Isolation of Yeasts from Various Food Products and Detection of Killer Toxin Activity In vitro

Abstract

Yeasts produce killer toxin, which gives them a selective advantage against susceptible yeasts. In this study we isolated 8 various non-pathogenic yeasts from 12 different food products and detected killer toxin activity in them against a clinical isolate of Cryptococcus neoformans by chloroform exposure method. The experiment was performed in two sets that had 3 replicates each. The first set plates and the second set plates were exposed to chloroform once and twice respectively. Among the 8 yeasts, 5 yeasts namely Sachharomyces cerevisiae, Candida pintolopesii, Candida tropicalis, Pichia anomala and Dekkera spp. showed significant amount of killer toxin activity against Cryptococcus neoformans in all the replicates, followed by candida parapsilosis and Trichosporon asahii, which showed killer toxin activity only in two of the three replicates. Geotrichum candidum showed no killer toxin activity. Killer toxin activity was observed in vitro in non-pathogenic yeast strains against medically important Cryptococcus neoformans.  Keywords: Yeasts; Killer toxin; Chloroform exposure. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i2.4159               J. Sci. Res. 2 (2), 407-411 (2010)