Induction of low-temperature tolerant yeast mutants by chemical mutagens and evaluation of their performance

Yeasts have been used for thousands of years to make fermented foods and bread. Therefore, it was necessary to improve its fermentation ability at low temperatures and used in making bread process during the winter without the need to provide certain conditions. Therefore, we have inducing yeast mutants that tolerate low temperatures below 4°C. In this study, a total of 64 yeast isolates were isolated from five food samples and two commercial yeast: Mango juice (N=13), Strawberry juice (N=12), sugarcane juice (N=9), Milk (N=8), Cheese (N=9), Compressed yeast (N=6) and powdered yeast (N=7). The results showed that, 14 out of 51 yeast isolates which isolated from food samples are growing rapidly on YPD medium at 10 ºC. Two mutants out of eight mutants CH1EMS and CH2EMS were able to tolerate of low temperature. Five low temperature tolerant strains, designated MD4UV, ST2UV, ML2UV, M1UV and CH2UV, were finally developed by streak-culturing colonies showing dominant growth at 4 °C. Fermentations were performed at 4, 6, 8 and 10 °C, using different mutants yeast induced by Ethyl Methane Sulfonate (EMS). In the present work randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) with six primers was applied to determine the genetic similarity between 10 yeast mutants and one yeast wild type. RAPD-PCR analysis of the different yeast isolates gave distinctive band profiles that allowed a clear differentiation of all the considered isolates.