Isolation of biosurfactant\|producing bacteria and optimization of carbon and nitrogen sources
生物表面活性剂产生菌的分离鉴定及碳氮源优化

Microorganisms capable of producing biosurfactants were isolated by enrichment culture and blue agar plate based on the surface tension of the fermentation liquor. One indigenous microorganism, strain S2, which produced biosurfactants was isolated from oil sludge samples collected from Yangzi Refinery, Jiangsu Province, China. Its physiological morphology, growth, and the biosurfactant properties of the metabolite it produced were analyzed. Strain S2 was identified as belonging to Pseudomonas aeruginosa. The surface tension of its fermentation liquor is stable and can be lowered from initial 75 mN·m-1 to 35 mN·m-1. The critical micelle concentration is 0.25 g·L-1, which is much lower than normal chemical surfactants. The fermentation liquor is emulsified much better by the biosurfactant than by typical chemical surfactants such as SDS and CTAB. Furthermore, it is shown that the optimum carbon and nitrogen sources for the growth of the strain are vegetable oil and NaNO3, respectively. Under these conditions, the production of biosurfactant by P. aeruginosa S2 can reach as high as 4.7 g·L-1.