Abstract
Abstract Seventy eight yeasts were isolated from different foodstuffs. Out of the seventy eight isolates four yeast species namely C. parapsilosis Q3, C. solani F8, C. versatilis J3 and K. jensenii H1 were selected to study their biological activity. The four strains termed as killer yeast by observing its activity against microorganisms. Killer yeasts secrete proteinaceous killer toxins lethal effect against some of Gram positive and negative bacteria, molds and yeasts. The antagonistic effect of the four killer yeast strains on the growth of different microorganisms recorded as zone of inhibition (mm), demonstrated that C. versatilis J3 was an active stains against majority test microorganisms. Consumed sugar determined for the four strains and showed that C. versatilis J3 and C. parapsilosis Q3 reached to its maximum on the 12 hours of incubation both yeast consumed 97.5 and 95% of initial sugar (sugar utilization efficiency) while both of C. solani F8 and K. jensenii H1 sugar utilization efficiency was recorded on the 24 hours being 99.65 and 99.30%, respectively.