The biodegradation of single phenol and sodium salicylate (SA) and their binary mixtures in water by free Pseudomonas putida (P putida) CCRC 14365 was experimentally studied at 30 degrees C and pH 7. The initial concentration of the cells, adapted with either phenol or SA, was maintained at 0.025 g/L. Single substrate experiments were performed in the substrate level range 0.53-3.18 mM. The Haldane model has shown that phenol was biodegraded more quickly (mu(max) = 0.245 h(-1)) than SA (0.137 h(-1)) under the ranges studied, and SA had a more inhibitory effect on cell growth (K-I = 5.21 mM) than phenol (12.6 mM) at low substrate levels even by SA-adapted cells. Binary substrate experiments were carried out at two fixed total substrate levels of 1.06 and 3.18 mM, with a varying molar concentration ratio of 0.33-3.0. The presence of a small amount of phenol to SA could significantly enhance the biodegradation of SA, particularly when the phenol-adapted cells were employed. On the other hand, the addition of a small amount of SA to phenol would retard the biodegradation of phenol, especially at higher total substrate levels (3.18 mm). (c) 2006 Elsevier B.V. All rights reserved.