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WHENEVER CONFIDENTIAL INFORMATION IS OMITTED HEREIN (SUCH OMISSIONS ARE DENOTED
BY AN ASTERISK*), SUCH CONFIDENTIAL INFORMATION HAS BEEN SUBMITTED SEPARATELY TO
THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL
TREATMENT.

                               FIRST AMENDMENT TO
                    TECHNOLOGY ALLIANCE AND OPTION AGREEMENT

     This First Amendment to Technology Alliance and Option Agreement (this
"Amendment") dated as of September 8, 2005 (the "Effective Date") is by and
between ADM Polymer Corporation, a corporation duly incorporated and validly
existing under the laws of the State of Delaware, with headquarters located at
4666 Faries Parkway, Decatur, IL 62526 ("ADM Sub"), and Metabolix, Inc., a
corporation duly incorporated and validly existing under the laws of the State
of Delaware, with headquarters located at 21 Erie Street, Cambridge, MA
021394260 ("MBX") (MBX and ADM Sub are collectively the "Parties" and each is a
"Party").

                                    RECITALS

     WHEREAS, MBX and ADM Sub entered into that certain Technology Alliance and
Option Agreement dated as of November 4, 2004 (the "Agreement"); and

     WHEREAS, MBX and ADM Sub now desire to modify the terms of the Agreement as
set forth herein.

     NOW, THEREFORE, in consideration of the recitals and the mutual covenants
and promises contained herein, and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the Parties hereto
do hereby agree as follows:

                                    ARTICLE 1
                                   DEFINITIONS

     1.1 DEFINITIONS. Capitalized terms used but not defined herein shall have
the meaning ascribed to them in the Agreement.

                                   ARTICLE 2
                        AMENDMENTS AND ADDITIONS TO TERMS

     2.1 AMENDMENT TO ARTICLE 1. Article 1 of the Agreement is hereby amended by
deleting the existing definition for "Fermentation Performance Parameters" and
replacing it with the following text:

          "FERMENTATION PERFORMANCE PARAMETERS" means the various parameters for
     production of PHA Cell Paste through fermentation at the * scale as set
     forth on AMENDED EXHIBIT B.

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     2.2 AMENDMENT OF SECTION 3.1. The Agreement is hereby amended by deleting
the existing Section 3.1 in its entirety and replacing it with the following
text:

          "3.1 GOAL OF TECHNOLOGY ALLIANCE PROGRAM. The goal of the Technology
     Alliance Program is to (i) produce PHA Cell Paste, in a fermenter having a
     capacity of approximately *, and at ADM Sub's option then in a fermenter
     having a capacity of approximately *, in all cases, in a manner and with
     results that meet the applicable Fermentation Performance Parameters; (ii)
     demonstrate recovery of PHA Material in a manner and with results that meet
     the Recovery Performance Parameters (the items listed in the foregoing
     "(i)" and "(ii)" collectively are the "Technical Aspects of the Goal"); and
     (iii) based upon the results of (i) and (ii) above, have ADM Sub develop
     and the TAC agree upon a completed master plan for Construction of the ADM
     Sub Manufacturing Facility, including without limitation, surveys,
     blueprints, and engineering studies, which master plan shall be organized
     into a detailed, multiphase process for undertaking and completing
     Construction of the ADM Sub Manufacturing Facility and which shall have a
     project budget with projected detailed expenditures provided for each phase
     of the Construction process, all of which shall be, in form and substance,
     suitable for ADM Sub's management and board of directors to make a
     determination to approve the expenditures for the ADM Sub Manufacturing
     Facility as and to the extent required by ADM Sub's corporate governance
     polices and procedures (the "ADM Sub Construction Master Plan and Budget")
     (collectively the "Goal"). Successful completion of the Goal is intended to
     confirm the potential economics of producing PHA Material at commercial
     scale as part of a long-term commercial alliance."

