Combined utilization of nutrients and sugar derived from wheat bran for D-Lactate fermentation by Sporolactobacillus inulinus YBS1-5

To decrease D-Lactate production cost, wheat bran, a low-cost waste of milling industry, was selected as the sole feedstock. First, the nutrients were recovered from wheat bran by acid protease hydrolysis. Then, cellulosic hydrolysates were prepared from protease-treated samples after acid pretreatment and enzymatic saccharification. The combined use of nutrients and hydrolysates as nitrogen and carbon sources for fermentation by S. inulinus YB1-5 resulted in D-Lactate levels of 99.5 g/L, with an average production efficiency of 1.94 g/L/h and a yield of 0.89 g/g glucose. Moreover, fed-batch simultaneous saccharification and fermentation process at 40 °C, 20% (w/v) solid loading and 20 FPU/g solid cellulase concentration was obtained. D-Lactate concentrations, yield, productivity, and optical purity were 87.3 g/L, 0.65 g/g glucose, 0.81 g/L/h and 99.1%, respectively. This study provided a feasible procedure that can help produce cellulosic D-Lactate using agricultural waste without external nutrient supplementation.