Studies on optimization of biosurfactant production by Pseudomonas aeruginosa F23 iso- lated from oil contaminated soil sample

Abstract

A biosurfactant producing strain was isolated from soil sample obtained from a coconut oil mill and identified as Pseudomonas aeruginosa F23, based on physiological, biochemical tests and 16S rRNA sequence analysis. Primary screening for biosurfactant producer was carried out by observing hemolysis on superimposed blood agar, zone of clearance on Tributyrine agar and blue halo around the growth on N-cetyl- N, N, N-trimethyl ammonium bromide agar. Maximum biosurfactant yield was obtained in optimized SM medium containing 2% coconut oil and 0.3% potassium nitrate (C:N ratio 7:1) at pH 8 incubated at 30 o C under shaker conditions (120 rpm) for 96 h with 4% inoculum (0.8 OD 530nm ) of the isolate.The biosurfactant was partially purified using acetone and rotary vacuum evaporator and quantitatively estimated by anthrone assay, which was found out to be 2.8 g/L. The biosurfactant could reduce the surface tension upto 31 mN/m with 60% emulsification index in 36h. HPTLC analysis of the product demonstrated Rhamnose to be a sugar moiety and FT-IR results confirmed it to be rhamnolipid type of biosurfactant. It showed stability on exposure to high temperature (up to 100 o C) and also demonstrated antibacterial activity.