An integrated paradigm for cellulosic biorefineries: utilization of lignocellulosic biomass as self-sufficient feedstocks for fuel, food precursors and saccharolytic enzyme production

Simultaneously achieving economic, environmental and social sustainability is a major challenge for the emerging renewable fuel industry. We approach this problem by demonstrating a cellulosic biorefinery paradigm which produces ethanol and food precursors using lignocellulosic biomass as the exclusive source for carbohydrates and minerals. Enzymatic hydrolysate from Ammonia Fiber Expansion (AFEX)-pretreated corn stover at 18% w/w solids loading was found to be nutrient-rich. This hydrolysate was fermented completely within 48 h in two stages to produce ethanol and native yeast cells. An in-house saccharolytic enzyme production using AFEX-pretreated corn stover as carbohydrate source greatly reduces the dependence on commercial enzymes. The inducer mixture is 2.5-7 times more potent than lactose, a common enzyme inducer. Economic analysis indicates that the proposed paradigm is substantially more cost-effective relative to the 2005 NREL model. This improvement is largely attributed to the native yeast cells co-production and the reduction of enzyme cost through the in-house production.