The aromatic compounds metabolism in particular phenol and its derivates is a subject of intensive studies in prokaryotes. Nowadays the investigations of different yeast species that metabolize aromatic compounds are of significant scientific interest. Trichosporon yeast strains, isolated from various sources, polluted with toxic compounds are among the most studied yeast with respect to aromatic compound biodegradation in eukaryotes. Usually the environmental pollution is a result of different compounds simultaneously.
The object of present study is a strain Trichosporon cutaneum R 57 able to grow and degrades phenol as a sole carbon and energy source up to 1 g/l in a short period of time (16-18h). The strain is also able to degrade phenol in a very short period of time in rich medium despite the presence of additional carbon source (such as peptone or amino acid).
The aim of the present investigation is to carry out the influence of additional carbon sources such as glucose and acetate on the phenol degradation in Trichosporon cutaneum R57 strain. The activity of two key enzymes for catabolism of phenol as phenol hydroxylase [EC 1.14.13.7] and catechol -1,2- dioxygenase [EC 1.13.11.1] were determined in cells grown in a medium Yeast Nitrogen Base without Amino Acids used for analyses of carbon assimilation in yeast strains comprising different mixtures of the mentioned above carbon sources.
The effect of glucose and acetate on the phenol degradation ability of Trichosporon cutaneum R57 strain was examined in the condition of batch cultivation. It was established that in YNB w/o AA medium the glucose and phenol assimilation flowed simultaneously so that the assimilation rate of glucose was much higher than that of phenol. Some delay in phenol degradation was observed in the experiments for studying the acetate influence in the medium. In these experiments however the phenol was completely degraded by the time of acetate assimilation.
The results obtained after enzymes analyses in the cells cultivated in the medium with two carbon sources such as phenol and acetate that are known to be utilized by Trichosporon cutaneum R57 are of special interests. In our experiments in a culture medium with 0,5 g/l phenol included the presence of acetate (1.8 g/l) did not influence negatively the phenol hydroxylase activity (0,833 U/mg protein), compared to the activity in the same medium without other than phenol carbon source (1,14 U/mg protein), but obviously lowered twice the activity of catechol-1,2-dioxygenase (0,108 U/mg protein and 0,206 U/mg protein respectively).
On the contrary, the influence of glucose presence in the media had much stronger influence on the activity of both investigated enzymes. In a culture medium containing 0.5 g/l phenol and 1.5 g/l glucose the activity of the phenol hydroxylase dropped to 0.225 U/mg protein and catechol-1,2-dioxygenase activity was 0.65 U/mg protein. It should be pointed that some basal activity of both enzymes (3-5 mU/mg protein) was established even in cells cultivated in a medium with glucose as a sole carbon source.
Our results showed that in these experiments the presence of acetate, respectively glucose do not repress and /or inactivate phenol degradation enzymes such as phenol hydroxylase and catechol 1,2 dioxygenase in the investigated Trichosporon cutaneum R 57 strain.
On the basis of our previous and recent analyses, the investigated strain could be considered to have a good potential for application in remediation of phenol contaminated environment and improvement of phenol removing treatment of industrial wastewaters.
