement
and each Stock Exchange Agreement.  The Purchaser acknowledges that by operation
hereof, the Majority Shareholders (which may not include the Purchaser) will
have the right and power to diminish or eliminate certain rights of the
Purchaser under this Agreement.

                                      -57-
<PAGE>

          (b) The Company agrees that all holders of Shares and Conversion
Shares shall be notified by the Company in advance of any proposed amendment,
waiver, modification or termination, but failure to give such notice shall not
in any way affect the validity of any such amendment, waiver, modification or
termination.  In addition, promptly after obtaining the written consent of the
holders as herein provided, the Company shall transmit a copy of any amendment,
waiver, modification or termination which has been adopted to all holders of
Shares and Conversion Shares then outstanding, but failure to transmit copies
shall not in any way affect the validity of any such amendment, waiver,
modification or termination.

SECTION 17.  EXCHANGE OF SHARES; CANCELLATION OF SURRENDERED   SHARES;
             REPLACEMENT

          (a) Subject to Section 6 hereof, at any time at the request of any
holder of Shares to the Company at its address provided under Section 18 hereof,
the Company at its expense (except for any transfer tax arising out of the
exchange) will issue and deliver to or upon the order of the holder in exchange
therefor a new certificate or certificates therefor in such amount or amounts as
such holder may request in the aggregate representing the number of Shares
represented by such surrendered certificates, and registered in the name of such
holder or otherwise as such holder may direct.

          (b) Any Share certificate which is converted into Conversion Shares in
whole or in part shall be canceled by the Company, and no new Share certificates
shall be issued in lieu of any Shares which have been converted into Conversion
Shares.  The Company shall issue a new certificate with respect to any Shares
which were not converted into Conversion Shares and were represented by a
certificate which was converted in part.

          (c) Upon receipt of evidence satisfactory to the Company of the loss,
theft, destruction or mutilation of any Share certificate and, in the case of
any such loss, theft or destruction, upon delivery of an indemnity agreement
reasonably satisfactory to the Company (unsecured in the case of an
institutional holder), or in the case of any such mutilation, upon surrender of
such Share certificate (which surrendered Share certificate shall be canceled by
the Company), the Company will issue a new Share certificate, of like tenor in
lieu of such lost, stolen, destroyed or mutilated Share certificate as if the
lost, stolen, destroyed or mutilated Share certificate were then surrendered for
exchange.

SECTION 18.  NOTICES

                                      -58-
<PAGE>

     All notices, requests, demands, consents and other communications hereunder
shall be in writing and shall be delivered by hand or shall be sent by telex or
telecopy (confirmed by registered, certified or overnight mail or courier,
postage and delivery charges prepaid), if to the Company at the address
indicated below, or if to the Purchaser at the address indicated on Schedule I
hereto, or at such other address as a party may from time to time designate as
its address in writing to the other party to this Agreement.  Whenever any
notice is required to be given hereunder, such notice shall be deemed given and
such requirement satisfied only when such notice is delivered or, if sent by
telex or telecopier, when received.

          (a)  If to the Company:

               Energy BioSystems Corporation
               4200 Research Forest Drive
               The Woodlands, Texas 77381
               Attn:  Vice President of Finance

               With a copy to:
               Andrews & Kurth L.L.P.
               4200 Texas Commerce Tower
               Houston, Texas 77002
               Attn:  William N. Finnegan, IV

          (b) If to the Purchaser, at the address
               of the Purchaser set forth on Schedule I.

SECTION 19.  MISCELLANEOUS

          (a) The Stock Purchase Agreements (including all schedules and
exhibits thereto) and, upon the closing hereunder, the Series B Certificate of
Designations, together with any further agreements entered into by the Purchaser
and the Company at the closing hereunder, contain the entire agreement between
the Purchaser and the Company, and supersede any prior oral or written
agreements, commitments, terms or understandings regarding the subject matter
hereof.

          (b) Any provision of this Agreement which is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.  To the extent permitted by applicable law, the parties
hereby waive any provision of law which may render any provision hereof
prohibited or unenforceable in any respect.

                                      -59-
<PAGE>

          (c) If the Company fails to pay any amount required to be paid to a
holder of Shares or Conversion Shares or to a party under this Agreement (not
including dividends not declared by the Board of Directors), within thirty (30)
days after notice from such holder or such party demanding such payment
(together with reasonably detailed supporting information), then the Company
agrees to pay such holder or such party interest on any such overdue amount at a
rate of 10% per annum from the date of such notice from such holder or such
party until such overdue amount is paid in full.

          (d) Unless otherwise expressly provided herein, any provision of this
Agreement relating to the consent, determination, decision or waiver of a holder
or holders of Shares or Conversion Shares means such holder's consent,
determination, decision or waiver in such holder's sole discretion.

          (e) This Agreement shall be binding upon and inure to the benefit of
the parties hereto and their respective successors and assigns, whether so
expressed or not; provided, that the Company may not assign any of its rights,
duties or obligations under this Agreement, except in connection with a
transaction permitted by Section 7.11 or with the Purchaser's written consent.

