Highly efficient and regioselective production of an erythorbic acid glucoside using cyclodextrin glucanotransferase from Thermoanaerobacter sp. and amyloglucosidase

In order to continuously supply erythorbic acid (EA) for long-term cell cultures, we synthesized a stable EA derivative, 2-O-α-d-glucopyranosyl-d-erythorbic acid (EA-2G), as a useful tool for analyzing the biological function of EA. The specific and efficient production process of EA-2G consisted of two steps: transglycosylation by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. and hydrolysis by amyloglucosidase from Aspergillus niger. EA-2G was regioselectively formed by CGTase using EA and γ-cyclodextrin in pH 4.0 acetate buffer at 40 °C for 24 h. It seemed that several EA-2-oligoglucosides were also formed in this reaction mixture. Additional hydrolysis at 60 °C for 2 h of the reaction mixture by glucoamylase resulted in efficient production of EA-2G. EA-2G was obtained in two steps in 49.1% overall yield from EA.