초록
<P><B>Abstract</B></P> <P> <I>Saccharomyces cerevisiae</I> has a natural ability to produce higher alcohols, making it a promising candidate for production of isobutanol. However, the several pathways competing with isobutanol biosynthesis lead to production of substantial amounts of <SMALL>L</SMALL>-valine and <SMALL>L</SMALL>-isoleucine in mitochondria and isobutyrate, <SMALL>L</SMALL>-leucine, and ethanol in cytosol. To increase flux to isobutanol by removing by-product formation, the genes associated with formation of <SMALL>L</SMALL>-valine (<I>BAT1</I>), <SMALL>L</SMALL>-isoleucine (<I>ILV1</I>), isobutyrate (<I>ALD6</I>), <SMALL>L</SMALL>-leucine (<I>LEU1</I>), and ethanol (<I>ADH1</I>) were disrupted to construct the <I>S. cerevisiae</I> WΔGBIALA1_2vec strain. This strain showed 8.9 and 8.6 folds increases in isobutanol concentration and yield, respectively, relative the corresponding values of the background strain on glucose medium. In a bioreactor fermentation with a gas trapping system, the WΔGBIALA1_2vec strain produced 662 mg/L isobutanol concentration with a yield of 6.71 mg<SUB>isobutanol</SUB>/g<SUB>glucose</SUB>. With elimination of the competing pathways, the WΔGBIALA1_2vec strain would serve as a platform strain for isobutanol production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Deleting the pathways for valine and isoleucine in mitochondria was effective. </LI> <LI> Deleting the pathways for isobutyrate and leucine did not affect isobutanol titer. </LI> <LI> A batch fermentation with gas trapping resulted in 662 mg/L isobutanol titer. </LI> </UL> </P>