GRE2 from Scheffersomyces stipitis as an aldehyde reductase contributes tolerance to aldehyde inhibitors derived from lignocellulosic biomass

Authors: WANG, XU - Sichuan Agricultural University; MA, MENGGEN - Sichuan Agricultural University; Liu, Zonglin; XIANG, QUANJU - Sichuan Agricultural University; LI, XI - Sichuan Agricultural University; LIU, NA - Sichuan Agricultural University; ZHANG, XIAOPING - Sichuan Agricultural University

Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2016
Publication Date: 3/22/2016
Citation: Wang, X., Ma, M., Liu, Z.L., Xiang, Q., Li, X., Liu, N., Zhang, X. 2016. GRE2 from Scheffersomyces stipitis as an aldehyde reductase contributes tolerance to aldehyde inhibitors derived from lignocellulosic biomass. Applied Microbiology and Biotechnology. 100(15):6671-6682. doi: 10.1007/s00253-016-7445-4.

Interpretive Summary: Aldehyde inhibitors have been identified recently as a major class of toxic compounds derived from lignocellulosic biomass pretreatment. Yeast tolerance has been studied intensively and mechanisms of in situ detoxification and an aldehyde reduction gene family were identified for industrial yeast Saccharomyces cerevisiae. However, functions of many genes for Scheffersomyces (Pichia) stipitis, a naturally occurring xylose utilization yeast, remain to be identified. This study characterized an unknown open reading frame of PICST_72153 in S. stipitis and provided comprehensive evidence identifying it as an aldehyde reductase attributing tolerance to aldehyde inhibitors furfural and 5-hydroxymethylfurfural. Results of this research contributes to gene annotation of S. stipitis as well as understanding mechanisms of yeast tolerance. New knowledge obtained from this study also aids more tolerance strain development for biofuels production from lignocellulosic materials.

Technical Abstract: Scheffersomyces (Pichia) stipitis is one of the most promising yeasts for industrial bioethanol production from lignocellulosic biomass. S. stipitis is able to in situ detoxify aldehyde inhibitors [such as furfural and 5-hydroxymethylfurfural (HMF)] to less toxic corresponding alcohols. However, the reduction enzymes involved in this reaction remain largely unknown. In this study, we reported that an uncharacterized open reading frame PICST_72153 (putative GRE2) from S. stipitis was highly induced in response to furfural and HMF stresses. Overexpression of this gene in S. cerevisiae improved yeast tolerance to furfural and HMF. GRE2 was identified as an aldehyde reductase which can reduce furfural to furan ethanol (FM) with either nicotinamide adenine dinucleotide (NADH) or nicotinamide adenine dinucleotide phosphate (NADPH) as the co-factor, reduce HMF to furan dimethanol (FDM) with NADPH as the co-factor. This enzyme can also reduce multiple aldehydes to their corresponding alcohols. Amino acid sequence analysis indicated that it is a member of the subclass ‘intermediate’ of the short-chain dehydrogenase/reductase (SDR) superfamily. Although GRE2 from S. stipitis is similar to GRE2 from Saccharomyces cerevisiae in three-dimensional structure, some differences were predicted. GRE2 from S. stipitis forms loops at D133-E137 and T143-N145 locations with two a-helices at E154-K157 and E252-A254 locations, different GRE2 from S. cerevisiae with an a-helix at D133-E137 and a ß-sheet at T143-N145 locations and two loops at E154-K157 and E252-A254 locations. This research provided guidelines for study of other SDR enzymes from S. stipitis and other yeasts on tolerant mechanisms to aldehyde inhibitors derived from lignocellulosic biomass.