ABSTRACT
In the present study fourteen cultures were isolated from soil samples, fruits and fermented products, of which
seven were found to be yeasts. These seven yeasts were subjected to thorough identification scheme upto
species level by cultural, morphological, microscopic, biochemical and physiological studies and by comparing
the results with reference strain Saccharomyces cerevisiae MTCC 170. The yeasts were characterized with respect
to temperature tolerance, ethanol tolerance and osmotolerance. Batch stationary fermentation was carried out in
Erlenmeyer flasks for bioethanol production. Growth and fermentation kinetics were calculated for stationary
fermentation. Three species (TA, C2 and K2) were identified as Saccharomyces cerevisiae, two (S1 and S2) were
identified as Saccharomyces rosinii, and the other two (K1 and S3) were identified as Saccharomyces exiguus and
Rhodotorula minuta respectively. Among all yeasts Saccharomyces cerevisiae TA and C2 strains were high ethanol
tolerant (tolerated 14% ethanol), high osmotolerant (tolerated 20% sugar) and high bioethanol producing
strains with a yield of 32 and 28 g/l for TA and C2 respectively. Results indicated that fermentation kinetics with
S. cerevisiae TA and C2 strains were faster than other yeast strains including the reference strain MTCC 170 with
the ethanol yield (Yp/s= 0.160 and 0.155 g g-1), volumetric substrate uptake (QS= 2.638 and 2.50 g L-1 h-1),
conversion rate into ethanol (16.80 and 15.50 %) and volumetric product productivity (Qp,= 0.44 and 0.38 g L-1 h-
1) respectively
ABSTRACTIn the present study fourteen cultures were isolated from soil samples, fruits and fermented products, of whichseven were found to be yeasts. These seven yeasts were subjected to thorough identification scheme uptospecies level by cultural, morphological, microscopic, biochemical and physiological studies and by comparingthe results with reference strain Saccharomyces cerevisiae MTCC 170. The yeasts were characterized with respectto temperature tolerance, ethanol tolerance and osmotolerance. Batch stationary fermentation was carried out inErlenmeyer flasks for bioethanol production. Growth and fermentation kinetics were calculated for stationaryfermentation. Three species (TA, C2 and K2) were identified as Saccharomyces cerevisiae, two (S1 and S2) wereidentified as Saccharomyces rosinii, and the other two (K1 and S3) were identified as Saccharomyces exiguus andRhodotorula minuta respectively. Among all yeasts Saccharomyces cerevisiae TA and C2 strains were high ethanoltolerant (tolerated 14% ethanol), high osmotolerant (tolerated 20% sugar) and high bioethanol producingstrains with a yield of 32 and 28 g/l for TA and C2 respectively. Results indicated that fermentation kinetics withS. cerevisiae TA and C2 strains were faster than other yeast strains including the reference strain MTCC 170 withthe ethanol yield (Yp/s= 0.160 and 0.155 g g-1), volumetric substrate uptake (QS= 2.638 and 2.50 g L-1 h-1),conversion rate into ethanol (16.80 and 15.50 %) and volumetric product productivity (Qp,= 0.44 and 0.38 g L-1 h-
1) respectively
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