Document:

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                                                                EXHIBIT 10.22

                               SECOND AMENDMENT

The License Agreement ("Agreement") between Mycogen Corporation ("MYCOGEN") and
Diversa Corporation ("DIVERSA"), dated December 19, 1997, was amended on March
6, 1998 ("March 6/th/ Amendment").  In order to avoid possible misunderstandings
as to the rights and obligations arising under the Agreement, as amended, the
following understandings are hereby confirmed:

1.   MYCOGEN Technology is defined in Section 1.6 of the Agreement.  MYCOGEN
     Technology includes information, techniques, data, materials and chemicals
     relating to MYCOGEN's proprietary [*****] gene expression system.  In
     particular, MYCOGEN Technology includes, but is not limited to, the host
     strains and expression plasmids of [*****] which were provided to DIVERSA
     by MYCOGEN, and all information pertaining to the use of such strains,
     including methods and materials used to cultivate these strains and recover
     Products, which were provided to DIVERSA by MYCOGEN.

2.   Pursuant to Section 11.2 of the March 6/th/ Amendment, DIVERSA agreed that
     it shall not make any improvements, adaptations, modifications to, or
     reverse engineer any part of the MYCOGEN Technology. Consistent with the
     March 6th Amendment, DIVERSA will not improve, adapt, modify or reverse
     engineer the host strains, expression plasmids, or cultivation and recovery
     methods of [*****] provided to DIVERSA by MYCOGEN, with the exception of
     any modifications to methods of cultivation of the [*****] host strains or
     recovery and expression of the proteins that are required to be made by
     DIVERSA in order to allow DIVERSA to economically commercialize Products.
     In particular, prohibited improvements, adaptations or modifications of
     MYCOGEN Technology include, but are not limited to, [*****] of the [*****]
     host strains provided to DIVERSA by MYCOGEN and [*****] to improve or
     modify the [*****] host strains that are part of the MYCOGEN Technology.

3.   Appendix A to this Second Amendment further exemplifies: (i) Know-How owned
     or Controlled by MYCOGEN, which is included in the definition of MYCOGEN
     Technology in the Agreement, and (ii) improvements to MYCOGEN Technology as
     described in the March 6/th/ Amendment.

4.   Any improvements, adaptations or modifications of MYCOGEN Technology made
     by DIVERSA to allow DIVERSA to express, recover and commercialize Products
     in the System become the sole property of MYCOGEN pursuant to Section 11.2
     of the March 6/th/ Amendment. DIVERSA shall promptly disclose to MYCOGEN
     any such improvements, adaptations or modifications of MYCOGEN Technology
     made by DIVERSA including any improvement, adaptation or modification of
     the [*****] host strains and expression plasmids transferred to DIVERSA by
     MYCOGEN and methods used to cultivate the organisms and recover Products or
     other enzymes. MYCOGEN shall have the right to use such improvements,
     adaptations and modifications for the production of enzymes, including the
     production of enzymes for third parties.

5.   The license granted to DIVERSA under the MYCOGEN Technology, pursuant to
     Section 2.1 of the Agreement, is to use the System to produce, make, have
     made, use, offer for sale, sell and import Product(s) and other enzymes.
     The System is defined in Section 1.8 of the Agreement to mean MYCOGEN's
     proprietary [*****] gene expression system, including the host strain,
     expression plasmids, and proprietary cultivation and recovery methods
     transferred to DIVERSA by MYCOGEN under the terms of the license. The
     license granted to DIVERSA by MYCOGEN under the Agreement, as amended on
     March 6, 1998, is limited to use of the System as defined in the Agreement.
     No rights are granted to use any improvements, adaptations or modifications
     of MYCOGEN's proprietary [*****] host strains and expression plasmids,
     except as provided in Paragraphs 2 and 4 of this Second Amendment. It is
     understood that the Agreement as amended does not prevent DIVERSA from
     using information that is both subject to the exceptions in Section 5.2(a)
     to (d) of the Agreement and not covered by patents owned or controlled by
     MYCOGEN or its Affiliates to independently develop gene expression systems
     without the aid, application or use of Confidential Information received
     from MYCOGEN.

6.   Nothing in the Agreement or the March 6/th/ Amendment shall be construed to
     grant to DIVERSA any rights in MYCOGEN's Know-how developed after December
     19, 1997, except with respect to improvements, adaptations or modifications
     that are derived by MYCOGEN from DIVERSA Know-How, as provided in Section
     11.1 of the March 6/th/ Amendment,

                                       1.      *Confidential Treatment Requested
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     where this DIVERSA Know-how is Confidential Information of DIVERSA received
     by MYCOGEN and this Confidential Information is not subject to any
     exception in Section 5.2 of the Agreement.

7. This Second Amendment is a confirmation and clarification of obligations
     existing under the Agreement and March 6/th/ Amendment and as such shall be
     deemed effective as of March 6, 1998. The definitions of terms defined in
     the Agreement and March 6/th/ Amendment are incorporated herein to the
     extent such terms have not been expressly explained or clarified by this
     Second Amendment.

                            ACCEPTED AND AGREED TO:

MYCOGEN CORPORATION                        DIVERSA CORPORATION

/s/ Ronald L. Meeusen                      /s/ Jay M. Short
-----------------------------              -------------------------------
Name:                                      Name:  JAY M. SHORT
Title: V.P. R&D                            Title: CEO
Date:  7-30-99                             Date:  7-20-99

                                      2.       *Confidential Treatment Requested
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                                  APPENDIX A

            Exemplification of MYCOGEN Technology and Improvements

"MYCOGEN Technology", as defined in the License Agreement of December 19, 1997
between MYCOGEN and DIVERSA ("Agreement"), includes, but is not limited to, the
following Know-How owned or Controlled by MYCOGEN on the Effective Date of the
License Agreement that in each case was transferred to DIVERSA by MYCOGEN under
the terms of the Agreement:

A. [*****]

B. [*****]

C. [*****]

     1.  [*****]

     2.  [*****]

     3.  [*****]

     4.  [*****]

     5.  [*****]

     6.  [*****]

     7.  [*****]

     8.  [*****]

                                      1.  *Confidential Treatment Requested
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     9.  [*****]

     10. [*****]

     11. [*****]

     12. [*****]

     13. [*****]

     14. [*****]

     15. [*****]

     16. [*****]

     17. [*****]

D.  All documentation for regulatory submissions relating to products produced
in [*****], including TSCA premanufacture notices and toxicology data

E.  Confidential Information related to business information of MYCOGEN and its
affiliates pertaining to plans for development and commercialization of [*****]
gene expression system

                                      2.  *Confidential Treatment Requested
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IMPROVEMENTS TO MYCOGEN TECHNOLOGY

Improvements, adaptations and modifications of the MYCOGEN Technology, which are
described as "Improvements" in the March 6, 1998 Amendment of the Agreement
include, but are not limited to, changes in the Know-How provided by MYCOGEN
related to [*****] host strains, plasmids, vectors, raw material
specifications, or recipe variables to produce make or have made Products or
other enzymes. Products and Know-How are defined in the Agreement.
<PAGE>

                      IMPROVEMENTS TO MYCOGEN TECHNOLOGY

                                                                    CONFIDENTIAL

                                   AMENDMENT

March 6, 1998

Effective immediately, the License Agreement between Diversa Corporation
(hereinafter "DIVERSA"), and Mycogen Corporation (hereinafter, "MYCOGEN"),
effective December, 1997, is hereby amended as follows:

1.  Article 1 - Definitions shall be amended to include the following
definitions:

1.10      "DIVERSA Inventions" means all inventions, discoveries, modifications,
improvements, technical information and know-how, whether patentable or not made
by DIVERSA's employees or agents alone or in conjunction with employees or
agents of third parties.

1.11      "MYCOGEN Inventions" means all inventions, discoveries, modifications,
improvements, technical information and know-how, whether patentable or not,
made by MYCOGEN's employees or agents alone or in conjunction with employees or
agents of third parties.

1.12      "Joint Inventions" means all inventions, discoveries, modifications,
improvements, technical information and know-how, whether patentable or not,
made jointly by DIVERSA's and MYCOGEN's employees or agents.

