Enzymatic transformation of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) by immobilized α-cyclodextrin glucanotransferase from recombinant Escherichia coli

This work aims to produce 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) from ascorbic acid and beta-cyclodextrin with immobilized alpha-cyclodextrin glucanotransferase (alpha-CGTase) from recombinant Escherichia coli. Molecular sieve (SBA-15) was used as an adsorbent, and sodium alginate was used as a carrier, and glutaraldehyde (GA) was used as a cross-linker. The effects of several key variables on alpha-CGTase immobilization were examined, and optimal immobilization conditions were determined as the following: glutaraldehyde (GA, cross-linker) 0.01% (v/v), SBA-15 (adsorbent) 2 g/L, CaCl2 3g/L. sodium alginate 20 g/L, adsorption time 3 h, and immobilization time 1 h. In comparison with free alpha-CGTase, immobilized alpha-CGTase had a similar optimal pH (5.5) and a higher optimal temperature (45 degrees C). The continuous production of AA-2G from ascorbic acid and beta-cyclodextrin in the presence of immobilized alpha-CGTase was carried out, and the highest AA-2G production reached 21 g/L, which was 2-fold of that with free alpha-CGTase. The immobilization procedure developed here was efficient for alpha-CGTase immobilization, which was proved to be a prospective approach for the enzymatic production of AA-2G. (C) 2010 Elsevier B.V. All rights reserved.