Disruption of URA7 and GAL6 improves the ethanol tolerance and fermentation capacity of Saccharomyces cerevisiae

Abstract

Screening of the homozygous diploid yeast deletion pool of 4741 non-essential genes identified two null mutants (Deltaura7 and Deltagal6) that grew faster than the wild-type strain in medium containing 8% v/v ethanol. The survival rate of the gal6 disruptant in 10% ethanol was higher than that of the wild-type strain. On the other hand, the glucose consumption rate of the ura7 disruptant was better than that of the wild-type strain in buffer containing ethanol. Both disruptants were more resistant to zymolyase, a yeast lytic enzyme containing mainly beta-1,3-glucanase, indicating that the integrity of the cell wall became more resistance to ethanol stress. The gal6 disruptant was also more resistant to Calcofluor white, but the ura7 disruptant was more sensitive to Calcofluor white than the wild-type strain. Furthermore, the mutant strains had a higher content of oleic acid (C18 : 1) in the presence of ethanol compared to the wild-type strain, suggesting that the disruptants cope with ethanol stress not only by modifying the cell wall integrity but also the membrane fluidity. When the cells were grown in medium containing 5% ethanol at 15 degrees C, the gal6 and ura7 disruptants showed 40% and 14% increases in the glucose consumption rate, respectively.

Progress in Metabolic Engineering of Saccharomyces cerevisiae

“…Results point to modified cell wall integrity and membrane fluidity as the reasons for the disruptants' improved capability to cope with ethanol stress (394). In addition, gTME offers a promising alternative approach to access polygenic traits such as multiple stress tolerance.…”

Generation and characterisation of stable ethanol-tolerant mutants of Saccharomyces cerevisiae

“…It is perhaps not surprising that research on ethanol tolerance mechanisms in S. cerevisiae has mostly involved isolating ethanol-sensitive mutants to identify genes that are necessary for growth under ethanol stress [34]. While this has provided some insight into ethanol tolerance per se, the mechanisms associated with ethanol sensitivity do not necessarily translate into eVective strategies for improving ethanol tolerance [15].…”

Identification of novel genes responsible for salt tolerance by transposon mutagenesis in Saccharomyces cerevisiae

“…A few studies demonstrated that the disruption of specific gene(s) led to creation of strains tolerant to several kinds of stressors [21,22]. More recently, two clones with enhanced growth in 8 % ethanol and 10 osmotolerant clones were identified by screening of a single gene knockout library [23].…”