prospects of microorganisms in detoxifying environmental pollutants

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Prospects of Microorganisms in Detoxifying Environmental Pollutants Md. Fahmid Hossain Bhuiyan Department of Genetic Engineering and Biotechnology Shahjalal University of Science and Technology

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Page 1: Prospects of microorganisms in detoxifying environmental pollutants

Prospects of Microorganisms in Detoxifying Environmental Pollutants

Md. Fahmid Hossain BhuiyanDepartment of Genetic Engineering and BiotechnologyShahjalal University of Science and Technology

Page 2: Prospects of microorganisms in detoxifying environmental pollutants

Pollutants

A pollutant is a substance introduced into the environment that has undesired effects or which adversely affects the usefulness of a resource. In short, pollutants are substances which cause pollution. Pollutants may be gaseous, liquid or solid.

Page 3: Prospects of microorganisms in detoxifying environmental pollutants

Harmful Effects of Pollutants

1. Environment Degradation2. Diseases3. Global Warming 4. Acid Rain5. Ozone Layer Depletion6. Infertile Land7. Bio-magnification of toxic substances

Page 4: Prospects of microorganisms in detoxifying environmental pollutants

Classification of Pollutants

Pollutants are classified into two groups according to their natural disposal-1. Stock pollutants: Pollutants towards which the environment has little or no absorptive

capacity are called stock pollutants. Example: Plastics, heavy metals etc.2. Fund Pollutants: Pollutants for which environment has some absorptive capacity are

called fund pollutants. Example: Carbon dioxide, food waste etc.

Page 5: Prospects of microorganisms in detoxifying environmental pollutants

Most Harmful Pollutants

Stock pollutants

Reasons to be the most harmful-

1. Tendency of building up in concentration in the environment2. Non bio-degradable 3. Toxic

Page 6: Prospects of microorganisms in detoxifying environmental pollutants

Detoxification

Detoxification means the removal of toxic substances.Detoxification which is done using microorganisms is known as microbial detoxification.

Page 7: Prospects of microorganisms in detoxifying environmental pollutants

Substances Requiring Microbial Detoxification

1. Recalcitrant compounds2. Heavy metals3. Azo dyes4. Municipal waste

Page 8: Prospects of microorganisms in detoxifying environmental pollutants

Principle of Microbial Detoxification

Microbes can be used for detoxification following two simple rules-1. Energy source2. Toxicity

Page 9: Prospects of microorganisms in detoxifying environmental pollutants

Catechol and Protocatechuate

Catechol Protocatechuate

Page 10: Prospects of microorganisms in detoxifying environmental pollutants

Ortho Cleavage and Meta Cleavage

Ortho cleavage Meta cleavage

Page 11: Prospects of microorganisms in detoxifying environmental pollutants

Accumulation

Studies have shown that microbes accumulate toxic material in cells following different methods-1. Intracellular chelation2. Compartmentalization3. Bio-sorption4. Efflux pump5. Extra cellular complexation6. Cell wall binding etc.

Page 12: Prospects of microorganisms in detoxifying environmental pollutants

Recalcitrant Compounds

There are different types of recalcitrant compounds-1. Poly chlorinated biphenyls2. Synthetic polymer3. Alkyl benzene sulphonates4. Oil mixture

Page 13: Prospects of microorganisms in detoxifying environmental pollutants

Poly Chlorinated Biphenyls (PCBs)

PCBs are two covalently linked benzene rings in which hydrogen atoms are replaced by chlorine atoms.

The degradation of PCBs are divided into 2 pathways-1. Upper pathway2. Lower pathway

Upper pathway: Conversion of biphenyl to chlorobenzoate

Page 14: Prospects of microorganisms in detoxifying environmental pollutants

Poly Chlorinated Biphenyls (PCBs)

Most bacteria doesn’t have the necessary enzymes to complete both of the pathways.

Enzymes required-1. Biphenyl dioxygenase2. 2,3-dihydrodiol dehydrogenase3. Dihydroxybiphenyl dioxygenase4. Hydrolase

Bacterial species-1. Pseudomonas pseudoalcaligenes2. Sphingomonas paucimobilis3. Comamonas testosterone4. Tannerella forsythia

Conversion of chlorobenzoate to hydroxybenzoic acid

Page 15: Prospects of microorganisms in detoxifying environmental pollutants

Synthetic Polymers

Industrially produced chemical substances consisting of a number of molecules  linked together with covalent bonds. Example: Polyethers, polyesters, polyethelene etc.

Polymers are first broken down to dimer, monomers using depolymerases.

There are many types of polymers with different compositions. Enzymes from different bacteria are being used to degrade them. Some polymers are accumulated in bacterial cells Some of these bacteria are-1. Pseudomonus sp.2. Alcaligenes sp.3. Corynebacterium sp.

