Exhibit 4.2

          

          

      

      
            D  E  L  A  W  A  R  E     Z  Y  M  R  G  E  N  ,  I  C  .  C  O  E  R  P  O  R  A  N  T  E  SEALApril
            24,2013    ZY  This certifies that  is the record holder ofFULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, $0.001 PAR VALUE PER SHARE, OFZymergen, Inc., a public benefit corporationtransferable on the books of the Corporation in person or
            by duly authorized attorney upon surrender of this Certificate properly endorsed. This Certificate is not valid until countersigned by the Transfer Agent and registered by the Registrar.WITNESS the facsimile seal of the Corporation and the
            facsimile signatures of its duly authorized officers. Dated:  INCORPORATED UNDER THE LAWS OF THE STATEOF DELAWARE  COUNTERSIGNED AND REGISTERED:AMERICAN STOCK TRANSFER & TRUST COMPANY, LLC  (BROOKLYN, NY)  TRANSFER AGENT AND
            REGISTRAR  BY:  AUTHORIZED SIGNATURE  CHIEF EXECUTIVE OFFICER  SECRETARY  CUSIP XXXXXX XX XSEE REVERSE FOR CERTAIN DEFINITIONS AND LEGENDS 

      

    

     

    
      
        


    

    
      
        

      

      
         The Corporation shall furnish without charge to each stockholder who so requests a statement of the
            powers, designations, preferences and relative, participating, optional or other special rights of each class of stock of the Corporation or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights.
            Such requests shall be made to the Corporation’s Secretary at the principal office of the Corporation.KEEP THIS CERTIFICATE IN A SAFE PLACE. IF IT IS LOST, STOLEN, OR DESTROYED THE CORPORATION WILL REQUIRE A BOND INDEMNITY AS A CONDITION TO THE
            ISSUANCE OF A REPLACEMENT CERTIFICATE.The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicablelaws or regulations:  Additional
            abbreviations may also be used though not in the above list.  TEN COM – as tenants in common TEN ENT – as tenants by the entiretiesJT TEN – as joint tenants with right ofsurvivorship and not as tenants in commonCOM PROP – as community
            property  UNIF GIFT MIN ACT – ......................... Custodian .........................  (Cust) (Minor)under Uniform Gifts to Minors  Act..............................................................................(State)  UNIF TRF MIN ACT
            – ................. Custodian (until age ..................)(Cust)..................................... under Uniform Transfers(Minor)to Minors Act............................................................(State)  FOR VALUE RECEIVED, hereby
            sell(s), assign(s) and transfer(s) unto  PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE         sharesof the capital stock represented by within Certificate, and do hereby irrevocably constitute and appoint
            attorney-in-fact to transfer the said stock on the books of the within named Corporation with full power of the substitution in the premises.Dated   X X NOTICE: THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON
            THEFACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATSOEVER.  By THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION, (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND
            CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT TO S.E.C. RULE 17Ad-15. GUARANTEES BY A NOTARY PUBLIC ARE NOT ACCEPTABLE. SIGNATURE GUARANTEES MUST NOT BE DATED.  Signature(s) Guaranteed:  (PLEASE
            PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)