Optimization of Culture Medium Ingredients and Culture Conditions for Bacteriocin Production in Lactococcus lactis NCU036019.

Bacteriocin lactococcin036019 was identified and characterized from Lactococcus lactis NCU036019, which displayed significant antibacterial activity toward foodborne pathogenic bacteria Staphylococcus aureus under various conditions. However, the in situ low-level expression of lactococcin036019 severely limited its wide application in food industry. In this study, we optimized the medium ingredients and culture conditions of L. lactis NCU036019 for maximum production of lactococcin036019. The effects of different carbon sources, nitrogen sources, inorganic salts, growth factors, surfactants, and buffer salts on the production of bacteriocin were studied using antibacterial titer and diameter of inhibitory zone as evaluation indexes. Through single-factor experiments, Plackett-Burman (PB) experiment, steepest ascent experiment and response surface methodology, yeast extract, zinc sulfate, sodium acetate, mannitol, Tween-80, and dipotassium hydrogen phosphate were identified to display significant influence on the production of bacteriocin. By optimizing Man Rogosa and Sharpe (MRS) culture medium ingredients, the antibacterial activity of lactococcin036019 in the cell-free supernatant raised from 46.19 to 300.14 Au/mL, namely, 6.5 times increased. Furthermore, the culture conditions, such as inoculation amount, culture time, and culture temperature, were optimized, and this further increased the antibacterial activity to 409 Au/mL, namely, 8.8 times increased. This study investigated the effects of culture media and conditions on the production of lactococcin036019, and they were optimized for a maximum harvest of bacteriocin, and the significant increase of bacteriocin production in L. lactis NCU036019 facilitates the application of the antibacterial substance in future work.