Efficient l‐lactic acid production from purified sweet sorghum juice coupled with soybean hydrolysate as nitrogen source by Lactobacillus thermophilus A69 strain

Abstract

AbstractBACKGROUNDHigh‐efficiency utilization of sweet sorghum juice can bring significant economic feasibility of l‐lactic acid production. However, an expensive nitrogen source increases the capital cost, and the complex composition of sweet sorghum juice could limit the yield.RESULTSIn the present study, a bioprocess was developed to enhance the efficiency of l‐lactic acid production using purified sweet sorghum juice and cheap nitrogen supply strategies. It was first demonstrated that cheaper soybean hydrolysate could be used as a low‐cost nitrogen source for efficient l‐lactic acid production by Lactobacillus thermophilus A69, the optimal soybean hydrolysate concentration being 25 g L−1. It was then proved that the efficiency of l‐lactic acid production was significantly boosted using sweet sorghum juice purified via clarification treatment. Finally, on combining the cheap nitrogen source and the clarification strategy, 114.6 g L−1 l‐lactic acid with a productivity of 2.61 g L−1 h−1 was produced by A69 strain in a 5 L bioreactor.CONCLUSIONThis study provides a simple, practical and economic approach to promote l‐lactic acid production using sweet sorghum juice as feedstock. © 2019 Society of Chemical Industry