Fermentable sugar yields from AFEX-treated corn fiber and switchgrass at low enzyme levels

The presumably high cost of cellulase enzymes is seen as a major economic hurdle in ethanol fuel production from lignocellulosic biomass. One way to reduce cellulase costs is to use much less enzyme per unit of biomass hydrolyzed. The ammonia fiber explosion (AFEX) process produces a highly reactive biomass but the relationship between AFEX treatment conditions, enzyme usage and hydrolysis yields has never been thoroughly explored. This paper reports here the effects of AFEX treatment of switchgrass (Alamo cultivar) and corn fiber on the rates and yields of sugar production at low enzyme levels (between 1 and 10 IU/gram dry substrate). Theoretical yields of total reducing sugars from both switchgrass and corn fiber (about 800 and 600 mg sugars/gram dry substrate, respectively) are possible after 24 hours hydrolysis at 5 IU/gram for switchgrass and at 1 IU/gram for corn fiber. The effects of treatment conditions and enzyme levels on hydrolysis profiles are reported in terms of total reducing sugars and specific individual sugars.The effects of switchgrass age (harvest time) on hydrolysis results are also described.