Biotech biofuels

Bacteria May Affordably Turn Plants into Diesel by 2012

by Ben Block on February 1, 2010

Photo courtesy Lawrence Berkeley National Laboratory

The manipulated E. coli strain creates more fatty acids than the bacterium itself requires and can generate biodiesel when interacted with biomass sugars." class="caption" align="" height="250" width="250">

Photo courtesy Lawrence Berkeley National Laboratory

The manipulated E. coli strain creates more fatty acids than the bacterium itself requires and can generate biodiesel when interacted with biomass sugars.

Bacteria that convert plants into diesel could become a widely available method for creating alternative fuels at commercial prices within the next two years.

U.S. researchers announced progress last week in converting sugars directly into biodiesel by modifying the Escherichia coli bacterium (E. coli). Their biodiesel, a fossil fuel alternative, can be transported in diesel pipelines and burned in standard diesel engines, releasing far fewer greenhouse gases than conventional diesel.

Analysts have linked grain-based biofuels such as corn ethanol to increased food prices and tropical deforestation. E. coli-generated biodiesel fuel may not compete with leading food sources, however, if the bacteria can effectively convert cellulosic feedstock such as switchgrass or corn husks.

The development, a collaboration of government, university, and private researchers, was hailed as a "milestone" in producing biodiesel at lower costs. Similar biodiesel efforts require expensive chemical processes to convert biomass into fuel.

"The fact that our microbes can produce a diesel fuel directly from biomass with no additional chemical modifications is exciting and important," said project leader Jay Keasling, chief executive officer for the U.S. Department of Energy's Joint BioEnergy Institute, in a prepared statement. "Given that the costs of recovering biodiesel are nowhere near the costs required to distill ethanol, we believe our results can significantly contribute to the ultimate goal of producing scalable and cost effective advanced biofuels and renewable chemicals."

U.S. Energy Secretary Steven Chu called Keasling last week to ask whether the E. coli process could become commercially viable without government subsidies. "He said we will know in two years," Chu said at an electric vehicle conference in Washington, D.C.

E. coli was previously known to synthesize fatty acids, key ingredients in forming biofuels efficiently. But the bacterium manufactures only as many fatty acids as it needs to survive - a limitation that had challenged inventors hoping to create enough biodiesel to replace conventional fuels.

The research team from the Joint BioEnergy Institute and biotech firm LS9 were able to manipulate an E. coli strain to create more fatty acids than the bacterium itself would need. When the E. coli interacted with Brazilian sugar cane, it fermented the plant's sugars and generated a surplus of fatty acids, producing biofuel straight from the biomass, the team explains in the current issue of the journal Nature..

LS9 and the U.S. Department of Energy's Argonne National Laboratory calculated that the newly developed biodiesel reduces greenhouse gas emissions 85 percent compared with conventional diesel, calculated over the fuel's life cycle.

LS9 Vice President Stephen del Cardayre described the breakthrough as "a significant step toward the development of scalable, low-cost drop-in-compatible cellulosic fuels and chemicals." The project's next step will be adapting the process for fibers other than sugar cane, expanding its potential applications to grass or crop waste.

After LS9 struggled for funding in 2008 and 2009 due to decreased oil prices and the economic recession, the company received support from several funders, including the U.S. government and oil company Chevron. LS9 plans to open a commercial-scale demonstration plant this year.

Ben Block is a staff writer with the Worldwatch Institute.