Efficient production of l-menthyl α-glucopyranoside from l-menthol via whole-cell biotransformation using recombinant Escherichia coli

l- Menthyl α -D-glucopyranoside ( α -MenG) is a glycoside derivative of l -menthol with improved water-solubility and new flavor property as a food additive. α -MenG can be synthesized through biotransformation, but its scale-up production was rarely reported. In this study, the properties of an α -glucosidase from Xanthomonas campestris pv. campestris 8004 (Agl-2) in catalyzing the glucosylation of menthol was investigated. Agl-2 can almost completely glycosylate l -menthol (> 99%) when using 1.2 M maltose as glycosyl donor. Accumulated glucose resulted from maltose hydrolysis and transglycosylation caused the inhibition of the glucosylation rate (40% reduction of the glucosylation rate in the presence of 1.2 M glucose) which can be avoided through whole-cell catalysis with recombinant E. coli. Interestingly, in spite of the poor solubility of menthol, the productivity of α -MenG reached 24.7 g/(L·h) in a 2 L catalyzing system, indicating industrialization of the reported approach.