Effects of Environmental factors on the Growth and Proliferation of Yeasts

Abstract

Yeast is one of the organisms that grow and survive in diverse conditions. The influence of environmental factors on its growth and proliferation were evaluated. The yeast used for the study was isolated from honey using Sabouraud Dextrose Agar and pour plate methods. The effects of temperature, pH and ultraviolet radiation on the growth of Rhodotorula, Debaryomyces, Zygosaccharomyces and Candida species were determined using standard methods. The growths of all the yeast isolates were greatly affected at 80oC.  Rhodotorulla species showed least growth at 50oC, but optimal growth was recorded at 30oC after 96 h of incubation. A similar trend was observed in Debaromyces species. Zygosaccharomyces species recorded high reduction in growth at 60oC after 96 h of incubation, though there were no significant differences in the growths of the isolates at 60oC and 80oC. Candida species recorded the least effect of temperature at 30oC and highest at 60oC and 80oC after 96 h of incubation. The results of the effect of pH on growth of the yeasts showed that  Rhodotorula and Zygosaccharomyces had optimum growth at pH of 5 and 4 respectively. All the isolates showed increase in growth with increase in incubation time. Exposure of the isolates to UV-rays negatively affected the growths of the isolates. The growths of the yeasts decreased with increase in exposure time. This study showed that yeast can survive adverse temperature and pH and can as well survive UV-ray exposure.