Optimization of fermentation conditions for high L-lactic acid production from cellobiose by Entercoccus mundtii QU 25: Impact of pH control and temperature on cell growth and changes in metabolites

Optimization of L-(+)-lactic acid production from cellobiose, one of the main cellulase inhibitors during saccharifaying process, was studied. Fermentation runs pH-controlled at 7.0 provided the highest lactic acid produced (18.6 g/L) and maximum lactic acid productivity (2.1 g/L/h) which were increased by 376% and 346%, respectively in comparison to non pH-controlled batches. Moreover, the maximum L-lactic acid yield and optical purity were obtained at pH 7.0 with 0.94 g/g and 100%, respectively. The optimum temperature was found to be 43°C, at which the lactic acid yield and maximum productivity were 1.0 g/g and 3.44 g/L/h, respectively. This study provides an encouraging means for economic production of optically pure L-lactic acid from pre-hydrolyzed cellulosic materials.