ANTIFUNGAL ACTIVITY OF SOME LACTIC ACID BACTERIA ISOLATED FROM MATERIALS OF VEGETAL ORIGIN

Lactic acid bacteria have been considered to be promising natural biological antagonists for mycotoxigenic fungi that contaminate various food commodities. Apart from important economic losses, mycotoxin producing fungi have harmful effects on human and animal health. The public necessity for high quality food, without addition of chemical preservatives, with extended shelf life, determined the search of new strains of bacteria able to produce lactic acid and their use to control the fungal growth of plant pathogenic and mycotoxigenic species. The effect of 27 strains of lactic acid bacteria have been assayed on the growth of Alternaria solani plant pathogenic fungi isolated from heavily infected tomatoes as well as on potential mycotoxin producing fungi Aspergillus ochraceus isolated from tomato roots grown in greenhouse and Penicillium digitatum isolated from infected oranges. Interaction between lactic acid bacteria and selected mycotoxigenic fungi was tested by overlay assay method. Discrete spots of liquid cultures of tested lactic acid bacterial strains were placed on MRS agar and after incubation, overlaid with soft PDA containing propagules of tested fungi. Data were collected after 48 hours concerning the diameters of clear visible inhibition zones of fungal growth around the lactic acid bacterial strain spots. Preliminary tests have shown that selected lactic acid bacteria could inhibit the development of test fungi. A number of 11 lactic acid bacterial strains have shown antifungal activity on both Aspergillus ochraceus and Penicillium digitatum. Another 5 strains of lactic acid bacteria did not inhibit any of the two mycotoxigenic fungal species. The effect of lactic acid bacteria on plant pathogenic species Alternaria solani did not provide conclusive results and need further study. The results could be used in future experiments for obtaining performing biological agents with application in food safety.