     2.3 ADDITION OF SECTION 3.2.4.1. The Agreement is hereby amended by adding
the following Section 3.2.4.1:

          "3.2.4.1 INITIAL RECOVERY OPERATIONS. The Parties hereby agree that
     MBX will enter into an agreement to obtain access to toll recovery
     services, from a Third Party (the "Toll Producer") on substantially the
     terms set forth in the tolling agreement attached hereto as Schedule A (the
     "Tolling Agreement"). These recovery services are anticipated to last until
     approximately March of 2006 and to result in the recovery of up to
     approximately thirty five (35) metric tons of PHA Material (the "Initial
     Recovery Services"). Except as specifically set forth herein, the Parties'
     rights and obligations with respect to the Initial Recovery Services and
     the PHA Material produced in connection therewith shall be governed by the
     Agreement as activities conducted under Section 3.2.4. Responsibility for
     the fees charged by the Toll Producer under the Tolling Agreement for the
     Initial Recovery Services, related equipment and capital expenses, and the
     reasonable out-of-pocket expenses of the Parties in performing technical
     support or auditing of the Initial Recovery Services, including, for
     example, travel and lodging expenses, but excluding, salary and benefits
     paid or payable to employees or representatives of the Parties
     participating in such activities (collectively, "Tolling Expenses") shall
     be shared equally by the Parties, subject to the limitations set forth
     herein. The Parties shall, determine reasonable


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     methods for promptly accounting for the total Tolling Expenses on a monthly
     basis and making such payments as are necessary in order to give effect to
     the equal sharing of the Tolling Expenses. Notwithstanding the foregoing:
     (i) MBX shall be solely responsible for the operating expenses (including
     its internal costs and the costs of the Toll Producer but excluding the
     related equipment and capital expenses) until (y) the earlier of TAC's
     determination that the recovery of PHA Material during a Recovery Campaign
     was achieved in a manner and with results that met the Recovery Performance
     Parameters as defined in Amended Exhibit E on any one of the three
     specified compositions, or ADM Sub's payment of the milestone payment set
     forth in Section 5.1 related to the Recovery Performance Parameters, and
     (z) ADM's receipt of a letter from the U.S. Drug Enforcement Administration
     advising that polyhydroxyalkanoate containing gamma-hydroybutyric acid as
     part of the polymer chain will not be regulated as a controlled substance
     under the Controlled Substances Act and any Drug Enforcement Administration
     regulations, (ii) ADM shall not be obligated to pay in excess of * of
     Tolling Expenses hereunder; (iii) ADM shall not be obligated to pay in
     excess of * of the equipment and capital expenses comprising the Tolling
     Expenses hereunder; and (iv) ADM shall not be responsible for any Tolling
     Expenses incurred after the end of the term of this Agreement as set forth
     in Section 8.1, except as otherwise provided under the Commercial Alliance
     Agreements, if applicable. In the event ADM terminates this Agreement or
     decides not to exercise the Option, then MBX shall pay ADM an amount equal
     to one half of the depreciated book value of any removable assets (i.e.,
     not fixtures) that are listed on the Consignment Agreement or any Addendum
     to Consignment Agreement (as such agreement and such addendum are
     referenced in the Tolling Agreement), the purchase price for which was
     funded equally by the Parties. MBX agrees to provide ADM with equal access
     to the facility of the Toll Producer as and to the extent such access is
     made available to MBX and its designees under the Tolling Agreement. The
     PHA Material produced in connection with the Initial Recovery Services
     shall be part of the Technology Alliance Output or Marketing Material as
     determined under Section 3.3, and, in the event it is sold by MBX, all
     revenues generated by such sales shall be applied against Tolling Expenses
     before such expenses are allocated for payment by the Parties. The Parties
     agree to work together to determine the costs (capital expenditures and
     operating costs) to use ADM's Vitamin C facility for pilot sourcing of PHA
     Material in the event ADM exercises the Option; provided, however, nothing
     herein shall preclude ADM from utilizing all or any portion of the Vitamin
     C facility for other uses."

     2.4 AMENDMENT OF SECTION 3.3. The Agreement is hereby amended by deleting
the existing Section 3.3 in its entirety and replacing it with the following
text:

          "3.3 OUTPUT FROM TECHNOLOGY ALLIANCE PROGRAM. ADM Sub will use
     Commercially Reasonable Efforts to produce PHA Cell Paste in such amounts
     as result from the operations set forth in the Technology Alliance Plan
     until it has satisfied the Fermentation Performance Parameters (the
     "Technology Alliance Output") and such additional amounts thereafter as the
     Parties may agree to in


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     writing (the "Marketing Material") for use by MBX in developing the market
     for PHA Material. The Technology Alliance Output and the Marketing Material
     will be made available by ADM Sub to MBX as set forth in this Section 3.3."

