Chitosan Disrupts Membrane Permeability of Lactic Acid Bacteria

Chitosan, an inexpensive, non-toxic, biodegrable polymer, has been studied for its antimicrobial activity. Recent evidence has shown that exposure to chitosan inhibits the growth of lactic acid bacteria in beer. This study investigated the effect of chitosan (0.5 g/L) on the growth rate of four strains: Lactobacillus brevis CCC 96S1L, Lactobacillus brevis BSO31h, Lactobacillus casei CCC B9657, and Pediococcus claussenii CCC B1098NR and assessed the permeability of the cellular membrane. A turbidity assay confirmed a decreased growth rate in all strains exposed to chitosan. A fluorescent staining assay showed that chitosan disrupted the structure of the cellular membrane. Although the pH assay showed a decrease in intracellular pH soon after the bacteria were exposed to chitosan, some complications arose in the assay which interfered with meaningful interpretation of the results. Overall, the florescent staining and turbidity assays demonstrated that chitosan exerted its effect by disrupting the cellular membrane. However, further investigation needs to done to determine the exact mechanism of chitosan’s antimicrobial activity.