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

Abstract

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.

Evaluation of Screening Methods for the Isolation of Biosurfactant Producing Marine Bacteria

“…Earlier reports on screening of biosurfactant producing microbes discussed either a single method or combination of two or three methods like hemolytic assay, BATH assay, drop collapse method, oil spreading assay and surface tension measurement [20][21][22]. Few reports have 6 to 8 screening methods but with no surface tension measurement.…”

“…Carrillo et al [36] found an association between hemolytic activity and surfactant production and they recommended the use of blood agar lysis as a primary method to screen biosurfactant production. None of the studies reported in the literature [21][22][23][36][37][38] mention the possibility of biosurfactant production without a hemolytic activity. However, in some studies hemolytic assay excluded many good biosurfactant producers and in some reports strains with positive hemolytic activity were found negative for biosurfactant production [21].…”

“…There are nine different screening methods that have been reported as criteria to screen biosurfactant producing microbes such as hemolytic assay [16,17], bacterial adhesion to hydrocarbons (BATH) assay [18,19], drop collapse assay, oil spreading assay [20,21], emulsification assay [22,23], surface tension measurement, titled glass slide test, blue agar plate and hydrocarbon overlay agar assay [23]. Methods discussed above have both advantages and disadvantages.…”

Assessment of Antibacterial Capability of Rhamnolipids Produced by Two Indigenous Pseudomonas aeruginosa Strains

“…MASH1 biosurfactant produced by MASH1 (26) using soybean oil as sole carbon source was cultivated in SOM medium composed of (g/L): NaNO 3 . Seed cultures were inoculated (2% v/v) in 250 ml flasks containing 50 ml of production medium followed by incubation at 200 rpm and 30 °C for 6 days.…”

Analysis of Biosurfactant Production by a New Thermophilic and Halotolerant Bacterium, Geobacillus sp. QT

“…There appeared several colonies and pure cultures of each morphologically distinct colonies were obtained by repetitive streaking onto solid LB medium. To isolate the strains capable of biosurfactant production, oil spreading method [2,12] and hemolytic activity [13] were applied. Among several bacterial strains isolated, a potent biosurfactantproducing bacterial strain was identified and examined as creation of significant clear zone on the oil surface and maintained on LB agar medium at 4°C for further experiments.…”