“…Under certain circumstances, B. coagulans produces protease, amylase, cellulase, vitamins and reduces sugar and other substances (Kapse, Engineer, Gowdaman, Wagh, & Dhakephalkar, 2019). As an important lactic acid-producing bacterial species, thermophilic B. coagulans can produce L-lactic acid of optical purity, which means the high ratio of the L-lactic acid of optical rotation in a sample consisting of two enantiomeric L-and D-lactic acid, with excellent tolerance to high temperature and nutrition deprivation (Jiang, Xu, & Tao, 2019). L-lactic acid plays a vital role in industry, including food processing, chemical production and agriculture (Wang, Cao, Luo, Qi, & Wan, 2019).…”