Physiochemical and Structural Characterization of Biosurfactant Produced by Halophilic Pseudomonas aeruginosa ENO14 Isolated from Seawater

Objectives: The aim of this study was to isolate a potent biosurfactant producing bacterium and characterize the produced biosurfactant for its application in pharmaceutical, petrochemical, cosmetic and food industry. Methods: Enrichment method was carried out followed by serial dilution technique to isolate the bacteria from oil contaminated seawater. Various qualitative assays such as haemolytic assay, oil displacement assay, foaming index and emulsification index was carried out for the screening of the best isolate. Morphological, biochemical, physiological and 16S rDNA sequencing was used to identify the potent bacterium. For the production of biosurfactant, Bushnell Hass Broth (BHB), supplemented with 1% glucose was used. Various physiochemical and structural analysis of biosurfactant were carried out by different techniques. Results: The bacteria producing biosurfactant were isolated and screened for biosurfactant production using various qualitative assays from crude oil contaminated seawater. A potent bacterial isolate was selected on the basis of oil displacement activity and highest biosurfactant producing capability. Based on the morphological, physio-biochemical characteristics and sequencing of 16S rDNA of the isolate, ENO14, was revealed to be Pseudomonas aeruginosa. The biosurfactant exhibited high surface activity (critical micelle concentration, CMC=3.85 mg/ml) and excellent emulsifying activity against different hydrocarbons (emulsifying activity, EA₂₄ =100% against crude oil). The biosurfactant showed stability over a temperature range of 20-70°C, pH range of 2-12 and salinity range of 2- 12% (w/v). Compositional analysis of the purified biosurfactant by chemical method as well as by Ultraviolet-Visible Spectroscopy (UV-Vis), Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), reveals it is a type of glycolipid biosurfactant. Conclusion: We conclude that Pseudomonas aeruginosa ENO14 is an efficient biosurfactant producer. The produced biosurfactant was well characterized for its application in pharmaceutical, petrochemical, food and cosmetic industry.