BIODEGRATION OF CRUDE OIL BY BACTERIA ISOLATED FROM PRISTINE SOIL

1.1Background to the Study

In recent years, the demand for petroleum as a source of energy and raw material for chemical industries has resulted in a tremendous increase in world production. This increase in production, refining and distribution of crude oil has also brought with it an ever- increasing problem of environmental pollution (Gopinathan et al., 2012; Abioye et al., 2013; Sojinu and Ejeromedoghene, 2019).

Petroleum hydrocarbons can seep into the soil and contaminate underlying ground water. Runoff from unregulated sites can carry petroleum contaminants off site into nearby waterways. Indiscriminate dumping of petroleum waste products can lead to an elevated level of petroleum hydrocarbons in the soil, which results in a significant decline in the quality of the soil, makes it unfit for use and becomes a threat to healthy soil microorganisms. Oil spills and waste discharges into the sea from refineries, factories or shipping contain poisonous compounds that are potentially dangerous to plants and animals. These poisons can pass through the food web which may eventually be eaten by humans (Abioye et al., 2013; Ikuesan, 2017).

Several methods are used to remediate a contaminated site or oil polluted soil and these include the use of physical, chemical and biological methods. The biological method is the use of a biological agent such as microorganisms and green plants. Microorganisms are also equipped with a metabolic machinery to use petroleum as carbon and energy source. Crude oil by its nature is biodegradable, thus, biological methods (bioremediation technique) have

been developed and improved for cleaning up oil contaminated sites and have become alternatives to chemical and physical techniques (Abioye et al., 2013; Kure et al., 2018).

The degradation of hydrocarbon which is one of the trait possess by microbes is not limited to certain genera but widely distributed in nature. Some genera of bacteria with the capability to degrade hydrocarbon includes Pseudomonas, Rhodococcus, Bacillus, Xanthomonas, Cornybacterium, Acinetobacter (Morais and Tauk-Tornisielo, 2009 ;Ajao et al., 2014; Hamzah et al., 2017).

The genus Pseudomonas and Bacillus in particular have been the subject of numerous studies. The Pseudomonas sp is one of the best crude oil degraders. An interesting and useful characteristic of many Pseudomonas sp. is their ability to utilize a wide variety of organic substrates for growth. Pseudomonas sp. utilizes crude oil organic compounds as sole source of nutrients which includes saturated and aromatic compounds (Gopinathan et al., 2012).

Bacillus on the other hand has the ability to grow on different substrates. They have the ability to degrade different hydrocarbons by the production of biosurfactants, which facilitates the hydrocarbon degradation. They also produce a variety of enzymes, which are involved in biodegradation (Gopinathan et al., 2012).

Biodegradation efficiency is determined with the provision of favourable conditions to the microbes which will enhance their rapid growth, such condition include oxygen, nutrient, pH, temperature other conditions. Only then will these organisms able to degrade and breakdown pollutants (e.g hydrocarbon) at a correspondingly faster rate. The most important principle of biodegradation is that microorganisms can be used to destroy hazardous

contaminants or transform them to less harmful forms (Abioye et al., 2013; El-Borai et al., 2016).

Several catabolic pathways that controls biodegradation have been identified and are generally located on the large, transmissible plasmids usually found in Pseudomonas sp. Molecular information about an ecosystem contamination is useful in order to develop improve bioremediation strategies (Arvanitis, 2008).