Redwood City, California and Minnetonka, Minnesota
April 16, 2002

Codexis, Inc., a wholly-owned subsidiary of Maxygen, Inc. (Nasdaq: MAXY), and Cargill Dow LLC announced today the signing of a collaboration agreement focused on the development of a novel synthesis for a key raw material for Cargill Dow's NatureWorks(TM) PLA (polylactide). Codexis will apply its proprietary protein modification technologies towards the creation of a novel natural-based process for the production of lactic acid, a key component in NatureWorks PLA.

The goal of the collaboration is to further improve Cargill Dow's novel low-cost process for the production of lactic acid from natural sugars derived from annually renewable resources, such as corn. Cargill Dow has worldwide commercialization rights for products generated from this improved production process. Codexis will receive technology access payments, and full research funding, and may receive research and commercialization milestones and royalties on any sales of products manufactured using its technologies.

NatureWorks(TM) PLA and NatureWorks(TM) fibers represent a shift to a future where raw materials are derived from annually renewable resources such as corn, rather than from the limited fossil resources used to make most conventional plastics today. Cargill Dow's breakthrough products will be shipped around the world for use in an array of consumer items including clothing, food packaging and bedding. NatureWorks PLA uses 20 to 50 percent less fossil resources than comparable petroleum based products because it is derived from annually renewable resources. This feature adds environmental benefits to the performance attributes of PLA.

"Codexis' proprietary technologies are ideally suited to create new molecules and catalyze novel chemical syntheses for important commercial products," said Dr. Alan Shaw, President of Codexis. "This relationship demonstrates the broad application of our technologies to diverse commercial markets and is further validation of our ability to affect multiple fermentation-based processes, enabling the transition towards cost effective and environmentally friendly manufacturing of industrially relevant chemicals. Cargill Dow's experience and manufacturing and marketing capabilities make them the ideal partner to commercialize this novel process."

"Cargill Dow feels strongly that more sustainable process development is key to the future success of business," says Dr. Pat Gruber, vice president and chief technology officer for Cargill Dow. "Codexis is one of the leading companies helping develop a new industrial revolution where renewable resources replace petroleum-based resources."

"This collaboration is a natural fit for Codexis," said Tassos Gianakakos, Director of Business Development for Codexis. "Cargill Dow is a pioneer in developing plastics, fibers and chemicals from natural sources and Codexis has developed a suite of technologies using nature's own catalysts to perform complex chemical reactions. Cargill Dow is committed to investing in technology and process improvements and recently announced the opening of their global-scale manufacturing
facility in Blair, Nebraska."

Founded in 1997, Cargill Dow LLC is based in Minnetonka, Minn. It is the first company to offer its customers a family of polymers derived entirely from annually renewable resources with the cost and performance necessary to compete with packaging materials and traditional fibers. The company has achieved this breakthrough by applying its unique technology to the processing of natural plant sugars to create a proprietary polylactide polymer (PLA).

Codexis, Inc., a wholly owned subsidiary of Maxygen, Inc., is a provider of high-value chemical products and services to the worldwide life science and fine chemical industry. Its proprietary technologies were designed for the rapid discovery and development of catalysts and processes for the efficient and cost-effective synthesis of valuable chemicals. Codexis intends to supply customers with catalysts, bulk pharmaceutical actives, advanced pharmaceutical intermediates, and chemical building blocks and intermediates. Its broad technology platform has been validated with the signing of six strategic alliances in the chemicals field, and Codexis has over 18 potential products and processes in its research pipeline, seven product candidates in development and three processes at commercial scale.

Codexis is a trademark of Codexis, Inc.; Maxygen is a trademark of Maxygen, Inc. and NatureWorks is a trademark of Cargill Dow LLC.  NatureWorks(TM) Trademark of Cargill Dow LLC