Production of Rhamnolipid using Moderate Halophilic Pseudomonas aeruginosa SH-6 isolated from a Saline Lake

Biosurfactants are tensio-active, amphipathic biomolecules, which can reduce the surface tension of liquids. Synthetic surfactants are predominantly toxic, resistant to degradation, and exhibit narrow range of activity, whereas surface-active biosurfactants are non-toxic and biodegradable. Biosurfactants from halophilic microorganisms have significant attributes of being able to work under diverse spectrum of salt concentration, pH and temperature. This research was focussed on biosurfactant producing halophilic organism from a saline lake and the production of biosurfactant. Out of 32 bacterial isolates from saline water, and 18 bacterial isolates from saline soil, only the isolates growing on inorganic salt media amended by adding 3% NaCl and 1% Kerosene as carbon source and an inducer and passing the two stages of screening; SH-6 isolate was found to be a relatively better isolate (oil displacement zone = 2.96 ± 0.05 cm, E24= 64.66 ± 0.57%, 47.33 ± 0.57% reduction in surface tension). Using 16S rRNA technique along with the phylogenetic analysis, a moderate halophilic strain SH-6 (optimum growth at 3% NaCl) was identified to be Pseudomonas aeruginosa (NCBI Accession number PP567277). Acid precipitation along with solvent-based extraction (using non-polar Chloroform and polar Methanol) was adopted to obtain biosurfactant with a resultant yield of 0.31 ± 0.01 g %. With Rhamnolipid R-90 (90% pure) as a standard reference and using primary chromatographic characterization like Column and Thin Layer chromatography, followed by HPLC and HPTLC the biosurfactant was found to be similar to Rhamnolipid. There is a future prospect to optimize Rhamnolipid production and investigate the applications in bioremediation, agriculture.