遺傳學的 方法에 의한 澱粉醱酵 酵母菌株의 醱酵能 增進
(The) improvment of fermentability of the starch fermenting yeast strainby genetic methods
vii, 76 p.
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The purpose of this research is to improve the fermentation characteristics of the haploid starch-fermenting yeast strain, and to optimize the conditions of the starch-fermention for the efficient production of ethanol from starch. The fermentation characteristics include ethanol-tolerance, high temperature and sugar tolerance, fermentation efficiency, and fermentation rate. The starch-fermenting haploid yeaset used in this investigation was K114/YIpMS△R(LEU2/URA3) clone 1 which secretes both α-amylase and glucoamylase. K114/YIpMS△R(LEU2/URA3) clone 1 was hybridized with 1177 lys- strain having the high activity of glucoamylase. Among the resulting hybrid, HH64 having good ability of starch-fermentation has been selected. K114/YIpMS△R(LEU2/URA3) clone 1 was rare-mated with K35 petite mutant which has good fermentation-characteristics such as ethanol-tolerance, high temperature and sugar-tolerance, and fermentation rate. Among the resulting hybrids, the best strain RH51 was selected. The optimum temperature for starch-fermentation was 30℃ for HH64 strain and 34℃ for RH51 strain. The optimum pH for both strains was 5. The optimum size of inoculum for RH51 strain was 2% as the pellet (w/v) of yeast cells. The hybrid strain RH51 produced 7.0% ethanol (w/v) from 20% (w/v) soluble starch, but the conventional yeast K35 formed almost no ethanol, 0.3% (w/v). RH51 strain produced 7.5% (w/v) ethanol after 8 days in a fermenter with a capacity of 2.5 liter containing 800 ml of fermentation medium having 20% (w/v) soluble starch. The residual starch content was 1.68% (w/v), and therefore almost all the starch was fermented completely.