Comparative approach for detection of biosurfactant-producing bacteria isolated from Ahvaz petroleum excavation areas in south of Iran

The current study was undertaken to compare four analytical methods including drop collapse, oil spreading, surface tension (SFT) measurements, and blood agar lysis tests for detection of biosurfactant-producing bacteria. Among 32 biosurfactant-producing bacteria isolated from Ahvaz oil fields, in south of Iran, 16 isolates (50%) exhibited highest biosurfactant production. Eleven isolates (MASH.1 to MASH.11) demonstrated a reduction in surface tension from 65 mN/m to less than 41 mN/m. The results showed that about 91% of these highly biosurfactant producers had the same response levels of "++++" and "+++" in the case of both SFT and oil spreading methods. Among these, seven isolates had the haemolysis diameter less than 1 cm or between 1 and 2 cm on blood agar. As 64% of the best biosurfactant producers did not completely lyses blood, the ability of biosurfactant-producers for haemolysis may not always be trustworthy. According to our data, there is a good consistency between oil spreading technique and surface tension. As a conclusion, oil spreading method is the fastest, simplest and most consistent analytical method to be suggested for accurate measurements of biosurfactant producers.