Exhibit 10.6

JOINDER AGREEMENT

THIS JOINDER IN MASTER SECURITY AGREEMENT, (this “Joinder”) is executed as of
July 24, 2009 by PetroAlgae Inc., a Delaware corporation (“Joining Party”) and
PA LLC (f/k/a PetroAlgae, LLC) (“PA”) and delivered to LV Administrative
Services, Inc. as administrative and collateral agent (the “Agent”) for
PetroTech Holdings, Corp. (“PetroTech” and together with Agent, individually,
each a “Creditor Party” and collectively, the “Creditor Parties”). Except as
otherwise defined herein, terms used herein and defined in the Master Security
Agreement (as defined below), as applicable, shall be used herein as therein
defined.

W I T N E S S E T H:

WHEREAS, PA and the Agent, have entered into a Master Security Agreement dated
August 21, 2008 and amended and restated as of the date hereof (as further
amended, restated, modified and/or supplemented from time to time, the “Master
Security Agreement”);

WHEREAS, the Joining Party shall become an Assignor under the Master Security
Agreement;

NOW, THEREFORE, in consideration of the foregoing and other benefits accruing to
the Joining Party, the receipt and sufficiency of which are hereby acknowledged,
the Joining Party hereby makes the following representations and warranties to
the Creditor Parties and hereby covenants and agrees with the Creditor Parties
as follows:

NOW, THEREFORE, the Joining Party agrees as follows:

1. By this Joinder, the Joining Party becomes an Assignor for all purposes under
the Master Security Agreement.

2. PA and the Joining Party agrees that, upon the Joining Party’s execution
hereof, the Joining Party will become an Assignor under, and as defined in, the
Master Security Agreement, and will be bound by all terms, conditions and duties
applicable to an Assignor under the Master Security Agreement. Without
limitation of the foregoing and in furtherance thereof, as security for the due
and punctual payment of the Obligations (as defined in the Master Security
Agreement), PA and the Joining Party hereby pledges, hypothecates, assigns,
transfers, sets over and delivers to the Agent for the benefit of PetroTech and
grants to the Agent for the benefit of PetroTech a security interest in all
Collateral (as defined in the Master Security Agreement), if any, now owned or,
to the extent provided in the Master Security Agreement, hereafter acquired by
it.

3. In connection with the grants by the Companies and the Joining Party,
pursuant to paragraphs 2 above, of a security interest in all of its right,
title and interest in the Collateral (as defined in each of the Master Security
Agreement and the

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Equity Pledge Agreement) in favor of the Agent for the benefit of PetroTech, the
Joining Party (i) agrees to execute (if necessary) and deliver to the Agent such
financing statements, in form acceptable to the Agent, as the Agent may request
or as are necessary or desirable in the opinion of the Agent to establish and
maintain a valid, enforceable, first priority perfected security interest in the
Collateral (as defined in each of the Master Security Agreement) owned by the
Joining Party, (iii) authorizes the Agent to file any such financing statements
without the signature of the Joining Party where permitted by law (such
authorization includes a description of the Collateral as “all assets and all
personal property, whether now owned and/or hereafter acquired” of the Joining
Party (or any substantially similar variation thereof)) and (iv) agrees to
execute and deliver to the Agent assignments of United States trademarks,
patents and copyrights (and the respective applications therefor) to the extent
requested by the Agent.

4. Without limiting the foregoing, the Joining Party and the Companies, hereby
makes and undertakes, as the case may be, each covenant, representation and
warranty made by each Assignor pursuant to the Master Security Agreement and
agrees to be bound by all covenants, agreements and obligations of an Assignor
pursuant Master Security Agreement, and all other related agreements to which it
is or becomes a party.

5. Schedule A to the Master Security Agreement is hereby amended by
supplementing such Schedule with the information contained on Schedule A
attached hereto as Annex I.

6. This Joinder shall be binding upon the parties hereto and their respective
successors and permitted assigns and shall inure to the benefit of and be
enforceable by each of the parties hereto and its successors and permitted
assigns, provided, however, PA nor the Joining Party may assign any of its
rights, obligations or interest hereunder without the prior written consent of
the Creditor Parties. THIS JOINDER SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE
WITH AND GOVERNED BY THE LAW OF THE STATE OF NEW YORK. This Joinder may be
executed in any number of counterparts, each of which shall be an original, but
all of which shall constitute one instrument. In the event that any provision of
this Joinder shall prove to be invalid or unenforceable, such provision shall be
deemed to be severable from the other provisions of this Joinder which shall
remain binding on all parties hereto.

7. The effective date of this Joinder is July 24, 2009.

IN WITNESS WHEREOF, the Joining Party and the Companies have caused this Joinder
to be duly executed as of the date first above written.

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PETROALGAE INC. By:   /s/ David P. Szostak   Name: David P. Szostak   Title:
  President PA LLC By:   /s/ Ottmar Dippold   Name: Ottmar Dippold   Title:
  CEO

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Accepted and Acknowledged by:

LV ADMINISTRATIVE SERVICES, INC.,

as Agent

By:   /s/ Patrick Regan   Name: Patrick Regan   Title:   Authorized Signatory
PETROTECH HOLDINGS, CORP. By:   /s/ Patrick Regan   Name: Patrick Regan   Title:
  Authorized Signatory

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ANNEX I

SCHEDULE A

 

Entity

   Jurisdiction of Formation    Organizational
Identification Number

PA LLC

   Delaware    4224141

PETROALGAE INC.

   Delaware    4421184