Application of Response Surface Methodology in Medium Optimization to Improve Lactic Acid Production by Lactobacillus paracasei SRCM201474

The aim of this study was to establish the optimal medium composition for enhancing L(+)-lactic acid (LLA) production using response surface methodology (RSM). Lactobacillus paracasei SRCM201474 was selected as the LLA producer by productivity analysis from nine candidates isolated from kimchi and identified by 16S rRNA gene sequencing. Plackett-Burman design was used to assess the effect of eleven media components on LLA production, including carbon (glucose, sucrose, molasses), nitrogen (yeast extract, peptone, tryptone, beef extract), and mineral (NaCl, K2HPO4, MgSO4, MnSO4) materials. Glucose, sucrose, molasses, and peptone were subsequently chosen as promising media for further optimization studies, and a hybrid design experiment was used to establish their optimal concentrations as glucose 15.48 g/l, sucrose 16.73 g/l, molasses 39.09 g/l, and peptone 34.91 g/l. The coefficient of determination of the equation derived from RSM regression for LLA production was mathematically reliable at 0.9969. At optimum parameters, 33.38 g/l of maximum LLA increased by 193% when compared with MRS broth as unoptimized medium (17.66 g/l). Our statistical model was confirmed by subsequent validation experiments. Increasing the performance of LLA-producing microorganisms and establishing an effective LLA fermentation process can be of particular benefit for bioplastic technologies and industrial applications.