Biodegradation of Phenol by the Yeast Candida tropicalis: An Investigation by NMR Spectroscopy

The process of phenol biodegradation by the yeast Candida tropicalis NCIM 3556 in aqueous medium was studied by ¹H, ¹³C, and DOSY NMR techniques. Samples at regular intervals were centrifuged to separate the cells, and ¹H spectral data were collected at 400 MHz. Though a gradual decrease in the concentration of phenol was observed, after an incubation period of ~8 h, formation of any intermediate products could not be detected. Experiments carried out with uniformly ¹³C-labeled phenol also failed to detect formation of any carboxylic acid intermediates during degradation. The studies indicated that the phenol was completely degraded to carbon dioxide and water in approximately 20 h. Self-diffusion coefficient measurements showed that the lifetime of phenol in the bound form is too small to impart any change in its diffusion behavior and the intermediates formed are converted to carbon dioxide and water at a very fast rate.