Biodegradation is the breakdown of organic materials by microorganisms like bacteria and fungi. There are three types of biodegradation: primary, acceptable, and ultimate. Primary biodegradation changes the structure but not fully degrade, acceptable removes toxicity, and ultimate fully mineralizes into CO2, H2O and minerals. Factors like substrate properties, microbe characteristics, and environment conditions affect biodegradation rate. Common microbes responsible include bacteria and fungi in soil and water. Substrates can be categorized as immediately usable, usable after acclimatization, or recalcitrant.

1. BIODEGRADATION

2. Degradation
 Degradation is breakdown of complex organic
material into simpler one.
 Different ways of degradation:
 1. Photodegradation by natural day light
 2. Oxidation by chemical additives(Catalysts)
 3. Thermal degradation by heat
 4. Mechanical degradation by mechanical force
 5. Biodegradation by Microorganisms.

3. Degradation
 Three levels of degradations:
 1. Rapid degradation(day- week): HC compounds
 2. Slow breakdown(Months- years): HC polymers/
Halogenated compounds
 3. No degradation: Recalcitrant/ Xenobiotic: Plastic

4. Biodegradation
 “Natural and complex process of
decomposition facilitated by biochemical
reactions.”
 It is biological transformation of a complex organic
material to simpler by MOs.
 Reduced organic materials are thermodynamically
unstable and oftenly attacked by microbial
enzymes.
 Biodegradibility: Quality, representing the
susceptibility of the substrate to biological
transformation.

5. Types of Biodegradation
1. Primary biodegradation:
 Biochemical ways of catalysts where
transformation or alteration in chemical structure of
a compound occurs by biochemical reactions.
 Results in loss of specific property- partial
biodegradation and leaves molecule mostly intact.
 Not desirable due to toxicity issues.
 Ex. Change in toxic halogen group from Pera to
Meta position.
 Azo dye Amino benzene

6. Types of Biodegradation
2. Acceptable biodegradation:
 Biological conversion of toxic compounds to non
toxic by biological means.
 Removal of undesirable characteristics occurs.
 Complete removal of toxic entity occurs.

7. Types of Biodegradation
3. Ultimate biodegradation:
 The level of degradation where the compound is
totally utilized and results in production of CO2,
water and mineral constituents.
 Molecular cleavage is so extensive that it removes
all chemical, biological and toxic properties.
 The ultimate products are highly stable and can’t
be degraded further.

8. Reactions involved in
Biodegradation
 Oxidative reaction
 Reductive reaction
 Hydrolytic reaction (water)
 Conjugative reaction (Methylation, Acetylation)

9. Factors affecting Biodegradation
Substrate
related
Organis
m related
Environme
nt related

10. Factors affecting Biodegradation
Substrate
related Nature of pollutants
Physiochemical properties
Concentration
Biodegradability
Toxicity
Chemical nature
Volatility
Polarity

11. Factors affecting Biodegradation
Organism
related
Population density
Composition
Intra/ Inter specific interaction
Enzyme activity
Turn over number
Adaptation

12. Factors affecting Biodegradation
Environment
related
Temperature
pH
Oxygen availability
Nutrient sources- C & e-
Salinity

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--------Complex material-----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
 Other lower organism- algae and invertebrates too
possess some of the criteria- Earthworm, but their
biodegradative potential is still unknown.
 Marine bio-degraders: Bacteria and Fungi
 Soil bio-degraders: Bacteria and Fungi
 Mutations are very often in bacteria and is very
useful for progressive adaptation towards the
biodegradation pathways.
 Not all microbe are equipped with all enzyme, so
many of them follow….COMETABOLISM

15. Organisms responsible for
biodegradation

16. Biodegradation
 Three categories of biodegradation:
I. Usable immediately II. Usable following
acclimatization III. Recalcitrant IV.

17. Reactions involved in
Biodegradation
 I. Usable immediately
 Simple sugars, amino acids and fatty acids- direct
utilization.
 The enzymes required for breakdown are either
constitutive or inducible.
 This requires minimum acclimatization period.
 II. Usable following the acclimatization:
 A lag phase is required for adaptation where no
degradation or very little degradation occurs.

18. Reactions
involved in
Biodegradation
 During lag phase induction of enzyme occurs
 Duration of acclimatization period varies from few
hrs to days or even weeks depending on
biodegradability.
 Example: lag phase of 50 days in pyrazon
degradation.
 III. Recalcitrant/ Xenobiotic:
 Naturally occurring substances such as lignin as
well as anthropogenic.