Researchers have identified four novel salt-tolerant β-glucosidase genes from saline soil in Karamay, Xinjiang, China, which show significant potential for the bioconversion of soybean isoflavone glycosides. Published in AMB Express, the study details the metagenomic mining of these genes, their heterologous expression in Escherichia coli DH5α, and the subsequent characterization of two specific enzymes, B0-BG30 and B0-BG36. These enzymes exhibit high hydrolytic activity toward glycosides, a process that converts them into more bioactive aglycones, a transformation with substantial applications in the food, fuel, and pharmaceutical industries.
β-Glucosidase, classified under EC 3.2.1.21, functions by hydrolyzing β-glycosidic bonds. This enzymatic activity is critical for breaking down complex glycosides, such as soybean isoflavone glycosides and ginsenosides, into their simpler, more bioactive aglycone forms.
The research team, led by Qin Duan and colleagues, cloned the four identified genes, designated b0-bg30, b0-bg32, b0-bg36, and b0-bg40, and expressed them in E. coli DH5α. Through systematic screening using cellobiose and isoflavone substrates, the study pinpointed B0-BG30 and B0-BG36 as the most effective candidates. Both enzymes were purified and subjected to detailed biochemical characterization to evaluate their stability and catalytic efficiency under various environmental conditions, providing a comprehensive profile of their functional capabilities.
Biochemical analysis revealed distinct optimal conditions for the two enzymes. B0-BG30 exhibited an optimal temperature of 40 °C and an optimal pH of 5.6, while B0-BG36 showed an optimal temperature of 55 °C and an optimal pH of 5.0. Notably, B0-BG30 demonstrated remarkable stability, retaining full activity after a two-hour incubation at 35 °C and maintaining broad pH stability across a range of 5.0 to 10.0.
A key finding of the study is the exceptional salt tolerance of B0-BG30. The enzyme’s activity was not only maintained but enhanced by more than 130% in the presence of 0.5 to 3.5 M NaCl.
Both B0-BG30 and B0-BG36 displayed high specific hydrolytic activity toward genistin, a representative isoflavone glycoside. The measured activities were 5.36 ± 0.27 U/mg for B0-BG30 and 3.46 ± 0.25 U/mg for B0-BG36. To understand the structural basis of this catalytic efficiency, the researchers employed molecular docking to investigate substrate recognition and catalytic mechanisms. The analysis indicated that Asn-414 in B0-BG30 and Glu-166 in B0-BG36 are key residues involved in substrate binding and catalysis, forming hydrogen-bond networks that stabilize the substrates within the active site.
The structural insights from molecular docking were consistent with the enzymatic data, providing a mechanistic explanation for the enzymes’ performance toward both cellobiose and genistin. Furthermore, the study validated the feasibility of a high-throughput screening method using high-performance liquid chromatography (HPLC) and a glucose oxidase-based approach. This methodological advancement offers a technical foundation for the rapid identification and evaluation of other glycoside hydrolases with similar hydrolytic capabilities, potentially accelerating the discovery of new biocatalysts for industrial use.
In summary, this study provides robust candidate biocatalysts for the green bioconversion of isoflavones into aglycones. By identifying novel β-glucosidases from a saline environment and characterizing their unique salt-tolerant properties, the research lays a technical foundation for high-throughput screening and mechanistic investigation of glycoside hydrolases.
Subject of Research: Characterization of salt-tolerant β-glucosidases from saline soil for isoflavone bioconversion
Article Title: Salt-tolerant β-glucosidases from Karamay saline soil for soybean isoflavone bioconversion
Article References: Duan, Q., Zhu, Q., Zhang, Y.-J., Shao, Z.-J., Zhang, X., Li, M.-S., Wang, X., Chen, Y., Li, C.-J., Li, J.-L., Lv, Z.-H., Yang, Z.-F., Zhu, D., Hu, W., & Yin, Y.-R. (2026). Salt-tolerant β-glucosidases from Karamay saline soil for soybean isoflavone bioconversion. AMB Express. https://doi.org/10.1186/s13568-026-02104-7
Image Credits: AI Generated
DOI: 10.1186/s13568-026-02104-7
Keywords: β-glucosidase, soybean isoflavones, saline soil, metagenomics, bioconversion, salt tolerance, molecular docking, glycoside hydrolases, biocatalysts, Karamay, Salt-tolerant, glucosidases
News Source: Gregory Coleman. (November 8, 2026). Saline Soil Enzymes Convert Soybean Isoflavones. Scienmag.
