FTIR stress response assay could lead the development of industrial yeast strains with high tolerance to lignocellulose-to-ethanol inhibitors. 32nd International Specialized Symposium on Yeasts: Yeasts Biodiversity and Biotechnology in the twenty-first century.

Introduction. Robust yeast strains with high inhibitors tolerance remain a critical requirement for the production of lignocellulosic bioethanol. These stress factors are known to severely hinder yeast growth and fermentation performance (Almeida et al. 2007). Fourier Transform InfraRed Spectroscopy (FTIR), recently applied in quick bioassays to obtain the metabolomic fingerprint of cells challenged with different chemicals (Corte et al. 2010), has never been used for the phenotypical characterization of industrial yeast strains under stressing conditions. Materials and methods. A FTIR-based bioassay was employed to explore the yeast metabolomic and viability responses to four inhibitors commonly found in lignocellulosic hydrolyzates: acetic acid, formic acid, furfural and 5-hydroxymethyl-2-furaldehyde. Among the 160 previously screened for inhibitors tolerance, three different Saccharomyces cerevisiae strains were selected as representative for the uppermost, medium and low robustness, respectively (Favaro et al. 2013; Favaro et al. 2014). The strains were assessed for their ability to withstand increasing concentrations of single inhibitors as well as binary, ternary and quaternary inhibitors mixtures. Results. The yeast reacted to increasing levels of single inhibitors with a strain-specific metabolomic and viability response. Moreover, for the first time, this study highlighted antagonistic interactions between inhibitors, whose effects were confirmed by both metabolomic and mortality values detected for the tested strains. The antagonism of inhibitors mixtures on yeast metabolism revealed to be strain-specific and was measured by qualitative and quantitative parameters. Discussion. FTIR analysis classified and characterized the selected strains in agreement with the results obtained in previous laborious investigations, demonstrating that FTIR-based assay is a powerful tool for screening and assessing bioethanol industrial fitness in yeast. The antagonistic effects of inhibitors mixtures described in this study are worth of further studies to understand the related mechanism and to assist strain selection towards the development of highly tolerant yeast strains.