Characterization of a novel isoflavone glycoside-hydrolyzing β-glucosidase from mangrove soil metagenomic library

For the beneficial pharmacological properties of isoflavonoids and their related glycoconjugates, there is increasingly interest in their enzymatic conversion. In this study, a novel beta-glucosidase gene isolated from metagenomic library of mangrove sediment was cloned and overexpressed in Escherichia coli BL21(DE3). The purified recombination beta-glucosidase, designated as r-Bgl6 6, showed high catalytic activity for soy isoflavone glycosides. It converted soy isoflavone flour extract with the productivities of 0.87 mM/h for daidzein, 0.59 mM/h for genistein and 0.42 mM/h for glycitein. The k(cat)/K-m values for daidzin, genistin and glycitin were 208.73, 222.37 and 288.07 mM(-1) s(-1) , respectively. In addition, r-Bgl66 also exhibited the characteristic of glucose-tolerance, and the inhibition constant K-i was 471.4 mM. These properties make it a good candidate in the enzymatic hydrolysis of soy isoflavone glycosides. This study also highlights the utility of metagenomic approach in discovering novel beta-glucosidase for soy isoflavone glycosides hydrolysis. (c) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).