Exploration and Characterization of Novel Glycoside Hydrolases from the Whole Genome of and Enriched Production of Minor Ginsenoside Rg3() by a Recombinant Enzymatic Process.

Background: Several studies have reported that ginsenoside Rg3() is effective in treating metastatic diseases, obesity, and various cancers, however, its presence in white ginseng cannot be estimated, and only a limited amount is present in red ginseng. Therefore, the use of recombinant glycosidases from a Generally Recognized As Safe (GRAS) host strain is a promising approach to enhance production of Rg3(), which may improve nutritional activity, human health, and quality of life.

Method: EMML 3041, which was isolated from Korean fermented pickle (kimchi), presents ginsenoside-converting abilities. The strain was used to enrich the production of Rg3() by fermenting protopanaxadiol (PPD)-mix-type major ginsenosides (Rb1, Rb2, Rc, and Rd) in four different types of food-grade media (1, MRS; 2, Basel Food-Grade medium; 3, Basel Food-Grade medium-I, and 4, Basel Food-Grade medium-II). Due to its tendency to produce Rg3(), the presence of glycoside hydrolase in was proposed, the whole genome was sequenced, and the probable glycoside hydrolase gene for ginsenoside conversion was cloned.

Results: The EMML 3041 strain was whole genome sequenced to identify the target genes. After genome sequencing, 12 sets of glycoside hydrolases were identified, of which seven sets (α,β-glucosidase and α,β-galactosidase) were cloned in BL21 (DE3) using the pGEX4T-1 vector system. Among the sets of clones, only one clone (BglL.gin-952) showed ginsenoside-transforming abilities. The recombinant BglL.gin-952 comprised 952 amino acid residues and belonged to glycoside hydrolase family 3. The enzyme exhibited optimal activity at 55 °C and a pH of 7.5 and showed a promising conversion ability of major ginsenoside Rb1→Rd→Rg3(). The recombinant enzyme (GST-BglL.gin-952) was used to mass produce Rg3() from major ginsenoside Rb1. Scale-up of production using 50 g of Rb1 resulted in 30 g of Rg3() with 74.3% chromatography purity.

Conclusion: Our preliminary data demonstrated that this enzyme would be beneficial in the preparation of pharmacologically active minor ginsenoside Rg3() in the functional food and pharmaceutical industries.