Introduction of a feed back resistant alpha-isopropylmalate synthase gene of Saccharomyces cerevisiae into sake yeast
1994
Suizu, T. (Gekkeikan Sake Co. Ltd., Kyoto (Japan)) | Kotani, K. | Yasui, K. | Ichikawa, E. | Kawato, A. | Imayasu, S.
A mutant LEU4 gene (LEU4fbr-2), responsible for both the overproduction of iso-amyl alcohol in yeast and the phenotype of yeast resistant to 5,5,5-trifluoro-DL-leucin (TFL), was isolated from a TFL-resistant mutant of Saccharomyces cerevisiae F-7. The single copy number of LEU4fbr-2 complemented the leucine auxotrophy of S. cerevisiae HB190 (a, leu4, leu5), and also transformed it to TFL-resistant. Leucine-insensitive alpha-isopropylmalate synthase activity was detected in the crude extract of the Leu+ transformant. Also sake yeast Kyokai no.7 (K-7) was transformed by the LEU4fbr-2 gene to TFL-resistant. The resulting transformants produced 3-30-fold higher levels of iso-amyl alcohol (approx., 50-475 ppm) in shaking cultures, while in static cultures the increase in productivity was only 2.5-fold compared with that of recipient strain K-7. The isolated LEU4fbr-2 gene may be useful as a positive selectable marker for the transformation of industrial yeast
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