枯草芽胞杆菌重组表达的Pantoea dispersa UQ68J蔗糖异构酶制备异麦芽酮糖的研究

Preparation of isomaltulose by Pantoea dispersa UQ68J sucrose isomerase recombinantly expressed in Bacillus subtilis

异麦芽酮糖是蔗糖的同分异构体,具有多种优秀的生理功能,广泛应用于食品行业。蔗糖异构酶可以将蔗糖异构为异麦芽酮糖,与其他微生物来源的蔗糖异构酶相比,Pantoea dispersa UQ68J来源的蔗糖异构酶转化蔗糖时异麦芽酮糖产率高,副产物少。为了更好地将异麦芽酮糖应用于食品领域,该研究将P.dispersa来源的蔗糖异构酶在食品安全微生物枯草芽孢杆菌(Bacillus subtilis)中重组表达,研究重组蔗糖异构酶的酶学性质并优化其制备异麦芽酮糖的反应条件。结果表明,重组酶的最适pH值为6.0,最适温度为30℃,在pH 5.0~8.0稳定性良好,在45℃下的半衰期为68 min。用该重组酶制备异麦芽酮糖,当蔗糖质量浓度为400 g/L,加酶量为20 U/g,在30℃、pH 6.0条件下转化10 h时,异麦芽酮糖产率可达90.61%,当蔗糖质量浓度提高到700 g/L,异麦芽酮糖产率仍可达89.20%。该研究提高了蔗糖异构酶的安全特性,实现了异麦芽酮糖的高产率,为工业生产异麦芽酮糖奠定了基础。

Isomaltulose is an isomer of sucrose and has many excellent physiological functions,so it is widely used in the food industry.Sucrose isomerase can isomerize sucrose into isomaltulose.Compared with sucrose isomerase derived from other microorganisms,the sucrose isomerase derived from Pantoea dispersa UQ68J can obtain higher yield of isomaltulose and fewer by-products when converting sucrose.In order to better apply isomaltulose to the food field,P.dispersa sucrose isomerase was recombinantly expressed in food safety microorganism Bacillus subtilis,the enzymatic properties of recombinant sucrose isomerase were studied and the reaction conditions for preparing isomaltulose were optimized in this study.The results showed that the optimal pH and temperature of recombinant sucrose isomerase were 6.0 and 30℃,respectively.The recombinant sucrose isomerase had good stability in the range of pH 5.0-8.0,and its half-life at 45℃was 68 min.Using this recombinant sucrose isomerase to prepare isomaltulose,the yield was 90.61%with 400 g/L sucrose as the substrate,when the amount of enzyme was 20 U/g,at 30℃and pH 8.0 for 10 h.When the sucrose concentration increased to 700 g/L,the yield of isomaltulose still reached 89.20%.This research improves the safety characteristics of sucrose isomerase,realizes the high yield of isomaltulose,and lays the foundation for the industrial production of isomaltulose.