Biodegradation and bioremediation

Biodegradation and Bioremediation, an environmental friendly treatment methods to sustain natural environment unchanged. This is the Reliable, and cost effective application.

1. Anwar Hussain
For Class BS-IV
Institute of Microbiology
Faculty of Natural Science
Biodegradation and Bioremediation
Shah Abdul LatifUniversity,
Khairpur
1

2. XENOBIOTICS
•It is derived from a greek word “XENOS” meaning
‘foreign or strange’.
•Xenobioticsare those chemicals which are man-
made and do not occur naturally in nature.
•They are usually synthesized for industrial or
agricultural purposes e.g. aromatics, pesticides,
hydrocarbons, plastics , ligninetc.
•They are also called RECALCITRANTS as they can
resist degradation to maximum level.
Xenobiotics
2

3. SOURCES OF XENOBIOTICS
•1. Petrochemical industry :
-oil/gas industry, refineries produces basic chemicals
e.g. vinyl chloride and benzene
•2. Plastic industry :
-closely related to the petrochemical industry
-uses a number of complex organic compounds
-such as anti-oxidants, plasticizers, cross-linking agents
Sources of Xenobiotics
3

4. Continued…..
•3. Pesticide industry :
-most commonly found.
-structures are benzene and benzene derivatives,
•4. Paint industry :
-major ingredient are solvents,
-xylene, toluene, methyl ethyl ketone , methyl
•5. Others :
-Electronic industry, Textile industry, Pulp and Paper
industry, Cosmetics and Pharmaceutical industry,
Wood preservation
Continued…
4

5. 1. Acenaphthlene
2. Benzidine
3. Carbon tetrachloride
4. Chlorinated phenols
5. Dichlorobenzene
6. Hexachloroethane
7. Naphthalene
8. Polynucleatedaromatic hydrocarbons ( benzopyrine, toluene)
9. Polychlorinated biphenyls (PCBs)
10.Hexachlorocyclohexane-BHC
11. Pesticides-aldrin, DDT, endrinetc
EPA list of some organic pollutants injected into
environment by human activities—
5

6. Biodegradation
•According to the definition by the International Union of
Pure and Applied Chemistry, the term biodegradation is
“Breakdown of a substance catalyzed by enzymes in vitro
or in vivo.
•In other words, defined as the ability of microorganisms
to convert toxic chemicals (xenobiotics) to simpler non-
toxic compounds by synthesis of certain enzymes
•Biodegradation of xenobioticscan be affected by
substrate specificity, nutrition source, temperature, pH
etc.
Biodegradation
6

7. Bioremediation Effectiveness
Depends on:
• Microorganisms
• Environmental factors
• Contaminant type & state
Bioremediation effectiveness
7

8. Microorganisms
Aerobic bacteria:
•
Examples include: Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and
Mycobacterium.
• Shown to degrade pesticides and hydrocarbons; alkanesand polyaromatics.
• May be able to use the contaminant as sole source of carbon and energy.
• Methanotrophs:
• Aerobic bacteria that utilize methane for carbon and energy.
• Methane monooxygenasehas a broad substrate range.
• active against a wide range of compounds (e.g. chlorinated aliphaticssuch as
trichloroethylene and 1,2-dichloroethane)
• Anaerobic bacteria:
• Not used as frequently as aerobic bacteria.
• Can often be applied to bioremediation of polychlorinated biphenyls (PCBs) in river
sediments, trichloroethylene (TCE) and chloroform.
• Fungi:
•
Able to degrade a diverse range of persistent or toxic environmental pollutants.
Microorganisms
8

9. How Microbes Use the Contaminant
Contaminants may serve as:
Primary substrate
enough available to be the sole energy source.
Secondary substrate
provides energy, not available in high enough
concentration.
Co metabolic substrate
Utilization of a compound by a microbe relying on
some other primary substrate.
How microbe use contaminants
9

10. Microorganisms can live at different
pH conditions
Microbes at Different pH ranges
10

11. MO’s can live at any temperature
conditions
Microbes at different Temperature ranges
11

12. Environmental Factors
•Bioavailability
•Moisture
•Air
•Temperature
•Nutrients
Factors for growth
12

13. Type of contaminants
Bio-degradable
Petroleum products (gas, diesel, fuel oil) •crude oil
compounds (benzene, toluene, xylene, naphthalene) •some
pesticides (malathion) some industrial solvents •coal
compounds (phenols, cyanide in coal tars and coke waste)
Partially degradable / Persistent
TCE (trichlorethane) threat to ground water •PCE
(perchloroethane) dry cleaning solvent •PCB’s (have been
degraded in labs, but not in field work ) •Arsenic, Chromium,
Selenium
Not degradable / Recalcitrant
Uranium •Mercury •DDT
Types of contaminants
13

14. BioremediationBioremediation
14

15. Bioremediation SchemeBioremediation Scheme
15

16. In-situ bioremediation (Engineered)
16

17. Ex-Situ engineered methodEx-Situ Bioremediation (Engineered)
17

18. Water treatment
18

19. Disadvantages
•The process of bioremediation is slow. Time
required is in day to months .
•Heavy metals are not removed completely.
•For in situ bioremediation site must have soil
with high permeability.
•It does not remove all quantities of
contaminants.
Disadvantages
19

20. Disadvantages continued….
•Lab strains become food source for soil protozoa.
•Inability of GEMs to contact the compounds to be
degraded.
•Failure of GEMs to survive/compete indigenous
microorganisms.
•Contaminant solubility may be increased leading
to greater environmental damage and the
possibility of leaching.
•A stronger scientific base is required for rational
designing of process and success.
Disadvantages
20