重组4-α-糖基转移酶转化淀粉制备大元环糊精的条件优化

4-α-糖基转移酶能够以淀粉为底物通过分子内转糖基作用制备大元环糊精。本研究成功构建了产超嗜热菌 Aquifex aeolicus来源的4-α-糖基转移酶重组菌的 E.coli BL21（DE3）/pET-24a（+）-AaAM。对重组菌进行摇瓶发酵，培养27h破壁上清酶活达到0.99 U/mL。以马铃薯淀粉为底物，对酶转化生成大元环糊精进行了条件优化。结果表明，在底物质量浓度为1 g/dL时，经异淀粉酶脱支预处理后，调节初始pH为7.0，反应温度为75 ℃，加酶量为20 U/g，在10 h时大元环糊精的转化率达到最高24.8%，为大元环糊精的工业生产奠定了基础。
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