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 80^oC.  Rhodotorulla species showed least growth at 50^oC, but optimal growth was recorded at 30^oC after 96 h of incubation. A similar trend was observed in Debaromyces species. Zygosaccharomyces species recorded high reduction in growth at 60^oC after 96 h of incubation, though there were no significant differences in the growths of the isolates at 60^oC and 80^oC. Candida species recorded the least effect of temperature at 30^oC and highest at 60^oC and 80^oC 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.