Applying Various Methods for Screening Biosurfactant Producers from Oil-degrading Microorganisms

Twenty eight bacterial strains were isolated from petroleum wastewaters and screened for biosurfactant/bioemulsifier production in liquid culture containing diesel as the sole carbon source. Blood agar lysis, drop collapse method, oil spreading technique and surface tension measurements were used to detect biosurfactant producers. Emulsification activity of culture broth was tested using diesel oil. Twelve isolates reduced surface tension at varying levels with strain ZA1 resulting in the lowest surface tension of 32.2 mN/m and the highest biosurfactant production on basal minimal salt medium with glucose as the carbon source (2 g/l). The critical micelle concentration of biosurfactant was estimated by plotting the surface tension versus biosurfactant concentration as 83 mg/l. Effect of carbon source on biosurfctant production was carried out using six substrate (glucose, diesel, crude oil, olive oil sun flower oil and date syrup) added to basal mineral salt medium. Among the six substrate tested, ZA1 produced a maximum of 4.3 g/l biosurfactant with sunflower oil.

کلیدواژه ها:

Biosurfactant ، Screening ، Surface Tension ، Emulsification