Oxidized bacterial cellulose membrane as support for enzyme immobilization: properties and morphological features

Abstract

Bacterial cellulose (BC) membrane can be architected to covalently immobilize biomolecules, generating materials with new functionality. The processes of purification (via alkaline treatment) and chemical modification (via NaIO4) to the wet BC membrane is the innovation of this work. This wet oxidized BC (OxBC) membrane could act as a support matrix for covalent immobilization of enzymes. BC produced over 5 days of static fermentation, followed by purification with K2CO3 (BC-5d-K2CO3) was selected for our study due to high porosity and surface area, which are properties that favor its chemical modification. This wet BC membrane proven suitable for NaIO4 oxidation. Time and temperature conditions were evaluated in the oxidation reaction, with oxidation BC (OxBC) performed at 1% (w/v) NaIO4 for 6 h at 55 °C under most advantageous conditions, as it provided 50% oxidation degree and preserved its morphological structure. BC and OxBC were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Scanning electron microscopy, mechanical test, and thermal analysis. The oxidation reaction decreased BC crystallinity, tensile strength, and thermal stability and compacted the cellulose layers. BC and OxBC showed non-cytotoxicity. Fourier transform infrared confirmed that OxBC can covalently immobilize papain and that after immobilization the enzyme showed a recovered enzymatic activity of 93.1%. In addition, the oxidized membrane presented greater amount of immobilized papain in its study than BC, proving to be a more efficient support for enzymatic immobilization.