초록
<P><B>Highlights</B></P><P>► We engineered <I>Saccharomyces cerevisiae</I> for increased isobutanol production. ► Ehrlich pathway was enhanced by overexpressing suitable KDC and ADH enzymes. ► Ethanol flux was altered by combining <I>ILV2</I> overexpression and <I>PDC1</I> disruption.</P> <P><B>Abstract</B></P><P>The production of higher alcohols by engineered bacteria has received significant attention. The budding yeast, <I>Saccharomyces cerevisiae</I>, has considerable potential as a producer of higher alcohols because of its capacity to naturally fabricate fusel alcohols, in addition to its robustness and tolerance to low pH. However, because its natural productivity is not significant, we considered a strategy of genetic engineering to increase production of the branched-chain higher alcohol isobutanol, which is involved in valine biosynthesis. Initially, we overexpressed 2-keto acid decarboxylase (KDC) and alcohol dehydrogenase (ADH) in <I>S. cerevisiae</I> to enhance the endogenous activity of the Ehrlich pathway. We then overexpressed Ilv2, which catalyzes the first step in the valine synthetic pathway, and deleted the <I>PDC1</I> gene encoding a major pyruvate decarboxylase with the intent of altering the abundant ethanol flux via pyruvate. Through these engineering steps, along with modification of culture conditions, the isobutanol titer of <I>S. cerevisiae</I> was elevated 13-fold, from 11mg/l to 143mg/l, and the yield was 6.6mg/g glucose, which is higher than any previously reported value for <I>S. cerevisiae</I>.</P>