Biosurfactant production and concomitant degradation of spent engine oil by Alcaligens faecalis ULAG3AF isolated from Lagos Lagoon

Abstract

Alcaligens faecalis strain ULAG3AF was isolated from the Lagos Lagoon, an estuarine environment. The aim of the study was to  investigate the biosurfactant production potentials of this organism and explore the antimicrobial potential of the biosurfactant. The  bacterial isolate was screened for its biosurfactants production potentials using the drop collapse, oil displacement tests and  emulsification index. The strain was cultivated in an enrichment medium, Bushnell Haas Medium, supplemented with 1%, 2%, 3% and 4%   spent engine oil and grown at different temperatures including 15 ^oC, 25 ^oC, 30 ^oC, 35 ^oC and 40 ^oC and salinity (10 mg/l, 20 mg/l,  30 mg/l and 40 mg/l of NaCl). The optimisation process involved analysing the effect of substrate concentration, temperature, and salinity  on biosurfactant production by the bacterium using the onevariable-at-a-time (OVAT) approach. Gas Chromatography and Mass  Spectrometry (GC-MS) and emulsification index were used to determine the rate of hydrocarbon degradation and the concentration of biosurfactant produced by the organism respectively. The bacterium demonstrated the ability to biodegrade different polyaromatic  hydrocarbon components of spent engine oil and produced biosurfactants with an emulsifying index of 80.9% when cultivated in a  medium containing 2%  of spent engine oil, 2% salinity (20 ^o mg/l of NaCl) and a temperature of 40 ^oC after 7 days. The biosurfactant  produced was a glycolipid with antimicrobial activities against Klebsiella pneumonia, Pseudomonas aeruginosa, Bacillus subtilis and  Staphylococcus aureus.