2.  Article 11 - Intellectual Property Ownership shall be added to the Agreement
and shall read as follows:

11.1      Improvements to DIVERSA Know-How. MYCOGEN agrees that it shall not
make any improvements, adaptations or modifications (collectively
"Improvements") to, or reverse engineer any part of DIVERSA Know-How,
Notwithstanding the foregoing, any Improvements to DIVERSA Know-How made by
MYCOGEN shall become the sole property of DIVERSA.

11.2      Improvements to MYCOGEN Technology. DIVERSA agrees that it shall not
make any Improvements to, or reverse engineer any part of, the MYCOGEN
Technology. Notwithstanding the foregoing, any Improvements to the MYCOGEN
Technology made by DIVERSA shall become the sole property of MYCOGEN. All such
Improvements will be incorporated into the license granted to DIVERSA pursuant
to this Agreement.

11.3      Except as set forth in Sections 11.1 and 11.2, DIVERSA shall have
exclusive ownership and title to DIVERSA's Inventions, and MYCOGEN shall have
exclusive ownership and title to MYCOGEN's Inventions.

11.4      Except as set forth in Sections 11.1 and 11.2, DIVERSA and MYCOGEN
shall have joint ownership and title to Joint Inventions. Further, in the event
of any such Joint Invention, the parties shall grant to each other a
nonexclusive, irrevocable, royalty free license, without the right to grant
sublicenses, to make, use, import, sell, offer to sell, have made and have used
any such Invention resulting from work under this Agreement.

11.5      DIVERSA shall have the right to prepare, file, prosecute and maintain
patent applications and patents, continuations, continuations-in-part,
divisionals, reissues, additions, renewals, or extensions thereof covering
DIVERSA's Inventions, in countries and regions of its choice throughout the
world, for which DIVERSA shall bear all costs.

11.6      MYCOGEN shall have the right to prepare, file, prosecute and maintain
patent applications and patents, continuations, continuations-in-part,
divisionals, reissues, additions, renewals, or extensions thereof covering
MYCOGEN's Inventions, in countries and regions of its choice throughout the
world, for which MYCOGEN shall bear all costs.

                                      1.  *Confidential Treatment Requested
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11.7      DIVERSA shall have the right to prepare, file, prosecute and maintain
patent applications and patents, continuations, continuations-in-part,
divisionals, reissues, additions, renewals, or extensions thereof covering Joint
Inventions, in countries and regions of choice throughout the world, for which
DIVERSA and MYCOGEN shall share all costs equally with the following exceptions:

          (a) In the event MYCOGEN elects not to protect nor share in the
aforementioned costs to protect any Joint Invention, and DIVERSA desires to
file, prosecute or maintain a patent application or patent in that country.
DIVERSA may do so in the name of both DIVERSA and MYCOGEN subject to MYCOGEN's
consent which consent shall not be unreasonably withheld. Upon this election,
MYCOGEN agrees to promptly appoint DIVERSA as its attorney-in-fact for the
limited purpose of executing all documents and performing any other act
necessary to file, prosecute or maintain a patent application or patent in any
country of choice.

          (b) In the event DIVERSA elects not to protect nor share in the
aforementioned costs to protect any Joint Invention and MYCOGEN desires to file,
prosecute or maintain a patent application or patent in that country, MYCOGEN
may do so in the name of both MYCOGEN and DIVERSA, subject to DIVERSA's consent
which consent shall not be reasonably withheld. Upon this election, DIVERSA
agrees to promptly appoint MYCOGEN as its attorney-in-fact for the limited
purpose of executing all documents and performing any other act necessary to
file, prosecute, or maintain a patent application or patent in any country of
choice.

DIVERSA shall invoice MYCOGEN for MYCOGEN's share of such expenses, which
invoice shall be paid by MYCOGEN within thirty (30) days.

11.8      Each party shall provide reasonable assistance to the other party to
facilitate filing and prosecution of all patent applications and maintaining and
extending patents covering inventions and discoveries subject to this section
and shall execute all documents deemed necessary or desirable therefor.

All of the other terms and conditions of the Agreement shall remain in full
force and effect.

                                                                    CONFIDENTIAL

IN WITNESS WHEREOF, the parties have caused this instrument to be executed by
their duly authorized officers as of the day and year set forth below.

ACCEPTED AND AGREED TO:

Mycogen Corporation

/s/ Andrew L. Barnes
-------------------------------

Print Name: Andrew L. Barnes
           --------------------

Print Title: Exec. VP
            -------------------

Date:    3/10/98
     --------------------------

Diversa Corporation

 /s/ Patrick Simms
-------------------------------
Patrick Simms
Vice President

Date:    3/6/98
     --------------------------

                                      2.  *Confidential Treatment Requested
<PAGE>

                               License Agreement

     This License Agreement (the "Agreement"), dated as of December, 1997 (the
"Effective Date"), is made by and between Mycogen Corporation, a California
corporation 92121 ("MYCOGEN"), and Diversa Corporation, a Delaware corporation
having its principal offices at 10665 Sorrento Valley Road, San Diego,
California 92121 ("Diversa").

                                   Recitals

     Whereas, MYCOGEN possesses a proprietary gene expression System (as defined
below) and other proprietary rights, know-how and experience relating to gene
expression;

     Whereas, DIVERSA desires to obtain immediate access and a worldwide,
exclusive license to utilize such gene expression System to produce Product(s);
(as defined below) ;

     Whereas, MYCOGEN desires to  grant DIVERSA immediate access and a
worldwide, exclusive license to utilize such gene expression System to produce
Product(s);

     Now, Therefore, in consideration of the mutual covenants and promises set
forth in the Agreement, the parties agree as follows:

                            Article 1 - Definitions

1.1  "Affiliate" means an individual, trust, business trust, joint venture,
partnership, corporation, association or any other entity which owns, is owned
by or is under common ownership with a party. For the purposes of this
definition, the term "owns" (including, with correlative meanings, the terms
"owned by" and under common ownership with") as used with respect to any party,
shall mean the possession (directly or indirectly) of more than 50% of the
outstanding voting securities of a corporation or comparable equity interest in
any other type of entity.

1.2  "Confidential Information" means all information and materials received by
either party from the other party pursuant to this Agreement and all information
and materials developed in the course of the Research Activities, including,
without limitation, Know-How of each party. Confidential Information disclosed
in tangible form shall be marked " Confidential," "Proprietary" or in some other
manner to indicate its confidential nature. If disclosed orally, Confidential
Information shall be designated as confidential at the time of disclosure and
reduced to a written summary by the disclosing party and shall be marked in a
manner to indicated its confidential nature and delivered to the receiving party
within 45 days after disclosure.

1.3  "Control" means the ability to grant a license or sublicense as provided
for herein without violating the terms of any agreement with or other
arrangement with any Third Party.

1.4  "Gross Revenues" means the gross amount received by DIVERSA as a direct
result of sale of Product(s) and other enzymes by DIVERSA, its Affiliates or
their distributors, less allowances on returned or rejected goods, prepaid
freight, sales or other taxes (other than taxes based on net income) refunds
transportation charges (if separately stated or invoiced), rebates, cash, trade
and quantity discounts actually paid. Transfer of a Product to an Affiliate for
sale by the Affiliate shall not be considered a sale. In the case of such a
transfer to an Affiliate, the Gross Revenues shall be based on the gross amount
invoiced for the Product(s) by the Affiliate as invoiced to its customer. Sale
of a Product to an Affiliate by Diversa shall be considered a sale and shall be
included in Gross Revenues. In the event a Product is sold as a Combination
Product, Gross Revenues, for purposes of determining royalty payments on the
Combination Product shall be calculated as provided in this paragraph. The term
"Combination Product", shall mean a product consisting of a Product and at least
one other Biologically Active Component. The term "Biologically Active Component
shall mean a biologically active component of a Combination Product that is
itself essential to the function of the Combination Product. For purposes of
this Agreement, a Product is not a Combination Product if it consists solely of
one or more Product(s) and one or more other components that are not
Biologically Active Components (Gross Revenues in a Combination Product shall be
calculated by multiplying Gross Revenues of the Combination Product by the
fraction A/(A+B) where A is the value of the Product(s) without the other
biologically Active Components, and B is the value of the other biologically
Active Components without the Product(s).

