Effect of Immobilization Method in the Electrocatalytic Properties of Alcohol-Dehydrogenase Enzyme

Alcohol dehydrogenase enzyme (ADH) from Saccharomyces cerevisiae is immobilized on glassy carbon surface by two methods: physical adsorption and covalent-bonding in order to compare the electrocatalytic properties as a function of the immobilization method. Physical adsorption was carried out by deposition of a mixture composed with nicotinamide-adenine dinucleotide (NAD) as coenzyme, Nafion^® (5 wt%) as a binder and ADH onto a graphite surface. Physical adsorption was carried out by deposition of a mixture composed with nicotinamide-adenine dinucleotide (NAD) as coenzyme, Nafion^® (5 wt%) as a binder and ADH onto a graphite surface. The covalent-bonding immobilization consisted of a polyaniline film (previously synthesized by cyclic voltammetry on graphite surface) which naturally bonds with NAD and tetra-butylammonium bromide (TBAB) in the presence of ADH. Cyclic voltammetry was used to evaluate the redox behavior and confirm the presence of ADH. Furthermore, the electrocatalytic activity of both bio-electrode arrays was evaluated in terms of the ethanol oxidation reaction showing excellent performance. These interesting bio-electrode arrays offer potential possibilities of application as electrocatysts in direct ethanol biofuel cells.