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ABSTRACT
In this study, 11 bacteria isolated from Tapis crude oil–contaminated sites were identified by using biochemical tests and 16S rDNA gene sequencing. Their abilities to biodegrade Tapis crude oil was determined by gas chromatography before they were further screened for biosurfactant activity by employing qualitative (blood agar hemolysis, microplate assay, drop-collapse test), semiquantitative (emulsification formation), and quantitative (surface tension measurement) methods. Four isolates, namely, Acinetobacter baumanii UKMP-12T, Pseudomonas aeruginosa UKMP-14T, Rhodococcus sp. UKMP-5T, and Rhodococcus sp. UKMP-7T, exhibited high percentages in total petroleum hydrocarbon (TPH) degradation. A strong correlation between the emulsification index (E 24) and surface tension measurement (r s = +.866) as shown by Spearman rank correlation analysis suggested that these two methods were more reliable to predict biosurfactant activity. The TPH removal was also positively correlated to the ability of bacterial isolates to reduce the surface tension of growth medium, as revealed by Pearson correlation test (rp = +.886). In conclusion, not all the biosurfactant detection protocols employed were effective. Nevertheless, the measurement of surface tension and E 24 determination provided a rather rapid, easy, reproducible, and accurate result in identifying bacteria with biosurfactant-producing ability.
ACKNOWLEDGMENTS
Financial support from e-Science Fund 06-01-02-SF0469 is greatly acknowledged. Special appreciation is given to School of Biosciences and Biotechnology, Faculty of Science and Technology, the National University of Malaya, for laboratory facilities. We acknowledge Chian Wei Ng for advices in statistical analysis.