High-titer lactic acid production from NaOH-pretreated corn stover by Bacillus coagulans LA204 using fed-batch simultaneous saccharification and fermentation under non-sterile condition

•A thermophilic LA producing strain was identified as B. coagulans LA204.•LA204 produces LA with high yield (0.52–0.75g/g straw) from several agro straws.•LA yield reached 0.68g/g straw and the titer reached 97.59g/L in SSF process.•A non-sterile feasible process was established to produce LA from corn straw. Lactic acid (LA) is an important chemical with various industrial applications. Non-food feedstock is commercially attractive for use in LA production; however, efficient LA fermentation from lignocellulosic biomass resulting in both high yield and titer faces technical obstacles. In this study, the thermophilic bacterium Bacillus coagulans LA204 demonstrated considerable ability to ferment glucose, xylose, and cellobiose to LA. Importantly, LA204 produces LA from several NaOH-pretreated agro stovers, with remarkably high yields through simultaneous saccharification and fermentation (SSF). A fed-batch SSF process conducted at 50°C and pH 6.0, using a cellulase concentration of 30FPU (filter paper unit)/g stover and 10g/L yeast extract in a 5-L bioreactor, was developed to produce LA from 14.4% (w/w) NaOH-pretreated non-sterile corn stover. LA titer, yield, and average productivity reached 97.59g/L, 0.68g/g stover, and 1.63g/L/h, respectively. This study presents a feasible process for lignocellulosic LA production from abundant agro stovers.