Highly efficient enzymolysis and fermentation of corn stalk into L-lactic acid by enzyme-bacteria friendly ionic liquid pretreatment

Abstract

Ionic liquids (ILs) have been widely used in the pretreatment of biomass. However, the effects of residual ILs on the enzymolysis and fermentation of biomass are still unknown. Therefore, a large quantity of water-washing is usually followed after biomass pretreatment to eliminate the inhibition of residual ILs on subsequent hydrolysis and fermentation steps. In this work, the effect of choline glycine ([Ch][Gly]) concentration on the activity of cellulase and Bacillus sp. strain P38 was systematically investigated to explore the impacts of residual ILs on enzymolysis and fermentation. The results confirmed that the activities of them were almost not inhibited in low concentrations (less than 0.5 wt%) of [Ch][Gly]. Under optimal pretreatment conditions, the maximum cellulose digestibility was 99.23%. Enzymatic hydrolysate was suitable for L-lactic acid fermentation without appreciable inhibition, and the highest sugar-acid conversion rate of 96.33% was obtained by simplified detoxification. This work provides an economic route to produce fermentable sugar and L-lactic acid, which shows an industrial application prospect in lignocellulosic biorefinery.