Pyrene biodegradation by halo-tolerant yeast Basidioascus persicus

Poly-aromatic hydrocarbons are one of the most important toxic compounds of crude oil and environmental pollutants. The purpose of this study was to isolate halo-tolerant pyrene- degrading yeast.   Isolation of yeasts from contaminated and saline soils of oil-rich southern regions was carried out, at first. Then, screening of yeast isolates was performed based on their ability to grow in the salty medium and biodegrade oil. After screening and molecular identification of the optimal strain, its ability to tolerate salt and grow in the presence of pyrene, as well as the ability to degrade pyrene and other low molecular weight hydrocarbons were studied.   In this study, EBL-C16 was selected as the superior isolate, with growth in salt concentrations of 0-15% and eliminating 75.51% of the crude oil. Molecular identification of this isolate showed 100% similarity to Basidioascus persicus. Growth analysis showed the ability of this yeast isolate to grow in salt concentrations of 0 to 20 %. Growth and removal studies in the presence of 500 mg/l of pyrene and 2.5% salt showed 78.57% pyrene removal after 21 days, with the growth rate of 1.4 g/l of dry weight, as well as CO2 production of 3.1 mg. B. persicus had the ability to break down phenanthrene and anthracene, as well.   The results can be used to use halo-tolerant yeasts for bioremediation of oil-contaminated saline areas.