重组左聚糖蔗糖酶生产左聚糖工艺优化

Process Optimization of Levan Production by Recombinant Levansucrase

利用5 000 L发酵罐中试所得的大肠杆菌重组枯草芽孢杆菌左聚糖蔗糖酶酶制剂转化蔗糖生产左聚糖,并优化其工艺条件。选择反应pH值、反应温度和蔗糖质量浓度为主要影响因素,分别以蔗糖转化率和左聚糖产量为响应值,利用Box-Behnken响应面试验对酶法合成左聚糖工艺条件进行优化。响应面试验结果表明:在重组左聚糖蔗糖酶浓度1.6 U/mL、反应pH6.3、反应温度26℃、410 g/L蔗糖的条件下反应30 h,得到的左聚糖产量最高,为(138.59±2.90)g/L,比优化前提高了约80%。在酶浓度1.6 U/mL、反应pH6.5、反应温度24℃、310 g/L蔗糖的条件下反应30 h,得到最高蔗糖转化率(36.73±0.60)%,比优化前提高了约19%。上述优化条件在5 L反应体系中可保持稳定的生产效率,为规模化酶法生产左聚糖的工业应用提供了技术基础。

This study aimed to optimize the process conditions to produce levan from sucrose by recombinant Bacillus subtilis levansucrase in Escherichia coli. Levansucrase was produced in a 5 000 L fermentor. Reaction pH,temperature,and sucrose concentration were selected as influencing factors. The process conditions were optimized by response surface methodology with Box-Behnken design. Response values were the conversion yield of sucrose to levan and levan yield,respectively. Response surface methodology revealed that the maximum levan yield(138.59±2.90) g/L was obtained at an enzyme concentration of 1.6 U/mL,reaction pH of 6.3,reaction temperature of 26 °C,and sucrose concentration of 410 g/L for 30 h. The yield was approximately 80% higher than that before optimization. The maximum conversion yield of sucrose(36.73±0.60)% was obtained at an enzyme concentration of 1.6 U/mL,reaction pH of 6.5,reaction temperature of 24 °C,and sucrose concentration of310 g/L for 30 h. This yield was approximately 19% higher than that before optimization. The optimized conditions could maintain stable production efficiency in the 5-L reaction system,which provides a technical foundation for the industrial application of enzymatic production of levan.