Abstract:

This study aimed to produce L-lactic acid from enzymatic hydrolysis solution of soybean straw by fermentation. Lactobacillus casei was selected out from four species of Lactobacillus for producing L-lactic acid because of its good performance and high reducing sugar utilization rate and L-lactic acid yield. And its fermentation characteristics were investigated. The results indicated that the optimum temperature, inoculation size and pH are 30℃, 10% and 5.5, repectively; With sugar concentration rising, the lactic acid yield produced by Lactobacillus casei increases correspondingly. After 24-h fermentation, the residual concentration of sugar in hydrolysis solution of soybean straw is close to zero. At that time, the L-lactic acid yield increases with the substrate concentration increasing. When the substrate concentration is up to 34.98 g/L, the production of L-lactic acid is not inhibited any more.

Key words: soybean straw, Lactobacillus casei, fermentation, L-lactic acid