Degradation of phenol by aerobic granules and isolated yeast Candida tropicalis

Aerobic granules effectively degrade phenol at high concentrations. This work cultivated aerobic granules that can degrade phenol at a constant rate of 49 mg‐phenol/g·VSS/h up to 1,000 mg/L of phenol. Fluorescent staining and confocal laser scanning microscopy (CLSM) tests demonstrated that an active biomass was accumulated at the granule outer layer. A strain with maximum ability to degrade phenol and a high tolerance to phenol toxicity isolated from the granules was identified as Candida tropicalis via 18S rRNA sequencing. This strain degrades phenol at a maximum rate of 390 mg‐phenol/g·VSS/h at pH 6 and 30°C, whereas inhibitory effects existed at concentrations >1,000 mg/L. The Haldane kinetic model elucidates the growth and phenol biodegradation kinetics of the C. tropicalis . The fluorescence in situ hybridization (FISH) and CLSM test suggested that the Candida strain was primarily distributed throughout the surface layer of granule; hence, achieving a near constant reaction rate over a wide range of phenol concentration. The mass transfer barrier provided by granule matrix did not determine the reaction rates for the present phenol‐degrading granule. Biotechnol. Bioeng. 2007;96:844–852. © 2006 Wiley Periodicals, Inc.