Abstract: Three culture medium components including glucose, sodium acetate and sodium citrate and fermentation time were identified as key factors that affect bacteriocin production by Lactobacillus acidophilus NX2-6 using a Plackett-Burman design and their optimal levels were investigated using response surface methodology based on a Box-Behnken experimental desiign. The optimal levels of glucose, sodium acetate and sodium citrate concentrations and fermentation time were determined to be 60.0 g/L, 8.0 g/L, 5.0 g/L and 36 h, respectively based on the established quadratic polynormial regression equation for inhibition zone diameter of fermentaton broth. Under these conditions, the predicted inhibition zone diameter of fermentaton broth was 0.9918. The optimized culture medium resulted in an increase of approximately 80.0% in the antibacterial activity of fermentation broth compared to the basic culture medium. Therefore, response surface methodology can provide an economic, effective and reasonal strategy for the optimization of fermentation conditions for bacteriocin production by Lactobacillus acidophilus NX2-6.

Key words: L.acidophilus, bacteriocins, fermentation conditions, optimization