A novel production process for optically pure l-lactic acid from kitchen refuse using a bacterial consortium at high temperatures

We investigated l-lactic acid production in static batch fermentation of kitchen refuse using a bacterial consortium from marine-animal-resource (MAR) composts at temperatures ranging from 30 to 65 °C. At relatively low temperatures butyric acid accumulated, whereas at higher temperatures l-lactic acid was produced. In particular, fermentation at 50 °C produced 34.5 g L−1 l-lactic acid with 90% lactic acid selectivity and 100% optical purity. Denaturing gradient gel electrophoresis indicated that dominant bacteria present in the original MAR composts diminished rapidly and Bacillus coagulans strains became the dominant contributors to l-lactic acid production at 45, 50 and 55 °C. This is the first report of the achievement of 100% optical purity of l-lactic acid using a bacterial consortium.