Glycyrrhizin stimulates growth of Eubacterium sp. strain GLH, a human intestinal anaerobe

Abstract

Eubacterium sp. strain GLH was isolated from human feces and produced two kinds of β-D-glucuronidase (Ec 3.2.1.31), one new enzyme specific for glycyrrhizin (GL) and the other for phenyl β-D-glucuronides. GL or p-nitrophenyl-mono-β-D-glucuronide (pNPG) stimulated the production of GL or pNPG β-glucuronidases and the growth of strain GLH in a basal medium lacking carbohydrate. D-Glucuronic acid also stimulated the growth of the bacterium, but glycyrrhetic acid did not. The increase of GL β-glucuronidase paralleled the growth of the Eubacterium strain in pure culture. These results suggest that glucuronides such as GL and pNPG stimulate the growth of the Eubacterium strain in a nutrient-poor medium by providing D-glucuronic acid through the activity of β glucuronidases. The increase of GL β-glucuronidase activity in the presence of GL was observed during the cultivation of human intestinal flora in a general anaerobic medium. During mixed cultivation of the Eubacterium strain with Streptococcus faecalis, which does not produce GL β-glucuronidase, GL β-glucuronidase was also increased by GL or pNPG, but not by glycyrrhetic acid and p-nitrophenol. It is suggested that GL stimulates the growth of strain GLH even in the mixed culture.