Characterization of Ethanol Producing Yeasts for Their Efficiency in Ethanol production, Salt Tolerance, and Utilization of Glucose and Xylose.

Abstract

Yeast are the mainstay in ethanol production industry. Search for efficient yeast strains that are salt tolerant and utilize both hexoses (glucose) and pentoses (xylose and arabinose) is important in fermentation industry. In this regard,12 yeast strains, viz., CDBT1-12, were isolated from various sources and characterized. Molecular characterization of the yeast strains was done by sequencing 26S rRNA gene, D1D2 region. Out of 12 isolates, 10 were found to be Saccharomyces cerevisiae , CDBT7 was Wikerhamomyces anomalous , and CDBT8 was Cyberlindnera fabianii . The yeast isolates were characterized in terms of their ethanol production efficiency, salt tolerance and ability to utilize of glucose and xylose. All the strains were found to be good ethanol producers. Yeast strain CDBT2 was found to have tolerance for high salt (up to 15%) and ethanol (up to 16%) concentrations. Yeast strain CDBT7 was found to utilize both glucose and xylose without compromising on ethanol production efficiency. The CDBT7 strain was also salt tolerant (up to15%).Yeast strain CDBT2 when grown in an electrochemical cell with low levels of applied external voltage, alcohol dehydrogenase (ADH1) and pyruvate decarboxylase (PDC1) mRNA levels were increased by 2.78 ± 0.80 and 1.12 ± 0.37 fold, respectively. We believe, the latter observation is novel and it has not been reported previously. It also further supports our previous observation of increase in level of alcohol production by CDBT2 strain in the presence of applied electrical current.