Characterization, production and optimization of lipopeptide biosurfactant by new strain Bacillus pumilus 2IR isolated from an Iranian oil field

Abstract

Characterization and production of biosurfactant by a novel bacterial strain isolated from an Iranian oil field was investigated. Biosurfactant has wide applications in oil recovery. A number of ten strains of Bacillus sp. were isolated from oil-contaminated soil samples to study biosurfactant production. Among strains studied, the strain 2IR was selected as a potent biosurfactant-producing bacterium. The identification of the strain 2IR was carried out using scanning electron microscopy, biochemical tests and partial 16S rRNA gene sequencing with generating a phylogenetic tree. Accordingly, the new strain was identified as Bacillus pumilus 2IR. The biosurfactant produced by the strain 2IR was characterized by high performance liquid chromatography, fourier transform infrared spectroscopy and proton nuclear magnetic resonance test. The tests results characterized the biosurfactant produced as a lipopeptide type. In order to attain the highest surface tension reduction of the lipopeptide biosurfactant, culture medium of the strain 2IR was optimized. Experimental results showed that glucose, crude oil, potassium nitrate and ammonium sulfate were pivotal components of the culture medium for biosurfactant synthesis by B.pumilus 2IR. Similar results revealed that optimum medium compositions were 30.31g/L glucose, 0.8% (v/v) crude oil, 2.88g/L potassium nitrate and 2.4g/L ammonium sulfate. A surface tension value of 30mN/m was obtained in optimum conditions. This research presents new indigenous strain B. pumilus 2IR for synthesis of biosurfactant usable for possible in situ oil recovery.