          (f) In addition to any assignment by operation of law, the Purchaser
may assign, in whole or in part, any or all of its rights (and/or obligations)
under this Agreement to any permitted transferee of any or all of its Shares or
Conversion Shares, except as provided in Section 8.10, and (unless such
assignment expressly provides otherwise) any such assignment shall not diminish
the rights the Purchaser would otherwise have under this Agreement or with
respect to any remaining Shares or Conversion Shares held by the Purchaser.

          (g) No course of dealing and no delay on the part of any party hereto
in exercising any right, power, or remedy conferred by this Agreement shall
operate as a waiver thereof or otherwise prejudice such party's rights, powers
and remedies.  No single or partial exercise of any rights, powers or remedies
conferred by this Agreement shall preclude any other or further exercise thereof
or the exercise of any other right, power or remedy.

          (h) The headings and captions in this Agreement are for convenience of
reference only and shall not define, limit or otherwise affect any of the terms
or provisions hereof.

          (i) This Agreement shall be governed by, and construed in accordance
with, the laws of the State of Delaware (other than any conflict of laws rule
which might result in the application of the laws of any other jurisdiction).

                                      -60-
<PAGE>

          (j) This Agreement may be executed by the parties hereto in separate
counterparts, each of which when so executed and delivered shall be an original,
but all such counterparts shall together constitute one and the same instrument,
and all signatures need not appear on any one counterpart.

          (k) WAIVER OF JURY TRIAL.  THE COMPANY AND THE PURCHASER HEREBY WAIVE
THEIR RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED
UPON OR ARISING OUT OF THIS AGREEMENT, THE SERIES B CERTIFICATE OF DESIGNATIONS,
THE SHARES OR THE CONVERSION SHARES, OR ANY DEALINGS BETWEEN THEM RELATING TO
THE SUBJECT MATTER OF THIS TRANSACTION.  THE SCOPE OF THIS WAIVER IS INTENDED TO
BE ALL-ENCOMPASSING OF ANY AND ALL DISPUTES THAT MAY BE FILED IN ANY COURT AND
THAT RELATE TO THE SUBJECT MATTER OF THIS TRANSACTION, INCLUDING WITHOUT
LIMITATION, CONTRACT CLAIMS, TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER
COMMON LAW AND STATUTORY CLAIMS. THE COMPANY AND THE PURCHASER FURTHER WARRANT
AND REPRESENT THAT EACH HAS REVIEWED THIS WAIVER WITH ITS LEGAL COUNSEL, AND
THAT EACH KNOWINGLY AND VOLUNTARILY WAIVES ITS JURY TRIAL RIGHTS FOLLOWING
CONSULTATION WITH LEGAL COUNSEL.  THIS WAIVER IS IRREVOCABLE, MEANING THAT IT
MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING, AND THIS WAIVER SHALL APPLY TO
ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO (OR
ASSIGNMENTS OF) THIS AGREEMENT, THE CERTIFICATE OF DESIGNATIONS, THE SHARES OR
THE CONVERSION SHARES.  IN THE EVENT OF LITIGATION, THIS AGREEMENT MAY BE FILED
AS A WRITTEN CONSENT TO A TRIAL (WITHOUT A JURY) BY THE COURT.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as of the date first above written.

                                   ENERGY BIOSYSTEMS CORPORATION


                                   By    /s/ John H. Webb
                                         ----------------
                                   Name:  John H. Webb
                                   Title: President


          Accepted and Agreed to as of
          the date first above written by


                                      -61-
<PAGE>

         the undersigned Purchaser:
          (See Omnibus Signature Page)



          By  ____________________________
               Name:
               Title:

                                      -62-
<PAGE>

                                                              SCHEDULE I
                                                              TO THE STOCK
                                                              PURCHASE AGREEMENT

                                                    Purchase
       Name of Purchaser           Number of Shares          Price
       -----------------           ----------------          -----



       (a)  address for communications:




            Attn:

       (b)                                                         address for
                                                                   payments by
                                                                   wire
                                                                   transfer:


            Attn:

            (providing sufficient
            information with such
            wire transfer to identify
            the source and application
            of such funds)

                                      -63-
<PAGE>

                                SCHEDULE II TO
                                   THE STOCK
                              PURCHASE AGREEMENT

                        Summary of Registration Rights


1. Piggyback registration rights granted by the Company pursuant to that certain
First Amendment to License and Technology Assistance Agreement, dated June 25,
1992, between the Company and Institute of Gas Technology.

2. Demand and piggyback registration rights granted by the Company pursuant to
that certain Registration Agreement, dated January 30, 1992, by and among the
Company, The Travelers Indemnity Company, The Travelers Indemnity Company of
Rhode Island, The Phoenix Insurance Company and Gryphon Ventures II, Limited
Partnership.

3. Demand and piggyback registration rights granted by the Company pursuant to
that certain Registration Agreement, dated April 29, 1991, by and between the
Company and Gryphon Ventures II, Limited Partnership.

4. Registration rights granted by the Company to the holders of the Series A
Preferred Stock pursuant to those certain Stock Purchase Agreements dated
October 27, 1994.

5. Registration rights granted by the Company to the parties exchanging shares
of Series A Preferred Stock for shares of Series B Preferred Stock pursuant to
those certain Stock Exchange Agreements dated February 21, 1997.


                                 Indebtedness
                                 ------------

                                     NONE.

                                      -64-