We describe a novel “tentacle-type” porous membrane that allows adsorption of enzymes in multilayers in amounts about 50-fold those permitted by monolayer adsorption. A diethylamino (DEA) group as an anion-exchanger was appended to a polymer chain, grafted onto the pores of a hollow-fiber membrane. A urease solution was forced to permeate through the pores of the anion-exchange membrane, which had a DEA group density up to 2.9 mmol per gram of membrane and a thickness of 0.8 mm. The grafted chain with a higher DEA group density provided a larger number of three-dimensional adsorption (tentacle-like binding) sites for urease. The binding capacity exceeded one gram of urease per gram of the membrane at DEA group densities higher than 1.6 mmol per gram, which amounted to a more than 37-fold greater amount of adsorbed enzyme compared to monolayer adsorption. In addition, urease captured by the DEA on the graft chain could be quantitatively eluted with retention of 90% of the feed urease activity.
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