IMMOBILIZATION OF ALCOHOL-DEHYDROGENASE ENZYME IN A LANGMUIR-BLODGETT-FILM OF STEARIC-ACID - ITS APPLICATION AS AN ETHANOL SENSOR

A stable monolayer of alcohol dehydrogenase (ADH) enzyme has been prep ared by spreading an aqueous solution of ADH on a water subphase conta ining stearic acid monolayer. This ADH-stearic acid monolayer has been successfully transferred onto a conducting polypyrrole-coated glass e lectrode by the Langmuir-Blodgett (LB) technique. ADH catalyses the re action between the coenzyme beta-NAD + (beta form of oxidized nicotina mide adenine dinucleotide) and ethanol to produce NADH and acetaldehyd e. Conducting polypyrrole acts as a mediator for transferring electron s produced on NADH oxidation. This LB-immobilized polypyrrole-mediated enzyme electrode can be used as an ethanol sensor. It shows better se nsitivity than sensors consisting of ADH immobilized by chemical cross -linking with glutaraldehyde. This LB sensor can be used for low ethan ol concentration (in the micro-molar range).