Biosurfactants producing bacteria from oil-polluted soil in Abeokuta, Ogun State

Abstract

Biosurfactants are amphiphilic compounds produced by a variety of microorganisms as extracellular compounds. Biosurfactants are preferable over the chemical surfactant because of their effectiveness, degradability and environmentally friendly nature. This study focuses on the isolation, identification and screening of biosurfactants-producing bacteria. Soil samples were collected from different automobile shops in Abeokuta, Ogun State. Bacteria were isolated and screened for their ability to produce biosurfactant using different methods in a stepwise process such as haemolytic test, drop collapse test, bacterial adhesion to hydrocarbon test and the confirmatory test which was the emulsification test that was assayed every 4 hours. Forty-one bacteria isolates showed beta-haemolysis, 20 exhibited alpha haemolysis and 47 exhibited gamma haemolysis. All positive isolates from the beta haemolytic test were screened for drop collapse test and result showed that 14 isolates were positive to the drop-collapse test. The isolates adhered to hydrocarbon at different rates. Proteus mirabilis had the lowest hydrophobicity value of 41% and the highest was Pseudomonas aeruginosa with a hydrophobicity value of 72%. The result showed that Pseudomonas aeruginosa had the maximum emulsification capacity of 65% at 24 hours while the least emulsification capability for biosurfactant production was exhibited by Proteus mirabilis (43%). This result showed that P. aeruginosa is a better organism for biosurfactant production and are good choice of organisms in many industries because of their emulsion capability.

Keywords: Biosurfactant, Bacteria, Hydrocarbon, Soil, Screening