ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002530051206
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