Production of lactic acid from soybean stalk hydrolysate with Lactobacillus sake and Lactobacillus casei

In order to make full use of soybean stalk produced in large quantity annually in China, a process is proposed for production of lactic acid from soybean stalk hydrolysate with Lactobacillus sake and Lactobacillus casei. Experiments were conducted using the proposed process and experimental results indicate that the potential of 242 mg (g stalk)−1 fermentable sugar is released from hydrolysate through enzymatic saccharication with a saccharication of 51%. The main sugar released from pretreated soybean stalk through enzymatic hydrolysis was a mixture of glucose, xylose and cellobiose at a ratio of 3.9:1.7:1. Fermentation of soybean stalk hydrolysate by L. sake and L. casei yielded the lactic acid conversion of 48% and 56%, respectively, however, lactic acid conversion increased to 71% by co-inoculation of both strains. L. sake and L. casei were able to degrade glucose, but unable to completely assimilate xylose and cellobiose. The proposed process can be used to produce lactic acid from soybean stalk hydrolysate.