We examined the performance of an integrated biooxidation and acid dehydration process for aromatic monohydroxylation using the production of o-cresol from toluene as the model conversion. A toluene cis-glycol dehydrogenase gene (todD)-disrupted mutant of Pseudomonas putida T-57 was employed as the whole cell biocatalyst for oxidizing toluene to toluene cis-glycol (TCG). After bioconversion of toluene to TCG, o-cresol was produced by adding HCl to the culture medium, since it was found that TCG became unstable at a low pH and underwent spontaneous dehydration. When the todD-disrupted mutant cells were grown in a two-liquid-phase culture system with oleyl alcohol as the organic solvent, this integrated process produced 40 g l(-1) of o-cresol in the organic solvent phase at 30 h. The total concentration of o-cresol in the two-liquid-phase culture reached 6.6 g l(-1) at 30 h, which was approximately four-fold greater than that in the single-liquid-phase culture. (c) 2006 Elsevier Ltd. All rights reserved.