Liu Zhenfeng, Shen Yanmin, Li Weiwei, Zhang Wen, Li Tao, Ren Baozeng
School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, 450001, China,
Bioprocess Biosyst Eng. 2015 May;38(5):833-9. doi: 10.1007/s00449-014-1326-y. Epub 2014 Nov 19.
The synthesis of D-isoascorbyl stearate from D-isoascorbic acid and stearic acid with immobilized lipase (Novozym(®)435) as catalyst was studied. Response surface methodology and Box-Behnken design with six variables and three levels were employed to evaluate the effects of processing conditions on the conversion of D-isoascorbic acid. The results confirmed that the response surface method and statistical analysis were proved to be useful in developing optimal conditions for D-isoascorbyl stearate synthesis. The optimum conditions were predicted as follows: reaction temperature 48 °C, reaction time 17.7 h, immobilized lipase amount 50.0 % (w/w, of D-isoascorbic acid), substrate molar ratio 9:1 (stearic acid to D-isoascorbic acid), D-isoascorbic acid concentration 0.14 mol/L (based on solvent), 4A molecular sieve addition 200 g/L (based on solvent), and the optimal conversion was 90.6 %. Through the kinetics model fitting of the esterification, it was considered that the esterification conformed to a Ping-Pong bi-bi kinetic model with D-isoascorbic acid inhibition, and the obtained kinetic constants showed that the inhibition of D-isoascorbic acid and the enzyme affinity to substrate were abate with the increase of the reaction temperature.
研究了以固定化脂肪酶（诺维信（®）435）为催化剂，由D-异抗坏血酸和硬脂酸合成D-异抗坏血酸硬脂酸酯的过程。采用响应面法和具有六个变量、三个水平的Box-Behnken设计来评估工艺条件对D-异抗坏血酸转化率的影响。结果证实，响应面法和统计分析被证明有助于为D-异抗坏血酸硬脂酸酯的合成开发最佳条件。预测的最佳条件如下：反应温度48℃，反应时间17.7小时，固定化脂肪酶用量50.0%（w/w，基于D-异抗坏血酸），底物摩尔比9:1（硬脂酸与D-异抗坏血酸），D-异抗坏血酸浓度0.14mol/L（基于溶剂），4A分子筛添加量200g/L（基于溶剂），最佳转化率为90.6%。通过对酯化反应的动力学模型拟合，认为酯化反应符合具有D-异抗坏血酸抑制作用的乒乓双底物动力学模型，所得动力学常数表明，随着反应温度的升高，D-异抗坏血酸的抑制作用和酶对底物的亲和力减弱。
