Glycosylation and sulfation of 4-methylumbelliferone by Gliocladium deliquescens NRRL 1086

The aim of the study was to expand the substrate scope of Gliocladium deliquescens NRRL 1086 and generate coumarin glycosides using 4-methylumbelliferone (4-MU) as a substrate. The obtained results indicated that 4-MU can be metabolized to its glucoside (M1) and sulfate conjugate (M2), and the structures of the metabolites were elucidated by spectroscopic or enzymatic methods. Time course experiments detected that nearly 90% of 4-MU could be metabolized within 24 h, and the maximum yield of M1 could reach as high as 32%. Further tests revealed that the glucose concentration in the medium had little effect on the yield of M1 but time of 4-MU-adding could markedly affect the glycosylation procedure, and the favorable time to accumulate M1 was in the 12 or 24 h-old stage II culture, while in the 36 h-old or even older stage II culture, the substrate was almost metabolized to M2. The attempts to alter the ratio between M1 and M2 were performed by addition of quercetin and S-tetrahydroberberrubine or reduction of the sulfate concentration in the culture medium. Herein we describe, to the best of our knowledge, the first example of simultaneously microbial glycosylation and sulfation of coumarins.