Statistical optimization of physical parameters for enhanced bacteriocin production by L. casei

Antimicrobial proteinaceous compounds such as bacteriocins produced from Lactobacillus sp. are widely known. They have potential antimicrobial activities towards closely related bacteria and several pathogens associated with food spoilage and hence can be a potential food bio-preservative agent. Bacteriocin production requires optimized process, complex media and well-controlled physical conditions including pH and temperature. A probiotic strain of L. casei LA-1 isolated from mango pickle was used in the present study. The influence of physical parameters viz. temperature (15 ?? 45°C), pH (4.0 ?? 7.0), incubation time (up to 48 h) and inoculum size (0.7 ?? 2.0 O.D) on bacteriocin production was analyzed. The effect of all the parameters was first investigated using the one-factor-at-a-time method (OFAT) to see the significance of these parameters on bacteriocin production and then further optimized by response surface methodology (RSM). Following OFAT analysis, all factors were found to have a significant effect on bacteriocin production. Bacteriocin production of 2,844 AU/mL was obtained at temperature 37°C, pH 6.7 and inoculum size 1.8 O.D at an incubation time of 20 h and it was produced during the stationary phase of growth. Statistical analysis showed that three variables-pH, temperature and incubation time have significant effects on bacteriocin production. RSM proved to be a powerful tool in the optimization of bacteriocin production by L. casei LA-1 with a two-fold increase, giving a production of 4652.15 AU/mL at pH 7.19, temperature 33.3°C and incubation time of 22.2 h.