Screening and Characterization of Emulsifying Hydrocarbon- Degrading Bacteria from Coastal Waters of the Caspian Sea

Abstract

As a result of 400 cultures screening isolated from the contaminated coastal zones of the Caspian Sea, 4 new strains were selected that had a stable growth and utilized oil with NaCl concentration close to that of seawater. Stenotrophomonas chelatiphaga wkal49, Stenotrophomonas chelatiphaga wkal51, Sphingobacterium kitahiroshimense wkar54, and Achromobacter sp. wkar55 were identified based on an analysis of the direct nucleotide sequence of the 16S rRNA gene fragment. The degree of oil degradation by these strains was above 50%. The hydrophobicity of the cell surface, emulsifying activity, the degree of influence on the viscosity of crude oil, and also the ability to produce surfactants were the four key factors that made up the studied parameters for the selected strains. The studied strains formed an emulsion layer on the surface of the culture medium. The most active producers of extracellular bioemulsifiers were the Stenotrophomonas chelatiphaga wkal49 and Stenotrophomonas chelatiphaga wkal51 strains. Both demonstrated the highest hydrophobicity, emulsification index, and the highest value for decreasing oil viscosity.