Phenols and N-heterocyclic compounds are found to co-exist in actual wastewater, especially in petrochemical and coking wastewater. Lysinibacillus cresoliyorans, a bacterium capable of phenol-biodegradation was used to study the substrate interactions of m-cresol and pyridine as single and dual substrates. The cell growth and substrate biodegradation kinetics were also investigated with initial m-cresol concentrations varying from 0 to 1200 mg/L and pyridine concentrations varying from 0 to 150 mg/L The single substrate kinetics was well described by the Haldane kinetic models. The single-substrate parameter values of m-cresol on cell growth were mu(max) = 0.89 h(-1), K-s = 426.25 mg/L, K-i = 51.26 mg/L and mu(max) = 0.0925 h(-1), K-s= 60.28 mg/ L, K-i =16.17 mg/L for cell growth on pyridine. Inhibitory effects of substrates were observed when cells were grown on the mixed substrates. The interaction parameter I-m,I-p, (0.76) was greater than I-m,I-p (0.11), which indicated that m-cresol inhibited the utilization of pyridine much more than pyridine inhibited the biodegradation of m-cresol. The study showed a good potential of L cresolivorans in degrading mixed substrates of m-cresol and pyridine. (C) 2010 Elsevier B.V. All rights reserved.