Amperometric phenol biosensor based on a thermostable phenol hydroxylase.

Phenol hydroxylase (EC 1.14.13.7) was produced using Bacillus stearothermophilus in a 5-1 batch fermentation leading to approximately 17 units after 6 h. The partially purified phenol hydroxylase was entrapped in a sol-gel matrix. The enzyme-loaded silica gel was attached to the sensitive top of a Clark-type oxygen electrode and its application as a phenol biosensor was tested. There was linearity between the maximal rate of oxygen consumption and phenol concentration in the range between 2.5 and 400 microM at 40 degrees C and pH 7.6. The signal could be read off after 10 s at a concentration of 400 microM phenol. The sensor lost 20% of its activity within 7 days. Para-substituted phenols were not detectable.