A novel renewable tyrosinase-based biosensor was developed for the detection of phenol by immobilizing tyrosinase on a colloidal gold modified carbon paste electrode. Anionic colloidal gold was beneficial to the immobilization of tyrosinase and to the retention of its bioactivity to a large extent. The biosensor showed a sensitive electrochemical response to the reduction of the oxidation product of phenol by dissolved O-2 in the presence of immobilized tyrosinase. The effects of pH, operating potential and the volume of the colloidal gold solution for sensor preparation on the amperometric response were explored for optimum analytical performance. The best performing biosensor exhibited a fast response (less than 5 s), a high sensitivity (12.3 muA cm(-2) muM(-1)) and good storage stability for monitoring phenol. The linear range spanned the concentration of phenol from 4 to 48 muM with a correlation coefficient of 0.9973 (n = 12) and a detection limit of 6.1 nM at 3sigma. The response showed Michaelis-Menten behavior at larger phenol concentrations. The K-M(app) value of immobilized tyrosinase on colloidal gold was calculated to be (53.6 +/- 3.2) AM using phenol as the substrate.