PAHs, detergents etc

1. ENVIRONMENTAL
BIOTECHNOLOGY
ASSIGNMENT
TOPICS-
 Biotechnology & organic pollution
 Biodegradation of halogenated hydrocarbons
 Polycyclic Aromatic Hydrocarbons(PAHs)
 Pesticides
 Detergents
Submitted by-
ANCHAL GARG
MSC EM- 3 SEM
ROLL NO-05

2. (1)Biotechnology and organic pollution
 A compound foreigntobiological systemis knownas xenobiotic
compound.
 Anthropogenic organic pollutants are nowdispersedthroughout the
environment andcan be highly recalcitrant tobiodegradationby
microorganisms.
 Xenobiotics canbe- weak, recalcitrant andpersistent.
 Weak xenobiotics canbe degradedor easily convertedintonontoxic one.
 Recalcitrant- compounds totally resistant tobiodegradation(unusual
chlorine substitution,unusual bondsequences (3΄ & 4΄), highly condensed
aromatic rings, and excessive molecular size (polyethylene))
 Persistent Organic Pollutants (POPs)- are chemical substances that persist
in the environment, bioaccumulate through foodweb, and pose a risk of
causing adverse effects tohumanhealthand the environment.
POP Global Historical Use/Source
aldrin and dieldrin
Insecticides used on crops such as
corn and cotton; also used for termite control.
Chlordane
Insecticide used on crops, including vegetables, small grains, potatoes,
sugarcane, sugar beets, fruits, nuts,
citrus, and cotton. Used on home
lawn and garden pests. Also used extensively to control termites.
DDT
Insecticide used on agricultural crops, primarily cotton, and insects that carry
diseases such as malaria and typhus.
Endrin
Insecticide used on crops such as
cotton and grains; also used to control rodents.
Mirex
Insecticide used to combat fire ants, termites, and mealybugs.
Also used as a fire retardant in plastics, rubber, and electrical products.
Heptachlor
Insecticide used primarily against soil insects and termites. Also used against
some crop pests and to combat malaria.
hexachlorobenzene
Fungicide used for seed treatment.
Also an industrial chemical used to make fireworks, ammunition, synthetic

3. POP Global Historical Use/Source
rubber, and other substances.
Also unintentionally produced during combustion and the manufacture of
certain chemicals.
Also an impurity in certain pesticides.
PCBs
Used for a variety of industrial processes and purposes, including in electrical
transformers and capacitors, as heat exchange fluids, as paint additives, in
carbonless copy paper, and in plastics.
Also unintentionally produced during combustion.
Toxaphene
Insecticide used to control pests on crops and livestock, and to kill unwanted
fish in lakes.
dioxins and furans
Unintentionally produced during most forms of combustion, including burning
of municipal and medical wastes, backyard burning of trash, and industrial
processes.
Also can be found as trace contaminants in certain herbicides, wood
preservatives, and in PCB mixtures.
EPA list of some organic pollutants injectedintoenvironment by human
activities—
1. Acenaphthlene
2. Benzidine
3. Carbon tetrachloride
4. Chlorinatedphenols
5. Dichlorobenzene
6. Hexachloroethane
7. Naphthalene
8. Polynucleatedaromatic hydrocarbons ( benzopyrine, toluene)
9. Polychlorinatedbiphenyls (PCBs)
10.Hexachlorocyclohexane-BHC
11. Pesticides- aldrin, DDT, endrinetc

4. Some of the microbes whichcan degrade various chemicals-
chemicals microbes
Hydrocarbons Pseudomonas, Nocardia, Arthrobacter, Mycobacterium
PCBs Pseudomonas, Candida, Alcaligenes
Phenolics Pseudomonas, Flavobacterium, Trichosporon, Bacillus,
Candida, Aspergillus
PAHs Arthrobacter, Nocardia, Alcaligenes, Pseudomonas
Naphthalene Pseudomonas, Nocardia
Organophosphates Pseudomonas
Benzene Mycobacterium, Alcaligenes

5. AEROBIC & ANAEROBIC BIODEGRADATIONOF ORGANIC COMPOUNDS
Aerobic degradation- extent of degradation is correlated with the rate of oxygen
consumption. Mono-oxygenaseand dioxygenases and also peroxidases enzymes have the
ability to degrade organic compounds by aerobic method.
Anaerobic degradation- though this is slow method, but needs long retention time and
produceH2S gas, yet it is more advantageous than aerobic one due to its non dependence
of oxygen supply. Itthus savethe cost of energy for oxygen transfer. Materials like cellulose
and fats which remain unaffected by aerobic process, breakdown under this situation.

