Unveiling the fitness of Saccharomyces cerevisiae strains for lignocellulosic bioethanol: a genomic exploration through fermentation stress tests

Abstract

Lignocellulosic biomass holds significant promise as a substrate for bioethanol production, yet the financial viability of lignocellulosic fermentation poses challenges. The pre-treatment step needed for lignocellulosic substrates generates inhibitors that impede Saccharomyces cerevisiae growth, affecting the fermentation process and overall yield. In modern sugarcane-to-ethanol plants, a rapid succession of yeast strains occurs, with dominant strains prevailing. Therefore, yeast strains with both dominance potential and inhibitor tolerance are crucial towards the development of superior strains with industrial fitness. This study adopted a hybrid approach combining biotechnology and bioinformatics to explore a cluster of 20 S. cerevisiae strains, including industrial and oenological strains exhibiting diverse phenotypic features. In-depth genomic analyses focusing on gene copy number variations (CNVs) and single nucleotide polymorphisms (SNPs) were conducted and compared with results from fermentation tests once inoculated in multiple strains kinetics under stressing conditions such as low nitrogen availability and high formic or acetic acid levels. Some strains showed high resistance to biotic stress and acetic acid. Moreover, four out of 20 strains – namely S. cerevisiae YI30, Fp89, Fp90 and CESPLG05 - displayed promising resistance also to formic acid, the most impactful weak acids in pre-treated lignocellulosic biomass. These strains have the potential to be used for the development of superior S. cerevisiae strains tailored for lignocellulosic bioethanol production.