It's a basic knowledge about Hydrocarbon Degradation- type of hydrocarbon Degradation

1. VIVEKANANDHA
ARTS AND SCIENCE COLLEGE FOR WOMEN
Veerachipalayam -637 303 , Sankagiri , Salem(Dt), Tamil Nadu
HYDROCARBON DEGRADATION
C. Prabha
I M. Sc Microbiology,
Department of
Microbiology,
Vivekanandha Arts and
Science College for Women,
Sankagiri.
DEPARTMENT OF MICROBIOLOGY
GUIDED BY,
Dr. R. Dinesh kumar
Assistant professor,
Department of Microbiology,
Vivekanandha Arts and Science college
for Women, Sankagiri.
SUBJECT :BIOREMEDIATION

2. INTRODUCTION
• Hydrocarbons in the environment are biodegraded primarily by
bacteria, yeast, and fungi. The reported efficiency of
biodegradation ranged from 6% [29] to 82% [30] for soil fungi,
0.13% [29] to 50% [30] for soil bacteria, and 0.003% [31] to 100%
[32] for marine bacteria.
• Hydrocarbons are major constituents of crude oil and petroleum.
They can be biodegraded by naturally-occurring microorganisms in
freshwater and marine environments under a variety of aerobic
and anaerobic conditions.

3. HYDROCARBON DEGRADATION
• Hydrocarbons are compounds composed entirely of carbon and hydrogen.
Aromatic hydrocarbons, alkanes, alkenes, cycloalkanes, alkynes, and
combinations of these compounds comprise different types of
hydrocarbons. Complex mixtures of hydrocarbons occur naturally in crude
oil and gasoline. Most can be used as substrates in metabolism by bacteria,
archaea, fungi, and algae.
• Fungi and algae degrade hydrocarbons aerobically, bacteria and archaea
are capable of both aerobic and anaerobic degradation.

4. Components of hydrocarbon biodegradation
Understanding and facilitatingbiodegradation at a contaminated site requires knowledge of the environmental conditions,
compound properties, and microorganisms present.

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TYPES OF HYDROCARBON DEGRADATION
1. Aerobic Degradation
 Alkanes and Alkenes.
 Aromatic Hydrocarbons.
2. Anaerobic Degradation
 Strategies For Activating Hydrocarbons Without
Oxygen.
TYPES OF HYDROCARBON DEGRADATION
1. AEROBIC DEGRADATION
• Alkanes and Alkenes
• Aromatic Hydrocarbons.
2. ANAEROBIC DEGRADATION
• Strategles For Activating Hydrocarbons Without Oxygen.

6. AEROBIC DEGRADATION
 Hydrocarbons are readily degraded under aerobic conditions.
Bacteria, fungi, and algae are all capable of aerobic hydrocarbon
degradation.In general alkenes (hydrocarbons containing double
bonds) and short-chain alkanes (hydrocarbons containing only single
bonds) are the most easily degraded, followed by branched alkanes
(alkanes with side chains) and then aromatics (hydrocarbons in a
stable ring structure).
 Degradation rates vary based on environmental parameters and
decrease as hydrocarbon complexity increases.
AEROBIC DEGRADATION
• Hydrocarbons are readily degraded under aerobic conditions. Bacteria, fungi, and
algae are all capable of aerobic hydrocarbon degradation.In general alkenes
(hydrocarbons containing double bonds) and short-chain alkanes (hydrocarbons
containing only single bonds) are the most easily degraded, followed by branched
alkanes (alkanes with side chains) and then aromatics (hydrocarbons in a stable
ring structure).
• Degradation rates vary based on environmental parameters and decrease as
hydrocarbon complexity increases.

7. alkanes are saturated hydrocarbons—that is, hydrocarbons that contain only single bonds. Alkenes contain one or more
carbon-carbon double bonds.
ALKANES AND ALKENES
• Alkanes are saturated hydrocarbons is hydrocarbons that
contain only single bonds. Alkenes contain one or more
carbon-carbon double bonds.
• Alkanes containing 14 carbons or fewer are prone to
volatilization, while alkanes containing more carbons are less
volatile.
• Alkanes and alkenes, with the exception of cyclic alkanes
(alkanes in a ring structure), are the most readily degraded
hydrocarbons with reported degradation of alkanes containing
up to 44 carbons.

8. AROMATIC HYDROCARBONS
• Aromatic hydrocarbons are generally more difficult to degrade than
shorter alkanes and alkenes due to their greater toxicity, yet they are
readily degraded aerobically by many bacteria and fungi (Polycyclic
Aromatic Hydrocarbons (PAHs).
• The general pathway for degradation of aromatic compounds begins with
the addition of O2 by mono and di-oxygenases.
• Fungal degradation occurs by non-specific extracellular oxidizing enzymes
that form radical intermediates, although many reactions are similar to
those found in bacteria.

9. ANAEROBIC DEGRADATION
• Hydrocarbon degradation under anaerobic conditions is often slower
compared to aerobic degradation, due to less favorable reaction
energetics with alternate electron acceptors.
• Despite this limitation, both facultative and obligately anaerobic
bacteria and archaea are known to degrade hydrocarbons without
oxygen.
• Despite slow growth rates, complete degradation of many different
types of hydrocarbons occurs in the absence of oxygen.
• Example: Degradation of polycyclic aromatic hydrocarbons .

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11. • Anaerobic degradation of benzene and alkylbenzenes. Acetate and
H2 are consumed in reactions 1, 2, and 3, keeping the fermentation
reaction energetically favorable.
• When external electron acceptors (e.g., nitrate, iron or sulphate)
are no longer available, methanogens consume acetate and
hydrogen.

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• Anaerobic microbes use terminal electron acceptors other than oxygen in
respiration, including compounds such as nitrate, sulfate, carbon dioxide,
oxidized metals, or even certain organic compounds.
• At a contaminated site, microbes tend to use electron acceptors sequentially as a
function of decreasing reduction potential in the order of oxygen, nitrate, ferric
iron, sulfate, and H2 .
• Anaerobic microbes use diverse strategies to activate hydrocarbons without
requiring molecular oxygen (O2).
• Each strategy is discussed separately below, and is applicable to both aliphatic
and aromatic compounds.

13. DEGRADATION OF NITROAROMATIC COMPOUNDS
INTRODUCTION
• Nitroaromatic compounds have at least one nitro group attached to the aromatic ring,
likenitrobenzene, nitrotoluenes, nitrophenols, etc. In nature, nitroaromatic compounds
are mostlyfound in natural products from different plants, fungi, and bacteria .
• The best knownexample of this is chloramphenicol, which is produced by Streptomyces
venezuelae .Therole of some nitroaromatic compounds in cellular signaling has also
been established. Forexample, 2-nitrophenol and 4-methyl-2-nitrophenol are well-
known pheromones for ticks thatenable them to aggregate and attach to mammals.

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SYNTHETIC NITRO AROMATIC COMPOUNDS
• The versatile chemistry of the nitro group ensures that nitroaromatic compounds serve
as important feed stocks in different industrial processes.
• These compounds are commonly used in the manufacture of pharmaceuticals.
• For example, substituted nitrobenzenes and nitropyridines are used in the production
of indoles, which are active components of several drugs and agrochemicals .
• Some nitroaromatics like nitrobenzene, nitrotoluene, and nitrophenols are used in the
synthesis of pesticides. For example, fluorodifen.

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