전분질의 에탄을 직접발효에 유용한 Saccharomyces diastaticus의 glucoamylase 생산성 향상을 위하여 glucoamylase 유전자 STA1을 함유한 재조합 plasmid pYES 18을 갖는 S. diastaticus의 형질전환 균주에서 성장속도가 plasmid의 안정성에 미치는 영향과 plasmid 안정성에 따른 glucoamylase 생산성을 조사하였다. 최소 선택배지에서는 plasmid가 일정한 수준에서 안정하게 유지되었으나, 균체의 증식과 glucoamylase 생산성은 매우 미약하였다. Starch가 포함된 완전배지에서는 glucose를 첨가해 줌으로써 생육속도를 촉진시킬 수 있었으며 생육속도의 촉진에 의해 plasmid 안정성이 증가되었고 이에 따라 glucoamylase 생산성이 향상됨을 알았다.
For the purpose of improving glucoamylase productivity of Saccharomyces diastaticus, useful yeast in direct ethanol fermentation of starch, the effects of growth rate on the plasmid stability and glucoamylase productivity of S. diastaticus harboring recombinant plasmid pYES 18 containing glucoamylase gene STA 1 were investigated. In a selective medium, the recombinant plasmids were maintained stably at constant level but glucoamylase productivity was very low. On the other hand, in the complex medium containing starch, growth rate of the cell was stimulated by the supplementation of glucose and plasmid stability was improved by growth stimulation. We can conclude that glucoamylase productivity of S. diastaticus harboring the recombinant plasmid was increased as the maintaining of high plasmid stability in the cell.
