Electrochemical recycling of gold nanofibrous membrane as an enzyme immobilizing carrier

A gold nanofibrous membrane was shown to be an enzyme-immobilizing carrier that can be recycled on-site in a continuous flow-through reactor using a simple electrochemical treatment. The membrane was prepared by electrospinning a polyacrylonitrile/gold salt solution, followed by electroless gold plating. Laccase, used as a model enzyme, was immobilized on the gold membrane surface by a combination of formation of amino-terminated self-assembled monolayers and glutaraldehyde treatment. Enzyme desorption at neutral pH was confirmed by a 98% decrease in enzymatic activity, based on oxidation of a 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) substrate, after electrochemical treatment for desorption, and surface characterization using X-ray photoelectron spectroscopy. The enzymatic activity after re-immobilization on the membrane was restored to 90%, and decreased to 1.0% after redesorption. These results showed that recycling of the gold nanofibrous membrane as an enzyme-immobilizing carrier was possible. The laccase-immobilized membrane was used in a flow-through reactor; the activities of the immobilized and re-immobilized enzymes on the membrane were 62.7% and 58.5% of the respective initial activities after operation for 7 d.