PETROLEUM DEGRADING POTENTIALS OF BACTERIA AND FUNGI STRAINS ISOLATED AS CONTAMINANTS FROM HYDROCARBON CONTAINING CULTURE MEDIA IN BENSON IDAHOSA UNIVERSITY MICROBIOLOGY LABORATORY

ABSTRACT

This study was carried out to determine the petroleum degrading potentials of bacterial and fungal species isolated as contaminants from hydrocarbon containing media in the Microbiology laboratory of Benson Idahosa University, Benin City, Nigeria. The isolates were purified and identified according to standard microbiological techniques. Isolates were screened for their potential to grow on media containing 5% benzene, toluene, xylene, chloroform, petroleum ether or crude oil. Selected isolates were further evaluated for their crude oil degrading capacity in a28-day enrichment assay on minimal salt medium supplemented with 2% Escravos light crude oil (ELCO). The population density of the microbial cultures during enrichment study were determined (along with pH and optical density) at 48 h intervals using standard spread plate technique. And the extent of crude oil degradation was assessed using gas chromatography (GC). The bacterial isolates were presumptively identified as Corynebacterium species (3), Bacillus firmus (8), Bacillus smithii (9), Azotobacter species (S3) and Bacillus species (S2); while the fungal isolates were presumptively identified as Penicillium species (X2), Aspergillus niger (X3), Aspergillus flavus (X4), Candida species (K2), and Geotrichum species (K3). The highest mean bacterial count (2.34 × 10²cfu/ml) was observed in Bacillus species (S2) on day 26; while that of fungi (1.74 × 10² cfu/ml) was observed in Geotrichum species (K3)on day 6. The pH varied between 7.58 and 9.84 for bacterial treatments; and between 7.04and 9.94 for fungi treatments. The optical density of the cultures during enrichment assay ranged from 0.212 to 0.674 (bacteria) and between 0.233 and 0.590 (fungi). The total petroleum hydrocarbon (TPH) degrading potentials for bacterial and fungi isolates varied between 48.98% and 83.42%, and 4.50% to 99.97% respectively; whereas their aliphatics degrading potentials ranged from 54.84% to 85.24% (bacteria) and 5.44% to 99.97% (fungi). The PAH fractions were generally increased by the bacterial and fungi treatments up to 461% and 539% respectively; except in treatments containing Geotrichum species where the isolate completely (100%) mineralize the PAH components of ELCO. The current study demonstrated that Geotrichum species was the best petroleum degrading isolate with great potentials for application in the bioremediation of petroleum polluted sites in Nigeria and elsewhere.