Isolation and identification of biosurfactant producing yeasts from soil contaminated with petroleum hydrocarbons

Biosurfactants are surface active molecules synthesized by bacteria, yeast and fungi. Biosurfactants have distinct advantages over chemically produced family due to their low toxicity, high biodegradability, higher foaming capacity and remarkable properties such as high activity at pH levels and salinity at extreme temperatures. In recent years, the increase in work done with biosurfactants has also increased the potential to replace chemical surfactants. All of these isolates were subjected to 3 different screening methods (Parafilm M, Oil Spreading and Drop collapse) and were identified as 20 yeast isolate biosurfactants producing at least two positive results. Subsequently, the surface tension of these isolates was measured by the Du-Nouy ring method. The surface tension of the negative control water was 70.2 mN / m, whereas the surface tension of the positive control SDS of 1% was 37.9 mN / m. As a result of the measurements, it was determined that the surface tension was decreased in 20 samples. The best results showed isolates GS33, OS16, GS22 with 34.7 mN/m, 35.3 mN/m and 37.8 mN/m, respectively. Genotypic identification of biosurfactant isolates was done by 5,8 ITS-PCR and 26S rDNA PCR.As a result of both sequence analyzes, 6 Yarrowia lipolytica, 3 Candida tropicalis, 3 Trichosporon loubieri, 2 Geotrichum candidum, 2 Rhodotorula mucilaginosa, 1 Galactomyces geotrichum, 1 Rhodotorula sp, 1 Sporobolomyces lactosus are diagnosed. Yeast strain identified as Candida davisiana by 26S rDNA sequence analysis was identified as Sporobolomyces lactosus according to sequence analysis of ITS region.