Novel pH control strategy for efficient production of optically active l-lactic acid from kitchen refuse using a mixed culture system

• Published in: Bioresource technology Vol. 216; pp. 52 - 59
• Main Authors: Tashiro, Yukihiro, Inokuchi, Shota, Poudel, Pramod, Okugawa, Yuki, Miyamoto, Hirokuni, Miayamoto, Hisashi, Sakai, Kenji
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2016
• Subjects: Bacillus; Bioreactors - microbiology; Fermentation; Garbage; Hydrogen-Ion Concentration; Kitchen refuse; l-lactic acid production; Lactic Acid - biosynthesis; Mixed culture; Novel pH control strategy; Refuse Disposal - methods; Novel pH control strategy; OP; LA; MKR; Mixed culture; l-lactic acid production; SLA; Kitchen refuse
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2016.05.031

•Not-yet reported factors were investigated for l-LA production in meta-fermentation.•l-LA production with 100% optically purity was achieved without sterilization.•Constant pH control strategy did not improve l-LA production in meta-fermentation.•Novel pH control by switching from swing to constant was the most efficient method.•We indicated the importance of unusual manner of meta-fermentation system differently from pure culture system. Uninvestigated control factors of meta-fermentation, the fermentative production of pure chemicals and fuels in a mixed culture system, were examined for production of optically pure l-lactic acid (LA) from food waste. In meta-fermentations by pH swing control, l-LA production with 100% optical purity (OPl-LA) was achieved even using unsterilized model kitchen refuse medium with preferential proliferation of l-LA-producing Bacillus coagulans, a minor member in the seed, whereas agitation decreased OPl-LA drastically. pH constant control shortened the fermentation time but decreased OPl-LA and LA selectivity (SLA) by stimulating growth of heterofermentative Bacillus thermoamylovorans. Deliberately switching from pH swing control to constant control exhibited the best performance for l-LA production: maximum accumulation, 39.2gL−1; OPl-LA, 100%; SLA, 96.6%; productivity, 1.09gL−1h−1. These results present a novel pH control strategy for efficient l-LA production in meta-fermentation based on a concept different from that of pure culture systems.