Biodegradation & Bioremediation

Biodegradation & Bioremediation
FST-202
General Microbiology

SubmittedTo:-
Mam Sadia Yasin
Sahiba
7/21/2018 3
Fst-202 General Microbiology
(Session Fall 2017-21)

SubmittedBy:-
Ghulam Qadir
7/21/2018 4

Sr. No. Title Page. No.
1. Introduction 6
2. Biodegradation 7 – 8
3. Biodegradation Processes 9 – 14
4. Bioremediation 15 – 17
5. Bioaugmentation 18 – 19
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Introduction
• The Metabolic activities of microbes can also be
exploit in complex natural environments for
beneficial outcomes. Examples are
1. The use of microbial communities to carry out
biodegradation, bioremediation, and environmental
maintenance processes.
2. The addition of microorganisms to soils or plants for
the improvement of crop production.
7/21/2018 6

Biodegradation
• Has at least three outcomes:-
1. A minor change in an organic molecule, leaving the
main structure still intact.
2. Fragmentation of a complex organic molecule in such
a way that the fragments could be yield the original
structure.
3. Complete mineralization, which is the transformation
of organic molecules to inorganic forms.
7/21/2018 7

Biodegradation
• Definition :-
• “ ‘Biodegradation’ is the breakdown of organic
matter by microorganisms.”
• The removal of toxic industrial products in soil and
aquatic environments is a daunting and necessary task.
• Compounds Such as perchloroethylene (PCE),
Trichloroethylene (TCE), and Polychlorinated biphenyls
(PCBs) are common contaminants.
7/21/2018 8

Biodegradation Processes
• Degradation of complex compounds requires several
discrete stages, usually performed by different
microbes.
• Initially contaminants are converted to less toxic
compounds that are more readily degraded.
• The 1st step for many contaminants, including
organochloride pesticides, alkyl solvent, and aryl
halides, is “reductive dehalogenation”.
7/21/2018 9

• This is the removal of a halogen substituent ( e.g.
chlorine, bromine, fluorine) while at the same time adding
electrons to the molecule.
• This can occur in two ways:-
1. In hydrogenolysis, the halogen substituent is replaced by
a hydrogen atom
2. Alternative, dihaloelimination removes two halogen
substituents from adjacent carbons while interesting an
additional bond between the carbons
7/21/2018 10

• The dehalogenation of PCBs uses electrons derived
from water
• Alternatively hydrogen can be the electron donor for
the dehalogenation of different chlorinated
compounds.
• Major genera with species that carry out this process
include Desulfitobacterium, Dehalospirillum, and
Desulfomonil.
7/21/2018 11

• Another important factor that influences
biodegradation is a compound’s chirality or hardness.
• Microorganisms often degrade one isomer of
substance but not to the other, which will remain in
the environment.
• At least 25% of herbicides are chiral.
• Thus, it is critical to add the herbicides effective and
also degradable.
7/21/2018 12

• Degradation processes that occur in soils also can be
used in large-scale degradation of hydrocarbons or
wastes from agricultural operations.
• The waste material is incorporated into the soil or
allowed to flow across the soil surface, where
degradation occurs.
• While this is often very effective, sometimes such
degradation processes doses not reduce toxicity.
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• An important example of this problem is the
degradation of trichloroethylene (TCE), a widely used
solvent.
• When degraded under anoxic conditions, the
dangerous carcinogen vinyl chloride can be formed.
7/21/2018 14

Bioremediation
• Definition:-
• “ The use of microbes to transform these
contaminants to non-toxic degradation products is
called ‘Bioremediation ’ ”.
• Bioremediation usually involves stimulating the
degradative activities of microorganisms already
present in contaminated water or soils.
7/21/2018 15

Bioremediation
• These existing microbial communities cannot carry
out biodegradation processes at a desired rate due to
limiting physical or nutritional factors.
• For example, biodegradation may be limited by low
levels of oxygen, nitrogen, phosphorus, or other
nutrients.
• In these case, it is very necessary to determine the
limiting factors and supply the needed materials or
modify the environment.
7/21/2018 16

Bioremediation
• Often the addition of easily metabolized organic
matter such as glucose increases biodegradation of
recalcitrant compounds that otherwise would not be
use as carbon and energy sources by microorganisms.
• This process is called “Cometabolism”.
7/21/2018 17

Bioaugmentation
• Definitions:-
• The acceleration of microbiological processes by the
addition of known active microorganisms to soil, waters,
or other complex systems is called “Bioaugmentation”.
• This is not a new concept; commercial culture
preparations have long been available to facilitate
silage formation and to improve septic tank
performance.
7/21/2018 18

Bioaugmentation
• However, the magnitude of contamination coupled
with an increased awareness of some of the dangers
cleanup can introduce has stimulate the growth of the
bioremediation industry.
• For instance, an oil dispersant consisting of several
non-pathogenic Bacillus species, wetting agent, and
nutrients is now commercially available.
7/21/2018 19

Biodegradation & Bioremediation

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