Petroleum is made of hydrocarbon, hydrocarbon are compound that is made of hydrogen and carbon. Although it contributes major percentage to the source of energy used by man on earth, however hydrocarbon components belong to the family of carcinogens and neurotoxic organic pollutants. It is well known all over the world that man and his environment is faced daily with hydrocarbon pollution resulting from oil spillage, petroleum pipeline linkage, and heavy duty machine repairing workshop as well as oil drilling and refinery sites, and also due to the increments in underground oil reservoir discovering and high demand of crude oil all over the world. The inappropriate drilling, transportation and usage as a matter of fact lead to increment of soil, air and water body hydrocarbon pollution. If this menace is not put in check as a matter of urgency, it can cause epidemic outbreak in an affected communities, shortage in agricultural produces output, threatening of soil useful microbial biome and environmental disaster. Bioremediation as promising modern biotechnology is capable of mineralizing hydrocarbon pollutants into water, carbon dioxide, cells proteins and inorganic compound. It involves the use of indigenous or genetically modified microbes to break down organic pollutants into a less toxic form. It not only potent in degrading organic pollutants, it is cheap compared to chemical and mechanical methods and also environmental friendly. Therefore, this paper combined and presents a review of empirical researches done on microbial bioremediation of petroleum hydrocarbons in different countries.

1.  Introduction

 Introduction Hydrocarbon carbon contamination with human environment have been a big threat to human and his natural surroundings, the conscious and unconscious introduction of harmful substances into the environment by human through his daily activities, which In return cause harm to his environment is term pollution. The media that received these contaminations are soil, water and air ( Agamuthu., et al, 2013). It brings change in the environment that resulted in way of introducing harmful effects that altered the quality of human life, animals, plants and microorganisms (Ewetola, 2013). To reduce the harms caused by pollution, the three media mention above need to be subjected to physical, chemical, mechanical or biological treatment (Agamuthu., et al, 2013). However in china, according to  (Guangwei,2014 andJayanta Kumar Saha et al.2017) Chinese researchers recently realized how severed and the extent of pollution on their vast area of soil and it's negative effects on their farmland. This was estimated to be more than 8% of china's arable land. This was reaffirmed by (Mariana .M et al 2010) stating that one fifth of China’s farmland is polluted, and an area the size of Taiwan is so polluted that farming should not be allowed there at all. The United States Environmental Protection Agency most targeted sites of hazardous wastes cleanup programs are made of 600 of 1408 different kinds of hydrocarbons (Okere and Semple, 2011; Duan et al.,2013 and Thamaraiselvan et al.2015 ). Soil pollution is considered to be a life threatening problem because all the plant consumed by human and the animal is cultivated from the soil, therefore, proper attention most paid to soil pollution to reduce it to the barest minimal if not totally eliminated. Although soil remediation is of a high capital and labor intensive project, but due to man poise for cheaper method for a polluted soil remediation, much have been done using microorganisms to bio remediate  contaminated soil which proved positive . This method termed to be labor and capital cheap and environmentally friendly. However, not all bacteria have the adaptability to degrade pollutants like petroleum hydrocarbon especially in the soil, according to Zulfa A et al (2016) it has been proven that microorganisms capability and adaptability to degrade pollutants, depend on the individual strains to produce suitable biosurfactans and the formation of biodegrading association that is very strong and reliable throughout the degradation period. Also, it depend on the adaptability of the microorganism to carry out  its physiological functions under natural condition that is characterized with limited water supply, low availability of nutrients and adverse pH condition

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