耐高温葡萄糖异构酶重组菌发酵与转化条件研究

摘要

耐高温的葡萄糖异构酶(glucose isomerase,GI)在高温下可将D-葡萄糖异构化为D-果糖,获得的高果糖浆可作为甜味剂应用于食品诸多领域.对Thermus oshimai GI重组菌发酵产酶条件和全细胞转化D-葡萄糖生成D-果糖工艺进行研究.确定诱导温度28℃,诱导剂终浓度0.1 mmol/L,发酵培养基添加5 mmol/L Mn2+的最优产酶发酵条件;将最优转化体系放大,包括20 g/L湿菌体、10 mmol/L Mn2+和200 g/L底物,于95℃和pH7.5条件下生物转化4h,D-果糖得率高达57.34％.该工艺具备一步法生产F55型高果糖浆的可能性,可简化后续浓缩分离等步骤,为进一步使用食品安全的表达系统生产F55型高果糖浆提供理论依据.%Thermophilic glucose isomerase (GI) can catalyze conversion of D-glucose to D-fructose at elevated temperature.The obtained high fructose corn syrup served as sweetener,is widely used in various food fields.Herein the fermentation and conversion conditions of E.coli BL21 (DE3)/pET28b/ToGI were studied.The results showed that the optimum fermentation should be performed at 28 ℃ by adding 0.1 mmol/L Isopropyl β-D-1-thiogalactopyranoside (IPTG) and 5 mmol/L Mn2+ Then,the amplified biotransformation reaction was conducted at the condition of 20 g/L wet cell,10 mmol/L Mn2+,200 g/L D-glucose and pH 7.5.After bioconversion at 95 ℃ for 4 h,the yield of D-fructose reached 57.34％.One-step production process of F55 high fructose corn syrup (HFCS) using this craft has the advantage of simplifying the subsequent step of enriching D-fructose,and it provided an important reference for industrial application of HFCS production using food safety expression system.