Profiling of Saccharomyces cerevisiae transcription factors for engineering the resistance of yeast to lignocellulose-derived inhibitors in biomass conversion

Abstract

Background: Yeast transcription factors (TFs) involved in the regulation of multidrug resistance (MDR) were investigated in experiments with deletion mutants, transformants overexpressing synthetic genes encoding TFs, and toxic concentrations of lignocellulose-derived substances added to cultures as complex mixtures or as specific compounds, viz. coniferyl aldehyde, 5-hydroxymethylfurfural, and furfural.

Results: In the presence of complex mixtures of toxic substances from spruce wood, transformants overexpressing YAP1 and STB5, TFs involved in oxidative stress response, exhibited enhanced relative growth rates amounting to 4.589 ± 0.261 and 1.455 ± 0.185, respectively. Other TFs identified as important for resistance included DAL81, GZF3, LEU3, PUT3, and WAR1. Potential overlapping functions of YAP1 and STB5 were investigated in experiments with permutations of deletions and overexpression of the two genes. YAP1 complemented STB5 with respect to resistance to 5-hydroxymethylfurfural, but had a distinct role with regard to resistance to coniferyl aldehyde as deletion of YAP1 rendered the cell incapable of resisting coniferyl aldehyde even if STB5 was overexpressed.

Conclusions: We have investigated 30 deletion mutants and eight transformants overexpressing MDR transcription factors with regard to the roles the transcription factors play in the resistance to toxic concentrations of lignocellulose-derived substances. This work provides an overview of the involvement of thirty transcription factors in the resistance to lignocellulose-derived substances, shows distinct and complementary roles played by YAP1 and STB5, and offers directions for the engineering of robust yeast strains for fermentation processes based on lignocellulosic feedstocks.

Keywords: Lignocellulosic biomass conversion; Multidrug resistance; STB5; Saccharomyces cerevisiae; Transcription factors; YAP1.

Fig. 1

Heatmap of relative growth rate in the screening experiments with deletion mutants. The deletion mutants were cultivated with 1.0 mM coniferyl aldehyde (CFA), 10.4 mM furfural (FUR), 14.0 mM HMF, sugarcane bagasse pretreatment liquid (BPL), and spruce pretreatment liquid (SPL). The data indicate: relative growth rate < 0.5 , 0.5 ≤ relative growth rate < 0.9 , 0.9 ≤ relative growth rate ≤ 1.1 , 1.1 < relative growth rate ≤ 1.5 , and relative growth rate > 1.5 . The result with the NGG1 deletion mutant was not included in the figure, since the growth of the NGG1 deletion mutant in the SC medium was slower than that of BY4741. The numerical data for relative growth are included in Additional file 1: Table S1

Fig. 2

Relative growth rate of the transformants. The transformants were cultivated with sugarcane bagasse pretreatment liquid (grey square) and spruce pretreatment liquid (red square)

Fig. 3

Cell growth and glucose consumption during flask experiments. BY4741, M-Y, M-S, SIY and YIS were cultivated in control medium (a), medium with 1.1 mM coniferyl aldehyde (b), and medium with 24 mM HMF (c). The data indicate: OD of BY4741 (filled black square), M-Y (filled red circle), M-S (filled orange triangle), SIY (filled inverted blue triangle), YIS (filled green rhombus), and glucose concentration of BY4741 (open black square), M-Y (open red circle), M-S (open orange triangle), SIY (open inverted blue triangle), YIS (open green rhombus)