Journal of Advanced Microbiology

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Abstract: Soil, is an enriched source of natural fermenting microorganisms including yeasts, which are

capable of producing bioethanol. The present study was carried out to isolate and identify yeast strains from

soil and screentheir ethanol tolerance capacity with a viewto select efficient yeast strains for industrial bioethanol

production. Twelve yeast strains (YS1-YS12) were isolated from soil. On the basis of morpho-physiological

characteristics and biochemical characterization, these yeast strains were identified as six strains of S.cerevisiae

(YS1, YS2, YS4, YS5, YS7 and Y10), three strains of Candidaalbicans (YS3, YS8 and YS9) and three strains each

of Trycosporoncapitatum (YS6, YS11 and YS12). Screening of ethanol tolerance capacity of these strains

revealed that the two strains YS2 andYS3 tolerated ethanol concentration up to 12 % (v/v), while other two

isolated strains YS1 and YS5 showed tolerance up to 10 % of ethanol concentration. The remaining eight strains

showed tolerance of 9 % (v/v). Further these identified strains were evaluated for their comparative bioethanol

production capacity in different carbohydrate substrates (grape juice, mahua flower extract, molasses, sugarcane

juice and saccharified sweet potato root flour broth). Taking different strains and substrate conditions into

account, strain YS2 showed in overall the highest ethanol production and ethanol tolerance capacity in

comparison to the other strains indicating as an efficient strainfor its use in ethanol production purpose.