Potato starch saccharifying and ethanol yielding strains of Saccharomyces cerevisiae

Three starch hydrolyzing and ethanologenic strains of Saccharomyces cerevisiae were isolated from a sewage water sample on a selective medium (M-1) comprising of potato powder 5g, yeast extract 0.3g,Agar agar 1.5g and chloramphenicol 0.5mg/dl-1. The yeasts were optimized for different growth conditions in malt-yeastglucose- peptone (YM) broths. Strains Sn-1Y and Sn-5Y showed highest growth at 34ºC with initial pH of 5.0. While the isolate Sn-4Y showed highest growth at 37ºC with initial pH of 6.0. This strain yielded 2.58% ethanol and 3.91mg of glucose/ ml of the medium M-II, comprising of 5% potato powder and 0.3% yeast extract after 192 hours of incubation at 37ºC. The ability of same microorganism to saccharify the potato starch and subsequently ferment the sugars into ethanol is highly valuable both for economical reasons as well in the scenario of suspect energy crisis in the future which would be seeking the solution in generating biofuels.