Alkali pretreated corn stalk combined with enzyme cocktail at low cellulase dosage for the high-titer L-lactic acid production

Abstract

High cellulase cost is the major barrier to the commercialization of L-lactic acid (L-LA) production from abundant lignocellulosic biomass. In current work, an enzyme cocktail that consisted of the commercial cellulase and the additives was prepared to generate the mono-sugars from the alkali pretreated corn stalk for high concentration L-LA fermentation. A statistical mixture design approach was employed to clarify the synergistic effect of the key components in the cellulase cocktail on mono-sugars production. Based on the optimized proportion (8 mg/g xylanase, 8 mg/g laccase, 0.6 mg/g of LiCl, 12.0 mg/g of Tween80 and 13.6 mg/g of bovine serum albumin (BSA) mixed with the base cellulase) of the enzyme cocktail, fed-batch saccharification was conducted with extreme-low base cellulase (4 FPU/g pulp) loading, and allowing 171.8 g/L of mono-sugars production from 22 % (w/v) of the corn stalk pulp. A maximized 129.4 g/L of L-LA production with 0.917 g/g (total mono-sugars) of yield were realized in the following fermentation using the corn stover hydrolysate.