Engineered E. coli from Rice University part of USDA-funded project to develop drop-in fuels from biomass

1 March 2013

A process developed by researchers at Rice University is part of a USDA-funded $6.6-million project to convert lignocellulosic biomass to infrastructure-compatible renewable diesel, bio-lubricants, animal feed and biopower. (Earlier post.)

Patent-pending fermentation processes created by Rice bioengineer Ka-Yiu San and his colleagues use genetically modified E. coli bacteria to produce fatty acids from hydrolysates. Dr. San said his lab already gets an 80-to-90% yield of fatty acids from model sugars and hopes to improve that over the next few years. (San and his team also recently published a paper on their work on engineering E. coli to produce succinate (an ester of succinic acid) from soybean mash in the journal Bioresource Technology. (Earlier post.)

Adding another 1 or 2 percent doesn’t seem like much, but when you’re talking about making several million tons per year, it’s huge.

—Ka-Yiu San

The project, one of four projects receiving about $25-million in awards from the USDA, is led by Ceramatec Inc., a Utah-based company.

There are two ways to make fuel [from biomass]. You either make alcohols, or you make petroleum-like fuels that can go into current infrastructure. Our program is for infrastructure-compatible transportation fuels. There aren’t many ways to go from sugars to a diesel-like compound. The best way is to make fatty acids from the sugars microbially, as many labs have tried to do. But the Rice University process is definitely the winner.

—Mukund Karanjikar, innovation manager at Technology Holding LLC, project administrator

Postdoctoral researchers Xiujun Zhang and Mai Li have been nudging their bacteria toward efficient production of fatty acids for four years, San said. Zhang is responsible for the development of enzymes in E. coli that promote the efficient formation of free fatty acids, while Li, now at GlycosBio, worked to build microbial host strains for high-yield production.

The researchers screened hundreds of strains of E. coli and genetically combined the best qualities to reach a high yield.

One of the strains we developed is very interesting: Instead of excreting the fatty acid, it wants to keep it inside. So more than 70% of the weight of these cells is fatty acid. These are obese E. coli.

—Ka-Yiu San

Since the project began, the researchers have increased their production from a titer of 0.4 grams per liter to 14 grams per liter and are looking at ways to fine-tune the process.

The E. coli strains were developed in a project funded by the National Science Foundation’s Engineering Research Center for Renewable Chemicals. San is Rice’s E.D. Butcher Professor of Bioengineering and a professor of chemical and biomolecular engineering.

Resources

• Mai Li, Xiujun Zhang, Arpita Agrawal, Ka-Yiu San (2012) Effect of acetate formation pathway and long chain fatty acid CoA-ligase on the free fatty acid production in E. coli expressing acy-ACP thioesterase from Ricinus communis, Metabolic Engineering, Volume 14, Issue 4Pages 380-387 doi: 10.1016/j.ymben.2012.03.007

• Xiujun Zhang, Arpita Agrawal, Ka-Yiu San (2012) Improving fatty acid production in escherichia coli through the overexpression of malonyl coA-Acyl carrier protein transacylase. Biotechnology Progress, doi: 10.1002/btpr.716