Side Letter dated September 11, 2007



 EXHIBIT 10.8 
 [*] Certain information in this document has been omitted and filed separately with the Securities and Exchange Commission. Confidential treatment has been requested with respect to the omitted portions. 
  

			
	

	  	 Maxygen, Inc.
 200 Penobscot Drive

Redwood City, CA 94063
 650.298.5300 main
 650.364.2715 fax
 www.maxygen.com


 September 11, 2007 
 Codexis. Inc. 
 Attn: Doug Sheehy 
 200 Penobscot Drive 
 Redwood City, CA 94063 
  

	 	Re:	License Agreement effective as of March 28, 2002, by and between 

 Maxygen, Inc. and Codexis, Inc., as amended (the “Agreement”) 
 Dear Doug: 
 This letter confirms that, based on Codexis’ representations in its letter dated March 30, 2007, Codexis has satisfied the requirements of
(i) Section 2.1.6(a) of the License Agreement for SubField 8, Category (a), set forth on Exhibit G to the Agreement, and (ii) Section 2.1,6(d) of the Agreement for SubField 8, Category (b), set forth on Exhibit G to the
Agreement. 
 Accordingly, Maxygen agrees that, as of March 30, 2007, the fuels and fuel additives (and intermediates thereof) specified below, shall be
Supplemental Products: 
  

	 	a.	Fuel and/or fuel additives, where Biomass is the starting material for the applicable fuel and/or fuel additive, including without limitation the manufacture of compounds (e.g.,
fermentable sugars) which are intermediates in the process of producing fuel or fuel additives, where Biomass is the starting material for the applicable fuel and/or fuel additive and such intermediates are used solely in the production of fuel or
fuel additives, but specifically excluding the fuels and/or fuel additives in Category (b) below. 

  

	 	b.	Fuel and/or fuel additives made by the conversion of Biomass-derived oils into such fuel and/or fuel additives, including without limitation the manufacture of compounds which are
intermediates in the process of converting Biomass-derived oils into fuel and/or fuel additives, where such intermediates are used solely in the production of fuel or fuel additives. 

 For purposes of clarification, “fuel additives” means substances which are intended to be added to fuel to modify the characteristics of such
fuel, including, for example, biodegradability, combustibility, viscosity and/or emissions profile. 
 “Biomass” shall mean organic,
non-fossil, Plant-derived matter available on a renewable basis, including, for example, crops and/or trees grown or harvested for use for fuel 








 
and/or fuel additive production, agricultural food and feed crops, aquatic plants and, in each case, organic wastes derived from the foregoing, including
municipal wastes (e.g., newspapers). 
 Notwithstanding the above, no right or license is granted by this letter to Codexis to use any
Enabling Technology to alter or modify any gene(s) of any Plant to (a) [*], or (b) [*]; provided, however, Codexis may produce in Category II Plants chemicals that are Supplemental Products as set forth above. 
 In addition, Maxygen agrees that, in accordance with Section 1.55 of the Agreement, the Reserved SubField Termination Date for the Modified SubFields (i.e.,
SubFields 3, 8, 9 and 10) is extended until the period ending seven (7) years after the Amendment Date. 
 Capitalized terms used but not otherwise
defined herein shall have the meanings set forth in the Agreement. 
 Please indicate Codexis’ agreement to the foregoing by countersigning below.

  

	
	Yours sincerely,
	
	/s/ Michael S. Rabson
	Michael S. Rabson


  

			
	UNDERSTOOD AND AGREED
	BY CODEXIS, INC.
		
	By:	 	 /s/ Douglas Sheehy

	Name:	 	Douglas Sheehy
	Title:	 	VP, General Counsel
	Date:	 	September 12, 2007

  

 [*] Certain information in this document has been omitted and filed separately with the Securities and Exchange
Commission. Confidential treatment has been requested with respect to the omitted portions.