     2.5 AMENDMENT OF SECTION 3.3.1. The Agreement is hereby amended by deleting
the existing Section 3.3.1 in its entirety and replacing it with the following
text:

          "3.3.1 ANALYSIS OF TECHNOLOGY ALLIANCE OUTPUT. MBX will use the
     Technology Alliance Output to demonstrate recovery of PHA Material in
     accordance with Section 3.2.4 and the Technology Alliance Plan, and ADM
     shall provide the Technology Alliance Output to MBX as MBX may require to
     perform such recovery demonstration, including the Initial Recovery
     Services. Further, the Technology Alliance Output will be used by the
     Parties to perform such evaluation and analysis as is necessary or useful
     in determining whether the Parties have achieved the Goal. Without limiting
     the foregoing statement, the Technology Alliance Output will be evaluated
     and analyzed by the Parties, in accordance with the procedures and methods
     set forth in the Technology Alliance Plan, to determine whether the
     Technology Alliance Output meets the Fermentation Performance Parameters
     and whether PHA Material recovered from the Technology Alliance Output
     meets the Recovery Performance Parameters."

     2.6 AMENDMENT OF SECTION 3.3.2. The Agreement is hereby amended by deleting
the existing Section 3.3.2 in its entirety and replacing it with the following
text:

          "3.3.2 PURCHASE OF TECHNOLOGY ALLIANCE OUTPUT BY MBX; COST SHARING FOR
     MARKETING MATERIAL. MBX shall have the right, but not the obligation, to
     purchase the Technology Alliance Output that is not required to perform the
     recovery demonstration described in Section 3.3.1 above from ADM Sub at a
     price of * of PHA Material contained within the PHA Cell Paste, on a one
     hundred percent (100%) purity basis; provided such price shall be reduced
     to * at such times as ADM is responsible for equally sharing the Tolling
     Expenses (including the operating expenses) pursuant to Section 3.2.4.1.
     MBX shall purchase the Marketing Material, irrespective of whether the
     Marketing Material meets the applicable specifications or not, at fifty
     percent (50%) ADM Sub's Manufacturing Cost, F.O.B. Decatur, Illinois. MBX
     may exercise this purchase option at any time, and from time-to-time,
     during the Technology Alliance Program and up to thirty (30) days after the
     expiration or termination of the Technology Alliance Program, by written
     notice to ADM Sub, stating its desire to purchase, the quantity to be
     purchased (up to the total amount that is then available) and shipping and
     delivery instructions. ADM Sub shall invoice MBX for amounts so purchased
     no sooner than at the time of delivery and the purchase price for amounts
     ordered and delivered in accordance herewith shall be payable by MBX within
     thirty (30) days of receipt of an invoice from ADM Sub by wire transfer of
     immediately available funds to an account in the United States designated
     by ADM Sub. Technology Alliance Output and Marketing Material purchased
     hereunder shall be purchased "as is," without warranty of any kind other
     than that the Technology Alliance Output and Marketing Material shall have


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     been stored and handled, from the time of production until the delivery to
     MBX, in accordance with the requirements of the Technology Alliance Plan or
     as otherwise agreed by the Parties. Technology Alliance Output and
     Marketing Material purchased by MBX shall be used by MBX for performing its
     obligations pursuant to this Agreement and for market development
     activities benefiting the Parties and the potential Commercial Alliance
     between them. Technology Alliance Output that is not purchased by MBX shall
     be used by ADM Sub solely for internal research and development purposes,
     or if not so used, ADM Sub shall either store (for later sale to MBX or the
     Joint Sales Company or for later use by ADM Sub solely for internal
     research purposes) or dispose of the unused Technology Alliance Output, at
     ADM Sub's option."