6. Biodegradation of petroleum compounds;
Petroleum compounds arecategorized into 2 groups
 Aliphatic hydrocarbon e.g. alkane, alcohol, aldehyde
 Aromatic hydrocarbon e.g. benzene, phenol, toluene, catechol
Degradation of straight chain alliphatic hydrocarbons

7. BIODEGRADATION OF AROMATIC HYDROCARBONS

8. (2) Biodegradation of halogenated hydrocarbons
The recalcitrance of organic pollutants increases with increasing halogenation. Hence our
firstaim to degrade halogenated hydrocarbons is to dehalogenate the compound.
Following dehalogenation processes arecarried out for the removalof halogen atom from
the ring-
1. Oxidative dehalogenation
2. Hydrolytic dehalogenation
3. Reductive dehalogenation

9. Theoretical pathways of TCE oxidation by monooxygenases and dioxygenases

10. (3) PolycyclicAromatic Hydrocarbons
(PAHs)
 PAHs are aromatic compounds made up of 2 or more fused benzene rings. Theseare
recalcitrant and can persistin environment for long periodsbut are conduciveto
biodegradation by certain enzymes found in bacteria and fungi.
 Oxidoreductasesuch as laccase and cytochromeP450 monoxygenases havebeen
exploited for enzymatic degradation of naphthalene.
 Bacteria, fungi, yeasts, and algae havethe ability to metabolize both lower and
higher M.W. PAHs found in the naturalenvironment most bacteria have been found
to oxygenate the PAH initially to form dihydrodiolwith a cis-configuration, which can
be further oxidized to catechols.
 Most fungi oxidize PAHs via a cytochromeP450 catalyzed mono- oxygenasereaction
to formreactive arene oxides that can isomerize to phenols.

11. BIODEGRADATION OF NAPHTHALENE

12. (4) Pesticides
With the advent of Green revolution, there had been a quantum jump in
the use of synthetic pesticides throughout the world to sustain high
yielding crop varieties as they get easily attacked by pests.
A number of them found to contaminate surface and ground water
through run off from agricultural fields. Commonly used ones are- triazine
derivatives, carbamates, organophosphates, aldrin, parquet, diuran etc.
Although DDT is now banned, forits effect on Cental Nervous System as an
organochlorine pesticide, it has however, been reported to be degraded
to p-chlorophenyl acetic acid by a number of bacteria, algae and fungi.
The filamentous basidiomycetes fungus Phaenerocheate (lignin degrader)
is considered as versatile one and can degrade the fungicide
PCP(Pentachlorophenol) and DDT as well with the help of mixture of
peroxidase enzymes.
Pesticide degradation is the process by which a pesticide is transformed
into a benign substance that is environmentally compatible with the site
to which it was applied.
Globally, an estimated 1 to 2.5 million tons of active pesticide ingredients
are used each year, mainly in agriculture. Forty percent are herbicides,
followed by insecticides and fungicides.
Since the discovery ofsynthetic organochlorine compounds in the 1940s,
multiple chemical pesticides with different uses and modes of action have
been employed.
Pesticides are applied over large areas in agriculture and urban settings.
Pesticide use therefore represents an important source of diffuse chemical
environmental inputs.

13. Proposed pathways for the microbial degradation of DDT

14. (5) DETERGENTS
 A detergent is a surfactantor a mixture of surfactants with cleaning properties
in dilute solutions.
 These substances areusually alkylbenzenesulfonates,a family of compounds
that are similar to soap but are more solublein hard water, because the
polar sulfonate(of detergents) is less likely than the polar carboxyl(of soap) to
bind to calcium and other ions found in hard water.
 Increased useof synthetic detergents started in early fifties. They contain
some surfactants (surfaceactiveagents), some builders eg. tripolyphosphates
(to increase the washing efficiency) and some kind of fluorescentwhiteners.
 The bulk of the materials reaching the environment(soil and natural waters)
do so fromconsumer products via the use of sewage sludgeon land, effluents
fromwastewater treatment plants (WWTP) and industrialdischarges into
freshwater and marine sites.
 Primary degradation can be defined as to have occurred when the structure
has changed sufficiently for a molecule to lose its surfactantproperties.
Ultimate degradation is said to haveoccurred when a surfactantmolecule has
been rendered to CO2, CH4, water, mineral salts and biomass.
 LAS(linear alkylbenzene sulphonate) are generally regarded as biodegradable
surfactants. Very high levels of biodegradation (97–99%) havebeen found in
some WWTP using aerobic processes .In contrast, APE(alkylphenol
ethoxylates) are less biodegradable and values of 0–20% havebeen
quoted based on oxygen uptake and 0–9% based on spectroscopic techniques.
 The mechanism of breakdown of LAS involves the degradation of the straight
alkyl chain, the sulphonategroup and finally the benzene ring .The breakdown
of the alkyl chain starts with the oxidation of the terminal methyl group (ω-
oxidation) through the alcohol, aldehydeto the carboxylic acid .
 The reactions are enzymecatalysed by alkane monooxygenaseand two
dehydrogenases. Thecarboxylic acid can then undergo β-oxidation and the
two carbon fragmententers the tricarboxylic acid cycle as acetylCo-A.

15.  Itis at this stage that problems arisewith branched alkyl chains, a side chain
methyl group or a gem-dimethyl-branched chain cannotundergo β-oxidation
by microorganisms and mustbe degraded by loss of one carbon atom at a time
(α-oxidation).
 The second stagein LAS breakdown is the loss of the sulphonategroup.
 Three mechanisms have been proposed for desulphonation according to the
following reactions.
Hydroxyative desulphonation:
equation(1)
Monooxygenase catalysis under acid conditions:
equation(2)
Reductive desulphonation:
equation(3)

16. Refrences-
1. Environmental biotechnology( basic concepts and applications)- by Indu
shekhar Thakur
2. Introduction to environmental biotechnology- by Chatterjee
3. Wikipedia
4. Science direct journals
5. Slidesharepresentations
6. http://www.sciencedirect.com/science/article/pii/S0304415700000137
7. http://www.chem.unep.ch/pops/
8. http://www2.epa.gov/international-cooperation/persistent-organic-pollutants-global-
issue-global-response
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