Screening of Biosurfactant Production in Bacteria Isolated from Oil and Pesticide Contaminated Soil of Ranchi District

Abstract

Biosurfactants, the surface-active compounds are produced by a few microorganisms. As such biosurfactants are superior to synthetic surfactants in terms of cost of production and industrial application. Present study deals with the isolation, characterization, screening, and extraction of biosurfactant producing bacteria from motor oil dumped and pesticide contaminated agricultural fields of Ranchi District, Jharkhand, India. Mineral salt medium (MSM) supplemented with hydrocarbon was used for the enrichment of putative biosurfactant producers. Out of ten isolates, five isolates (F1 to F5) showed growth on hydrocarbon supplemented plate suggesting its use as main carbon source. Three isolates namely F1, F4 and F5 were from the waste oil contaminated soil and remaining two (F2 and F3) from pesticide contaminated site. Based on traditional microbiological methods, characterization and identification were made which showed that F1, F4 and F5 isolates belong to Staphylococcus aureus and F2 and F3 to Bacillus subtilis species. Biosurfactant production was tested by hemolysis, emulsification index (E24) and drop collapsing tests, results showed positive test for all the assay suggesting the potential of biosurfactant production by all the five isolates. Among all the five isolates, F1 showed maximum emulsification index (44.44%) followed by F4 (35%) both belonging to strains of Staphylococcus aureus. The remaining isolates F2, F3 and F5 also showed appreciable level of E24 (24-28%). Biosurfactants produced by all the five isolates were extracted using solvents, the dry weight showed close correlation with E24. Further work is needed to confirm the identity of all the isolates using 16S rRNA sequencing and chemical characteristics of biosurfactants employing standard analytical techniques.