Simultaneous saccharification and fermentation of xylo-oligosaccharides manufacturing waste residue for L-lactic acid production by Rhizopus oryzae

High substrate cost and low lactic acid yield are the most pressing concerns in fermentative production of L-lactic acid by Rhizopus oryzae. In this study, waste residue from corncob after xylo-oligosaccharides (XOS) manufacturing was used as an alternative abundant, renewable, and inexpensive substrate for L-lactic acid production. After enzymatic hydrolysis, both glucose and xylose in the hydrolysate were converted to 34.0 g L-1 of L-lactic acid, equivalent to a yield of 0.34 g g(-1) dry waste residue, by R. oryzae in separate hydrolysis and fermentation. In contrast, a higher L-lactic acid titer (60.3 g L-1) and yield (0.60 g g(-1) dry waste residue) were achieved in simultaneous saccharification and fermentation (SSF) with 10% (w/v) substrate loading at 40 degrees C, demonstrating, for the first time, the feasibility of L-lactic acid production from XOS manufacturing waste residues. The SSF process for L-lactic acid production from XOS waste residues was also demonstrated in a 5-L stirred-tank bioreactor, although further optimization would be necessary. (C) 2014 Elsevier B.V. All rights reserved.