Isolation and Partial Purification of Polyphenol Oxidase from Banana for Biosensor Applications

An amperometric biosensor based on the enzyme polyphenol oxidase (PPO), isolated and partially purified from banana, was developed using catechol as substrate. Co-crosslinking method of immobilization was adopted using the proteinbased stabilizing agent, bovine serum albumin (BSA) on cellophane and nylon membranes with glutaraldehyde as the crosslinking agent. The parameters measured were the sensitivity, the concentration range of the linear dependence of the sensor response to catechol. The enzyme electrode gave detection limit of 10 x10-5 M and 5 x10-5 M and linear response range of 20-80 x10-5 M and 10-60 x10-5 M for catechol employing cellophane as well as nylon membrane respectively. Biosensor response reached steady state within 3 min for both cellophane and nylon membranes and exhibited maximum activity at 25 0C and pH 6.0.