Efficient lactic acid production from cassava bagasse by mixed culture of Bacillus coagulans and lactobacillus rhamnosus using stepwise pH controlled simultaneous saccharification and co-fermentation

In this study, cassava bagasse, a by-product contains starch and lignocellulosic fibers, was used to lactic acid production based on simultaneous saccharification and co-fermentation. During the process, starch and cellulosic fractions in cassava bagasse were co-saccharified by cocktail enzymes. Fermentation results indicated that the mixed culture of Lactobacillus rhamnosus and Bacillus coagulans significantly enhanced the lactic acid concentration and productivity when compared with the processes based on mono-culturing using the above strains. A highest lactic acid concentration and productivity of 112.5 g L−1 and 2.74 g L-1 h−1 were achieved under the optimized conditions. Besides, lactic acid yield of 0.88 g/g (of starch + cellulose + hemicellulose) was also obtained, which means the starch and lignocellulosic sugars were utilized simultaneously without pretreatment. The process presented in this work significantly improves the lactic acid production from cassava bagasse, which showed promising in economical waste disposal.