Enhanced enzymatic xylose/cellulose fractionation from alkaline liquor-pretreated corn cob by surfactant addition and separate fermentation to bioethanol

Xylanase xylose/cellulose fractionation can efficiently improve the utilization of xylose and cellulose. Improvement of xylanase performance during hemicellulose hydrolysis can increase xylose/cellulose fractionation efficiency. To utilize xylose and cellulose efficiently, an enzymatic xylose/cellulose fractionation and a separate fermentation bioethanol process were performed. Alkaline liquorpretreated corn cob was subjected to xylose/cellulose fractionation with xylanase in the presence or absence of the following mixed surfactants: polyoxyethylene(20)-sorbitan-monooleate (0.15% v/v), polyethylene glycol 6000 (0.15% w/v), bovine serum albumin (0.15% w/v), and rhamnolipid (0.005% v/v). The hemicellulose hydrolysis yield (HHY) in the presence of mixed surfactants was 70.5%, which was 66% higher than that of the control (no surfactants added). Optimization of other hydrolysis conditions, such as pH, temperature, liquid-to-solid ratio, xylanase loading, and incubation time, increased the HHY to 86.62%. The xylose in the enzymatic hydrolysate was fermented to ethanol by Candida shehatae, and the cellulose remaining in the solid residues was converted to ethanol by simultaneous saccharification and fermentation with Saccharomyces cerevisiae. In total, 40.67% of the hemicellulose and 76.14% of the cellulose in the raw corn cob was converted to ethanol.