Membrane chromatography for fast enzyme purification, immobilization and catalysis: A renewable biocatalytic membrane

Enzyme purification and subsequent immobilization usually require multiple steps and consume plenty of chemicals. Traditional dipping incubation operation is lengthy and the interior of porous carrier is not fully exploited due to the diffusion barrier. To solve these problems, one-step enzyme purification and immobilization was developed based on membrane chromatography concept. A membrane adsorber was prepared by polydopamine coating on a PVDF microfiltration membrane (or on a cheap and disposable cellulose filter paper) and subsequent polyethyleneimine grafting, without any solvent usage. Laccase was selectively immobilized on such membrane adsorber (enzyme activity: 39.9±4.4 U/mL; expressed activity: 19.6±3.0%) by directly capturing it from a crude fermentation broth without pH adjustment under flow-through mode. The immobilized laccase had a high purity of 92.2%, while the membrane permeability decreased due to the adsorption of laccase and impurities (“membrane fouling”). Thanks to the dominant convective transport, the enzyme loading was high and much faster than that by dipping incubation (5 min vs. 80 min). Moreover, enzyme reloading on membrane adsorber was easily realized by reversible desorption-adsorption process. The constructed biocatalytic membrane exhibited a commendable reusability for bisphenol A (BPA) removal only driven by its gravity.