Isolation of potent biosurfactant producing bacteria from oil spilled marine water and marine sediments

Abstract

Biosurfactants produced by bacteria are surface-active compounds involved in the degradation of  hydrocarbons. They are heterogeneous group of surface active molecules produced by microorganisms, which adhere to cell surface or are excreted extracellularly in the growth medium. These can be divided into low-  molecular weight molecules, that lower surface and interfacial tensions efficiently and high-molecular-weight polymers that bind tightly to surfaces. These surfactants, produced by a wide variety of microorganisms, have very different chemical structures and surface properties. It is therefore reasonable to assume that different  groups of biosurfactants have different natural roles in the growth of the producing microorganisms. In this  study, isolation and identification of biosurfactant producing bacteria were assessed from oil-spilled seawater  collected from harbors and docks from Arabian Sea (Mumbai), India. The potential application of these bacteria in microbial enhanced oil recovery (MEOR) was investigated. To confirm the ability of isolates in biosurfactant production, various biosurfactant activity assay tests and measurement of surface tension were conducted.  Hemolysis was used as a criterion for the primary isolation of biosurfactant producing bacteria. Effects of  different pH, salinity and temperature on biosurfactant production were also studied. Among all of the isolated strains, Pseudomonas sp. (MW2) showed high salt tolerance, successful production of biosurfactant in a vast pH and temperature domain and reduced surface tension of the medium to value below 40 mN/m. This strain is a potential candidate for MEOR. The MW2 biosurfactant component was detected as glycolipid in nature.

Key words: Biosurfactant, emulsification, extreme conditions, microbial enhanced oil recovery, marine water.