Studies on Biosurfactant Production by Pseudomonas aeruginosa R2 Isolated from Oil Contaminated Soil Sample

A biosurfactant producing strain was isolated from soil sample obtained from coconut oil mill and identified as Pseudomonas aeruginosa R2 based on physiological and biochemical test together with 16s rRNA sequence analysis. Primary screening for biosurfactant producer was carried out by observing hemolysis on Superimposed blood agar and zone of clearance on Tributyrin agar. Optimization of culture conditions involved use of various vegetable oils as carbon source and different organic as well as inorganic compounds as nitrogen source, of which 1 per cent coconut oil and 0.4 per cent ammonium nitrate at pH 7 when kept at 30°C for 120 rpm/96 hours showed maximum biosurfactant yield. The biosurfactant was partially purified using chloroform and ethanol mixture (2:1) and quantitatively estimated by Anthrone assay which was found out to be 1.7 g/L. The biosurfactant could reduce the surface tension up to 35 mN/m with 70 per cent emulsification index (E24) in 36hrs. TLC analysis of biosurfactant demonstrated rhamnose as a sugar moiety and FT-IR results confirmed it to be rhamnolipid type of biosurfactant. It also exhibited antimicrobial activity and showed stability on exposure to high temperature (up to 100°C). Emulsification activity found with the biosurfactant against hydrocarbons shows its possible application in bioremediation of environments polluted with oils.