Researchers with DOE’s Joint BioEnergy Institute (JBEI) have engineered the first strains of Escherichia coli bacteria that can digest switchgrass biomass and synthesize its sugars into all three of those transportation fuels. The microbes are even able to do this without any help from enzyme additives.
“This work shows that we can reduce one of the most expensive parts of the biofuel production process, the addition of enzymes to depolymerize cellulose and hemicellulose into fermentable sugars,” says Jay Keasling, CEO of JBEI and leader of this research. Keasling also holds appointments with Berkeley Lab and UC Berkley. “This will enable us to reduce fuel production costs by consolidating two steps – depolymerizing cellulose and hemicellulose into sugars, and fermenting the sugars into fuels – into a single step or one pot operation.”
Advanced biofuels made from the lignocellulosic biomass of non-food crops and agricultural waste are widely believed to represent the best source of renewable liquid transportation fuels. Unlike the simple sugars in corn grain, the cellulose and hemicellulose in plant biomass are difficult to extract in part because they are embedded in a tough woody material called lignin. Once extracted, these complex sugars must first be converted or hydrolyzed into simple sugars and then synthesized into fuels.
At JBEI, a DOE Bioenergy Research Center led by Berkeley Lab, one approach has been to pre-treat the biomass with an ionic liquid (molten salt) to dissolve it, then engineer a single microorganism that can both digest the dissolved biomass and produce hydrocarbons that have the properties of petrochemical fuels.