Antimicrobial Effect of Chitosan on the Growth of Lactic Acid Bacteria Strains Known to Spoil Beer

Abstract

Chitosan is a non-toxic compound that is known to possess anti-microbial activity. This study investigated the potential anti-microbial activity of chitosan against select lactic acid bacteria, specifically, Lactobacillus brevis, Lactobaccilus casei, Pediococcus claussenii and Pediococcus damnosus strains known to cause major beer-spoilage. The anti-microbial activity of chitosan was tested at a concentration of 0.5 g/L. A turbidity assay was used to monitor the growth of lactic acid bacteria strains in the presence and absence of chitosan. The growth of all lactic acid bacteria strains was decreased when chitosan was added. Lactic acid assay and diacetyl assay were used to measure beer spoilage. The presence of chitosan reduced the production of lactic acid. Also, the diacetyl assay showed that chitosan was able to reduce the amount of diacetyl to levels below its flavor threshold in cultures contaminated with Lactobacillus brevis BSO31, Lactobacillus casei CCC B9657 and Pediococcus damnosus Molson b76.