Selection of autochthonous yeast strains able to degrade biphenyl

In order to assess the role of yeasts in the natural detoxification process of sediments polluted with biaryl compounds, indigenous yeast species able to degrade biphenyl (BP) were isolated and identified. The degradation ability of 24 strains of the genera Candida spp., Cryptococcus spp., Pichia spp., Rhodotorula spp., Trichosporon spp. and Yarrowia spp. was evaluated by the identification of the BP-metabolites, by HPLC analysis. 4-Hydroxybiphenyl was the main derivative in the Candida krusei, C. tenuis, C. tropicalis, Pichia haplophila, Rhodotorula glutinis, Trichosporon pullulans and Yarrowia lipolytica cultures. 3-Hydroxybiphenyl was detected in minor amounts in the culture supernatant of C. tropicalis, C. krusei strains and R. glutinis. Further hydroxylation led to 3,4-dihydroxy and 2,3-dihydroxybiphenyl; the former in C. tropicalis, C. krusei and R. glutinis cultures, and the latter only in the R. glutinis assays. The cleavage product 4-phenyl-2-pyrone-6-carboxylic acid, was observed in R. glutinis and Y. lipolytica cultures. The degradation ability of the R. glutinis isolates was noteworthy; as four hydrolxylated intermediates and a ring-cleavage product were obtained in both strain cultures. The species studied in this report were dominant in polluted sediments; furthermore, R. glutinis had been mentioned as able to degrade other aromatic hydrocarbons and had high relevance in bioremediation experiments.