Submitted to: Yeasts International Symposium
Publication Type: Abstract only
Publication Acceptance Date: 7/6/2007
Publication Date: 7/1/2007
Citation: Liu, Z., Moon, J., Andersh, B.J., Slininger, P.J., Weber, S.A. 2007. Multiple gene mediated aldehyde reduction is a mechanism of in situ detoxification of furfural and 5-hydroxymethylfurfural by Saccharomyces cerevisiae [abstract]. Yeasts International Symposium. Abstract No. S-134. Interpretive Summary:
Technical Abstract: Furfural and HMF (5-hydroxymethylfurfural) are representative inhibitors to ethanologenic yeast generated from biomass pretreatment using dilute acid hydrolysis. Few yeast strains tolerant to inhibitors are available. We have developed tolerant strains of Saccharomyces cerevisiae with enhanced biotransformation ability to convert furfural to furan ethanol (FM), and HMF to furan di-methanol (FDM), and produce a normal yield of ethanol. Our recent identification and synthesis of the HMF metabolic conversion product, FDM, allowed studies on fermentation metabolic kinetics in the presence of HMF and furfural. Such obtained results enable us to further study mechanisms of the detoxification and tolerance of the yeast. We identified genes significantly induced by the inhibitors furfural and HMF which include functional enzymes, membrane protein transporters, and regulatory genes. In this study, we investigated functional enzymes that are directly involved in the detoxification of furfural and HMF. Among selected genes, some showed cofactor nicotinamide adenine dinucleotide (NADH)-dependant reduction activity, such as GRE3 and ALD4, while others demonstrated nicotinamide adenine dinucleotide phosphate (NADPH)-dependant enzyme activity such as ADH6. Reduction activities also varied on the substrates furfural or HMF. Enzymatic activities of whole cell lysate demonstrated clearly an aldehyde reduction coupled with both NADH and NADPH. A mutation of single gene deletion of the aldehyde reduction encoding enzyme did not affect the yeast to grow and detoxify the inhibitors. These suggested that the in situ detoxification of furfural and HMF was accomplished by the ethanologenic yeast through multiple gene mediated functions that collectively reduced the aldehyde function group with either or both NADH and NADPH.