Objective To characterize a recombinant isomerase that can catalyze the isomerization of sucrose into isomaltulose and investigate its application for the enzymatic production of isomaltulose. Results A sucrose isomerase gene from Erwinia sp . Ejp617 was synthesized and expressed in Escherichia coli BL21(DE3). The enzymatic characterization revealed that the optimal pH and temperature of the purified sucrose isomerase were 6.0 and 40 °C, respectively. The enzyme activity was slightly activated by Mn 2+ and Mg 2+ , but partially inhibited by Ca 2+ , Ba 2+ , Cu 2+ , Zn 2+ and EDTA. The kinetic parameters of K m and V max for sucrose were 69.28 mM and 118.87 U/mg, respectively. The time course showed that 240.9 g/L of isomaltulose was produced from 300 g/L of sucrose, and the yield reached 80.3% after bioreaction for 180 min. Conclusions This recombinant enzyme showed excellent capability for biotransforming sucrose to isomaltulose at the substrate concentration of 300 g/L. Further investigations should be carried out focusing on selection of suitable heterologous expression system with the aim to improve its expression level.

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重组蔗糖异构酶的表征及其在异麦芽酮糖酶促生产中的应用

目的表征一种可催化蔗糖异构化为异麦芽酮糖的重组异构酶，并探讨其在异麦芽酮糖酶法生产中的应用。结果 来自欧文氏菌的蔗糖异构酶基因。Ejp617 在大肠杆菌BL21(DE3) 中合成并表达。酶学表征表明，纯化的蔗糖异构酶的最佳 pH 值和温度分别为 6.0 和 40 °C。酶活性被Mn 2+ 和Mg 2+ 轻微激活，但被Ca 2+ 、Ba 2+ 、Cu 2+ 、Zn 2+ 和EDTA部分抑制。蔗糖的 K m 和 V max 动力学参数分别为 69.28 mM 和 118.87 U/mg。时间过程表明，300 g/L蔗糖可生成240.9 g/L异麦芽酮糖，生物反应180 min后产率达到80.3%。结论 该重组酶在底物浓度为 300 g/L 时显示出优异的将蔗糖生物转化为异麦芽酮糖的能力。应进一步研究选择合适的异源表达系统，以提高其表达水平。