                  1.      * Confidential Treatment Requested

<PAGE>

1.5  "Know-How" means information, techniques, data, materials and chemicals
(whether or not patentable), including, without limitation, inventions,
techniques, practices, methods, knowledge, know-how, skill, experience, test
data, analytical and quality control data, patent and legal data or
descriptions, sales and manufacturing data.

1.6  "MYCOGEN Technology" means the Know-How owned or Controlled by MYCOGEN
necessary or appropriate to develop, manufacture and commercialize Product(s),
including, without limitation, the Know-How relating to the System, including
the host strain and plasmid vectors.

1.7  "Product(s)" means any enzyme which is obtained by expressing any gene or
combination of genes owned by or licensed to DIVERSA using the System,
including, without limitation, any enzyme sold as an industrial enzyme or
pharmaceutical intermediate.

1.8  "System" means MYCOGEN's proprietary [****] gene expression system used to
produce the Product(s).

1.9  "Third Party" means any entity other than DIVERSA or MYCOGEN or an
Affiliate of DIVERSA or MYCOGEN.

                           Article 2 - License Grant

2.1  License. Subject to the terms and conditions set forth herein, MYCOGEN
hereby grants to DIVERSA an exclusive, worldwide license, including the right to
grant sublicenses pursuant to section 2.2, under the MYCOGEN Technology to use
the System to produce, make, have made, use, offer for sale, sell and import
Product(s) and other enzymes, with the exception that Diversa shall not use the
System to contract manufacture any enzyme for any third party. Notwithstanding
the foregoing, MYCOGEN and its Affiliates retain the rights to use the System
for the production of enzymes, including for the production of enzymes for third
parties by MYCOGEN.

2.2  Sublicense. MYCOGEN and DIVERSA contemplate that DIVERSA may from time to
time desire to grant sublicenses to third parties to use the System to produce
Product(s) for DIVERSA to be offered for sale by DIVERSA. Accordingly, DIVERSA
shall have the right to grant one or more sublicenses to any third party to use
the System to produce Product(s), provided that any such sublicense expressly
provides that (i) the sublicensees shall have no right to sublicense the System,
and (ii) the sublicensee shall be subject in all respects to provisions in this
Agreement.

                      Article 3 - Payments And Royalties

3.1  Payments. In partial consideration for the rights granted herein, DIVERSA
shall pay to MYCOGEN a [****], [****] of this Agreement.

3.2  Royalty. DIVERSA shall pay to MYCOGEN a royalty equal to [****].

3.3  [****]

                                      2.       *Confidential Treatment Requested
<PAGE>

3.4  Duration of Royalty Obligations. Royalty obligations shall continue for the
term of this Agreement.

3.5  Reduction in Royalty Rate. In the event that DIVERSA is or becomes
obligated to pay additional royalties to MYCOGEN or any third party under
separate license agreement(s) for use of the System, then up to 50% of the
additional or third party royalties owed shall be credited against royalties
owed to MYCOGEN under the terms of this Agreement. In no event, however, shall
the royalty obligation owed to MYCOGEN be reduced below 2% of Gross Revenues of
the Product(s) for any relevant royalty payment period.

                       Article 4 - Payments and Reports

4.1  Semi-Annual Payments. Royalties shall be calculated on a semi-annual basis,
and payable within 60 days after the end of each calendar six month period based
upon Gross Revenues during the previous calendar six month period. All payments
will be made in U.S. Dollars. The exchange rate for conversion of any currency
to U.S. Dollars will be the exchange rate prevailing at Citibank N.A. in New
York for the last business day of each such calendar period. Interest will be
paid on the outstanding balance of any late payments at the prime rate of
interest reported by Citibank, N.A. in New York, as such rate may change from
time to time plus 2% per annum from the due date until the date that such
payment in full is actually received. DIVERSA will assume the risk of any
inconvertibility of any currency.

4.2  Reports. DIVERSA shall furnish to MYCOGEN, at the same time as each royalty
payment is due, a written report of Gross Revenues of each Product and the
royalty due and payable, for the calendar six month period upon which the
royalty payment is based.

4.3  Records. DIVERSA shall keep full, complete and proper records and accounts
of Gross Revenues of each Product, in sufficient detail to enable the royalties
payable to MYCOGEN to be determined. Upon reasonable notice to DIVERSA, MYCOGEN
shall have the right through an independent certified public accountant to audit
DIVERSA's records pertaining to the Product(s) during normal business hours to
verify the royalties payable pursuant to this Agreement; provided, however, that
such audit shall not take place more often than once a year and shall not cover
such records for more than the preceding three years and provided further that
such accountant shall report to MYCOGEN only as to the accuracy of the royalty
reports and payments submitted by DIVERSA to MYCOGEN hereunder. Such audit shall
be at MYCOGEN expense; provided, however, in the event the audit discloses that
MYCOGEN was underpaid royalties by at least 5% for any calendar six month period
then DIVERSA shall reimburse MYCOGEN for audit costs together with an amount
equal to the additional royalties to which MYCOGEN is entitled. DIVERSA shall
preserve and maintain all such records and accounts required for audit for a
period of three years after the calendar six month period for which the record
applies.

                          Article 5 - Confidentiality

5.1  Nondisclosure. During the Term of this Agreement, and for a period of
five years thereafter, each party will maintain all Confidential Information as
confidential and will not disclose any Confidential Information to any Third
Party or use any Confidential Information for any purpose except (a) as
expressly authorized by this Agreement, (b) as required by law or court order,
or (c) to its Affiliates. Each party may use such Confidential Information only
to the extent required to accomplish the purposes of this Agreement. Each party
will use at least the same standard of care as it uses to protect proprietary or
confidential information of its own to ensure that its Affiliates, employees,
agents, consultants and other representatives do not disclose or make any
unauthorized use of the Confidential Information. Each party will promptly
notify the other upon discovery of any unauthorized use or disclosure of the
Confidential Information.

5.2  Exceptions. Confidential Information shall not include any information
which the receiving party can prove by competent evidence:

                                      3.       *Confidential Treatment Requested
<PAGE>

     a)  is now, or hereafter becomes, through no act or failure to act on the
         part of the receiving party, generally known or available;

     b)  is known by the receiving party at the time of receiving such
         information, as evidenced by its records;

     c)  is hereafter furnished to the receiving party by a Third Party, as a
         matter of right and without restriction on disclosure;

     d)  is independently developed by the receiving party without the aid,
         application or use of Confidential Information; or

     e)  is the subject of a written permission to disclose provided by the
         disclosing party.

             Article 6 - Representations, Warranties And Covenants

6.1  Corporate Power. Each party hereby represents and warrants that such party
is duly organized and validly existing under the laws of the state of its
incorporation and has full corporate power and authority to enter into this
Agreement and to carry out the provisions hereof.

6.2  Due Authorization. Each party hereby represents and warrants that such
party is duly authorized to execute and deliver this Agreement and to perform
its obligations hereunder.

6.3  Binding Agreement. Each party hereby represents and warrants that this
Agreement is a legal and valid obligation binding upon it and is enforceable in
accordance with its terms. The execution, delivery and performance of this
Agreement by such party does not conflict with any agreement, instrument or
understanding, oral or written, to which it is a party or by which it may be
bound, nor violate any law or regulation of any court, governmental body or
administrative or other agency having authority over it.

6.4  Disclaimer Of Warranties By Mycogen. EXCEPT AS EXPRESSLY SET FORTH IN THIS
AGREEMENT, MYCOGEN DOES NOT MAKE ANY REPRESENTATION OR WARRANTY TO DIVERSA OF
ANY NATURE, EXPRESS OR IMPLIED, THAT THE SYSTEM WILL BE USEFUL FOR, OR ACHIEVE
ANY PARTICULAR RESULTS. MYCOGEN SPECIFICALLY DISCLAIMS ANY WARRANTY OF
NONINFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

                       Article 7 - Term And Termination

7.1  Term. This Agreement shall commence as of January 1, 1998, and shall
continue unless terminated in accordance with the terms of this Agreement.

