Isolation of thermophilic L-lactic acid producing bacteria showing homo-fermentative manner under high aeration condition
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By applying non-sterile open fermentation of food waste, various thermotolerant L-lactic acid-producing bacteria were isolated and identified. The predominant bacterial isolates showing higher accumulation of L-lactic acid belong to 3 groups of Bacillus coagulans, according to their 16S rRNA gene sequence similarities. B. coagulans strains M21 and M36 produced high amounts of L-lactic acid of high optical purity and lactic acid selectivity in model kitchen refuse medium and glucose-yeast extract-peptone medium. Other thermotolerant isolates resembling to Bacillus humi, B. ruris, B. subtilis, B. niacini and B. soli were also identified. These bacteria produced low amounts of L-lactic acid of more than 99% optical purity. All isolated strains showed the highest growth rate at temperatures around 55-60℃. They showed unique responses to various oxygen supply conditions. The majority of isolates produced L-lactic acid at a low overall oxygen transfer coefficient (K_Lα); however, acetic acid was produced instead of L-lactic acid at a high K_Lα. B. coagulans M21 was the only strain that produced high, consistent, and reproducible amounts of optically pure L-lactic acid (>99% optical purity) under high and low K_Lα conditions in a homo-fermentative manner.
- Journal of bioscience and bioengineering
Journal of bioscience and bioengineering 117(3), 318-324, 2014-03
The Society for Biotechnology, Japan