Anomer-selective glucosylation of l-menthol by yeast α-glucosidase

L-Menthol was glucosylated by the α-glucosidase (EC 3.2.1.20) of Saccharomyces cerevisiae using maltose as the glucosyl donor. When 50 mg of l-menthol and 1.6 M maltose in 10 mM citrate-phosphate buffer (pH 5.5) were incubated at 45°C, l-menthyl α-D-glucopyranoside (α-MenG) was α-anomer-selectively formed as a product. The specificity of the α-linkage was confirmed by ¹³C-NMR analysis. In the reaction mixture after 2 h, α-MenG was mainly accumulated in a crystalline form and the concentration of dissolved α-MenG was constant at 1.4 mM. The molar conversion yield of α-MenG produced based on the supplied l-menthol was maximally 30.7% at 48 h of reaction.