biodegradation of hydrocarbons

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Biodegradation of petrochemicals KHUDA BAKHSH FA14-R02-002COMSATS ABBOTTABAD

1

What are petrochemicals?

Chemicals derived from petroleum or natural gasMajor petrochemicals are acetylene, benzene, ethane, ethylene, methane, propane, and hydrogenA huge variety of products are made with petrochemicalsIncluding plastics, soaps, pharmaceuticals, fertilizers, pesticides, detergents,

One of the major environmental problems caused by HCS: Resulting from activities of petrochemical industry. Accidental releases of petroleum products HCS belong to the family of carcinogens and neurotoxic organic pollutantsMain cause of water and soil pollutionAccumulation of pollutants in living cells may cause death or mutationsTheir removal is necessary

Degradation of HCSSeveral methods are utilized Chemical degradation BiodegradationBiodegradation involve Microbial remediation( effective method) Bacterial degradation Fungal degradation Phytoremediation (by using plants)

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 amidesCont.Microbial Degradation of Petroleum Hydrocarbons

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The susceptibility of HCS to microbes can be ranked: Linear alkanes Branched alkanes Small aromatics cyclic alkanesHigh molecular weight (PAHs)

Cont

Natural mechanism for degrading HCS:

by bacteria, yeast, and fungiMix population of these microbes are more efficientBacteria are the most active agents in petroleum degradation

Enzymes and microbes Participating in Degradation of HCSEnzymesSubstratesMicroorganismsReferencesSoluble MethaneMonooxygenasesC1C8 alkanes alkenes and cycloalkanesMethylococcusMethylomonasMcDonald et al.Particulate MethaneMonooxygenasesC1C5 (halogenated) alkanes and cycloalkanesMethylobacterMethylococcusMcDonald et al.AlkB relatedAlkaneHydroxylasesC5C16 alkanes, fatty acids, alkyl benzenes, cycloalkanes PseudomonasBurkholderiaRhodococcusMycobacteriumJan et al.Eukaryotic P450C10C16 alkanes, fatty acidsCandida maltosaCandida tropicalisYarrowia lipolyticaIida et alBacterial P450oxygenase systemC5C16 alkanes, cycloalkanesCaulobacterMycobacteriumIida et alDioxygenasesC10C30 alkanesAcinetobacter sp.Maeng et al

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 substratesProduction of biosurfactsants

11Biodegradation of Petroleum compoundsPetroleum compounds are categorized into 2 groupsAliphatic hydrocarbon e.g. alkane, alcohol, aldehyde Aromatic hydrocarbon e.g. benzene, phenol, toluene, catechol

H.C. (substrate) + O2 H.C.-OH + H2O

H.C. (substrate) + O2 H.C.OHOH

monooxygenasedioxygenase

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Straight chain aliphatic H.C.compounds

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Cyclic aliphatic H.C. compounds

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Aerobic degradationof aromatic compounds

15Polycyclic Aromatic Hydrocarbon (PAHs)

Anaerobic degradationUnder nitrate-reducing bacteria

Sulfate-reducing bacteria

17 under nitrate-reducing condition : Nitrate-reducing bacteria couple the oxidation of org. cpd. with water to the exergonic reduction of nitrate via nitrite to N2

OH

OH

O

Metabolicpool

3H2

H2O

H2

CH3

COOH

Factors Influencing Petroleum HCS DegradationA number of limiting factors affect the biodegradation of petroleum HCSChemistry of HCSPhysiological factorsNutrients

Temperature range.

conclusionCleaning 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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