Saccharification of Wheat and Rice Straw for Lactic acid Production

Abstract

The present study explores production of lactic acid (LA) from rice straw (RS) and wheat straw (WS), through a three-stage pretreatment process involving alkali hydrolysis and acid hydrolysis for fermentable sugars and acid-chlorite technique for cellulose separation. Dilute acid pretreatment of WS and RS biomass yielded significant amounts of reducing sugars (glucose and xylose) which were subsequently fermented to LA by Bacillus licheniformis (DGB), Bacillus sonorenesis (DGS15) and Lactobacillus reuteri. DGS15 demonstrated superior performance, achieving LA production of 7.47 mg/ml (0.183 g/g) from RS hydrolysate and 9.03 mg/ml (0.182 g/g) from WS hydrolysate, outperforming both Bacillus licheniformis (DGB) and Lactobacillus reuteri in both yield and productivity. Delignification and acid pretreated residues for cellulose separation achieved recovery rates of 57.63% and 67% from RS and WS, respectively. These findings suggest that Bacillus sonorenesis DGS15 is a favorable candidate for lactic acid production from lignocellulosic residues.