Abstract: Retention of NAD (H) was investigated in a self-built non-charged ultra-filtration membrane reactor. NAD (H) was retained effectively by ultra-filtration membrane in the presence of 50kDa polyethyleneimine (PEI). High retention ratio (R＝0.823) was obtained with PEI/ NAD+ molar ratio 5:1 in Tris-HCl buffer. The increase of solution ionic strength caused a decrease of coenzyme retention but an increase of the permeation flux. The addition of 0.5% or 1% bovine serum albumin enhanced the coenzyme retention，minimizing the effect of ionic strength. The retention ratio of NADH was higher than that of NAD+ in PEI system. The influence of PEI on the activities of glycerol dehydrogenase and 1,3-propanediol oxidoreductase was also studied.

摘要： 构建了无电荷超滤膜酶膜反应器，考察了影响辅酶截留率的多种因素。实验结果表明，连续超滤膜反应器中加入聚乙烯亚胺（PEI，50 kDa），NAD+能够有效地被超滤膜截留。在Tris-HCl 缓冲液中，PEI/ NAD+摩尔比为5:1时，达到较高的辅酶截留率（R＝0.823）。溶液离子强度的增加减少辅酶的截留率，但可增加超滤膜超滤流速。在含盐溶液中，添加0.5%或1.0%的牛血清白蛋白可增加NAD+截留率。本装置对NADH的截留率高于NAD+的截留率，因此PEI适用于辅酶再生体系。同时还考察了1,3-丙二醇酶催化体系中PEI对甘油脱氢酶和1,3-丙二醇氧化还原酶酶活力的影响。