Evaluation of rhamnolipid production by a halotolerant novel strain of Pseudomonas aeruginosa

This work was aimed to evaluate six qualitative and quantitative methods (hemolytic activity, cetyltrimethylammonium bromide agar plate method, oil spread method, drop collapse method, surface tension measurement and emulsification index) to study biosurfactant production by sixty-nine bacterial isolates which were obtained from petroleum crude contaminated soil and water samples. Among all isolates, Pseudomonas aeruginosa NCIM 5514 was evaluated as the most potent isolate producing rhamnolipid. Effectiveness of growth medium pH, inoculum size and concentration of NaCl on surface active properties and biomass & rhamnolipid production in fermentation medium were studied. Highest surface activity was obtained at 1% (v/v) inoculum at initial pH of the medium 7.2, which resulted 4.389 ± 0.019 and 3.146 ± 0.087 g/l biomass and rhamnolipid, respectively. Notable surface activity of rhamnolipid produced by P. aeruginosa NCIM 5514 makes it feasible to be used for industrial application.