ISOLATION AND IDENTIFICATION OF PHENOL DEGRADING YEASTS FROM CONTAMINATED SAMPLES

Background and Aim:Phenol is a major environmental pollutant in wastewater of various industries including oil refineries, pharmaceuticals, and plastic industries. The biodegradation of phenols is an environmentally friendly and cost-effective technology.Methods:Twenty-five contaminated soils and wastewaters samples were collected for isolation of high potential phenol degrading yeasts. Bushnell Hass Mineral Salts medium (BHMS) supplemented with 100, 200 and 250 mg/L phenol was used during three steps enrichment process. The screening of phenol degrading strains was carried out on solid BHMS medium and the maximum tolerance of different concentration of phenol (250, 500, 1000, 1500 mg/L) was assessed. Analysis of 26S rDNA and ITS were performed for the taxonomic characterization of isolated strains.Results:A total of 29 yeast strains were isolated as phenol degrading strains based on their ability to growth on solid media containing 250 mg/L of phenol. Different morphotypes were identified by sequencing of universal marker genes as Candida tropicalis, Candida blankii, Rhodosporidium paludigenum, Solicoccozyma aeria, Rhodotorula paludigenum and Exophialia oligosperma. The highest level of phenol tolerant was observed by Rhodotorula toruloides at 1500 mg/L. Candida tropicalis is previously known as a potent utilizer of high initial phenol concentration up to 2000 mg/L. However, to the best of our knowledge, there was not a previous record of phenol degradation for any of above mentioned species.Conclusion:These results indicated that the isolated strains possess a potential ability for removal of phenol pollution from wastewater and contaminated soil.

Keywords:

Phenol , Bioremediation , Soil , Waste water , Yeast