Membrane potential of Bombyx mori silk fibroin membrane induced by an immobilized enzyme reaction

Abstract

The membrane potential of Bombyx mori silk fibroin membrane induced by the reaction of glucose oxidase (GO) which was immobilized in the silk fibroin membrane, has been measured. The membrane potential increased rapidly after addition of the substrate, glucose, and reached a plateau. The degree of response depended on the concentration of glucose. From direct observation of the 13C NMR spectra of the product of the enzyme reaction in the silk fibroin membrane, it was concluded that the gluconolactone generated from the glucose was completely converted to gluconic acid in the silk fibroin membrane. In addition, a greater pH difference between the membrane surfaces after the enzyme reaction was determined. It was found that the effective anionic fixed charge density of silk fibroin membrane decreased with increasing gluconic acid concentration in the membrane.