Utilizing genetically engineered bacteria to produce plant-specific glucosides.

Plant-derived glucosides have attracted much attention due to their widespread applications. This class of products is difficult to isolate or to synthesize in pure form because of the resulting low yields. Thus, simple approaches for the generation of such glucosides would be highly beneficial. We purified and characterized a novel glucosyltransferase from plant cell suspension cultures of Rauvolfia serpentina, which showed rather low substrate specificity. We obtained its cDNA and expressed the active recombinant protein in bacteria (Escherichia coli) with excellent plant-specific glucosylation efficiencies. Compared with the plant system, the bacteria delivered the new enzyme, which was in the form of a soluble or matrix-bound enzyme, approximately 1800 times more efficiently for the synthesis of a wide range of glucosides. More importantly, the engineered E. coli strain allowed for in vivo glucosylation and release of the product into the culture medium, as shown by the formation of arbutin, which is a potent inhibitor of human melanin biosynthesis with commercial value.