Additive genetic effects of SEA4 in phenotypes of 5-(hydroxymethyl)furfural resistance and thermotolerance in industrial strains of Saccharomyces cerevisiae

Abstract

The second-generation ethanol industry is based on the fermentation of xylose, which is present in lignocellulosic biomass. Genetically modified strains of Saccharomyces cerevisiae are capable of assimilating this monosaccharide, but face unfavorable conditions typical to the industrial scale of production. The process generates inhibitors that negatively affect yeast performance and the conversion of sugars. Side products like 5-(hydroxymethyl)furfural (HMF) and the occurrence of temperature fluctuations are two big examples of inhibitors. In this context, the toxicity of the industrial environment fuels the search for robust strains that present phenotypes resistant to those adversities, allowing biosynthesis to prevail. In a study published in 2021, de Mello et al. identified new causative genes for HMF tolerance and thermotolerance in the strain SA-1, amongst them SEA4 - which positively regulates signaling in TORC1. Evidence suggests there may be additive genetic effects at play, pointing to a complex network of gene interactions that involves essential intracellular signaling pathways such as cell wall integrity (CWI) and target of rapamycin (TOR). This proposal is set to investigate the underlying genetic basis of this robust phenotype through the replacement of the alleles previously identified in pairs, to assess the presence of additive genetic effects and/or epistatic effects. Following through with this line of research brings about the possibility for continuous enhancement, with the discovery of more targets for the genetic and metabolic engineering of S. cerevisiae applied to xylose fermentation, and also, a greater understanding of the contribution of pathways CWI and TORC1 to industrial robustness.(AU)