7.2  Termination for Cause. Either party may terminate this Agreement upon 60
days written notice upon the occurrence of any of the following:

     a)  Upon or after the bankruptcy, insolvency, dissolution or winding up of
         the other party (other than dissolution or winding up for the purposes
         of reconstruction or amalgamation); or

     b)  Upon or after the breach of any material provision of this Agreement by
         the other party if the breaching party has not cured such breach or
         diligently proceeded to cure such breach within the 60 day period
         following written notice of termination by the other party.

7.3  Effects of Termination. Expiration or termination of this Agreement shall
not relieve the parties of any obligation accruing prior to such expiration or
termination. The provisions of Sections 4.3, 6.4 and 7.3 and Articles 5, 8 and 9
shall survive termination or expiration of this Agreement.

                        Article 8 - Dispute Resolution

8.1  Disputes. The parties recognize that disputes as to certain matters may
from time to time arise which relate to either party's rights and/or obligations
hereunder. It is the objective of the parties to

                                      4.
<PAGE>

establish procedures to facilitate the resolution of such disputes in an
expedient manner by mutual cooperation and without resort to litigation. To
accomplish this objective, the parties agree to follow the procedures set forth
in this Article 8 if and when such a dispute arises between the parties.

8.2  Procedure. If a dispute arises between the parties relating to the
interpretation or performance of this Agreement or the grounds for the
termination thereof, the parties agree to hold a meeting, attended by
individuals with decision-making authority regarding the dispute, to attempt in
good faith to negotiate a resolution of the dispute prior to pursuing other
available remedies. If, within 30 days after such meeting, the parties have
not succeeded in negotiating a resolution of the dispute, such dispute shall be
finally settled only in San Diego, California, in accordance with the rules and
procedures of the American Arbitration Association by three arbitrators
knowledgeable as to biotechnology industry standards. Each party shall select
one arbitrator within 30 days after the institution of the arbitration
proceeding and the third arbitrator will be selected by mutual agreement of
the other two arbitrators within 30 days of the appointment of the two
arbitrators selected by the parties. All of the arbitrators will be neutral,
impartial, independent of the parties and others having any known interest in
the outcome; will abide by the ABA and AAA Cannons of Ethics for neutral
arbitrators, and will have no ex parte communications about the case or about
the appointment of the third arbitrator or the arbitrator's views on matters of
law with either party in the appointing process or otherwise during the pendency
of the arbitration. The parties shall bear the costs of arbitration equally
unless the arbitrators, pursuant to their right, but not their obligation,
require the non-prevailing party to bear all or any unequal portion of the
prevailing party's costs. The arbitrators shall prepare and deliver a written,
reasoned opinion conferring their decision within 30 days of the final
arbitration hearing. The arbitrators shall not have the power to award punitive
damages under this Agreement and such an award is expressly prohibited. The
decision of the arbitrators shall be final and binding on all of the parties.
Judgment on the award so rendered may be entered in any court of competent
jurisdiction at the option of the successful party. The rights and obligations
of the parties to arbitrate any dispute relating to the interpretation or
performance of this Agreement or the grounds for the termination thereof shall
survive the expiration or termination of this Agreement for any reason.

                   Article 9 - Indemnification And Insurance

9.1   Patent Infringement Indemnification. DIVERSA will at all times during the
term of this Agreement and thereafter, indemnify, defend and hold harmless
MYCOGEN and its directors, officers, employees, and affiliates, against any
claim, proceeding, demand, liability, or expense (including legal expenses and
reasonable attorney's fees) which relates to any action brought by a third party
alleging infringement of a U.S. or foreign patent as a result of the activities
of DIVERSA under this Agreement, except to the extent that such alleged
infringement is the direct result of an activity of MYCOGEN.

MYCOGEN will at all times during the term of this Agreement and thereafter,
indemnify, defend and hold harmless DIVERSA and its directors, officers,
employees, and affiliates, against any claim, proceeding, demand, liability, or
expense (including legal expenses and reasonable attorney's fees) which relates
to any action brought by a third party alleging infringement of a U.S. or
foreign patent as a result of the activities of MYCOGEN under this Agreement,
except to the extent that such alleged infringement is the direct result of an
activity of DIVERSA.

9.2   Product Liability Indemnification. DIVERSA will at all times during the
term of this Agreement and thereafter, indemnify, defend and hold harmless
MYCOGEN and its directors, officers, employees, and affiliates, against any
claim, proceeding, demand, liability, or expense (including legal expenses and
reasonable attorney's fees) which relates to injury to persons or property, or
against any other claim, proceeding, demand, expense and liability of any kind
whatsoever resulting from the production, manufacture, sale, use, lease,
consumption or advertisement of Product(s), except to the extent that such
alleged infringement is the direct result of an activity of MYCOGEN.

9.3   Obligation of Agents.  DIVERSA will require all agents who are involved
with the development, manufacturing, use or sale of Product(s), process or
service relating to this Agreement to provide the same level of indemnification
as set forth in this section.

                                      5.       *Confidential Treatment Requested
<PAGE>

9.4   Survival.  This Clause 9 will survive expiration or termination of this
Agreement.

                          Article 10 - Miscellaneous

10.1  Assignment.

          (a)  Neither party will have the right to assign its rights or
      obligations under this Agreement with the prior written consent of the
      other party. Any attempted assignment in violation of this provision will
      be void. However, this Agreement shall survive any merger, reorganization
      or sale of all or substantially all of the assets of either party with or
      into another party and no consent for such transaction shall be required
      hereunder; provided, however, that in the event of such transaction, no
      intellectual property rights of the acquiring corporation shall be
      included in the technology licensed hereunder.

          (b) This Agreement shall be binding upon and inure to the benefit of
      the successors and permitted assigns of the parties. Any assignment not in
      accordance with this Agreement shall be void.

10.2  Force Majeure. Neither party shall lose any rights hereunder or be liable
to the other party for damages or losses on account of failure of performance by
the defaulting party if the failure is occasioned by government action, war,
fire, explosion, flood, strike, lockout, embargo, act of God, or any other
similar cause beyond the control of the defaulting party; provided, however,
that the party claiming force majeure has exerted all reasonable efforts to
avoid or remedy such condition.

10.3  Notices. Any notices or communications provided for in this Agreement to
be made by either of the parties to the other shall be in writing and delivered
personally or sent by United States mail, registered or certified, postage paid,
by overnight delivery service such as FedEx or UPS or by facsimile, with
confirmation of receipt, addressed as follows:

      If to DIVERSA:

          Diversa Corporation
          10665 Sorrento Valley Road
          San Diego, CA 92121
          Attn: Carolyn A. Erickson
                Director Intellectual property
          Phone No. (619)623-5104
          Fax No. (619)623-5190

      If to MYCOGEN:

          MYCOGEN Corporation
          5501 Oberlin Drive
          San Diego, CA 92121
          Attn: [*****]

Either party may by like notice specify or change an address to which notices
and communications shall thereafter be sent. Notices sent by facsimile shall be
effective upon confirmation of receipt, notices sent by mail or overnight
delivery service shall be effective upon receipt, and notices given personally
shall be effective when delivered.

10.4  Governing Law. This Agreement shall be governed by, construed and enforced
in accordance with the laws of the State of California, as such laws are applied
to contracts entered into and to be performed entirely within the State of
California by California residents.

                                      6.       *Confidential Treatment Requested
<PAGE>

10.5  Waiver. Except as specifically provided for herein, the waiver from time
to time by either of the parties of any of their rights or their failure to
exercise any remedy shall not operate or be construed as a continuing waiver of
same or of any other of such party's rights or remedies provided in this
Agreement.

10.6  Severability. If any term, covenant or condition of this Agreement or the
application thereof to any party or circumstance shall, to any extent, be held
to be invalid or unenforceable, then (a) the remainder of this Agreement, or the
application of such term, covenant or condition to parties or circumstances
other than those as to which it is held invalid or unenforceable, shall not be
affected thereby and each term, covenant or condition of this Agreement shall be
valid and be enforced to the fullest extent permitted by law; and (b) the
parties hereto covenant and agree to renegotiate any such term, covenant or
application thereof in good faith in order to provide a reasonably acceptable
alternative to the term, covenant or condition of this Agreement or the
application thereof that is invalid or unenforceable, it being the intent of the
parties that the basic purposes of this Agreement are to be effectuated.

