Enzymatic Transformation of 2-O-α-D-glucopyranosyl-L-ascorbic Acid by α-cyclodextrin Glucanotransferase from Recombinant Escherichia coli

The study aimed to produce 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) via the transglycosylation reaction by alpha-cyclodextrin glucanotransferase (alpha-CGTase) from recombinant Escherichia coli with L-ascorbic acid (AA) and beta-cyclodextrin (beta-CD) as the substrates. Liquid chromatography-tandem mass spectrometry analysis was conducted for AA-2G identification, and the glucoamylase treatment was carried out to produce AA-2G from AA-2-oilgosaccharides. The optimal temperature and pH for the enzymatic AA-2G production were 37 degrees C and 5.5, respectively, and the optimal alpha-CGTase concentration and substrate mass ratio (AA:beta-CD) for AA-2G synthesis were 160 U/mL and 1:1, respectively. At these optimal process conditions, maximal AA-2G production reached 13 g/L. This is the first report regarding the process optimization of enzymatic AA-2G production by alpha-CGTase from recombinant E. coli. The results may be useful for the industrial scale production of AA-2G.