Antifungal Activity of Selected Lactobacilli Intended for Sourdough Production

Background and objective: Presently, there is a growing interest in food produced without the addition of chemical preservatives. Lactic acid bacteria have a high potential to control the growth of undesirable microorganisms. In this work, the antifungal activity of eight strains of lactobacilli isolated from plant sources and foodstuffs (tartar sauce, wheat flour, barley flour, sourdough) were tested against Fusarium culmorum DMF301 and Penicillium expansum DMF04. Materials and methods: Antifungal activity of live cells of lactobacilli and their heat-treated supernatants was determined by agar diffusion method at 30°C, the radial growth of fungi was measured. Organic acid production of tested strains was examined by HPLC. Results and conclusion: Live cells of three Lactobacillus plantarum strains showed the highest antifungal activities. Fusarium culmorum DMF301 was more sensitive to the activity of lactobacilli. Heat-treated bacterial supernatants (100°C, 10 min) were also tested, being added at 10 or 20% v v^-1 to the culture medium; growth of Fusarium culmorum DMF301was inhibited by range of 80-90% compared to controls at 10% supernatant concentration and fully at 20%. However, after neutralization, only the heat treated supernatant from Lactobacillus plantarum CCDM 583 had partially effective antifungal activity. The mutual inhibition of lactobacilli strains reduced their antifungal activity. Statistically significant differences in activity against Fusarium culmorum DMF 301 were found using individual strains of Lactobacillus plantarum CCDM 583 and MP2 or their combination. For use in combination with other cultures, it is therefore necessary to verify the compatibility of various strains of lactobacilli.