10.7  Independent Contractors. It is expressly agreed that DIVERSA and MYCOGEN
shall be independent contractors and that the relationship between the two
parties shall not constitute a partnership or agency of any kind. Neither
DIVERSA nor MYCOGEN shall have the authority to make any statements,
representations or commitments of any kind, or to take any action, which shall
be binding on the other, without the prior written authorization of the party to
do so.

10.8  Entire Agreement; Amendment. This Agreement sets forth all of the
covenants, promises, agreements, warranties, representations, conditions and
understandings between the parties hereto, and supersedes and terminates all
prior agreements and understanding between the parties with respect to the
subject matter hereof. There are no covenants, promises, agreements, warranties,
representations conditions or understandings, either oral or written, between
the parties other than as set forth herein and therein. No subsequent
alteration, amendment, change or addition to this Agreement shall be binding
upon the parties hereto unless reduced to writing and signed by the respective
authorized officers of the parties.

10.9  Counterparts. This Agreement may be executed in two or more counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument.

                                      7.
<PAGE>

     In Witness Whereof, the parties have executed this License Agreement as of
the date first set forth above.

Mycogen Corporation                               Diversa Corporation

By: /s/ Andrew C. Barnes                           /s/ Patrick Simms
   ----------------------------------             ------------------------------
                                                  Patrick Simms
Name:   Andrew C. Barnes                          Vice President
     --------------------------------

Title:    Exec. VP
      -------------------------------

                                      8.<PAGE>

                                                                   EXHIBIT 10.23

                                               Confidential Treatment Requested
                                             Under 17 C.F.R. (S)(S) 200.80(b)(4)
                                                      200.83 and 230.406

                        PATENT CROSS-LICENSE AGREEMENT

          This agreement ("Agreement"), effective as of the 18/th/ day of
November, 1999 ("Effective Date"), is made by and between Terragen Discovery
Inc., a British Columbia corporation ("Terragen"), having its principal place of
business at Suite 300-2386 East Mall - UBC, Vancouver, British Columbia, Canada
V6T 1Z3, and Diversa Corporation, a Delaware corporation ("Diversa"), having its
principal place of business at 10665 Sorrento Valley Road, San Diego, California
92121.

          Whereas, Terragen is the owner of [*****] Terragen Patent Rights (as
hereinafter defined), and Diversa is the owner of [*****] Diversa Patent Rights
(as hereinafter defined), both embodying technologies applicable in discovery of
multi-gene pathways and biomolecules of interest;

          Whereas, each party is desirous of acquiring certain rights under the
other party's patent rights to use the other party's technology for the [*****];
and

          Whereas, each party is willing to grant the other party such rights in
accordance with the terms and conditions set forth in this Agreement.

          Now, Therefore, in consideration of the foregoing recitals and the
mutual covenants and conditions set forth herein, Terragen and Diversa hereby
agree as follows:

                                   ARTICLE 1

                                  DEFINITIONS

          "[*****]" shall mean a [*****]

          "Diversa Patent Rights" shall mean patents and patent applications set
forth in Exhibit A hereto, and all continuations-in-part, continuations,
divisionals, reissues, re-examinations or extensions thereof, and any foreign
patents and patent applications corresponding thereto. Diversa may modify
Exhibit A from time to time by providing written notice to Terragen to include
patents and patent applications that may be required in order for Terragen to
practice Diversa Patent Rights or Terragen Patent Rights.

          "Diversa Products" shall refer to all products made, use, sold,
offered for sale or imported by Diversa that but for the licenses granted herein
would infringe Terragen Patent Rights.

          "Field 1" shall mean small molecules for pharmaceutical applications.

          "Field 2" shall mean all fields except Field 1.

          "Patent Rights" shall refer to Terragen Patent Rights and Diversa
Patent Rights.

          "[*****]" shall mean a [*****].

           "Terragen Patent Rights" shall mean patents and patent applications
set forth in Exhibit B hereto, and all continuations-in-part, continuations,
divisionals, reissues, re-examinations or extensions thereof, and any foreign
patents and patent applications corresponding thereto, as well as any patents
and patent applications necessary to practice microdroplet screening
technologies as described in the patents and patent applications in Exhibit B.
Terragen may modify Exhibit B from time to time by providing written

                                      1.       *Confidential Treatment Requested
<PAGE>

notice to Diversa to include patents and patent applications that may be
required in order for Diversa to practice Diversa Patent Rights or Terragen
Patent Rights.

           "Terragen Products" shall refer to small molecules generated by the
expression of partial, complete or hybrid gene pathways made, used, sold,
offered for sale or imported by Terragen that but for the license granted herein
would infringe Diversa Patent Rights. It is understood that small molecules do
not include proteins or nucleic acids.

           "Valid Claim" shall mean: (i) a claim of an issued and unexpired
patent that has not been revoked or held unenforceable or invalid by a decision
of a court or other governmental body of competent jurisdiction, unappealable or
unappealed within the time allowed for appeal, and which has not been
statutorally disclaimed; or (ii) a claim included in a pending patent
application that is actively prosecuted and which has not been cancelled,
withdrawn, finally determined to be unallowable by the applicable governmental
body pursuant to an unappealable decision and/or abandoned in accordance with
the terms hereof.

                                   ARTICLE 2

                                 LICENSE GRANT

     2.1   Terragen License Grant. Subject to the terms and conditions set forth
herein, Terragen hereby grants to Diversa the following:

           (a)  a co-exclusive, non-royalty bearing, worldwide, [*****] license
under Terragen Patent Rights to [*****] in Field 2. This license shall [*****]
to the [*****]. During the term of the license, Terragen will [*****] to [*****]
under [*****] in Field 2 to [*****].

           (b)  a non-exclusive, non-royalty bearing, non-sublicenseable,
worldwide license under Terragen Patent Rights to [*****] in Field 1, provided
that [*****] from the Effective Date, the license under this subparagraph shall
[*****]. This license shall [*****].

     2.2   Diversa License Grant.  Subject to the terms and conditions set forth
herein, Diversa hereby grants to Terragen the following:

           (a)  a non-exclusive, non-royalty bearing, worldwide, [*****] license
under Diversa Patent Rights to [*****] in Field 1.

     2.3   License Limitations.

           (a)  Diversa agrees that it will not [*****] in [*****] of Diversa
Products in Field [*****] for a period of [*****] from the Effective Date.

           (b)  Terragen agrees that it will not [*****] in the [*****] and/or
[*****] of Terragen Products for a period of [*****] from the Effective Date.

                                   ARTICLE 3

                                 CONSIDERATION

     3.1  Fees.  In consideration of the licenses granted to Diversa by Terragen
under the terms of this Agreement, Diversa has granted the license referred to
in Section 2.2 and will pay Terragen the following:

           (a)  a one time up front payment of two million five hundred thousand
                dollars (US$2,500,000) within thirty (30) days of the Effective
                Date;

                                      2.       *Confidential Treatment Requested
<PAGE>

          (b)  an annual maintenance fee of one hundred thousand dollars
(US$100,000) within thirty (30) days of each anniversary date of the Effective
Date until all Valid Claims included in the Terragen Patent Rights have expired
unless the Agreement is terminated earlier pursuant to Article 7 below.

                                   ARTICLE 4

                             INTELLECTUAL PROPERTY

     4.1  Except as permitted below, in further consideration of the licenses
granted under the terms of this Agreement, Terragen will not institute a legal
action challenging the validity and/or enforceability of Diversa Patent Rights,
and Diversa will not institute any legal action challenging the validity and/or
enforceability of Terragen Patent Rights, in each case, during the term of this
Agreement. "Legal action challenging the validity and/or enforceability of
Diversa Patent Rights/Terragen Patent Rights" shall include, but is not limited
to, pre-grant or post-grant opposition proceedings, utility suits, reexamination
proceedings, declaratory judgement actions, and civil actions under 35 U.S.C.
(S) 291 (interfering patents).

     4.2  Except as permitted below, in further consideration of the licenses
granted under the terms of this Agreement, neither party shall take any action
to hinder or delay prosecution of patents or patent applications owned or
controlled by the other party and within the scope of Patent Rights without the
prior written consent of said other party during the term of this Agreement.
"Action taken to hinder or delay prosecution of patent applications" shall
include, but is not limited to, formal or informal protests and third-party
observations.

