摘要
报道了一个以游离脂肪酸和游离果糖为底物酶催化合成糖酯的新体系:甲乙酮-分子筛体系,即以甲乙酮作为反应溶剂以4分子筛吸附去除副产物水,并与被文献广泛采用的溶剂叔戊醇进行了比较,甲乙酮是一种良好的反应媒介,对底物有一定的溶解能力,同时又可保持酶的稳定性;分子筛可以快速吸附甲乙酮中的水分,使反应体系中的水分保持在一个较低含量水平,推动反应平衡向酯生成的方向移动,提高产物浓度。今对甲乙酮溶剂中酶法合成果糖酯的反应条件进行了优化,在最优条件下,即在甲乙酮溶剂中,10g·L-1的酶用量,85g·L-1的分子筛用量,50mmol·L-1果糖,75mmol·L-1硬脂酸,60℃的反应温度,反应在10h就达到了平衡,果糖的转化率是97.5%,硬脂酸的转化率是86%,固定化脂肪酶重复使用10次,12h产物浓度仅下降25%。
A novel enzymatic sugar ester synthesis method with the use of methyl ethyl ketone-molecular sieve system was studied. In the new method proposed, the free fructose and fatty acids were used as reactants, while the methyl ethyl ketone acts as solvent and the molecular sieve plays a role of remover of the by-product water. The comparison between the use of methyl ethyl ketone as solvent and the use of the most popularly used solvent, tert-amyl, in enzymatic synthesis of sugar ester was conducted, and in both cases, the molecular sieve was used as water remover. Since the reactants of enzymatic synthesis have good solubility in methyl ethyl ketone and in which the enzyme can maintain its most activity, it was found that methyl ethyl ketone is an excellent solvent for enzymatic sugar ester synthesis. Furthermore, since the molecular sieve can absorb the by-product water in methyl ethyl ketone effectively and can control the water concentration at a lower level, the reaction equilibrium is moved toward ester synthesis side and a high product concentration can be obtained. Under following optimum conditions： methyl ethyl ketone as solvent, the enzyme of 10 g.L^-1, molecular sieve of 85 g.L^-1, fructose of 50 mmol·L^-1 and stearic acid of 75 mmol·L^-1, the enzymatic synthesis reaction can reach equilibrium in 10 h, at the same time, the conversion ratio of fructose can be 97.5% and that of stearic acid is 86%. The study found that the enzyme is stable in this system, and in the tenth run, the product concentration after 12 h reaction only declines 25% compared with the first run.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2007年第5期905-910,共6页
Journal of Chemical Engineering of Chinese Universities
关键词
酶法合成
果糖酯
甲乙酮
分子筛
ezymatic synthesis
fructose ester
methyl ethyl ketone
molecular sieve
