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Deletion of alcohol dehydrogenase 2 gene in Pachysolen tannophilus improves ethanol production from corn stover hydrolysates

Sen Yang, Jiufeng Xie, Guangqing Pei, Shasha Zhang, Hui Xie, Fengqin Wang, Hongge Chen, Andong Song

Although ethanol derived from lignocellulosic biomass is a promising alternative biofuel, the conversion rate of xylose to ethanol by fermentation is not ideal due to the low efficiency of many common yeasts in utilizing xylose. Pachysolen tannophilus can convert hexose and pentose such as L-arabinose, xylose and glucose in lignocellulosic hydrolysates to ethanol simultaneously. To increase the conversion of corn stover hydrolysates to bioethanol, the effect of alcohol dehydrogenase 2 gene (adh2) deletion in P. tannophilus on bioethanol production from corn stover hydrolysates was investigated. Two adh2 deletants (heterozygote ND and homozygote MC) were constructed by using the short flanking homology PCR (SFH-PCR). The ND and MC strains showed lower alcohol dehydrogenase 2 (ADH2) activity than the initial strain P-01. In the fermented pentose and hexose sugars of MC and ND, the ethanol concentrations (g/L) reached 15.8 and 18.9 versus14.6 of the initial P-01, while in the corn stover hydrolysate medium, the ethanol concentrations (g/L) were 9.1 for MC and 9.8 for ND versus 7.5 for the initial strain P-01. This research provides useful information for improving the conversion efficiency of hexose and pentose to bioethanol by Pachysolen tannophilus.