     4.3  Upon the execution of this Agreement, a party who has brought a
pending legal action challenging the validity or enforceability of any patent or
patent application owned or controlled by the other party and within the scope
of Patent Rights, shall take appropriate steps to terminate said pending legal
action.

     4.4  Notwithstanding the provisions of sections 4.1 and 4.2, a party may
present and prosecute one or more claims that are directed to the same
patentable invention as any claim(s) of the other party. Claims may be presented
to satisfy the provisions of 35 U.S.C. (S) 135(b) or otherwise, e.g., at the
request of an Examiner.

     4.5  Notwithstanding the provisions of sections 4.1 and 4.2, in the event a
patent infringement action is brought against a party to this Agreement, the
party charged with infringement shall be permitted to raise all defenses
permitted by law, including invalidity or unenforceability of the patent
asserted against the party charged with infringement.

     4.6  Notwithstanding the provisions of sections 4.1 and 4.2, nothing in
this agreement shall prevent a party from disclosing material information to the
Patent and Trademark Office to satisfy the duty of disclosure under 37 C.F.R.
(S) 1.56.

     4.7  If the United States Patent and Trademark Office declares an
interference proceeding involving Terragen Patent Rights and Diversa Patent
Rights, the parties will negotiate a settlement of such an interference in good
faith. These negotiations will address all priority and non-priority issues that
could have been brought in the interference.

     4.8  Infringement by Third Parties.

          (a)  In the event that either party determines that a third party is
making, using, or selling a product that may infringe a patent included in the
Patent Rights, it will promptly notify the other party in writing.

          (b)  Except as provided under Section 4.8(c), the party in whose name
the allegedly infringed Patent Rights are registered shall be solely responsible
for determining whether to bring suit

                                      3.       *Confidential Treatment Requested
<PAGE>

against such alleged infringer and controlling such suit, and the other party
shall take all reasonable steps to assist in such suit, provided that the
expenses of the other party are paid by the controlling party.

          (c)  If the matter involves an alleged infringement of the Terragen
Patent Rights in Field 2, then Terragen shall be initially responsible for
determining whether to bring suit against such alleged infringer. In the event
Terragen decides to bring suit, it shall give prompt written notice to Diversa
of that fact, and Diversa shall take all reasonable steps to assist Terragen in
such suit. Terragen shall be entitled to all amounts recovered in such suit
(other than amount to be paid to Diversa, should Diversa elect to join in such
suit as provided for herein), except that Diversa shall have the right to elect
to pay up to fifty percent (50%) of the litigation costs and receive a
percentage of any recovery equal to the percentage of total litigation costs,
including reasonable attorneys' fees, paid by Diversa. Diversa must make such
election within sixty (60) days of its receipt of Terragen's notice that it has
decided to bring suit. Diversa shall also have the right to be represented by
separate counsel in any such suit. Terragen shall have control over any such
suit, and decisions as to settlement, methods and/or terms and conditions for
resolving the suit shall be made by Terragen after good faith consultation with
Diversa. Upon the earlier of (i) Terragen's election not to bring a suit against
the alleged infringer, as indicated by prompt written notice to Diversa, or (ii)
180 days after Terragen has notice of such alleged infringement if Terragen has
not been able to cause the alleged infringer to cease infringement, Diversa
shall have the right, at its option, to commence such action at its own cost and
expense, in which case Diversa shall have control over such suit and be entitled
to all amounts recovered in such action, subject to payment of any costs of
Terragen in assisting in such suit. Subject to the right to receive payment for
its costs out of amounts recovered as aforesaid, Terragen shall take all
reasonable steps to assist Diversa in such suit.

     4.9   Parties to Maintain Patent Rights. Each party shall have the
obligation and be responsible at its own cost and expense for maintaining and
extending those Patent Rights under its control for the term of this License.
Subject to Section 4.10, each party shall use good faith efforts to prosecute,
issue and maintain all Patent Rights.

     4.10  Notice of Patent Lapse of Patent Rights. In the event that a party
elects to abandon any of the Patent Rights under its control, it shall promptly
advise the other party of the grant, lapse, nullification, revocation,
surrender, or invalidation of any such Patent Rights at least in advance of any
abandonment to enable the other party (the "Assuming Party") to assume that
prosecution, at the Assuming Party's expense, should the Assuming Party not
agree to such abandonment.

                                   ARTICLE 5

                 LIMITED WARRANTIES/INDEMNIFICATION/LITIGATION

     5.1   Limited Warranty.  Each party warrants to the other that it has the
full right and power to make the representations and agreements set forth
herein. Terragen warrants that Exhibit B lists patent applications filed on or
before the Effective Date owned by Terragen, and Diversa warrants that Exhibit A
lists patent applications filed on or before the Effective Date owned by
Diversa.

     5.2   No Other Warranties by Terragen. WITH RESPECT TO TERRAGEN PATENT
RIGHTS AND TERRAGEN TECHNOLOGY, TERRAGEN EXPRESSLY DISCLAIMS ALL WARRANTIES OF
ANY KIND AND MAKES NO EXPRESS OR IMPLIED WARRANTIES WHATSOEVER INCLUDING,
WITHOUT LIMITATION, IMPLIED WARRANTIES OF MERCHANTABILITY, SATISFACTORY QUALITY
OR FITNESS FOR A PARTICULAR PURPOSE, EXCEPT AS EXPRESSLY PROVIDED IN PARAGRAPH
5.1 ABOVE. TERRAGEN EXPRESSLY DISCLAIMS ALL WARRANTIES AS TO THE VALIDITY OR
SCOPE OF TERRAGEN PATENT RIGHTS, OR THAT THE TERRAGEN TECHNOLOGY WILL BE FREE
FROM INFRINGEMENT OF PATENTS OR PROPRIETARY RIGHTS OF THIRD PARTIES, OR THAT NO
THIRD PARTIES ARE IN ANY WAY INFRINGING TERRAGEN PATENT RIGHTS. In no event
shall Terragen be liable for any consequential, indirect, or incidental damages.
Further, Diversa shall make no statements, representations or warranties
whatsoever to any third party which are inconsistent with this disclaimer by
Terragen.

                                      4.
<PAGE>

     5.3   No Other Warranties by Diversa. WITH RESPECT TO DIVERSA PATENT RIGHTS
AND DIVERSA TECHNOLOGY, DIVERSA EXPRESSLY DISCLAIMS ALL WARRANTIES OF ANY KIND
AND MAKES NO EXPRESS OR IMPLIED WARRANTIES WHATSOEVER INCLUDING, WITHOUT
LIMITATION, IMPLIED WARRANTIES OF MERCHANTABILITY, SATISFACTORY QUALITY OR
FITNESS FOR A PARTICULAR PURPOSE, EXCEPT AS EXPRESSLY PROVIDED IN PARAGRAPH 5.1
ABOVE. DIVERSA EXPRESSLY DISCLAIMS ALL WARRANTIES AS TO THE VALIDITY OR SCOPE OF
DIVERSA PATENT RIGHTS, OR THAT THE DIVERSA TECHNOLOGY WILL BE FREE FROM
INFRINGEMENT OF PATENTS OR PROPRIETARY RIGHTS OF THIRD PARTIES, OR THAT NO THIRD
PARTIES ARE IN ANY WAY INFRINGING DIVERSA

PATENT RIGHTS. In no event shall Diversa be liable for any consequential,
indirect, or incidental damages. Further, Terragen shall make no statements,
representations or warranties whatsoever to any third party which are
inconsistent with this disclaimer by Diversa.

     5.4  Infringement Litigation. Each party shall notify the other party in
writing in the event that any third party shall commence or threaten to commence
an action against Terragen or Diversa alleging that the practice of a method or
process embodied in one or more claims of Diversa Patent Rights or Terragen
Patent Rights infringes a patent of a third party. Each party shall keep the
other reasonably informed with respect to the progress of any such action from
time to time. Upon a party's reasonable request and at its expense, the other
party shall cooperate with the requesting party and its counsel with respect to
the defense of any such action against the requesting party.

                                   ARTICLE 6

                                CONFIDENTIALITY

     6.1  Definition of Confidential Information.  Confidential Information
shall mean any technical, business or other proprietary information, whether
orally or in writing, furnished by one party (the "Disclosing Party") to the
other party (the "Receiving Party) in connection with this Agreement. Such
Confidential Information shall include, without limitation, the terms of this
Agreement, Diversa Patent Rights, and Terragen Patent Rights.

