Overexpression of YAP1 gene increases the resistance of yeast strains to inhibitors found in lignocellulosic hydrolysates

Due to the constant increase in energy consumption, the production of biofuels from renewable sources, such as lignocellulosic waste, has become more frequent in the last several decades. Lignocellulosic waste consists of cellulose, hemicellulose and lignin and the yeast S. cerevisiae is not able to ferment it directly. Therefore, lignocellulosic waste is usually hydrolysed to release compounds that can be used for fermentation. However, the pretreatment also generates compounds that act as growth and fermentation inhibitors such as acetic and levulinic acid and 2-furaldehyde. In this study, newly constructed intraspecies hybrid diploids, obtained by crossing natural S. cerevisiae isolates, showed higher resistance to acetic and levulinic acid. Selected strains were also transformed with replicative vectors overexpressing yeast genes (e.g. ATR1, CTA1, FLR1, YAP1, ZWF1) encoding proteins involved in a stress response and the overexpression of YAP1 gene further increased the resistance to inhibitors. Therefore, our results suggest that the construction of intraspecies hybrids coupled with genetic engineering is a promising approach for construction of new biotechnologically relevant yeast strains.