Surface activity of extracellular products of a Pseudomonas aeruginosa isolated from petroleumcontaminated soil

Pseudomonas aeruginosa isolated from petroleumcontaminated soil of Nsukka, SouthEast Nigeria produces surfaceactive compounds when grown in different carbon sources tested. The surface properties of the culture supernatants of the isolate, using watersoluble and waterinsoluble carbon sources as substrates are described in terms of surface tension and emulsification index. Watersoluble substrates showed better surface activity than waterinsoluble substrates. The surface tension of the culture supernatants was lowest with glucose (34.5 dynes/cm) followed by sucrose (38.6 dynes/cm), glycerol (40.2 dynes/cm), fructose (41.8 dynes/cm), hexadecane (50.4 dynes/cm) and paraffin oil (56.4 dynes/cm). The culture supernatants showed emulsification index of between 52% and 85% and the emulsion formed remained stable during an extended ageing period of 30 days. The biosurfactants formed by the isolate retained surface active properties after exposure to high temperature (100°C), a wide range of pH (4 – 12) and high salinity (16%).