EXHIBIT 23.1
CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the 1996 Stock Option Plan and 2000 Employee Stock Purchase Plan of our report dated February 7, 2003, with respect to the financial statements of Kosan Biosciences Incorporated included in its Annual Report (Form 10-K) for the year ended December 31, 2002, filed with the Securities and Exchange Commission.
/s/ ERNST & YOUNG LLP
Palo Alto, California
September 3, 2003