Exhibit 10.3

EXECUTION VERSION

THIRD AMENDMENT TO SUBLEASE

THIS THIRD AMENDMENT TO SUBLEASE (“Third Amendment”) is effective as of July 12, 2011 (“Third Amendment Effective Date”), by and between FibroGen, Inc., a Delaware Corporation (“FibroGen”), and Solazyme, Inc., a Delaware corporation (“Solazyme”). This Third Amendment amends that certain Sublease entered into by and between Solazyme and FibroGen on December 31, 2009 (the “Original Sublease”), as amended by the First Amendment to Original Sublease on January 29, 2010 (the “First Amendment”) and the Second Amendment to Original Sublease on June 1, 2010 (the “Second Amendment” and together with the First Amendment are the “Prior Amendments”). The Prior Amendments together with the Original Sublease are hereinafter collectively referred to as the Sublease. Capitalized terms that are not defined in this Third Amendment shall have the meanings given to them in the Sublease.

BACKGROUND

A. Under the Sublease, Solazyme subleased from FibroGen office and laboratory space located, respectively, at 201 and 225 Gateway Boulevard, South San Francisco, California on the terms and conditions set forth therein.

B. FibroGen and Solazyme now desire to amend the Sublease to include approximately 22,011 rentable square feet located on the second floor of the building located at 201 Gateway Boulevard and thereby increase the Subleased Premises under the Sublease, as amended by this Third Amendment, from approximately 74,210 to 96,221 rentable square feet.

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THE PARTIES AGREE AS FOLLOWS:

“2.1 a) The area sublet by Solazyme subject to this Sublease is approximately 96,221 square feet of space (“Subleased Premises”) in the buildings located at 225 and 201 Gateway Blvd. as indicated in Attachment B-3 hereto.

The area comprising the Subleased Premises is calculated by adding the space exclusively occupied by Solazyme to the pro rata allocation (based upon a ratio of Solazyme’s square footage in the 201 and 225 Buildings relative to the balance of the building) of the common space in the 201 and 225 Buildings (including, but not limited to, common entrance and reception areas, common bathrooms, common hallways and common utilities), and the exterior walls and area under the drip line of the 201 and 225 Buildings.”

“7.1 Solazyme shall pay a monthly rent (“Base Rent”) to FibroGen for the Subleased Premises in phases corresponding to Rentable Area in the Subleased Premises as follows:

Solazyme shall pay Base Rent according to the following schedule:

The Base Rent amounts set forth in this Paragraph 7.1 shall be subject to equitable pro rata adjustment in the event occupancy of the Subleased Premises is not delivered to Subtenant on or before the dates set forth in the Original Sublease, the Prior Amendments or this Third Amendment. For the avoidance of doubt, Subtenant shall not incur or be obligated to pay monthly Base Rent for Building 201 prior to the 201 Building Occupancy Date; nor shall Solazyme be obligated to pay monthly Base Rent for the First Expanded Space prior to delivery of possession thereof; nor shall Solazyme be obligated to pay monthly Base Rent for the Second Expanded Space prior to delivery of possession thereof; nor shall Solazyme be obligated to pay monthly Base Rent for the Building 201 (2^nd Floor) Space prior to January 15, 2012 (“Rent Commencement”) thereof.”

“8.7 In the period between January 1, 2012 and January 14, 2012, Solazyme shall have early access to the Expanded Space for general business setup on a rent-free basis; provided, that, Solazyme shall pay the operating expenses (including PG&E, trash, etc.) for the Expanded Space arising during such early access period.”

“9.3 Upon execution of the Third Amendment, Solazyme shall provide a security deposit equal to the first full month’s rent for the Expanded Space. The Security Deposit shall be in the form of an irrevocable standby letter of credit, in form reasonably satisfactory to FibroGen.”

“10.4 Prior to January 15, 2012, FibroGen, at its sole cost and expense, shall professionally clean the Expanded Space, replace damaged ceiling tiles and window blinds, steam clean the carpets, patch the walls and touch up paint as needed in the Expanded Space. At Solazyme’s election, all or part of the existing cubicles and

furniture owned by FibroGen shall remain in place in the Expanded Space during the Term at no charge to Solazyme or removed, at FibroGen’s sole expense; provided that in the case of removal of any cubicles or furniture, Solazyme shall notify FibroGen of such election no later than February 15, 2012. Further, FibroGen shall deliver the Expanded Space in good working condition, including but not limited to, the roof, HVAC, electrical, plumbing, lighting and subject to the warranties and covenants set forth in this Section 10. Further, in accordance with Subparagraph 13.3, Solazyme shall deliver to FibroGen within 14 business days following January 15, 2012, a Damage List with respect to the Expanded Space and each of the parties’ respective rights and obligations under such Subparagraph shall apply in full to the Expanded Space.”

“20.2 FibroGen shall pay to Cornish & Carey Commercial all brokerage and other fees due in connection with the parties’ execution and delivery of the Third Amendment and indemnify, defend and hold harmless Solazyme with respect to any claims, costs and damages resulting from FibroGen’s breach of this Subparagraph 20.2 as provided in Subparagraph 20.1. The provisions of this Subparagraph 20.2 shall survive the termination of the Sublease, including the Third Amendment.”

“21.2 Prior to January 15, 2012, FibroGen shall remove at its sole expense existing building top-signage on the 201 Building.”

[IN WITNESS WHEREOF, the parties hereto have executed this Third Amendment effective as of the Third Amendment Effective Date.

Attachment B-3

Floor Plan-201 and 225 Gateway Boulevard