Elucidating cellular mechanisms of Saccharomyces cerevisiae tolerant to combined lignocellulosic-derived inhibitors using high-throughput phenotyping and multiomics analyses.

A robust cell factory that can tolerate combined inhibitory lignocellulosic compounds is essential for the cost-effective lignocellulose-based production of second-generation bioethanol and other bulk chemicals. Following high-throughput phenotyping of a yeast genomic overexpression library, we identified a Saccharomyces cerevisiae mutant (denoted AFb.01) with improved growth and fermentation performance under combined toxicity of acetic acid and furfural. AFb.01 carries overexpression of TRX1, which encodes for thioredoxin, a cellular redox machinery. Through comparative proteomics and metabolomics, the resulting cell-wide changes in the mutant were elucidated and these primarily target on the maintenance of energy and redox homeostasis and the minimization of stress-induced cell damages. In particular, the upregulation of the stress-response proteins Hsp26p and Fmp16p conferred tolerance of AFb.01 against protein denaturation and DNA damage. Moreover, increased levels of protectant metabolites such as trehalose, fatty acids, GABA and putrescine provided additional defense mechanisms for the mutant against oxidative and redox stresses. Future studies will concentrate on targeted genetic engineering to validate these mechanisms as well as to support the creation of more robust yeast strains, applicable for industrial, cost-competitive biorefinery production.