A Sustainable Wheat Straw Pretreatment Process by Self-Sufficient and Cyclical Crude Lactic Acid

Abstract

The purpose of this study was to investigate an environmentally friendly and recyclable pretreatment approach that would enhance the enzymatic digestibility of wheat straw. Wheat straw was pretreated using self-sufficiency crude lactic acid obtained from enzymatic hydrolysate fermentation by Bacillus coagulans. Experimentally, crude lactic acid at low concentration could achieve a pretreatment effect comparable to that of commercial lactic acid. After pretreatment at 180 °C for 60 min with 2% crude lactic acid, hemicellulose could be effectively separated and high recovery of cellulose was ensured, achieving cellulose recovery rate of 95.47% and hemicellulose removal rate of 92.65%. Excellent enzymatic hydrolysis was accomplished with a glucose yield of 99.65%. Moreover, the concentration of lactic acid was nearly unaltered during pretreatment, which still accomplished acceptable pretreatment and enzymatic hydrolysis effects after 3 repeated recycling. This sustainable approach can be easily extended to other straw biomass pretreatment with minor modification.

Keywords: Crude lactic acid, Wheat straw, Cyclical pretreatment, Home-made catalyst, enzymatic hydrolysis