Ganiyu Oladunjoye Oyetibo

Differential degradation of crude oil (Bonny Light) by four Pseudomonas strains.

Four hydrocarbon degraders isolated from enriched oil- and asphalt-contaminated soils in Lagos, Nigeria, were tested for their petroleum degradation potentials. All the isolates were identified as species of Pseudomonas. Pseudomonas putida P11 demonstrated a strong ability to degrade kerosene, gasoline, diesel, engine oil and crude oil while P. aeruginosa BB3 exhibited fair degradative ability on crude oil, gasoline, engine oil, anthracene and pyrene but weak on kerosene, diesel and dibenzothiophene. Pseudomonas putida WL2 and P. aeruginosa MVL1 grew on crude oil and all its cuts tested with the latter possessing similar polycyclic aromatic potentials as P11. All the strains grew logarithmically with 1-2 orders of magnitude and with generation time ranging significantly between 3.07 and 8.55 d at 0.05 level of confidence. Strains WL2 and MVL1 utilized the oil substrate best with more than 70% in 6 d experimental period, whereas the same feat was achieved by P11 in 12 d period. BB3 on the other hand degraded only 46% within 6 d. Interestingly, data obtained from gas chromatographic analysis of oil recovered from the culture fluids of MVL1 confirmed near-disappearance of major peaks (including aliphatics and aromatics) in the hydrocarbon mixture.

Microbial population changes in tropical agricultural soil experimentally contaminated with crude petroleum

Impacts of crude petroleum pollution on the soil environment and microbial population dynamics as well as recovery rates of an abandoned farmland was monitored for seven months spanning the two major seasons in Nigeria with a view to establishing process conditions necessary for development of effective strategies for bioremediation. The physico-chemistry of the control and contaminated soils differed just significantly (P soil showed significant diversity in structure and number of flora .There was an initial drop in microbial population densities at the onset of pollution but, a gradual increase was observed thereafter. Higher counts of microflora were obtained for April, May, June and July samples which coincided with the onset and peak of wet season. A rapid and significant reduction in residual oil concentration was observed during this period. Overall, nearly 100% of the crude oil pollutant was degraded within the 28-week study period. The residual oil concentration gave a high but negative correlation coefficient (r = - 0.84 to -0.90) with total heterotrophic and hydrocarbon-utilizing populations. On application of data generated to model equations, approximately 60.5 weeks would elapse before the contaminated soil could recover from the impact of the oil. Our results show that a natural population readily able to degrade crude oil is present in the soil chosen for this study. However, it may be necessary to monitor the level of inorganic nutrients and adjust some appropriately to enhance biodegradation of the organic pollutant.

Biodegradation of petroleum hydrocarbons in the presence of nickel and cobalt.

Bioremediation of environments co‐contaminated with hydrocarbons and heavy metals often pose a challenge as heavy metals exert toxicity to existing communities of hydrocarbon degraders. Multi‐resistant bacterial strains were studied for ability to degrade hydrocarbons in chemically defined media amended with 5.0 mM Ni2+, and Co2+. The bacteria, Pseudomonas aeruginosa CA207Ni, Burkholderia cepacia AL96Co, and Corynebacterium kutscheri FL108Hg, utilized crude oil and anthracene without lag phase at specific growth rate spanning 0.3848–0.8259 per day. The bacterial populations grew in hydrocarbon media amended with nickel (Ni) and cobalt (Co) at 0.8393–1.801 days generation time (period of exponential growth, t = 15 days). The bacteria degraded 96.24–98.97, and 92.94–96.24% of crude oil, and anthracene, respectively, within 30 days without any impedance due to metal toxicity (at 5.0 mM). Rather, there was reduction of Ni and Co concentrations in the axenic culture 30 days post‐inoculation to 0.08–0.12 and 0.11–0.15 mM, respectively. The metabolic functions of the bacteria are active in the presence of toxic metals (Ni and Co) while utilizing petroleum hydrocarbons for increase in biomass. These findings are useful to other baseline studies on decommissioning of sites co‐contaminated with hydrocarbons and toxic metals.

Extensive Biodegradation of Nigerian Crude Oil (Escravos Light) by Newly Characterized Yeast Strains

Abstract Because microbial degradation is known to be an efficient process in the in situ decontamination of oil-bearing environments, it is believed that development of effective bioremediation strategies will be aided by microbial sourcing of novel and competent hydrocarbon degraders with a broad and unusual substrate spectrum. Thus, in keeping with this objective, two Candida strains (MN1 and MC1) isolated after a repeated batch enrichment technique were tested for their biodegradation potentials on Nigerian crude oil, Escravos light. Axenic cultures of strains MN1 and MC1 grew at a rate of 1.623 and 0.586 d−1, respectively, in mineral salts medium supplemented with 8.4 g L−1 of crude oil. Whereas strain MN1 degraded aliphatic fractions by 97.6% and the aromatics by 74.61%, the corresponding values obtained for MC1 were 97.2% and 67.29% during the 14-day incubation period. The gas chromatography (GC) fingerprinting of aliphatic fractions showed major degradation of heptadecane (C17), octadecane (C18), nonadecane (C19), eicosane (C20), undodecane (C21), tricosane (C23), hexacosane (C26), octacosane (C28), and nonacosane (C29) in less than 6 days, whereas nearly 100% of these fractions including the isoprenoid molecules was metabolized in 14 days. Among the aromatic fractions that were nearly eliminated during the cultivation period were naphthalene, phenanthrene, fluoranthrene, chrysene, benzo(a)anthracene, benzo(b)fluoranthrene, and benzo(a)pyrene. Interestingly, substrate uptake studies showed that both strains grew very well on petroleum cuts, biphenyl, phenol, xylene, and quite a number of polycyclic aromatic hydrocarbons including pyrene, phenanthrene, and anthracene.

Degradation of Aroclor 1221 by microbial populations of the Lagos lagoon

Samples obtained from three locations in the Lagos lagoon were studied for the effect of Aroclor 1221 on their population dynamics. In all three cases, both control and experimental microcosms showed slight increases between day 5 and day 10 with the highest value of 4 × 1010 cfu/ml in control and 1.2 ×1011, 8 × 1010 and 9 × 1010 cfu/ml for Iddo, Apapa and Tin Can samples respectively. Three isolates namely, Bacillus subtilis, Alcaligenes eutrophus and Pseudomona aeruginosa were obtained from the microcosms after successive enrichment. All the isolates grew readily on 100 ppm of Aroclor 1221 concomitant with production of yellow metabolites in mineral salts medium. Whereas maximal growth was observed at day 12 on biphenyl, that of the polychlorinated biphenyl (PCB) mixture was on day 15. Generally, growth dynamics were similar irrespective of the substrate while typical generation times, with the exception of B. subtilis on Aroclor 1221, ranged insignificantly (P thus, suggesting that chlorine substitution has little or no effect on catabolic potentials of the organisms. The degradative capability of these strains suggest that they contribute immensely to the self-purification processes occurring in the lagoon, and this could be exploited for decontamination of PCB polluted aquatic ecosystems.