Optimization of Cycloamylose Preparation by Recombinant 4-α-Glucanotransferase

Abstract:

4-α-glucanotransferase can catalyze intramolecular glucan transfer reactions of amylose to produce cycloamylose. In this study，a recombinant E. coli BL21（DE3）/pET-24a（+）-AaAM derived from Aquifex aeolicus was constructed for intracellular production of 4-α- glucanotransferase. The AaAM produced in culture medium activity was 0.99 U/mL after 27 h in shake flask. Furthermore，the condition for cycloamylose preparation with potato starch by this enzyme was optimized. The optimized conditions for the conversion as follows: substrate concentration was 1 g/dL debranched potato starch, the initial pH was 7.0, the reaction temperature was 75 ℃, 4-α-glucanotransferase concentration was 20 U/g starch. Under this conditions, the cycloamylose yield is 24.8% for 10 h, which paved the way for indnstrial production of cycloamylose.