FUEL ALCOHOL PRODUCTION - ASSESSMENT OF SELECTED COMMERCIAL PROTEASES FOR VERY HIGH GRAVITY WHEAT MASH FERMENTATION

Seven commercial proteolytic enzymes were studied for use in very high gravity (VHG) fermentation. Wheat mashes containing 35 g dissolved solids per 100 ml were prepared and fermented at 20 degrees C with active dry Saccharomyces cerevisiae. Proteases were assessed for their ability to hydrolyze soluble wheat proteins toffee amino nitrogen and to reduce the viscosity of VHG wheat mashes. It was found that the increased levels of yeast-assimilable nitrogen and reduced mash viscosity stimulated the rate of VHG fermentation. Ethanol yield was not appreciably affected, nor did the addition of proteolytic enzymes adversely affect saccharification by the glucoamylase enzyme. Therefore, under VHG conditions, utilization of proteases could eliminate the need for supplementing wheat mash with assimilable nitrogenous yeast foods. These data further contribute to the industrial assessment of VHG fermentation technology for the manufacture of fuel alcohol from wheat.