NADH- vs NADPH-coupled reduction of 5-hydroxymethyl furfural (HMF) and its implications on product distribution in Saccharomyces cerevisiae

Abstract

Saccharomyces cerevisiae alcohol dehydrogenases responsible for NADH-, and NADPH-specific reduction of the furaldehydes 5-hydroxymethyl-furfural (HMF) and furfural have previously been identified. In the present study, strains overexpressing the corresponding genes (mut-ADH1 and ADH6), together with a control strain, were compared in defined medium for anaerobic fermentation of glucose in the presence and absence of HMF. All strains showed a similar fermentation pattern in the absence of HMF. In the presence of HMF, the strain overexpressing ADH6 showed the highest HMF reduction rate and the highest specific ethanol productivity, followed by the strain overexpressing mut-ADH1. This correlated with in vitro HMF reduction capacity observed in the ADH6 overexpressing strain. Acetate and glycerol yields per biomass increased considerably in the ADH6 strain. In the other two strains, only the overall acetate yield per biomass was affected. When compared in batch fermentation of spruce hydrolysate, strains overexpressing ADH6 and mut-ADH1 had five times higher HMF uptake rate than the control strain and improved specific ethanol productivity. Overall, our results demonstrate that (1) the cofactor usage in the HMF reduction affects the product distribution, and (2) increased HMF reduction activity results in increased specific ethanol productivity in defined mineral medium and in spruce hydrolysate.

Enhanced biofuel production through coupled acetic acid and xylose consumption by engineered yeast

“…The improved ethanol production from co-utilization of xylose and acetate was also demonstrated in synthetic medium and corn stover hydrolysates ( Supplementary Figs S9 and S10). In lignocellulosic hydrolysates, reduction of alternative electron acceptors such as furaldehyde compounds might also help improve xylose fermentation [31][32][33] . However, acetate reduction still occurred in the hydrolysates and improved ethanol yields by strain S-adhE as compared with S-nc, …”

Increased Furfural Tolerance Due to Overexpression of NADH-Dependent Oxidoreductase FucO in Escherichia coli Strains Engineered for the Production of Ethanol and Lactate

“…Thus, an effective microbial furfural reduction system has the potential to increase resistance to furfural. Furfural-resistant strains of S. cerevisiae have been isolated (2,20,22,23) and found to exhibit increased expression of aldehyde reductases, which may contribute to tolerance. In E. coli, many oxidoreductases were also induced by furfural, but none originally tested were found to reduce toxicity when overexpressed in the parent strain (29,30).…”

“…Furan alcohols (reduced products) are less toxic than the respective aldehydes (39,40). Several genes encoding oxidoreductases that reduce furfural and 5-hydroxymethylfurfural (5-HMF) (a dehydration product of hexose sugars) have been implicated in furan tolerance in Saccharomyces cerevisiae (2,20,21,22,23) and in Escherichia coli (29)(30)(31)38). Gene array studies identified more than 365 genes that changed in expression level during an HMF challenge, and these changes are proposed to be mediated by at least 5 different regulatory genes (24).…”

Roles of the Yap1 Transcription Factor and Antioxidants in Saccharomyces cerevisiae's Tolerance to Furfural and 5-Hydroxymethylfurfural, Which Function as Thiol-Reactive Electrophiles Generating Oxidative Stress

“…On the other hand, furfural and HMF can also be detoxified by oxidation by Ald6 aldehyde dehydrogenase (13). In line with these detoxification mechanisms, furfural-and/or HMF-tolerant yeast strains could be generated by the overexpression of ADH6, ADH7, and ALD6 (6,7,13). In addition, overexpression of ZWF1, involved in NADPH regeneration through a pentose phosphate pathway, also enhanced furfural tolerance (15).…”

“…These furan aldehydes are known as the most potent inhibitors of microbial cell growth (4,5). The toxic aldehyde groups of furfural and HMF can be reduced to hydroxyl groups by several oxidoreductases, including alcohol dehydrogenases (Adh1, Adh6, and Adh7) (6)(7)(8), aldehyde reductase (Ari1) (9), and methylglyoxal reductases (Gre2 and Gre3) in Saccharomyces cerevisiae cells (8,(10)(11)(12)(13) and aldehyde dehydrogenase (YqhD) and methylglyoxal reductase (DkgA) in Escherichia coli (14). These enzymes consume NADH and NADPH as cofactors during the reduction process.…”