POWER OF ATTORNEY

KNOW ALL BY THESE PRESENTS, that the undersigned hereby constitutes and appoints each of Douglas T. Sheehy and
Dave Swarthout, signing singly, with full power of substitution, as the undersigned's true and lawful
attorney-in-fact to:

(1)	prepare, execute in the undersigned's name and on the undersigned's behalf, and submit to the U.S.
Securities and Exchange Commission (the "SEC") a Form ID, including amendments thereto, and any other documents
necessary or appropriate to obtain codes and passwords enabling the undersigned to make electronic filings with
the SEC of reports required by Section 16(a) of the Securities Exchange Act of 1934 or any rule or regulation of
the SEC;

(2)	execute for and on behalf of the undersigned, in the undersigned's capacity as an officer and/or director
of Codexis, Inc. (the "Company"), and/or 10% holder of the Company's capital stock, Forms 3, 4, and 5 and any
amendments thereto in accordance with Section 16(a) of the Securities Exchange Act of 1934 and the rules
thereunder;

(3)	do and perform any and all acts for and on behalf of the undersigned which may be necessary or desirable
to complete and execute any such Form 3, 4, or 5, complete and execute any amendment or amendments thereto, and
timely file such form with the SEC and any stock exchange or similar authority; and

(4)	take any other action of any type whatsoever in connection with the foregoing which, in the opinion of
such attorney-in-fact, may be of benefit to, in the best interest of, or legally required by, the undersigned,
it being understood that the documents executed by such attorney-in-fact on behalf of the undersigned pursuant
to this Power of Attorney shall be in such form and shall contain such terms and conditions as such
attorney-in-fact may approve in such attorney-in-fact's discretion.

The undersigned hereby grants to each such attorney-in-fact full power and authority to do and perform any and
every act and thing whatsoever requisite, necessary, or proper to be done in the exercise of any of the rights
and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally
present, with full power of substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be done by
virtue of this power of attorney and the rights and powers herein granted. The undersigned acknowledges that the
foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor
is the Company assuming, any of the undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file
Forms 3, 4, and 5 with respect to the undersigned's holdings of and transactions in securities issued by the
Company, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing
attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 4th day of
September, 2012.

Signature: /s/ David O'Toole
		David O'Toole