Evaluation of different screening methods for biosurfactant producers isolated from Egyptian fresh water samples contaminated by oil spills using bacillus subtilis and bacillus licheniformis

Abstract EN

In all countries, oil exploration and use threatens the health of the environment and living creatures including humans.

An oil spill is the release of petroleum hydrocarbon into the environment.

One of the most applicable and safe method is the bioremediation treatment, using microorganisms.

This work aims at treating oil spills in fresh water and to compile information on types and properties of biosurfactant.

It also describes factors affecting these biosufactants production.

Different screening methods e.

g.

oil spreading assay, Emulsification index (E24), Drop collapse assay, Blood agar test, Hemolysis, MaCconkey agar test were tested.

Two isolates gave highly Emulsification tests named O3, O11, which were identified as Bacillus subtilis and Bacillus licheniformis respectively, were isolated from petroleum hydrocarbon contaminated water.

Optimization of two isolates were done and highest biosurfactant activity at temperature ranges from 10 oC to 50 oC and pH ranges from 3 to 10 and salinity ranges from 0% to 30% .

Also, the biosurfactant was characterized by Fourier transform infrared spectroscopy (FTIR) and surface tension measurement.

FTIR showed the production of biosurfactant from Bacillus subtilis similar to surfactin, while the biosurfactant from Bacillus licheniformis similar to lichenysins.

The use of microbial biosurfactants significantly decreases the hydrophobicity and increases the rate of hydrocarbon biodegradation.

Biosurfactants obtain demonstrated good surface tension reduction capacity by Bacillus subtilis and Bacillus licheniformis up to 30 and 36Nm/m and have emulsifying activity 71% and 65% respectively.