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Sci Rep. 2017 Nov 1;7(1):14850. doi: 10.1038/s41598-017-14073-w.

Identification and characterization of a novel β-glucosidase via metagenomic analysis of Bursaphelenchus xylophilus and its microbial flora.

Author information

1
Department of Life Science and Biotechnology, Nanyang Normal University, Nanyang, 473000, P.R. China.
2
State Key Laboratory of Cotton Biology, Henan Key Laboratory of Plant Stress Biology, School of Life Sciences, Henan University, Kaifeng, 475004, China.
3
Department of Life Science and Biotechnology, Nanyang Normal University, Nanyang, 473000, P.R. China. qiuhongniu@hotmail.com.

Abstract

β-glucosidases catalyze the final step of cellulose hydrolysis and are essential in cellulose degradation. A β-glucosidase gene, cen502, was identified and isolated from a metagenomic library from Bursaphelenchus xylophilus via functional screening. Analyses indicated that cen502 encodes a 465 amino acid polypeptide that contains a catalytic domain belonging to the glycoside hydrolase family 1 (GH1). Cen502 was heterologously expressed, purified, and biochemically characterized. Recombinant Cen502 displayed optimum enzymatic activity at pH 8.0 and 38 °C. The enzyme had highest specific activity to p-nitrophenyl-β-D-glucopyranoside (pNPG; 180.3 U/mg) and had K m and V max values of 2.334 mol/ml and 9.017 μmol/min/mg, respectively. The addition of Fe2+ and Mn2+ significantly increased Cen502 β-glucosidase activity by 60% and 50%, respectively, while 10% and 25% loss of β-glucosidase activity was induced by addition of Pb2+ and K+, respectively. Cen502 exhibited activity against a broad array of substrates, including cellobiose, lactose, salicin, lichenan, laminarin, and sophorose. However, Cen502 displayed a preference for the hydrolysis of β-1,4 glycosidic bonds rather than β-1,3, β-1,6, or β-1,2 bonds. Our results indicate that Cen502 is a novel β-glucosidase derived from bacteria associated with B. xylophilus and may represent a promising target to enhance the efficiency of cellulose bio-degradation in industrial applications.

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