Phenol biodegradation by the yeast Candida tropicalis in the presence of m-cresol

Biodegradation of phenol and m-cresol using a pure culture of Candida tropicalis was studied. The results showed that C. tropicalis could degrade 2000 mg l−1 phenol alone and 280 mg l−1m-cresol alone within 66 and 52 h, respectively. The capacity of the strain to degrade phenol was obviously higher than that to degrade m-cresol. The presence of m-cresol intensely inhibited phenol biodegradation. Only 1000 mg l−1 phenol can be completely degraded in the presence of 280 mg l−1m-cresol. On the contrary, the phenol of low concentration from 100 to 500 mg l−1 supplied a sole carbon and energy source for C. tropicalis in the initial phase of biodegradation and accelerated the assimilation of m-cresol, resulting in the fact that m-cresol biodegradation velocity was higher than that without phenol. Besides, the capacity of C. tropicalis for m-cresol biodegradation was increased up to 320 mg l−1 with the presence of 60–100 mg l−1 phenol. In addition, the intrinsic kinetics of cell growth and substrate degradation were investigated with phenol and m-cresol as single and mixed substrates in batch cultures. The results illustrated that the models proposed adequately described the dynamic behaviors of biodegradation by C. tropicalis.