Improved thermostability of a metagenomic glucose-tolerant β-glycosidase based on its X-ray crystal structure
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MeBglD2, a metagenomic β-glycosidase, is stimulated by various saccharides, including d-glucose, d-xylose, and maltose, and it promotes the enzymatic saccharification of plant biomass. To improve the thermostability of MeBglD2, its X-ray crystal structure was analyzed, and the amino acid residues responsible for its thermostability were identified using the structural information. Mutations in His8, Asn59, and Gly295 improved the thermostability of MeBglD2, and the combination of these mutations resulted in the highest thermostability. Compared with wild-type MeBglD2, thermostable MeBglD2 mutants promoted plant biomass saccharification using Trichoderma reesei cellulase. In addition to thermostability, the thermostable mutants exhibited higher tolerance to ethanol, dimethyl sulfoxide, and copper ions, indicating that the MeBglD2 mutants generated in this study were improved in their tolerance to not only high temperature but also to organic solvents and metal ions.
Keywordsβ-glycosidase Metagenome Biomass Thermostabilization
The alkaline-treated rice straw was kindly provided by Dr. Yoshinori Kobayashi (Japan Bioindustry Association). The X-ray diffraction data were obtained at Beam Line BL44XU at SPring-8, Hyogo, Japan, with approval of the Institute for Protein Research, Osaka University, Osaka, Japan (proposal nos. 2016A6657 and 2016B6657).
This study was funded by JSPS KAKENHI (Grant-in-Aid for Young Scientists B, Grant No. 26850067).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This study did not involve any human participants or animals.
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