葡萄糖硬脂酸酯的非水相酶法制备及其动力学研究

The preparation and dynamics of glucose stearic acid esters by lipase-catalyzed reaction in non-aqueous media

摘要:

研究了脂肪酶催化合成葡萄糖硬脂酸酯（GSAE）的非水相转化条件及其效果。从7种商品化脂肪酶中筛选适于非水相酶法制备GSAE的酶；在50 ml锥形瓶中加入一定量的葡萄糖、硬脂酸、脂肪酶、吸水剂、助溶剂等，分别探讨脂肪酶种类及用量、助溶剂种类及用量、酸糖比、水份、分子筛用量、摇床速率、反应温度、反应时间等因素对GSAE合成反应产率的影响。结果表明，丙酮是适宜的助溶剂，在丙酮反应体系中脂肪酶Novozyme 435 保持较高活性，适宜酶法制备GSAE，水份明显降低脂肪酶活性和酯化反应产率，底物、助溶剂和反应过程的除水对于该酯化反应是十分必要的。正交试验设计优化的酯化反应条件为：Novozyme 435酶用量0.08 g、分子筛用量0.8 g、硬脂酸 : 葡萄糖(摩尔比) = 3 : 1、反应温度45℃，丙酮用量10ml、摇床转速150r/min、反应时间5 h。此条件下最大反应速率Vm=0.749μmol/min?g和Km = 0.0203 mmol/L，GSAE产率达到64.11%。

Abstract:

Sugar esters are widely used in the food, cosmetic, detergent and phar-maceutical industry. The preparation and it’s dynamics of glucose stearic acid esters (GSAE) by lipase-catalyzed reaction were studied in this work. The available lipase of catalytic synthesis GSAE in non-aqueous media was screened from 7 commercial lipases. To facilitate these reactions, a certain volume of glucose, stearic acid, lipase, molecular sieve 3A, solvents etc were added in 50 ml tapered bottles, respectively. The results showed that lipase Novozyme 435 proved to be efficient catalysts of enzymatic preparation GSAE, acetone was appropriate solvent, and Novozyme 435 could keep high activity in acetone. And excessive water in the reaction system obviously decreased the activity of Novozyme 435 and the yield rate of GSAE, thus it was very necessary to add defined amount moisture absorber to remove the water of substrates, solvent and reaction process. The optimized esterification reaction conditions with 0.08 g Novozyme 435, 0.8 g 3A molecular sieve, the ratio of stearic acid and glucose = 3:1, 10 ml acetone, 150r/min shaking, 45℃ reaction temperature, 5 h reaction time were good for making the produce GSAE in non-aqueous media. In the optimized condition, the maximum reaction rate Vm was 0.749 μmol/min?g, Km was 0.0203 mmol/L and the GSAE yield rate was up to 64.11%.