1. Biodegradation of petrochemicals
KHUDA BAKHSH
FA14-R02-002
COMSATS ABBOTTABAD
1

2. 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,

3. 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 pollutants
Main cause of water and soil pollution
Accumulation of pollutants in living cells may
cause death or mutations
Their removal is necessary

4. Degradation of HCS
• Several methods are utilized
Chemical degradation
Biodegradation
 Biodegradation involve
Microbial remediation( effective method)
Bacterial degradation
Fungal degradation
Phytoremediation (by using plants)

5. Microbial Degradation of Petroleum
Biodegradation of HCS is a complex process depending on:
• the nature
• Amount of the hydrocarbons present
Petroleum 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 amides
Cont….
Hydrocarbons

6. The susceptibility of HCS to microbes can be
ranked:
• Linear alkanes
• Branched alkanes
• Small aromatics cyclic alkanes
• High molecular weight (PAHs)
Cont…

7. 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

8. Enzymes and microbes Participating in
Degradation of HCS
Enzymes Substrates Microorganisms References
Soluble Methane
Monooxygenases
C1–C8 alkanes alkenes and
cycloalkanes
Methylococcus
Methylomonas
McDonald et
al.
Particulate Methane
Monooxygenases
C1–C5 (halogenated) alkanes
and cycloalkanes
Methylobacter
Methylococcus
McDonald et
al.
AlkB related
Alkane
Hydroxylases
C5–C16 alkanes, fatty acids,
alkyl benzenes, cycloalkanes
Pseudomonas
Burkholderia
Rhodococcus
Mycobacterium
Jan et al.
Eukaryotic P450 C10–C16 alkanes, fatty acids Candida maltosa
Candida tropicalis
Yarrowia lipolytica
Iida et al
Bacterial P450
oxygenase system
C5–C16 alkanes, cycloalkanes Caulobacter
Mycobacterium
Iida et al
Dioxygenases C10–C30 alkanes Acinetobacter sp. Maeng et al

9. Mechanism of Petroleum HCS Degradation

10. • 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

11. Biodegradation of Petroleum compounds
11
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.
O
H
O
H
monooxyge
nase
dioxygenase

12. 12
Straight chain
aliphatic H.C.
compounds

13. Cyclic aliphatic
13
H.C.
compounds

14. Aerobic degradation
of aromatic compounds
14

15. 15

16. Anaerobic degradation
Under nitrate-reducing bacteria
Sulfate-reducing bacteria

17. • under nitrate-reducing condition : Nitrate-reducing
17
bacteria couple the oxidation of org. cpd. with
water to the exergonic reduction of nitrate via
nitrite to N2
OH OH O
Metabolic
pool
3H2 H2O
H2
COOH
CH3

18. Factors Influencing Petroleum HCS
Degradation
A number of limiting factors affect the
biodegradation of petroleum HCS
• Chemistry of HCS
• Physiological factors
• Nutrients

19. • Temperature range.

20. 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