Toxic Effects and Adaptive Response Mechanisms of Lignocellulose-Derived Phenolic Aldehydes in <i>Saccharomyces cerevisiae</i> during Cellulosic Ethanol Fermentation

Lignocellulose-derived phenolic aldehydes, including <i>p</i>-hydroxybenzaldehyde (P), vanillin (V), and syringaldehyde (S), exert synergistic inhibition on the fermentation performance of <i>Saccharomyces cerevisiae</i>. In this study, a robust <i>S. cerevisiae</i> S91 was obtained through adaptive laboratory evolution under increasing concentrations of a mixed phenolic aldehyde cocktail (P + V + S). Phenotypic analyses of <i>S. cerevisiae</i> S91 revealed enhanced phenolic aldehyde detoxification, improved cell morphology, and increased membrane integrity under inhibitory conditions. The evolved strain exhibited over 60% improvement in the conversion of phenolic aldehydes and demonstrated a 1.5-fold increase of ethanol titer in corn stover hydrolysate. Comprehensive transcriptomic, qRT-PCR, and fermentation evaluation revealed plasma membrane-associated genes, including <i>GEX1</i> and <i>PST2</i>, played a vital role in the improved phenolic aldehyde tolerance of the evolved strain. This work advanced our understanding of the physiological and molecular mechanisms underlying phenolic aldehyde tolerance in <i>S. cerevisiae</i> and provided a robust strain for cellulosic ethanol production.