1.0         INTRODUCTION

1.1       Background to the Study

Bioremediation is the treatment of contaminated environment by using biological mechanisms

(Adamet al., 2017). Biodegradation is defined as the biologically catalyzed reduction in the

complexity of chemical compounds (Alexander, 1973). These substances are transformed

through metabolic or enzymatic process. This transformation is based on two processes

namely growth and co-metabolism. In growth, organic pollutants are used as sole source of

energy and carbon while growth substrate is used in co-metabolism. The process results in a

complete degradation called mineralization (Roling et al., 2004;Fritscheand Hofritcher, 2008).

Biodegrading microorganisms are those that mineralize complex organic molecules into

simpler ones. Hydrocarbons are complex and heterogeneous groups of organic molecules that

are made up of carbon and hydrogen. Mycoremediation is a form of bioremediation where

fungi are used to degrade or sequester contaminants in the environment (Margesin and

Shinner 2001).The decomposition by the fungi is usually performed by the mycelia .The

mycelia secretes extracellular enzymes and acids that break down the organic matter (Medina-

Beliver et al., 2005).

The growth in petroleum hydrocarbon exploration in Nigeria and the world over has led to

increased oil pollution in the environment. Petroleum refining produces large amount of

effluents that are toxic and results in environmental pollution of receiving bodies of water and

soils. The exact composition cannot however be generalized as it depends on the refinery and

the units that are in operation at any specific time. Such contaminated habitats lose their

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capability to support both plants and animal lives and thus constitute public health and socio-

economic hazards as well as pose serious aquatic toxicity problems (Okerentugba and

Ezeronye, 2003). The Kaduna Refinery and Petrochemical Company (KRPC) was designed to

refine two types of crude oils namely the imported heavy crude and Nigerian light crude. The

increasing demand for petroleum and its products in the last ten decades has resulted in petroleum

spills. Despite fluctuations in its prices, oil will remain a major source of energy in the next

several decades because a reliable alternative has not yet been found (Adieze et al., 2003).

The impacts of crude petroleum, prospecting and production operations on oil producing

countries of the world had resulted in enormous pollution of air, water and particularly

agricultural land for food production (Ward et al., 1980; Atlas, 1981; Tealet al., 1992; Amund

et al., 1993; Wang, et al., 2011). Such contamination may result in an extensive damage to the

natural environments and these effects may be long term and extended over many seasons.

Generally speaking, effluents discharge into salt marsh ecosystems impart potential damage

to their physical and ecological integrity even in minimal spill level, let alone catastrophic

accidents like the Exxon Valdez in 1989 (36, 000 tons of crude oil covered approximately 500

kilometers of shoreline) (Miller, 1999). The removal of oil that has been accidentally or

purposely spilled into the environment is therefore of great concern to the petroleum industry

(Sanni and Ajisebutu, 2003).Previous investigations have shown that crude oil and other

related organic pollutants can be degraded (Okpokwasili and Okorie,1988;Ijah and Ukpe,

1992;Philips and Stewart, 1994; Ekpo and Ekpo, 2006). To remediate petroleum contaminants

in these environments, bio-stimulation and bio-argumentation are generally considered as

environmentally friendly techniques. However, the use of extrinsic microorganism is unlikely

to be acceptable to the public or introduction of a single species has a tendency to use limited

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compounds, and had low survival rates due to predation, parasitism and competition with

indigenous species in the limited environment. Predominant hydrocarbons are theoretically

degradable but the components are rather complicated. It contains aliphatic and polycyclic

aromatic hydrocarbons (PAH), for example, crude oil consists of paraffins 15 - 60%,

naphthenes 30 - 60%, aromatics 3-30% and asphaltic 6% by weight (Hyne, 2001).