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Disruption of the cytochrome c gene in xylose‐utilizing yeast Pichia stipitis leads to higher ethanol production
Author(s) -
Shi NianQing,
Davis Brian,
Sherman Fred,
Cruz Jose,
Jeffries Thomas W.
Publication year - 1999
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/(sici)1097-0061(199908)15:11<1021::aid-yea429>3.0.co;2-v
Subject(s) - pichia stipitis , salicylhydroxamic acid , biology , xylose , alternative oxidase , biochemistry , mutant , cytochrome c , cytochrome , cytochrome c oxidase , yeast , respiratory chain , fermentation , mitochondrion , gene , enzyme
The xylose‐utilizing yeast, Pichia stipitis, has a complex respiratory system that contains cytochrome and non‐cytochrome alternative electron transport chains in its mitochondria. To gain primary insights into the alternative respiratory pathway, a cytochrome c gene ( PsCYC1 , Accession No. AF030426) was cloned from wild‐type P. stipitis CBS 6054 by cross‐hybridization to CYC1 from Saccharomyces cerevisiae . The 333 bp open reading frame of PsCYC1 showed 74% and 69% identity to ScCYC1 and ScCYC7 , respectively, at the DNA level. Disruption of PsCYC1 resulted in a mutant that uses the salicylhydroxamic acid (SHAM)‐sensitive respiratory pathway for aerobic energy production. Cytochrome spectra revealed that cytochromes c and a·a 3 both disappeared in the cyc1 ‐Δ mutant, so no electron flow through the cytochrome c oxidase was possible. The cyc1 ‐Δ mutant showed 50% lower growth rates than the parent when grown on fermentable sugars. The cyc1 ‐Δ mutant was also found to be unable to grow on glycerol. Interestingly, the mutant produced 0·46 g/g ethanol from 8% xylose, which was 21% higher in yield than the parental strain (0·38 g/g). These results suggested that the alternative pathway might play an important role in supporting xylose conversion to ethanol under oxygen‐limiting conditions. Copyright © 1999 John Wiley & Sons, Ltd.