     2.7 AMENDMENT OF SECTION 4.3. The Agreement is hereby amended by deleting
the existing Section 4.3 in its entirety and replacing it with the following
text:

          "4.3 GRANT OF OPTION. MBX hereby grants to ADM Sub the right and
     option to enter into a commercial alliance for the further research,
     development, manufacture, use, sale and importation of the PHA Material and
     PHA Formulations on the terms and conditions set forth in the Commercial
     Alliance Agreements (the "Option"). The Option shall be exercisable by ADM
     Sub at any time after Effective Date and until thirty (30) days after the
     expiration of the term of this Agreement, by written notice to MBX;
     provided, however, that, in either case, the Option shall not be
     exercisable if and for so long as ADM Sub is in breach of this Agreement.
     Following the exercise of the Option, the Parties shall promptly execute
     and deliver the Commercial Alliance Agreements in accordance with this
     Agreement."

     2.8 AMENDMENT OF SECTION 5.1. The Agreement is hereby amended by deleting
the existing Section 5.1 in its entirety and replacing it with the following
text:

          "5.1 PAYMENTS. Within ten (10) days after the Effective Date, ADM Sub
     shall pay to MBX the amount of three million dollars ($3,000,000) as a
     non-refundable, non-creditable upfront payment. Within ten (10) days
     following the TAC's determination that the production of PHA Cell Paste in
     a fermenter having a capacity of approximately * was achieved in a manner
     and with results that met the applicable Fermentation Performance
     Parameters, ADM Sub shall pay to MBX the amount of five hundred thousand
     dollars ($500,000) as a non-refundable, non-creditable milestone payment.
     Within ten (10) days following the TAC's determination that the recovery of
     PHA Material was achieved in a manner and with results that met the
     Recovery Performance Parameters, ADM Sub shall pay to MBX the amount of
     five hundred thousand dollars ($500,000) as a non-refundable,
     non-creditable milestone payment. Within ten (10) days following the first
     to occur of: (i) the achievement of the Goal and (ii) the exercise of the
     Option by ADM Sub, ADM Sub shall pay to MBX the amount of one million
     dollars ($1,000,000) as a non-refundable, non-creditable milestone payment.
     Anything herein to the contrary notwithstanding, in the event that ADM Sub
     desires to exercise the Option in


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     accordance with Section 4.3, the above-described upfront payment and the
     three (3) milestone payments, to the extent not already paid, shall be due
     and payable in full as a pre-condition to the exercise of the Option.
     Amounts due under this Section 5.1 shall be payable by wire transfer of
     immediately available funds to an MBX bank account in accordance with
     instructions to be provided to ADM Sub by MBX."

     2.9 AMENDMENT OF SECTION 5.2. The Agreement is hereby amended by deleting
the existing Section 5.2 in its entirety and replacing it with the following
text:

          "5.2 OTHER EXPENSES. Except as provided in Section 5.1, Section
     3.2.4.1 and Section 3.3.2, each Party shall bear its own costs and expenses
     incurred in performing under this Agreement."

     2.10 AMENDMENT OF EXHIBITS. The Agreement is hereby amended by deleting the
existing Exhibit B and replacing it with the text set forth in Amended Exhibit B
attached hereto, by deleting existing Exhibit D and replacing it with the text
set forth in Amended Exhibit D attached hereto, and by deleting the existing
Exhibit E and replacing it with the text set forth in Amended Exhibit E attached
hereto.

                                   ARTICLE 3
                              CONFIRMATION OF TERMS

     3.1 CONFIRMATION OF TERMS. This Amendment shall be a part of the Agreement
and shall be governed in accordance with the terms and conditions set forth
therein, as the same are amended hereby, including without limitation, the terms
and conditions set forth in Article XI of the Agreement, entitled
"Miscellaneous." The Parties hereby agree and acknowledge that, except as
expressly set forth herein, the Agreement shall remain in full force and effect
in accordance with its terms.


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     IN WITNESS WHEREOF, the Parties hereto have caused this Amendment to be
executed by their duly authorized representatives as of the day and year above
written.

                                        ADM POLYMER CORPORATION


                                        By: /s/ John D. Rice
                                            ------------------------------------
                                        Name: John D. Rice
                                        Title: President


                                        METABOLIX, INC.


                                        By: /s/ James J. Barber
                                            ------------------------------------
                                        Name: James J. Barber
                                        Title: President


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