Chemical Process Produces Simple, Fermentable Sugars from Raw Biomass
A GLBRC research team has developed a promising new chemical method to liberate the sugar molecules trapped inside inedible plant biomass, a key step in the creation of cellulosic biofuels. The new chemical process combines ionic liquids and dilute acid to degrade cellulosic biomass without the use of cellulases. In this approach, ionic liquids make cell-wall polysaccharides accessible to chemical reactions by decrystallizing lignocellulosic biomass and dissolving cellulose. Then, dilute hydrochloric acid at 105°C is used to hydrolyze cellulose and hemicellulose into individual sugar subunits. Applying this process to pure cellulose resulted in nearly 90% yield of glucose, and applying it to raw corn stover achieved sugar yields of 70% to 80%. By adding the right balance of water to the mixture, the researchers reduced the formation of unwanted by-products and demonstrated significant improvement in fermentable sugar yields from ionic liquid treatment of lignocelluloses with yields comparable to those of enzymatic hydrolysis. Ionexclusion chromatography was used to separate sugars from the reaction mixture and recover the ionic liquids for reuse. Sugars recovered from the hydrolyzed stover were readily converted to ethanol by Escherichia coli and the yeast Pichia stipitis.
This research was reported in Binder, J. B., and R. T. Raines. 2010. “Fermentable Sugars by Chemical Hydrolysis of Biomass,” Proceedings of the National Academy of Sciences 107, 4516-21.