Biodegradation of Petroleum Hydrocarbons

By: Sheikh Amir Hamza.256-FBAS-BSBT-F12

What are petrochemicals?

Chemicals derived from petroleum or natural gas.

Major petrochemicals are acetylene, benzene, ethane, ethylene, methane, propane, and hydrogen.

A huge variety of products are made with petrochemicals.

Including plastics, soaps, pharmaceuticals, fertilizers, pesticides, detergents.

Molecular structures of hydrocarbons.

Cons of Hydrocarbons

HCS belong to the family of carcinogens and neurotoxic organic pollutants.

Main cause of water and soil pollution.Accumulation of pollutants in living cells

may cause death or mutations.Their removal is necessary.

Microbial Degradation of Petroleum Hydrocarbons

Biodegradation of HCS is a complex process depending on:the nature Amount of the hydrocarbons presentPetroleum HCS divided into four classes:The alephaticsThe aromaticsThe asphaltenes (phenols, fatty acids, ketones,

esters, and porphyrins), And the resins (pyridines, quinolines, carbazoles,

sulfoxides, and amides

Approaches In HC’s Degradation

Bioaugmentation:It is the introduction of biodegrading microbes at the site of spill to aid the indigenous microbial species.

Biostimulation:In Biostimulation nutrients and growth limiting factors are added to soil indigenous microbes.

Natural mechanism for degrading HCS

by bacteria, yeast, and fungi.Mix population of these microbes are

more efficient.Bacteria are the most active agents in

petroleum degradation.

Enzymes and microbes Participating in Degradation of HCS

Enzymes Substrates Microorganisms References

Soluble MethaneMonooxygenases

C1–C8 alkanes alkenes and cycloalkanes

Methylococcus

Methylomonas

McDonald et al.

Particulate MethaneMonooxygenases

C1–C5 (halogenated) alkanes and cycloalkanes

Methylobacter

Methylococcus

McDonald et al.

AlkB relatedAlkaneHydroxylases

C5–C16 alkanes, fatty acids, alkyl benzenes, cycloalkanes

Pseudomonas

BurkholderiaRhodococcusMycobacterium

Jan et al.

Eukaryotic P450 C10–C16 alkanes, fatty acids

Candida maltosa

Candida tropicalisYarrowia lipolytica

Iida et al

Bacterial P450oxygenase system

C5–C16 alkanes, cycloalkanes

CaulobacterMycobacterium

Iida et al

Dioxygenases C10–C30 alkanes Acinetobacter sp.

Maeng et al

Mechanism of Petroleum HCS Degradation

Mechanism of Petroleum HCS Degradation

Biosynthesis of cell biomass occurs from the central precursor metabolites, for example,

acetyl-CoA, succinate, pyruvate. Other mechanisms are

Attachment of microbial cells to the substrates.

Production of biosurfactsants.

Biodegradation of Petroleum compounds

Petroleum compounds are categorized into 2 groups

Aliphatic hydrocarbon e.g. alkane, alcohol, aldehyde

Aromatic hydrocarbon e.g. benzene, phenol, toluene, catechol

Straight chain Aliphatic Hydrocarbons

Cyclic Aromatic Hydrocarbons

Anaerobic degradation

Under nitrate-reducing bacteria

Sulfate-reducing bacteria

Factors Influencing Petroleum HCS Degradation

A number of limiting factors affect the biodegradation of petroleum HCSChemistry of HCSPhysiological factorsNutrients

Temperature Range

Conclusion

Cleaning up of petroleum HCS is a real world problem.

It depends on the indigenous microorganisms to transform or mineralize the organic contaminants.

Microbial degradation process aids the elimination of spilled oil from the environment after critical removal of large amounts of the oil by various physical and chemical methods.

This is possible because microorganisms have enzyme systems to degrade and utilize different hydrocarbons as a source of carbon and energy.

Therefore, based on the present review, it may be concluded that microbial degradation can be considered as a key component in the cleanup strategy for petroleum hydrocarbon remediation

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