(199b) Biocatalysis and Ion Separation with Pore Assembled Polypeptide Multilayers in Membranes

Functionalized materials and membranes are finding wide applications ranging from water treatment to reactors to advanced bio-separations. The development of biomimetic, tunable (singe layer and multi-layer assembly in pores) membranes provide added opportunities in permeate flux and separation/reactivity control. Depending on the types of functionalized groups (such as, chain length, charge of groups, biomolecule, etc.) and number of layers, these microfiltration membranes could be used in applications ranging from metal (or oxyanions) separation to biocatalysis. Thus, functionalization (one layer to multilayers) involving these polypeptides allows for the fabrication of both positively (poly-L-arginine, poly-L-lysine) and negatively (poly-L-glutamic acid) charged membranes. Through single-point covalent bonding (first layer) of charged multi-functional groups, the overall effective membrane charge is delocalized. Therefore, the potential field established by these functionalities extends well within the inner pore structure promoting electrostatic interactions with ionic species and proteins in solution. In order to build a stable assembly, the first polyelectrolyte layer was covalently attached to the membrane surface and inside the pore walls. Either polyglutamic acid (PLGA) or polylysine (PLL) were used in this step. Multilayer assemblies of polyelectrolytes provide excellent platform for protein/enzyme immobilization. After enzyme incorporation in the charged, multilayer assembly, the active site accessibility was comparable to that obtained in the homogeneous phase. The application results with these functionalized MF membranes include: (1) oxyanion and other divalent salt separations at very low pressure, (2) avidin-biotin interaction with high site accessibility, (3) enzymatic reactions and regenerability (glucose oxidase and alkaline phosphatase). This research was supported by NIEHS and by U.S. EPA STAR Program.