Optimization of Controlled pH Liquid Hot Water Pretreatment of Corn Fiber and Stover

摘要

Current US fuel ethanol production (in excess of 2 billion gallons annually) is based on the saccharification and subsequent fermentation of corn starch. A continued increase in fuel ethanol production requires cost effective methods for pretreating and hydrolysizing lignocellulosic plant biomass so that alternate sources of fermentable sugars for bioethanol and bioproduct production become available. Regardless of source, the recalcitrance of the cellulose polymers and biomass materials to hydrolysis has always posed technical challenges. This work reports the use of water for pertreating cellulosic material derived from the corn plant – either corn stover or corn fiber. Mechanisms of action of water for hydrating corn stover and corn fiber are compared. Process conditions are optimized to minimize the hydrolysis of the oligosaccharides to monosaccharides which would subsequently be degraded to fermentation inhibiting aldehydes. A fundamental understanding of the kinetics of the pretreatment reactions, mass transfer effects, and the effect of buffering capacity of the aqueous pretreatment material is required to effectively design a bioprocess that efficiently pretreats lignocellulose with minimal costs and undesirable side reactions. This paper reports results from the pretreatment of corn stover and the effect of particle size, pretreatment temperature and time, and the buffering capacity of the aqueous phase. Rate equations that reconcile pretreatment effects with subsequent enhancements of glucose and xylose production through enzyme hydrolysis are presented and used as a basis for comparing the impact of physical parameters of pretreatment on sugar and ethanol yields..