SOURCE:

Faculty: Biosences
Department: Applied Microbiology And Brewing

CONTRIBUTORS:

Nnamdi, U.P;
Odibo, F.J.C;

ABSTRACT:

Biosurfactants are valuable microbial amphiphilic molecules with effective surface-active and biological properties applicable to several industrial processes. They are synthesized by microbes, especially during growth on water–immiscible substrates, providing an alternative to chemically prepared conventional surfactants. In this study a rhamnolipid biosurfactant was produced from Pseudomonas aeruginosa. Four bacterial isolates recovered from Anambra river sediment using mineral salt agar media were assessed for their ability to produce biosurfactant using some standard parameters such as hemolytic test, drop collapsing test, oil displacement test, emulsification index, cetytrimethyl ammonium bromide (CTAB) agar test and surface tension measurement. One of the isolates identified as Pseudomonas aeruginosa using phenotypic characteristics and 16SrRNA gene sequencing analysis was chosen as the best biosurfactant producer as it showed positive results to all the standard parameters used. Biosurfactant synthesis was followed by measuring surface tension (33mN/m) and emulsifying index (96%) after 120h of incubation .The best results were obtained when using crude oil and ammonium nitrate as carbon and nitrogen sources respectively with a C: N ratio of 10( Crude oil 2%;Ammonium nitrate 2.0g). The surface tension and emulsification activity of the biosurfactant remained stable over a wide range of temperature (300C-500C) and pH (5.0-9.0). The crude biosurfactant has been extracted from supernatant culture growth by chilled acetone precipitation and the yield of crude biosurfactant was 1.44g/l-1.Structural attributes of biosurfactants were determined by biochemical tests, thin layer chromatography (TLC), gas chromatography which confirmed the biosurfactant was a rhaminolipid in nature. In addition to oil recovery, the Pseudomonas aeruginosa degraded crude oil within a 30days of exposure. The result of crude oil degradation also showed that C35 fractions of the crude oil were most degraded by the isolate. The ability of the biosurfactant to enhance secondary recovery of crude oil was assessed using a sand packed column. The application of Pseudomonas aeruginosa biosurfactant effected recovery of 90% of trapped crude oil over 0% recovery observed for the control (water). This study showed that exposed Pseudomonas aeruginosa as a potential of biosurfactant for use in petroleum industries and for bioremediation in crude oil polluted environments.