Rational engineering of Saccharomyces cerevisiae towards improved tolerance to multiple inhibitors in lignocellulose fermentations
Date
2021-08-28
Journal Title
Journal ISSN
Volume Title
Publisher
BMC (part of Springer Nature)
Abstract
Background: The fermentation of lignocellulose hydrolysates to ethanol requires robust xylose-capable Saccharomyces
cerevisiae strains able to operate in the presence of microbial inhibitory stresses. This study aimed at developing
industrial S. cerevisiae strains with enhanced tolerance towards pretreatment-derived microbial inhibitors, by identifying
novel gene combinations that confer resistance to multiple inhibitors (thus cumulative inhibitor resistance phenotype)
with minimum impact on the xylose fermentation ability. The strategy consisted of multiple sequential deltaintegrations
of double-gene cassettes containing one gene conferring broad inhibitor tolerance (ARI1, PAD1 or TAL1)
coupled with an inhibitor-specific gene (ADH6, FDH1 or ICT1). The performances of the transformants were compared
with the parental strain in terms of biomass growth, ethanol yields and productivity, as well as detoxification capacities
in a synthetic inhibitor cocktail, sugarcane bagasse hydrolysate as well as hardwood spent sulphite liquor.
Results: The first and second round of delta-integrated transformants exhibited a trade-off between biomass and
ethanol yield. Transformants showed increased inhibitor resistance phenotypes relative to parental controls specifically
in fermentations with concentrated spent sulphite liquors at 40% and 80% v/v concentrations in 2% SC media.
Unexpectedly, the xylose fermentation capacity of the transformants was reduced compared to the parental control,
but certain combinations of genes had a minor impact (e.g. TAL1 + FDH1). The TAL1 + ICT1 combination negatively
impacted on both biomass growth and ethanol yield, which could be linked to the ICT1 protein increasing transformant
susceptibility to weak acids and temperature due to cell membrane changes.
Conclusions: The integration of the selected genes was proven to increase tolerance to pretreatment inhibitors in
synthetic or industrial hydrolysates, but they were limited to the fermentation of glucose. However, some gene combination
sequences had a reduced impact on xylose conversion.
Description
CITATION: Brandt, B. A., et al. 2021. Rational engineering of Saccharomyces cerevisiae towards improved tolerance to multiple inhibitors in lignocellulose fermentations. Biotechnology for Biofuels, 14:173, doi:10.1186/s13068-021-02021-w.
The original publication is available at https://biotechnologyforbiofuels.biomedcentral.com
Publication of this article was funded by the Stellenbosch University Open Access Fund
The original publication is available at https://biotechnologyforbiofuels.biomedcentral.com
Publication of this article was funded by the Stellenbosch University Open Access Fund
Keywords
Lignocellulose -- Biotechnology, Saccharomyces cerevisiae, Saccharomyces cerevisiae -- Effect of stress on, Microbial inhibitors, Spent sulphite liquor, Saccharomyces cerevisiae -- Genetic engineering
Citation
Brandt, B. A., et al. 2021. Rational engineering of Saccharomyces cerevisiae towards improved tolerance to multiple inhibitors in lignocellulose fermentations. Biotechnology for Biofuels, 14:173, doi:10.1186/s13068-021-02021-w