Petroleum microbiology studies microbes that metabolize hydrocarbons and how they could be employed in oil prospecting and oil spillage control. Petroleum is a complex mixture of hydrocarbons (i.e. aliphatic and aromatic compounds) and other organic or inorganic constituents such as sulphur, oxygen and carbon; and some microbes metabolize hydrocarbons to generate their energy as well as other growth factors. Some microorganisms (e.g., Hormoconis resinae) depend solely on crude oil or other refined petroleum products which they degrade to generate nutrient molecules required for their nourishment and growth. H. resinae, a fungus produces more biomass than any other fungi, and this is likely to cause obstruction of pipes in the fuel tank of aircrafts where they colonize.
The organism also has the potential to grow between fuel and water and produce suspended solids in fuels, thus giving it the opportunity to cause microbial corrosion in aircraft tanks. Pseudomonas, Arthrobacter, Burkholderia, Sphingomonas, Acinetobacter, Bacillus and Rhodococcus are some bacterial genus that can metabolize and degrade hydrocarbon or organic compounds. However, it is the job of petroleum microbiologists to periodically check aircraft fuels and tanks for possible microbial contamination, and thus ensure that the microbial load of microorganisms are within accepted limits to avoid possible damage to the fuel tanks. In addition, this field of microbiology deals with the use of microbial action to control oil spillage and clean up of the environment.
More so, oil pipelines are usually used as carriages to transport petroleum products and other hydrocarbon-containing materials over a long distance. However, the ability of these pipelines to transport petroleum products is usually hampered following leakage and clogging caused by bacteria that mediate microbially induced corrosion (MIC). Sulphate reducing bacteria (SRB) and methanogens are implicated as important causative agents of MIC in oil industries and other allied industries. SRB’s are considered the most important bacteria involved in MIC. SRB are anaerobic bacteria that thrive in environments devoid of oxygen. They can either obtain their energy and carbon via the oxidation of organic nutrients or via the oxidation of H2 and the fixation of carbondioxide (CO2). Moreover, SRB reduce sulfate to H2S, which is a highly reactive and corrosive substance that adversely affects the metal works and the product quality in oil and non-oil industries in a process termed souring. The metabolic activities of SRB cause enormous economic loss to the oil industry if it is left uncontrolled.
Microbiologically influenced/induced corrosion (MIC) denotes the effect of microorganisms on the kinetics of the processes of material corrosion, especially metals, caused by microorganisms adhering to the material interface (as biofilms). The mechanism of MIC of metals may be either due to a direct or indirect effect of surface attached microorganisms. The direct effect is due to the utilization of electrons from the enzymatically-mediated oxidation of metallic iron. The electrons are then used for energy conservation during sulfate reduction by sulfate reducing bacteria (SRB). However, the indirect effect can be due to the microbial consumption of hydrogen (H2) that formed during cathodic corrosion of the metal or due to the formation of microbial metabolic end products of SRB’s including hydrogen sulfide (H2S) that can directly deteriorate the metal
Microorganisms play significant roles in the oil industry (especially in microbial enhanced oil recovery); and they also have the ability to degrade hydrocarbons and clean up the environment especially in oil spillage scenarios as is commonly obtainable in oil rigs and other oil processing and storage facilities (Figure 1). Hydrocarbon contamination of the terrestrial habitat and waterfronts resulting from the activities related to the petrochemical industry is one major environmental problem that is of global concern; and this is largely because hydrocarbons are carcinogenic in nature and some organic pollutants are neurotoxic and thus affect the health of humans, animals and even the aquatic life. However, bioremediation and/or biodegradation technology (which employs the metabolic activities of microbes) is currently been exploited for the treatment of hydrocarbon contaminated sites since it leads to complete mineralization of the hydrocarbons i.e. the transformation of organic compounds including hydrocarbons into simple inorganic molecules such as carbondioxide and water among others.
Oil spillage is a common phenomenon that occur in oil rigs and oil storage or processing facilities; and such development adversely affect both the terrestrial and aquatic environments and genetically-engineered microbes have the ability o cleanup the affected areas and restore it to its normal condition. Some microorganisms especially the thermophiles as shall be seen later in this textbook withstand several harsh environmental conditions; and these organisms are utilized in biodegradation to breakdown crude oils or hydrocarbons in ways that are beneficial to the environment. The biodegradation of hydrocarbons in the environment are primarily carried out by bacteria, yeast and fungi; and some of these microorganisms produce biosurfactants. Biosurfactants are surface active chemical compounds produced by some microbes and which enhances the solubilization and removal of hydrocarbons and other organic compound contaminants in the environment. Microbes are currently being used to prospect for crude oil; and the basis for this rationale is because some microbes metabolize hydrocarbons/organic compounds and the use of hydrocarbon-metabolizing microbes as indicators of hydrocarbon utilization gives a clue to the presence or absence of crude oil.
Figure 1.6: Schematic illustration of an oil rig.
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