Preliminary study on antimicrobial substance produced by Lactobacillus helveticus AJT

Lactobacillus helveticus strain AJT, isolated from traditional fermented dairy samples in Inner Mongolia, China, its antibacterial substance’s production increased continuously from 6h, and reached a maximum after 20h. Obtained through ethyl acetate and methanol extraction, the antibacterial substance, had strong antibacterial activity against Gram - positive bacteria such as Staphylococcus aureus, Gram - negative bacteria such as Escherichia coli and fungi such as Penicillium expansum after eliminating the effect of organic acids and hydrogen peroxide. The active principle was proteinaceous in nature or a mixed substance since the inhibitory activity decreased after treated with trypsin, pepsin, protease K and papain. The inhibitory activity was stable after heating at different temperature for 30min and over the pH range from 2. 0 to 5. 0, UV light did not affect the activity of the substance, which indicated the antimicrobial substance produced by AJT belong to bacteriocin-like substance.