     6.2  Obligations.  The Receiving Party agrees that it shall:

          (a)  Maintain all Confidential Information in strict confidence,
except that the Receiving Party may disclose or permit the disclosure of any
Confidential Information to its Affiliates, directors, officers, employees,
consultants and advisors who are obligated to maintain the confidential nature
of such Confidential Information and who need to know such Confidential
Information for the purposes set forth in this Agreement;

          (b)  Use all Confidential Information solely for the purposes set
forth in, or as permitted by, this Agreement; and

          (c)  Allow its Affiliates, directors, officers, employees, consultants
and advisors to reproduce the Confidential Information only to the extent
necessary to effect the purposes set forth in this Agreement, with all such
reproductions being considered Confidential Information.

Each Party shall be responsible for any breaches of this Section 6.2 by any of
its Affiliates, directors, officers, employees, consultants and advisors.

     6.3  Exceptions.  The obligations of the Receiving Party under Section 6.2
above shall not apply to any specific Confidential Information to the extent
that the Receiving Party can demonstrate by written record that such
Confidential Information:

          (a)  Was in the public domain prior to the time of its disclosure
under this Agreement;

                                      5.
<PAGE>

          (b)  Entered the public domain after the time of its disclosure under
this Agreement through means other than an unauthorized disclosure resulting
from an act or omission by the Receiving Party or its Affiliates, directors,
officers, employees, consultants, advisors or agents;

          (c)  Was or is independently developed or discovered by the Receiving
Party without use of the Confidential Information;

          (d)  Is or was disclosed to the Receiving Party at any time, whether
prior to or after the time of its disclosure under this Agreement, by a third
party having no fiduciary relationship with the Disclosing Party and having no
obligation of confidentiality to the Disclosing Party with respect to such
Confidential Information; or

          (e)  Is required to be disclosed to comply with applicable laws or
regulations (such as disclosure to the SEC, the EPA, the FDA, or the United
States Patent and Trademark Office or to their foreign equivalents), or to
comply with a court or administrative order, provided that the Disclosing Party
receives prior written notice of such disclosure and that the Receiving Party
takes all reasonable and lawful actions to obtain confidential treatment for
such disclosure and, if possible, to minimize the extent of such disclosure.

     6.4  Survival of Obligations.  The obligations set forth in Sections 6.1,
6.2 and 6.3 shall remain in effect after termination or expiration of this
Agreement, until such time as the Confidential Information falls into one of the
exceptions listed in Section 6.3.

     6.5  Publicity. The parties shall issue a joint press release regarding
this Agreement, the text of which shall be subject to mutual agreement of the
parties. Except for the information disclosed in the joint press release,
neither party shall use the name of the other party or reveal the terms of this
Agreement in any publicity or advertising without the prior written approval of
the other party, except that (i) either party may use the text of a written
statement approved in advance by both parties without further approval, and (ii)
either Party shall have the right to identify the other party and to disclose
the terms of this Agreement as required by applicable securities laws or other
applicable law or regulation, provided that the receiving party takes reasonable
and lawful actions to minimize the degree of such disclosure.

                                   ARTICLE 7

                             TERM AND TERMINATION

     7.1  Diversa License Term.  The term of the licenses granted to Diversa by
Terragen pursuant to this Agreement shall expire on a country by country basis,
upon the expiration of the last to expire Valid Claim within the Terragen Patent
Rights.

     7.2  Terragen License Term.  The term of the license granted to Terragen by
Diversa pursuant to this Agreement shall expire on a country by country basis,
upon the expiration of the last to expire Valid Claim within the Diversa Patent
Rights.

     7.3  Termination Upon Material Breach.  Either party may terminate the
licenses granted to the other party under this Agreement if such other party
breaches any material term of this Agreement and does not cure such breach
within sixty (60) days following written notice; except for non-payment of
money, in which case the cure period shall be reduced to fifteen (15) days. Any
right to terminate arising under this Section 7.3 shall be stayed until resolved
under Section 9.2 if, during the relevant cure period, the party alleged to have
been in default shall:

               (i)  have initiated arbitration in accordance with Section 9.2
below, with respect to the alleged default; and

                                      6.
<PAGE>

               (ii) be diligently and in good faith co-operating in the prompt
resolution of such arbitration proceedings.

     7.4  Termination Upon Bankruptcy.  If either party (the "Insolvent Party")
files for protection under bankruptcy laws, makes an assignment for the benefit
of creditors, appoints or suffers appointment of a receiver or trustee over its
property, files a voluntary petition under any bankruptcy or insolvency act or
has any such petition filed against it which is not discharged within sixty (60)
days of the filing thereof, then the other party may, at its sole election upon
notice to the Insolvent Party, terminate the rights granted to the Insolvent
Party by written notice to such Insolvent Party.

     7.5  Termination upon Patent Right Lapse.  Either party may terminate the
license granted to the other party under this Agreement if the other party's
Patent Rights have lapsed, been canceled or abandoned, been admitted to be
invalid or unenforceable through reissue or disclaimer or have been declared
invalid by decision or judgment of a court of competent jurisdiction.

     7.6  Termination Upon Licensed Rights Representing Majority of Assets.
Either party may terminate the licenses granted to the other party under this
Agreement if the licenses granted to the other party under this Agreement
represent more than 50% of the total assets of the other party.

     7.7  Terragen Termination Rights Upon Certain Diversa Acquisitions/Mergers.
Terragen may terminate the licenses granted to Diversa under this Agreement in
the event that Diversa transfers all or substantially all of its business
whether by way of merger, sale of stock, sale of assets or otherwise to a
[****] within two (2) years of the Effective Date.  In the event
the license to Diversa is terminated by Terragen pursuant this Section 7.7, such
termination will be effective upon the date of such transfer.

     7.8  Diversa Termination Rights Upon Certain Terragen Acquisitions/Mergers.
Diversa may terminate the license granted to Terragen under this Agreement in
the event that Terragen transfers all or substantially all of its business,
whether by way of merger, sale of stock, sale of assets or otherwise [****]
during the term of this Agreement. In the event the license to Terragen is
terminated by Diversa pursuant this Section 7.8, such termination will be
effective upon the date of such transfer. Further, in the event Terragen
transfers all or substantially all of its business, whether by way of merger,
sale of stock, sale of assets or otherwise to a [****] without prior written
approval from Diversa within five (5) years of the Effective Date, Terragen
shall reimburse Diversa the two (2) million five hundred thousand dollars
($2,500,000) paid Terragen by Diversa pursuant to Section 3.1 above, within
ninety (90) days of such transfer.

     7.9  Rights Upon Expiration. Upon expiration of the licenses granted
hereunder, neither party shall have any further rights or obligations with
respect to this Agreement in the countries with respect to which this Agreement
has then expired, except that expiration shall not relieve each party of any
obligations accruing prior to such expiration or of its obligations under
Articles 4, 5 and 6 herein. This Section 7.9 (and the sections referenced
herein) shall survive expiration of this Agreement.

     7.10 Rights Upon Termination. Upon termination of the licenses granted by
one party (the "Terminating Party") to the other party (the "Terminated Party")
under this Agreement, the licenses granted by the Terminated Party to the
Terminated Party shall remain in full force effect until expiration or
termination in accordance with this Agreement. Any termination of licenses
granted under this Agreement shall not relieve either party of any obligations
with respect to such licenses accrued prior to the date of such termination or
its obligations under Articles 4, 5 and 6 herein. This Section 7.10 (and the
sections referenced herein) shall survive termination of this Agreement.

                                      7.       *Confidential Treatment Requested
<PAGE>

                                   ARTICLE 8

           ASSIGNMENT, CHANGE OF OWNERSHIP, RIGHTS UPON DISSOLUTION

     8.1   Assignment.  Except as otherwise expressly provided herein, neither
this Agreement nor any interest hereunder shall be assignable, nor any other
obligation delegable, by either party without the prior written consent of the
other; provided, however, that (subject to sections 7.7 and 7.8 above) a Party
may assign this Agreement to any affiliate of it or to any successor by law or
by sale of all or substantially all of its assets, provided that the assigning
party shall guarantee and remain liable and responsible for the performance and
further observance of all the assigning party's duties and obligations
hereunder; provided further that, in the event of such transaction, no
intellectual property rights of any person (other than Diversa or Terragen) that
is an acquiring party shall be included in the technology licensed hereunder.
The terms and provisions of this Agreement shall be binding upon the successors
and permitted assigns of the parties. Any assignment not in accordance with this
Section 8.1 shall be void.

