Introduction

Petroleum hydrocarbons are introduced into the environment due to their extensive use as fuels and chemicals. Besides, leaks and accidental spills occur often during exploration, production, refining, transport and storage of petroleum and petroleum products which used to add an additional burden of hydrocarbons to soils and water systems. The technologies commonly used for soil remediation of petroleum hydrocarbons include mechanical burying, evaporation, dispersion and washing. These remedial measures are not only cost intensive and time consuming, but also not very effective. On the other hand, bioremediation leads to complete mineralization of organic compounds into CO2 and water by indigenous microorganisms and hence a preferred choice also being eco-friendly and cost-effective.

Anthropogenic hydrocarbon contamination of soil is a global issue throughout the industrialised world (Macleod et al. 2001; Brassington et al. 2007). In England and Wales alone, 12% of all serious contamination incidents in 2007 were hydrocarbon related. Soil acts as a repository for many hydrocarbons, which is a serious concern due to their adverse impact on human health and environmental persistence for a long time (Jones et al. 1996; Semple et al. 2001).

Alkanes are a major fraction (>50%) of the crude oil depending upon the oil source. Alkanes are saturated hydrocarbons and chemically very inert as apolar molecules (Labinger and Bercaw 2002). They may be classified as linear (n-alkanes), cyclic (cyclo-alkanes) or branched (iso-alkanes) and found in three states: gaseous (C1-C4), liquid (C5-C16) and solid (>C17) (Fig. 17.1). Although

S. N. Singh (&) • B. Kumari • S. Mishra Environmental Sciences Division, CSIR-National Botanical Research Institute, Lucknow 226 001, India e-mail: [email protected]

S. N. Singh (ed.), Microbial Degradation of Xenobiotics,

Environmental Science and Engineering, DOI: 10.1007/978-3-642-23789-8_17,

© Springer-Verlag Berlin Heidelberg 2012

Fig. 17.1 Examples of linear; n-Hexane

(a) branched; Iso-hexane

(b) and cyclic alkanes; Cyclopentane (c)

highly inflammable, alkanes are less reactive as organic compounds. They are highly essential for modern life, but their inertness poses serious ecological problems when released to the environment. However, microbes have developed effective strategies involving specific enzymes and metabolic pathways to use n-alkanes as a carbon source. Thus, microbes have the capability to degrade alkanes and convert them to easily metabolizable substrates.

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