中空纤维膜固定化甲酸脱氢酶催化CO_2合成甲酸

以紫外光表面接枝改性的聚乙烯(PE)中空纤维膜为载体,采用共价结合的方式固定化甲酸脱氢酶(FDH),考察了CO2通入方式、溶液pH值、缓冲液种类和还原型烟酰胺腺嘌呤二核苷酸(NADH)的浓度对酶催化CO2合成甲酸反应的影响.结果表明,与加压法相比,CO2鼓泡法更有利于甲酸的生成;磷酸盐缓冲液优于Tris-HCl和盐酸三乙醇胺缓冲液;体系pH值对反应的影响较大,固定化FDH的最佳pH值仍为6.0,但pH耐受性增强;随着辅酶NADH浓度的增加,反应初速度加快,收率下降;游离酶和固定化酶的最大酶活分别为0.246和0.138mmol/(L.h);固定化FDH在4℃贮存两周后活性仅下降4%,而游离酶活性下降50%.FDH催化膜重复利用10次后,活性没有明显降低.

Synthesis of Formic Acid from CO2 Catalyzed by Formate Dehydrogenase Immobilized on Hollow Fiber Membrane

Formate dehydrogenase(FDH) was covalently attached to surface-modified polyethylene(PE) hollow fiber membrane.The effects of inlet way of CO2,pH value,the type of buffer solution,and the concentration of the reduced coenzyme nicotinamide adenine dinucleotide(NADH) on the synthesis of formic acid from CO2 were investigated.The catalytic performance of PE-supported FDH and its reusability were studied.The results showed that the CO2 bubbling method was superior to pressing method.Phosphate buffer was more favorable to the formation of formic acid than Tris-HCl and triethanolamine-HCl buffer.Immobilized FDH was less sensitive to pH than free FDH,and the optimum pH value was 6.0 for both systems.With the increase of NADH concentration,the initial reaction rate ascended while the yield tended to decrease.Enzyme activity reached 0.246 and 0.138 mmol/(L.h),respectively,for free and immobilized FDH when using 100 mmol/L of NADH.The stability was greatly improved after immobilization.The activity of PE-attached FDH only decreased by 4% while that of free enzyme dropped to 50% of initial activity after stored in phosphate buffer at 4℃ for two weeks.Furthermore,immobilized FDH exhibited outstanding reusability,which almost kept original activity after undergoing 10 cycles.