Microbial Production of Glycyrrhetic Acid 3-O-Mono-β-D-Glucuronide from Glycyrrhizin by Cryptococcus magnus MG-27

It was found that Cryptococcus magnus MG-27, a yeast isolated from soil, selectively hydrolyzed the terminal β-glucuronyl linkage of glycyrrhizin (1) to yield glycyrrhetic acid 3-O-mono-β-D-glucuronide (MGGR, 3), a potent sweetener (relative sweetness to sucrose: × 941). The conditions for cultivation of this yeast with the maximum hydrolytic activity as well as the reaction conditions of 1 with the cells for the maximum yield of 3 were investigated. Based on the results, strain MG-27 was cultivated with a medium composed of 1.0% 1, 1.0% glucose, 0.5% Polypepton, and 0.3% yeast extract at 28°C for 24h. The reaction of the resulting cells and 1 at pH 5.7 at 45°C for 48 h afforded 3 in a yield of 95%.