Abstract
The capability of indigenous bacteria and microalgae in crude oil effluents to grow in and utilize crude oil as their sole source of carbon and energy provides an environmentally friendly and economical process for dealing with crude oil pollution and its inherent hazards. In view of the toxicity of crude oil spillages to indwellers of the affected ecosystems and the entire affected environment, the isolation of pure bacterial and microalgae cultures from crude effluents is a step in the right direction, particularly for bio-augmentation or bioremediation purposes. The total heterotrophic bacteria count and hydrocarbon utilizing bacteria count, as well as the microalgae count, were determined with the pour plate technique. The physicochemical properties of the effluent samples were also analyzed. Identification of the hydrocarbon utilizing bacteria was performed with phenotypic techniques. The result shows a mean total heterotrophic bacterium count of 5.91 log CFU/ml and a mean microalga count of 4.77 log cells/ml. When crude oil and polycyclic aromatic hydrocarbon (PAH) were used as sole carbon sources, total hydrocarbon utilizing bacteria counts were respectively estimated at 3.89 and 2.89 log CFU/ml. Phenotypic identification of hydrocarbon utilizing bacteria in the crude oil effluents revealed the presence of two main bacterial genera: Streptococcus and Pseudomonas. Data obtained from this study confirmed the biodegradative abilities of indigenous bacterial species, thus, ultimately resulting in the amelioration of the toxicity associated with the crude oil effluents.
Highlights
Petroleum hydrocarbons have undoubtedly emerged as significant environmental contaminants (Eriyamremu et al, 2007; Liu et al, 2010)
Ten-fold serial dilutions were performed on the crude oil effluent
To isolate the hydrocarbon utilizing bacteria in the crude oil effluent, 1 ml of each dilution was mixed with 20 ml of sterile molten oil-agar medium in a Petri dish The Petri dish was incubated at 30 C for 5 – 7 days
Summary
Petroleum hydrocarbons have undoubtedly emerged as significant environmental contaminants (Eriyamremu et al, 2007; Liu et al, 2010). Crude oil is a complex mixture of chemicals varying widely in their composition of hydrocarbon and hydrocarbon-like (polycyclic aromatic hydrocarbons; PAH) chemicals and may persist in the environment for prolonged periods, posing a major threat to ecosystems. Biodegradation by intrinsic microbial populations is one of the reliable tools through which a great deal of xenobiotic contaminants, comprising crude oil spill and effluents are gradually degraded and subsequently eradicated from the environment (Cappello et al, 2007). The most important means of aerobic PAH biodegradation is the primary oxidation of the aromatic benzene ring through which molecular oxygen is incorporated by the dioxygenase enzymes to form cis-dihydrodiols.
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