Transcriptional response and alterations in adenonucleotides and redox cofactors in S. cerevisiae upon treatment with HMF and furfural

Conference poster, 2012

Liberation of sugars monomers from the polysaccharides constituting lignocellulosic biomass requires pretreatment and hydrolysis. Harsh conditions during pretreatment promote the formation of a number of inhibitory compounds, among which the furaldehydes furfural and hydroxymethylfurfural (HMF) have shown to impede growth and limit ethanol productivity of the yeast Saccharomyces cerevisiae. In the present study, a recombinant xylose-utilizing S. cerevisiae strain was challenged with sub-lethal concentrations of furfural and HMF in anaerobic continuous and batch cultivations. The inhibitors concentration was as close as possible to lethal, yet allowing steady state in continuous cultivations. For batch cultivations, the chosen concentration completely inhibited growth, yet allowing growth resumption. Analysis of the transcriptome and the levels of intracellular metabolites connected to energy and redox metabolism was performed in comparison with cells grown in the absence of inhibitors. Exposure to furaldehydes caused a significant alteration of the fermentation products, especially in batch cultivations. Transcriptome analysis revealed that genes involved in xenobiotic transporter activity were significantly enriched among the up-regulated genes upon inhibitors treatment. Furthermore, inhibitors treatment significantly decreased both catabolic and anabolic reduction charges, indicating that HMF and furfural are draining the cells of reductive power during growth. In addition, HMF and furfural caused a reduction in the [ATP]/[ADP] ratio in treated cells, suggesting that the energy metabolism was affected. The results from the present study provide valuable insights into how S. cerevisiae deals with stress imposed by HMF and furfural, which potentially can result in development of strategies to improve stress tolerance during fermentation of wood hydrolysate.