Alcohol dehydrogenases fromScheffersomyces stipitis involved in the detoxification of aldehyde inhibitors derived from lignocellulosic biomass conversion. Applied Microbiology and Biotechnology,2013,97:8411-8425.
Menggen Ma1 & Xu Wang2 & Xiaoping Zhang2 & Xianxian Zhao2
1 Institute of Ecological and Environmental Sciences, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang, Sichuan 611130, People’s Republic of China
2 Department of Applied Microbiology, College of Resource and Environmental Sciences, Sichuan Agricultural University, Sichuan, China
Abstract: Aldehyde inhibitors such as furfural and 5-hydroxymethylfurfural (HMF) are generated from biomass pretreatment.Scheffersomyces stipitisis able to reduce furfural and HMF to less toxic furanmethanol and furan-2,5-dimethanol; however, the enzymes involved in the reductive reaction still remain unknown. In this study, transcription responses of two known and five putative alcohol dehydrogenase genes fromS. stipitiswere analyzed under furfural and HMF stress conditions. All the seven alcohol dehydrogenase genes were also cloned and overexpressed for their activity analyses. Our results indicate that transcriptions ofSsADH4 andSsADH6were highly induced under furfural and HMF stress conditions, and the proteins encoded by them exhibited NADH- and/or NADPH-dependent activities for furfural and HMF reduction, respectively. For furfural reduction, NADHdependent activity was also observed in SsAdh1p and NAD(P)H-dependent activities were also observed in SsAdh5p and SsAdh7p. For HMF reduction, NADPHdependent activities were also observed in SsAdh5p and SsAdh7p. SsAdh4p displayed the highest NADPHdependent specific activity and catalytic efficiency for reduction of both furfural and HMF among the seven alcohol dehydrogenases. Enzyme activities of all SsADH proteinswere more stable under acidic condition. For most SsADH proteins, the optimum temperature for enzyme activities was 30 °C and more than 50 % enzyme activities remained at 60 °C. Reduction activities of formaldehyde, acetaldehyde, isovaleraldehyde, benzaldehyde, and phenylacetaldehyde were also observed in some SsADH proteins. Our results indicate that multiple alcohol dehydrogenases in S. stipitis are involved in the detoxification of aldehyde inhibitors derived from lignocellulosic biomass conversion.
Keywords: Alcohol dehydrogenase, Aldehyde inhibitors, Detoxification, Ethanol, Lignocellulosic biomass, Scheffersomyces stipitis