Characterization, Toxicity, and Optimization for the Growth and Production of Bacteriocin-like Substances by Lactobacillus curvatus

This study aimed to characterize, evaluate toxicity and optimize the conditions for the growth and production of bacteriocin-like substances by Lactobacillus curvatus P99. The antibacterial activity of the cell-free supernatant (CFS) containing bacteriocin-like substances was evaluated by the agar diffusion technique. The stability of the CFS was also examined after heat treatment, refrigeration, freezing, pH variations, and treatment with different chemical substances. The toxic effect of CFS on Drosophila melanogaster diet was determined by calculating the survival rate of the flies. The effects of pH, temperature, and incubation time were the parameters used to optimize cell growth and production of bacteriocin-like substances through response surface methodology. The CFS was stable for 36 weeks under freezing and refrigeration, as well as under heat treatment, in acidic and basic pH and for all chemical substances tested. Fewer than 50,000 AU/mL of CFS added to D. melanogaster diet showed no toxic effect. The optimum growth condition was pH 6.3 at 29.3 °C for 18.6 h, and the optimum production of bacteriocin-like substances was under pH 6.22 at 30.6 °C for 17.9 h. The data on the optimization of cell growth and the characterization and optimization of bacteriocin-like substances provided information to support the industrial-scale production of this microorganism and its metabolites.