REMOVAL AND BIOCONVERSION OF PHENOL IN WASTE-WATER BY A THERMOSTABLE BETA-TYROSINASE

This study explores an enzymatic method for removing phenol from the w astewater created during the manufacture of phenolic resin. The enzyme used was a thermostable beta-tyrosinase catalyzing the synthesis of L -tyrosine from phenol, pyruvate, and ammonia. As the reaction proceeds , L-tyrosine precipitates as insoluble aggregates because L-tyrosine i s barely soluble in water The enzymatic removal of phenol was effectiv e at pH values ranging from 6.5-9.0 and temperatures below 70 degrees C. The optimal concentration of each substrate was determined as 60 mM phenol, 0.1 M pyruvate, and 0.4 M ammonia. When the enzyme was used i n an intact cell or acetone-dried cell stare instead of the cell-free extract, the optimal concentration of phenol was increased up to 120 n M. By treating wastewater containing 100 mM phenol with acetone-dried cells at 37 degrees C, we could reduce the concentration of phenol to 8 mM within 24 h.