Biodegradation of petrochemicals
KHUDA BAKHSH FA14-R02-002
COMSATS ABBOTTABAD
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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,
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 HCS
• Several methods are utilized Chemical degradation Biodegradation Biodegradation 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 alephatics• The aromatics• The asphaltenes (phenols, fatty acids, ketones, esters, and
porphyrins), • And the resins (pyridines, quinolines, carbazoles, sulfoxides,
and amidesCont….
Microbial Degradation of Petroleum Hydrocarbons
The susceptibility of HCS to microbes can be ranked: • Linear alkanes • Branched alkanes • Small aromatics cyclic alkanes• High molecular weight (PAHs)
Cont…
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
MethylococcusMethylomonas
McDonald et al.
Particulate MethaneMonooxygenases
C1–C5 (halogenated) alkanes and cycloalkanes
MethylobacterMethylococcus
McDonald et al.
AlkB relatedAlkaneHydroxylases
C5–C16 alkanes, fatty acids, alkyl benzenes, cycloalkanes
PseudomonasBurkholderiaRhodococcusMycobacterium
Jan et al.
Eukaryotic P450 C10–C16 alkanes, fatty acids Candida maltosaCandida 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
• 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
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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
• H.C. (substrate) + O2 H.C.-OH + H2O
• H.C. (substrate) + O2 H.C.OHOH
monooxygenase
dioxygenase
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Straight chain aliphatic H.C.compounds
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Cyclic aliphatic H.C. compounds
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Aerobic degradation
of aromatic compounds
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Anaerobic degradationUnder nitrate-reducing bacteria
Sulfate-reducing bacteria
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• 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 Degradation
A number of limiting factors affect the biodegradation of petroleum HCS• Chemistry of HCS• Physiological factors• Nutrients
• 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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