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The strain of Nuruk yeat No. 15 (NY-15) which ferments lactose in milk was isolated from Nuruk and identified as Saccharomyces marxaanus according to the API 20C profile index. The lactose hydrolysing ability of NY-15 was similar to that Saccharomyces fzagilis ATCC 8583 which has -galactosidase activity. Its optimum growth temperature, pH and time for the production of maximum enzyme activity showed 28 , 4.5 and 28hr, respectively. Galactose as well as sucrose as carbon sources, and urea as nitrogen source increased the production of enzyme. In order to test the production of alcohol, NY-15 was inocu´.ated in whey medium and whey medium added with sugar. In the former, NY-15 produced 2 alcohol and in the latter, it showed 12 alcohol production. The optimal medium pH for lactose hydrolysis of NY-15 is 4.5, whereas that of Saccharomyces fragilis ATCC 8583 is 3.5.
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