Assessment of Antifungal Activity of Lactic Acid Bacteria Strains Against Bread Spoilage Fungus Aspergillus ochraceus

Lactic acid bacteria (LAB) are generally recognized as safe and can be used against fungi that contaminate various food commodities. The aim of the research was to select LAB strains with high antifungal activity for the biocontrol of Aspergillus ochraceus. The antifungal activity of eight strains of lactic acid bacteria has been evaluated by overlay assay method against the spoilage fungus, Aspergillus ochraceus isolated from white bread. The antifungal effect was assessed by co-cultivation of lactic acid bacteria strains and Aspergillus ochraceus in liquid media and mycelium growth inhibition was monitored for over 14 days. The LAB strains Lpl, LAB 43 and LAB 13 presented intense antifungal activity with large inhibition zones of fungal growth and sporulation, but smaller for Lpa and LAB 15 strains. Total inhibition of mycelia growth was induced by the strains LAB 43, LAB 13 and Lpa. The strains LAB 15 and LAB 35 had a moderate inhibition activity on the mycelia growth. The results of this study demonstrated the antifungal activity of several LAB strains by overlay assay and by co-cultivation method. Therefore, it was confirmed the inhibitory effect of the strains LAB 43 and LAB 13 against Aspergillus ochraceus. The experiment revealed that these LAB strains could be further used as biocontrol agents

Comparative Antifungal Effect of Lactic Acid Bacteria Strains on Penicillium digitatum

Lactic acid bacteria (LAB) are natural alternative to chemical preservatives for fruits. The aim of the research was to select LAB strains with high antifungal activity against Penicillium digitatum for the biopreservation of fruits. The antifungal activity of eight lactic acid bacteria strains has been evaluated against Penicilliuum digitatum isolated from orange, by overlay assay method and by optical microscope examination. The reversion of inhibition zone after 96 h was recorded as a fungistatic effect while those with inhibition zone for at least 7 days were recorded as fungicidal. The antifungal effect of efficient LAB strains was assessed by comparing inhibition of fungal biofilm formation in liquid media. The strains Lpl, Lpa, LAB 13, LAB 15, LAB 43 and LAB 58 presented intense antifungal activity with clear inhibition zones diameter over 20 mm. The microscopy evidenced atypical hyphae and delaying of conidial chain formation. The strains Lpa, LAB 13, LAB 15 fully inhibited the mycelia growth, strains LAB 43 and LAB 58 partly with delaying of biofilm formation on the surface of culture medium. The results of comparative antifungal activity of LAB strains evidenced the highest inhibition of fungal biofilm formation and structural damages of hyphae and spores caused by the strains Lpa, LAB 13 and LAB 15. These strains could be efficient biocontrol agents of Penicillium digitatum in fruits