Factors Affecting the Production of Antibacterial Compounds by Lactobacillus plantarum Biofilm and Planktonic cells

Abstract

Abstract Lactobacillus plantarum has the ability to inhibit the growth of pathogenic bacteria through production of chemical compounds and bacteriocins. This study aimed to find out the effectiveness of the products of these bacteria against E. coli by altering the pH of the growth media, types of media, and for examining the effect of adding certain sugars concentration to inhibit E. coli. L. plantarum strain was cultured in different environmental conditions, by adding (sucrose, glucose, galactose, fructose, and starch) to MRS medium. The results revealed that biofilm supernatant had a 40% inhibitory effect on E. coli, with the optimal temperature of 37°C. The most effective pH for the L. plantarum growth showed an increase in the inhibition of E. coli at pH 7. Furthermore, higher sugar concentrations added to the MRS led to reduce production of inhibitory substances. MRS and TSB were identified as the best media for L. plantarum growth to give increasing the inhibition of E. coli. L. plantarum couldn’t grow on the MacConkey agar. Despite the importance of L. plantarum supernatants for inhibiting E. coli, the optimal temperature and pH conditions may enhance the inhibition of pathogenic bacteria that affect humans or causing food spoilage.