Expression of aldehyde dehydrogenase 6 reduces inhibitory effect of furan derivatives on cell growth and ethanol production in Saccharomyces cerevisiae

Yeast dehydrogenases and reductases were overexpressed in Saccharomyces cerevisiae D452-2 to detoxify 2-furaldehyde (furfural) and 5-hydroxymethyl furaldehyde (HMF), two potent toxic chemicals present in acid-hydrolyzed cellulosic biomass, and hence improve cell growth and ethanol production. Among those enzymes, aldehyde dehydrogenase 6 (ALD6) played the dual roles of direct oxidation of furan derivatives and supply of NADPH cofactor to their reduction reactions. Batch fermentation of S. cerevisiae D452-2/pH-ALD6 in the presence of 2 g/L furfural and 0.5 g/L HMF resulted in 20–30% increases in specific growth rate, ethanol concentration and ethanol productivity, compared with those of the wild type strain. It was proposed that overexpression of ALD6 could recover the yeast cell metabolism and hence increase ethanol production from lignocellulosic biomass containing furan-derived inhibitors.

► Dilute acid pretreatment of cellulosic biomass produces toxic furfural and HMF.
► Saccharomyces cerevisiae ALD6 oxidizes furfural and HMF and also supplies NADPH.
► ALD6 overexpression in S. cerevisiae increases cell growth and ethanol production.