2. Degradation
ī¨ Degradation is breakdown of complex organic
material into simpler one.
ī¨ Different ways of degradation:
ī¨ 1. Photodegradation by natural day light
ī¨ 2. Oxidation by chemical additives(Catalysts)
ī¨ 3. Thermal degradation by heat
ī¨ 4. Mechanical degradation by mechanical force
ī¨ 5. Biodegradation by Microorganisms.
3. Degradation
ī¨ Three levels of degradations:
ī¨ 1. Rapid degradation(day- week): HC compounds
ī¨ 2. Slow breakdown(Months- years): HC polymers/
Halogenated compounds
ī¨ 3. No degradation: Recalcitrant/ Xenobiotic: Plastic
4. Biodegradation
ī¨ âNatural and complex process of
decomposition facilitated by biochemical
reactions.â
ī¨ It is biological transformation of a complex organic
material to simpler by MOs.
ī¨ Reduced organic materials are thermodynamically
unstable and oftenly attacked by microbial
enzymes.
ī¨ Biodegradibility: Quality, representing the
susceptibility of the substrate to biological
transformation.
5. Types of Biodegradation
1. Primary biodegradation:
ī¨ Biochemical ways of catalysts where
transformation or alteration in chemical structure of
a compound occurs by biochemical reactions.
ī¨ Results in loss of specific property- partial
biodegradation and leaves molecule mostly intact.
ī¨ Not desirable due to toxicity issues.
ī¨ Ex. Change in toxic halogen group from Pera to
Meta position.
ī¨ Azo dye ī Amino benzene
6. Types of Biodegradation
2. Acceptable biodegradation:
ī¨ Biological conversion of toxic compounds to non
toxic by biological means.
ī¨ Removal of undesirable characteristics occurs.
ī¨ Complete removal of toxic entity occurs.
7. Types of Biodegradation
3. Ultimate biodegradation:
ī¨ The level of degradation where the compound is
totally utilized and results in production of CO2,
water and mineral constituents.
ī¨ Molecular cleavage is so extensive that it removes
all chemical, biological and toxic properties.
ī¨ The ultimate products are highly stable and canât
be degraded further.
13. Organisms responsible for
biodegradation
Most significant group of living organism involved in
biodegradation, responsible for 65% total metabolism
due higher growth rate and biomass.
Higher organism are also involved but not significantly,
inability to degrade complex molecule.
Microbes represent most diversified metabolism on
earth.
Microbes--------ī Complex material-----ī simpler form
Microbes utilize energy more efficiently in comparison to
higher organisms.
High rate of reproduction and mutation is the governing
factor.
14. Organisms responsible for
biodegradation
ī¨ Other lower organism- algae and invertebrates too
possess some of the criteria- Earthworm, but their
biodegradative potential is still unknown.
ī¨ Marine bio-degraders: Bacteria and Fungi
ī¨ Soil bio-degraders: Bacteria and Fungi
ī¨ Mutations are very often in bacteria and is very
useful for progressive adaptation towards the
biodegradation pathways.
ī¨ Not all microbe are equipped with all enzyme, so
many of them followâĻ.COMETABOLISM
17. Reactions involved in
Biodegradation
ī¨ I. Usable immediately
ī¨ Simple sugars, amino acids and fatty acids- direct
utilization.
ī¨ The enzymes required for breakdown are either
constitutive or inducible.
ī¨ This requires minimum acclimatization period.
ī¨ II. Usable following the acclimatization:
ī¨ A lag phase is required for adaptation where no
degradation or very little degradation occurs.
18. Reactions
involved in
Biodegradation
ī¨ During lag phaseī induction of enzyme occurs
ī¨ Duration of acclimatization period varies from few
hrs to days or even weeks depending on
biodegradability.
ī¨ Example: lag phase of 50 days in pyrazon
degradation.
ī¨ III. Recalcitrant/ Xenobiotic:
ī¨ Naturally occurring substances such as lignin as
well as anthropogenic.