Production and Purification of Lactic Acid from Rice Straw Using an Integrated Fermentation and Adsorption System

This study presents a sustainable process for the production of L-lactic acid from rice straw, an abundant agricultural residue. Rice straw was subjected to dilute acid pretreatment, followed by enzymatic hydrolysis to convert cellulose into glucose, which was subsequently fermented to produce lactic acid. An integrated process for in situ lactic acid removal during high cell density fermentation using nonsterile resin was studied. A systematic approach was adopted to study the adsorption characteristics of the resin and the impact of impurities present in the fermentation broth on the resin performance to improve the yield and purity of the lactic acid in downstream processing. An overall process yield of 77% and purity of 89% were achieved, representing a 39% improvement over conventional pH strategies, with 94% reduction in salt generation compared to conventional precipitation methods and productivity of 1.19 g/(L h), superior to recent literature values of 0.329–0.430 g/(L h).