Furfural and hydroxy-methyl-furfural (HMF) are produced by lignocellulosic biomass during heat or acid pretreatment and are toxic to yeast. Aldehyde reductase is the main enzyme to reduce furfural and HMF. To improve the conversion efficiency of lignocellulosic biomass into ethanol, we constructed Saccharomyces cerevisiae with overexpression of aldehyde reductase (encoded by ari1). The gene of aldehyde reductase (encoded by ari1) was cloned via polymerase chain reaction (PCR) and ligated with the expression vector pGAPZαC. Western blot coupled with anti-His tag confirmed overexpression of the ari1 gene. The growth curves of the wild and ari1-overexpressed strain in the YPD medium were found to be almost identical. Compare to the ari1-overexpressed strain, the wild strain showed a longer doubling time and lag phase in the presence of 20 mM furfural and 60 mM HMF, respectively. The real-time PCR results showed that furfural was much more potent than HMF in stimulating ari1 expression, but the cell growth patterns showed that 60 mM HMF was more toxic to yeast than 20 mM furfural. S. cerevisiae with ari1 overexpression appeared to confer higher tolerance to aldehyde inhibitors, thereby increasing the growth rate and ethanol production capacity of S. cerevisiae in an aldehyde-containing environment.
Keywords: Saccharomyces cerevisiae; aldehyde reductase; ethanol production; furfural; hydroxy-methyl-furfural.