Ethanol production using nuclear petite yeast mutants |
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Authors: | A Hutter S G Oliver |
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Institution: | (1) Department of Biomolecular Sciences, UMIST, PO Box 88, Sackville St., Manchester, M60 1QD, UK Tel.: +44 161 200 4203 Fax: +44 161 236 0409 e-mail: steve.oliver@umist.ac.uk, GB |
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Abstract: | Two respiratory-deficient nuclear petites, FY23Δpet191 and FY23Δcox5a, of the yeast Saccharomyces cerevisiae were generated using polymerase-chain-reaction-mediated gene disruption, and their respective ethanol tolerance and productivity
assessed and compared to those of the parental grande, FY23WT, and a mitochondrial petite, FY23ρ0. Batch culture studies demonstrated that the parental strain was the most tolerant to exogenously added ethanol with an inhibition
constant. K
i, of 2.3% (w/v) and a specific rate of ethanol production, q
p, of 0.90 g ethanol g dry cells−1 h−1. FY23ρ0 was the most sensitive to ethanol, exhibiting a K
i of 1.71% (w/v) and q
p of 0.87 g ethanol g dry cells−1 h−1. Analyses of the ethanol tolerance of the nuclear petites demonstrate that functional mitochondria are essential for maintaining
tolerance to the toxin with the 100% respiratory-deficient nuclear petite, FY23Δpet191, having a K
i of 2.14% (w/v) and the 85% respiratory-deficient FY23Δcox5a, having a K
i of 1.94% (w/v). The retention of ethanol tolerance in the nuclear petites as compared to that of FY23ρ0 is mirrored by the ethanol productivities of these nuclear mutants, being respectively 43% and 30% higher than that of the
respiratory-sufficient parent strain. This demonstrates that, because of their respiratory deficiency, the nuclear petites
are not subject to the Pasteur effect and so exhibit higher rates of fermentation.
Received: 22 September 1997 / Accepted: 7 December 1997 |
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