Assessment of different screening methods and identification of biosurfactant producing bacteria isolated from Egyptian oily polluted soil samples

Different screening methods namely hemolytic assay, oil spread technique, drop collapse method, emulsification index (E24), blue agar plate and measurement of surface tension were assessed for their efficiency to detect biosurfactant producing soil bacteria. The aim of the present study was to investigate biosurfactant-producing bacteria found in the oily polluted soil in Giza, Alexandria and El-Beheraa governorates, Egypt. Overall, 64 bacterial strains were Isolated, characterized, and purified from 12 soil samples. Screening for biosurfactant-producing bacterial strains was confirmed through 6 conventional screening tests. among this isolates 68.74% gram-positive, furthermore, 56.24% of the isolates showed hemolytic activity, 40.63 % exhibited positive results for oil-spreading test and E24, 9.38% produced positive results for cetyltrimethyl ammonium bromide (CTAB) agar plate assay, and drop-collapse activity was found in 32.81% of the isolates, the most potent biosurfactant producing bacteria confirmed by measuring their ability to reduce surface tension by tensiometer. The dominant species were Bacillus and Pseudomonas; with an occurrence rate of 30% for each. Results indicated that these isolates have significant role for environmental applications such as bioremediation and industrial biotechnology.