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Surface-Engineered Biocatalytic Composite Membranes for Reduced Protein Fouling and Self-Cleaning

Vanangamudi, Anbharasi, Saeki, Daisuke, Dumée, Ludovic F., Duke, Mikel, Vasiljevic, Todor, Matsuyama, Hideto, Yang, Xing
ACS applied materials & interfaces 2018 v.10 no.32 pp. 27477-27487
X-ray photoelectron spectroscopy, amino acids, asymmetric membranes, bovine serum albumin, chymotrypsin, confocal microscopy, cost effectiveness, digestion, fouling, gel electrophoresis, hydrophilicity, hydrophobicity, immobilized enzymes, models, nanofibers, nanopores, peptides, permeability, remediation, surface area, surface proteins, trypsin, ultrafiltration
A new biocatalytic nanofibrous composite ultrafiltration membrane was developed to reduce protein fouling interactions and self-clean the membrane surface. The dual-layer poly(vinylidenefluoride)/nylon-6,6/chitosan composite membrane contains a hydrophobic poly(vinylidenefluoride) cast support layer and a hydrophilic functional nylon-6,6/chitosan nanofibrous surface layer where enzymes were chemically attached. The intrinsic surface chemistry and high surface area of the nanofibers allowed optimal and stable immobilization of trypsin (TR) and α-chymotrypsin enzymes via direct covalent binding. The enzyme immobilization was confirmed by X-ray photoelectron spectroscopy and visualized by confocal microscopy analysis. The prepared biocatalytic composite membranes were nanoporous with superior permeability offering stable protein antiadhesion and self-cleaning properties owing to the repulsive mechanism and digestion of proteins into peptides and amino acids, which was quantified by the gel electrophoresis technique. The TR-immobilized composite membranes exhibited 2.7-fold higher permeance and lower surface protein contamination with 3-fold greater permeance recovery, when compared to the pristine membrane after two ultrafiltration cycles with the model feed solution containing bovine serum albumin/NaCl/CaCl₂. The biocatalytic membranes retained about 50% of the enzyme activity after six reuse cycles but were regenerated to 100% activity after enzyme reloading, leading to a simple and cost-effective water remediation operation. Such surface- and pore-engineered membranes with self-cleaning properties offer a viable solution for severe surface protein contamination in food and water applications.