Abstract
Eubacterium sp. GLH with Ruminococcus sp. PO1-3 and Clostridium innocuum ES24-06 possessing enzymes involved in the metabolism of glycyrrhizin (GL) was cultured in GAM medium with and without 1.0 mM GL or 1.0 mM glycyrrhetic acid (GA). GL (1.0 mM) enhanced 3α-hydroxyglycyrrhetinate (3α-hydroxyGA) dehydrogenase activity, GA (1.0 mM) suppressed 3α-hydroxyGA dehydrogenase activity, GL β-D-glucuronidase activity and the mixed bacterial growth, and GL and GA showed almost no change in a lower level of 3β-hydroxysteroid dehydrogenase (3β-HSD) activity during 5 d of culture. GL (1.0 mM) and GA (1.0 mM) were metabolized to a small amount of GA and a negligible amount of 3-oxo-glycyrrhetic acid (3-oxo-GA) and 3α-hydroxyGA, and to a negligible amount of 3-oxo-GA, respectively, by these mixed bacteria. These amounts coincided with those of metabolites produced from 1.0 mM GL and 1.0 mM GA added to these mixed bacteria after 24 h culture. Whole bacteria and sonicated bacteria derived from the collection of these mixed bacteria reached a maximal stage and metabolized GL to a relatively large amount of GA and 3-oxo-GA, and a negligible amount of 3α-hydroxyGA and GA to a small amount of 3-oxo-GA and 3α-hydroxyGA within 180 min. GL β-D-glucuronidase with 3β-HSD and 3α-hydroxyGA dehydrogenase partially purified from each bacterium was converted GL to 3α-hydroxyGA, production metabolites of about 60% after 10 min of incubation. These mixed bacteria possessed high enzyme activities could produce the metabolites of GL in under one hour under conditions.
