عنوان مقاله [English]
Phenol and phenolic compounds are environmental contaminants that are commonly found in industrial effluents from oil refineries, coal mines, and petrochemical plants. Phenol removal from industrial effluent is, therefore, of extreme importance for environmental protection. Phenol degradation is commonly accomplished by physicochemical methods that are not only costly but also produce hazardous metabolites. Recently, phenol biodegradation has attracted much attention due to its lower process cost. In this study, yeast, as a phenol-degrading agent, was initially isolated from samples in the surrounding environment (soil and water) taken from Zarand coking plant. The total heterotrophic and biodegrading yeasts were then counted. Compared to effluent samples, soil samples were found to exhibit higher yeast degrader counts. Yeast growths were measured after three passages and the two strains K1 and K11 were recorded as the ones with the highest growth rates. These same yeasts were the ones capable of removing phenol as evidenced by the remaining phenol content measured by the Gibbs reagent. The effects of four different phenol concentrations (0.1, 0.125, 0.2, and 0.275) were activities were measured in all the eleven yeasts isolated. Finally, part of the 18S rRNA gene section was cultured using primers (Euk-A, Euk-B) especially used for this gene and a series of biochemical tests were run for the molecular identification of the yeasts predominantly involved in phenol degradation. The sequences obtained were compared against the available gene banks and the highest homology (greater than 98%) was introduced as the genus and species of phenol degrader yeasts. The isolated yeasts belonged to the genera Trichosporon montevideense and Trichosporon cutaneum.
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