Enhanced biodegradation of 4-chlorophenol by Candida tropicalis PHB5 via optimization of physicochemical parameters using Taguchi orthogonal array approach

Candida tropicalis PHB5 was able to grow on 4-chlorophenol and to metabolize this substrate. 4-Chlorophenol degradation proceeds through a pathway involving transient production of three key metabolites 4-chlorocatechol, 4-chloropyrogallol and 4-carboxymethelenebut-2-en-4-olide which were identified by HPLC analysis. The Taguchi orthogonal array design methodology was used to improve the 4-chlorophenol biodegradation ability of strain PHB5. At 3 levels, an orthogonal array was selected to analyze the effects of the different physicochemical process factors. Experiments were undertaken to study the effects of eleven factors affecting the growth of C. tropicalis on 4-chlorophenol and its degradation. Taguchi methodology predicted that biomass yield on 4-chlorophenol could be increased from 409.7 mg l−1 to 1046.9 mg l−1 and the amount of 4-chlorophenol degraded could be increased from 314.5 mg l−1 to 949.7 mg l−1. Based on Taguchi methodology, an overall enhancement of growth by 155.5% and of 4-chlorophenol degradation by 201.9% were predicted. The predicted values were validated by experimental data which showed than under optimal cultural conditions, the biomass yield was increased by 141.62% and 4-CP degradation by 183%.

► 4-Chlorophenol degrading yeast strain Candida tropicalis PHB5 was isolated.
► Growth characteristics of the isolate were determined using Haldane model.
► Optimization of eleven process factors was carried out using Taguchi orthogonal array approach.
► Detection and kinetic study of key metabolites of 4-CP biodegradation by C. tropicalis PHB5.