Parametric Optimization of Lactic Acid Production by Immobilized Lactobacillus casei Using Box-Behnken Design

Abstract

Technological optimization of process parameters posses one of the open challenge for fermentative lactic acid (LA) production. Hence optimization of process parameters viz. sugar concentration, pH, biomass, incubation temperature and incubation time for maximizing fermentative lactic acid production from molasses sugar and corn steep liquor as a low cost carbon and nitrogen source, respectively by immobilized Lactobacillus casei MTCC 1423 cells has been carried out using Box Behnken Design (BBD). By applying multiple regressions on experimental data, quadratic models have been realized, explaining role of each variable and their quadratic interaction on LA production, LA productivity and yield coefficient. Analysis of variance has demonstrated that models are significant. The maximum LA production (132 g/(L fermentor volume) ), LA productivity of 2.36 g/(L×h) and yield coefficient of 0.936 g/(g substrate) have been estimated by the quadratic regression model for optimum process parameters values of sugar concentration (194 g/L), pH (6.85), biomass (310 mg, CDW), incubation temperature (37°C) and incubation time (57 h). The optimization validated experiments had resulted in LA production of 130±2.1 g/(L fermentor volume) ; LA productivity of 2.28±0.037 g/(L×h) and yield coefficient of 0.921±0.003 g/(g substrate) and which are substantially higher than those obtained with free cells of Lb. casei MTCC 1423 (2%, v/v inoculums size) at obtained optimized process parameters values. Thus resulted quadratic models provided an opportunity for scaling up the lactic acid production process and demonstrated the economic potential of using agro industrial waste molasses sugar for lactic acid production by Lb. casei MTCC 1423.