Auxilliary Hemicellulase Enzymes in Core Enzyme Cocktail

An international scientific research team from the United States and China (Michigan State University, Lucigen Corporation, and JiLin Rorgoo Renewable Energy Development Company) report the successful use of auxiliary hemicellulase enzymes with core cellulose enzymes to increase sugar yields in the saccharification of AFEX (Ammonia Fiber Explosion) pretreated corn stover.

Hemicellulases are enzymes which catalyze the conversion (sometimes called "saccharification") of hemicelluloses in plant biomass, into their component 5-carbon sugars (or pentoses). Cellulases, on the other hand, catalyze the saccharification of celluloses into their component 6-carbon sugars (hexoses). Both sugars are subsequently fermented to ethanol.

According to the researchers, AFEX- pretreatment of lignocellulosic plant biomass "cleaves lignin-carbohydrate complexes without physically extracting hemicellulose or lignin into separate process streams; hence, efficient hydrolysis of AFEX treated biomass to achieve both high glucose and xylose yields requires supplementing the cellulases with hemicellulases and other accessory enzymes."

Results showed that supplementing 'core fungal cellulases' with auxiliary hemicellulase enzymes in the 'enzyme cocktail' synergistically improved the saccharification of AFEX pretreated corn. Higher glucose and xylose yields (80% and 70%, respectively) were obtained at moderate enzyme loadings, when compared to commercially available enzymes. The full results of the study are published in the open-access journal, Biotechnology for Biofuels.