Epiphytic Yeasts from South Romania for Preventing Food Microbial Contamination

Epiphytic yeasts represent an important source for the development of novel strategies aiming to combat food microbial contamination. The present study deals with the characterization of nine yeast strains belonging to <i>Starmerella</i>, <i>Candida</i>, <i>Metschinikowia</i>, <i>Lachancea</i>, <i>Kodamaea</i> and <i>Pichia</i> genera, isolated from the surface of plants from the Botanical Garden "Dimitrie Brandza" (Bucharest, Romania) for use as antimicrobial and probiotic agents. The tests involved the determination of the safe status, cell growth under stress conditions, and activity against pathogenic <i>Candida</i> and bacteria strains, respectively, as well as phytopathogenic filamentous fungi and lipolytic activity. None of the nine strains showed all the characteristics for virulence and pathogenicity, with the rare positive results being explained rather by their adaptability to the habitats of origin. The strains <i>Lachancea thermotolerans</i> CMGB-ST12 and <i>Kodamaea ohmeri</i> CMGB-ST19 grew at 37 °C; <i>Metschnikowia reukaufii</i> CMGB-ST21.2, <i>M. reukaufii</i> CMGB-ST.8.1 and <i>M. reukaufii</i> CMGB ST10 grew in the presence of 10% NaCl, while <i>L. thermotolerans</i> CMGB-ST12 and <i>K. ohmeri</i> CMGB-ST19 tolerated both acidic and alkaline pH values well (3.0 to 12.0). The studied yeast strains showed good antimicrobial activity against <i>Candida krusei</i>, <i>Candida albicans</i> and Gram-negative bacterial strains, with <i>K. ohmeri</i> CMGB-ST19 and <i>Pichia membranaefaciens</i> CMGB-ST53 inhibiting up to 100% the development of filamentous fungi. All the strains produced lipases for tributyrin hydrolysis, the best producer being <i>Starmerella bombi</i> CMGB-ST1, and only <i>Candida magnoliae</i> CMGB-ST8.2 tested positive against other probiotic yeasts. Overall, our nine yeast strains show high potential for industrial applications, for obtaining probiotic products and for preventing the development of a wide range of microbial food contaminants.