     8.2   Diversa Rights Upon Dissolution, Liquidation, Winding Up of Terragen.
Diversa will have a right of first option to negotiate the purchase of the
Terragen Patent Rights in the event of the dissolution, liquidation or winding
up of Terragen (an "Event") (subject to Section 9.12 hereof and to applicable
bankruptcy laws) within five (5) years of the Effective Date. Terragen will
provide prompt written notice to Diversa of any Event or proposed Event. Diversa
may exercise its option to negotiate the purchase of the Terragen Patent Rights
by providing Terragen written notice within sixty (60) days after the date of
such notice to Diversa by Terragen. If Diversa elects to exercise such option,
the parties shall negotiate in good faith with the goal of entering into a
definitive agreement within ninety (90) days after the date of Diversa's notice
to Terragen. If Diversa does not exercise such option within the sixty (60) day
option period or the parties are unable to enter into a definitive agreement
within the ninety (90) day period after Diversa's notice to Terragen that is has
exercised the option (or such longer period as the parties may mutually agree in
writing), then Terragen shall be free to sell or otherwise transfer the Terragen
Patent Rights to a third party; provided that, for a period of six months
following the end of the negotiation period, Terragen may not sell or otherwise
transfer the Terragen Patent Rights to any third party containing terms and
conditions which, in the aggregate, are more favorable to such third party than
the terms and conditions last offered to Diversa by Terragen, unless Terragen
first offers Diversa the opportunity to purchase the Terragen Patent Rights on
such terms and conditions.

                                   ARTICLE 9

                              GENERAL PROVISIONS

     9.1  Independent Contractors.  Terragen and Diversa shall be independent
contractors and shall not be deemed to be partners, joint venturers or each
other's agents and neither party shall have the right to act on behalf of the
other except as is expressly set forth in this Agreement.

     9.2  Arbitration. The Parties shall mutually consult in good faith in an
attempt to settle amicably in the spirit of co-operation any and all disputes
arising out of or in connection with this Agreement or questions regarding the
interpretation of the provisions hereof. All controversies or claims under this
Agreement, the enforcement or interpretation hereof, or because of an alleged
breach, default or misrepresentation under the provisions hereof that cannot be
settled amicably within [*****] from the date of notification of either party to
the other of such dispute or question, which notice shall specify the details of
such dispute or question, shall be settled by final and binding arbitration in
English, by one arbitrator appointed by the American Arbitration Association
("AAA"). If the parties cannot agree on the arbitrator to be so appointed, each
party shall be entitled to appoint one (1) arbitrator, and the [*****]
arbitrators so appointed shall agree upon a third. The arbitrator(s) shall have
the technical expertise required to understand and arbitrate the dispute. The
arbitration shall be conducted in San Diego, California, if initiated by
Terragen and in Vancouver, British Columbia, if initiated by Diversa, in each
case, in accordance with the then-existing Commercial Arbitration Rules of the
AAA. Judgment upon the award rendered by the arbitrator(s) may be entered in any
court having jurisdiction thereof; provided, however, that the law applicable to
any controversy shall be the law of the State of California or Federal Patent
Law, as applicable, regardless of its or any other jurisdiction's choice of law
principles. Notwithstanding the foregoing, either party may

                                  8.       *Confidential Treatment Requested

<PAGE>

apply to any court of competent jurisdiction for a temporary restraining order,
preliminary injunction or other interim or conservatory relief, as necessary,
without breach of this arbitration agreement and without any abridgement of the
powers of the arbitrator. In no event shall the demand for arbitration be made
after the date when institution of a legal or equitable proceeding based on such
claim, dispute or other matter in question would be barred by the applicable
statute of limitations. The costs of any arbitration, including administrative
and arbitrators' fees, shall be shared equally by the parties and each party
shall bear its own costs and attorneys' and witness' fees, provided however,
that the prevailing party, if determined by the arbitrator(s), shall be entitled
to an award against the other party in the amount of the prevailing party's
costs (including arbitration costs) and reasonable attorneys' fees.

     9.3  Entire Agreement.  This Agreement, together with the Non-Disclosure
Agreement signed by the parties dated [*****] sets forth the entire agreement
and understanding between the parties as to the subject matter hereof. There
shall be no amendments or modifications to this Agreement, except by a written
document signed by both parties.

     9.4  California Law.  This Agreement shall be construed and enforced in
accordance with the laws of the State of California without giving effect to its
principles of conflicts of law.

     9.5   Severability.  If any provision of this Agreement is ultimately held
to be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

     9.6   No Waiver. Any delay in enforcing a party's rights under this
Agreement or any waiver as to a particular default or other matter shall not
constitute a waiver of a party's right to the future enforcement of its rights
under this Agreement.

     9.7   Notices. Any notices in writing and payments to be made provided
herein shall be deemed duly given and made if sent by courier or by certified or
registered mail, postage prepaid, to the addressees below. Either party may
change its address or its designated management representative by written notice
to the other party. The date of giving such notices and payments shall be the
date of mailing.

To Terragen:

Terragen Discovery Inc.
Suite 300
2386 East Mall
UBC Vancouver, British Columbia, Canada V6T 1Z3

Attention: Dr. Mario Thomas
           Chief Executive Officer

To Diversa Corporation:

Diversa Corporation
10665 Sorrento Valley Road
San Diego, California 92121

Attention: Dr. Jay Short
           CEO, CTO and President

     9.8   Captions.  Captions and headings are relied on for convenience only
and in no way are to be construed to define, limit or affect the construction or
interpretation hereof.

                                      9.
<PAGE>

     9.9   Governmental Approvals. Each party shall be responsible for obtaining
all necessary governmental approvals for the development, testing, production,
distribution, sale and use of any products discovered and developed by such
party using Diversa Technology or Terragen Technology licensed hereunder, at
such party's sole expense. Each party shall have sole responsibility for any
warning labels, packaging, instructions to use, and quality control with respect
to any such product.

     9.10  Compliance With Laws and Regulations. Each party shall comply with
all United States and foreign laws, regulations, rules and orders applicable to
use of the Diversa Technology or Terragen Technology, as applicable, the
development, testing, production, distribution, export, packaging, labeling,
sales and use of products derived from the use of the Diversa Technology or
Terragen Technology, as applicable.

     9.11  No Use of Name.  Neither party shall use in advertising, promotion or
sale of products, or the provision of services using the Diversa Technology or
Terragen Technology, as applicable, any trade name, trademark, servicemark,
trade-dress or other designation, or any confusingly similar variation thereof,
of the other party, unless consented to in writing by such other party.

     9.12  Section 365(n). All licenses granted under the Agreement will be
deemed licenses of rights to intellectual property for purposes of Section
365(n) of the US Bankruptcy Code and a licensee under the Agreement will retain
and may fully exercise all of its rights and elections under the US Bankruptcy
Code.

     9.13  Counterparts. This Agreement may be executed in counterparts, each of
which, when so executed and delivered, shall be deemed to be an original, and
all of which counterparts, taken together, shall constitute one and the same
instrument.

IN WITNESS WHEREOF, the parties have executed this Agreement as of the Effective
Date.

Terragen Discovery, Inc.                     Diversa Corporation

/s/ Mario Thomas                             /s/ Jay M. Short
--------------------------------             -----------------------------------
Dr. Mario Thomas                             Dr. Jay M. Short
President                                    CEO, President and CTO

                                      10.
<PAGE>

                                   EXHIBIT A

                             [*****] Patent Rights

Issued Patent Number/
Serial Number        Title

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

                                               *Confidential Treatment Requested
<PAGE>

                                   EXHIBIT B

                             [*****] Patent Rights

Issued Patent Number/
Serial Number        Title

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

[*****]                [*****]

                                               *Confidential Treatment Requested

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