Open Fermentative Production of L-Lactic Acid from Distillers’ Grains by Lactobacillus casei CICC 6056
Jin Zheng,
Yingying Liu,
Xiaohong Sun,
Qunhui Wang,
Hui Zou,
Juan Wang,
Ming Gao
Affiliations
Jin Zheng
Department of Environmental Engineering, School of Civil and Environmental Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Haidian District, Beijing 100083, China; China
Yingying Liu
China National Institute of Standardization, No.4 Zhi Chun Road, Haidian District, Beijing 100088, China; China
Xiaohong Sun
Beijing Academy of Agricultural and Forestry Sciences, No.11 Shuguang Garden Road, Haidian District, Beijing 100097, China; China
Qunhui Wang
Department of Environmental Engineering, School of Civil and Environmental Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Haidian District, Beijing 100083, China; China
Hui Zou
Department of Environmental Engineering, School of Civil and Environmental Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Haidian District, Beijing 100083, China; China
Juan Wang
Department of Environmental Engineering, School of Civil and Environmental Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Haidian District, Beijing 100083, China; China
Ming Gao
Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan; Japan
Distillers’ grains (DG) are potential fermentable sugar substrates for the production of value-added products. This study focused on the development of an open fermentation process for the production of L-lactic acid from DG using Lactobacillus casei CICC 6056. The open fermentation process was feasible, resulting in an L-lactic acid yield similar to that obtained with sterilized fermentation. However, a decrease in pH below 5.0 after 24 h resulted in a poor L-lactic acid concentration of 9.18 g/L and an inferior reducing sugar conversion rate of 53.6%. Therefore, an optimal pH adjustment method was sought. A pH adjustment to 6.5 every 24 h effectively improved the L-lactic acid concentration to 21.3 g/L with a 97.8% reducing sugar conversion rate. Furthermore, the application of a simultaneous saccharification and fermentation process at 50 °C in open condition increased the L-lactic acid concentration to 25.0 g/L. This yield was superior to L-lactic acid fermentation from DG using a separate hydrolysis and fermentation method (21.3 g/L) and from a commercial sugar in batch culture (23.6 g/L). These results demonstrated that L. casei CICC 6056 has great industrial potential as a superior candidate strain for the production of L-lactic acid from DG due to its broad applicability in a wide temperature range (from 37 to 50 °C).
