Antifungal activity of probiotic Lactobacillus strains isolated from natural fermented green olives and their application as food bio-preservative

The aim of this work was to characterize the antifungal activity of 14 probiotics Lactobacillus strains of (L. plantarum, L. pentosus and L. brevis), isolated from traditional fermented green olives. All the Lactobacillus strains and their cell-free-supernatants (CFS) showed high antifungal activity against molds (Aspergillus niger, Penicillium sp, Fusarium oxysporum, Rhizopus sp.) including biomass and mycelium growth inhibition, and against yeasts (Candida pelliculosa and Rhodotorula sp.). Some (9/14) of these Lactobacillus strains showed resistance and maintained their antifungal activity, against C. pelliculosa and P. digitatum, after 5 h of exposure to gastro-intestinal conditions (combination of 0.3% bile salts and pH 2.5). The antifungal compounds produced by the Lactobacillus strains were heat resistant (pasteurization and autoclaving), active in large pH values (3.8 to 7), with a proteinaceous, lipid or other nature. Among the Lactobacillus strains, L. plantarum S61 and its CFS showed important effectiveness as bio-preservative agent, and delayed the growth of P. digitatum in tomato puree and pear fruits for 15 and 10 days, respectively; while in apple juice, it decreased the C. pelliculosa population from 5 to 2.5 log CFU/mL, after 48 h of inoculation.