Page 16: Prospects of microorganisms in detoxifying environmental pollutants

Alkyl Benzene Sulfonates

Alkyl benzene sulfonates are mostly used as surfactants to reduce surface tension.Complete surfactant biodegradation was achieved by three importantsteps:1. Terminal oxidation of the alkyl chain2. Desulfonation3. Aromatic-ring cleavage.The breakdown of the alkyl chain starts with the oxidation of the terminal methyl group(ω-oxidation).The carboxylic acid can then undergo β-oxidation and the two carbon fragment enters the tricarboxylic acid cycle as acetyl-coA.

Page 17: Prospects of microorganisms in detoxifying environmental pollutants

Alkyl Benzene Sulfonates

Three mechanisms have been proposed for desulfonation.1. Hydroxydative desulfonation2. Monooxygenase catalysis under acid

conditions3. Reductive desulfonationEnzyme-1. Monooxygenase2. Dehydrogenase3. Reductase

Key microbes-1. Alcaligenes sp.2. Comamonas testosterone

Page 18: Prospects of microorganisms in detoxifying environmental pollutants

Oil Mixture

Oil mixture usually contains-

These compounds need different types of enzymes for degradation.

Some genes required for oil degradation-

Page 19: Prospects of microorganisms in detoxifying environmental pollutants

Oil Mixture

Development of Pseudomonus putida by Ananda Mohan Chakrabarty was a significant event in the history of biotechnology. Several bacteria are usually used to degrade oil due to oil spillage. Pseudomonus putida is able to degrade oil alone due to combination of different genes in it’s plasmids.

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Heavy Metal

Microbes show different mechanisms to defend against heavy metal toxicity. These mechanisms include-1. Exclusion2. Compartmentalization3. Metal binding proteins4. Efflux pump5. Cell wall binding

Page 21: Prospects of microorganisms in detoxifying environmental pollutants

Heavy Metal

These mechanisms are classified into passive and active mechanism. Illustration of different mechanism used by bacteria, algae, fungi.

Page 22: Prospects of microorganisms in detoxifying environmental pollutants

Azo Dyes

Azo compounds are compounds bearing the functional group R–N=N–R′, in which R and R′ can be either aryl or alkyl.As a consequence of п-delocalization, aryl azo compounds have vivid colors, especially reds, oranges, and yellows. Therefore, they are used as dyes, and are commonly known as azo dyes. General formula

of azo compoundsAzo compound degradation is done by three key enzymes-1. Azo reductase2. Peroxidase3. Laccase

These enzymes are collected from bacterial species like Bacillus subtilis, Pseudomonas aeruginosa and Psuedomonas putida.

Page 23: Prospects of microorganisms in detoxifying environmental pollutants

Municipal Waste

Municipal waste itself is not hard to degrade but it often contains recalcitrant substances, heavy metals, industry effluents etc. So various waste treatment systems are used to treat the waste using microbes mentioned earlier during the secondary treatment process.Some these systems are-1. Activated sludge process2. Trickling filter3. Rotating biological contractor4. Oxidation pond

Page 24: Prospects of microorganisms in detoxifying environmental pollutants

Gaseous Pollutants

Bio-reactors are being used to treat polluted gas using microorganisms as biological component. There are mainly 4 types of bioreactors which are currently being used to remove pollutant from gas.1. Bio-filter2. Bio-trickling filter3. Bio-scrubber4. Membrane bio-reactor

Page 25: Prospects of microorganisms in detoxifying environmental pollutants

Gaseous Pollutants

The diagram includes Schematic representation of four different types of bioreactors used in biological waste gas purification and close-up view of their respective microbial configurations.

a) Bio-filterb) Bio-trickling filterc) Bio-scrubberd) Membrane bio-reactor

Page 26: Prospects of microorganisms in detoxifying environmental pollutants

Modification of Microbes

In most scenarios microbes are doing a better job degrading pollutants. But the main problem is a single microbe can’t degrade a specific type of pollutant itself due to the necessity of different enzyme systems. Sometimes mixture of aerobic and anaerobic bacteria are required to use together. So maintaining both aerobic and anaerobic condition in a single system is difficult. So modifications have to be made using genetic engineering to develop such a strain of microbe that can degrade a specific type of pollutant all by itself. Such processes include plasmid transfer by conjugation, transduction and transformation, recombinant technology etc. By doing so microbial degradation can be made more efficient, cheap and easy to use.

Page 27: Prospects of microorganisms in detoxifying environmental pollutants

Conclusion

Microbial degradation of environmental pollutants is potential solution to the problems coming in the near future. Environment pollutants are polluting nature and harming ecology. Changes in ecology are affecting human lives directly. It affects agriculture, cultivation land, excessive amount of pesticide in agricultural products, diseases etc. The only viable solution to this is using microbes for pollutant degradation. It will not only save environment from further harm but it’s also cost friendly, no chance of human harm and efficient. So microbial degradation should be adapted in every waste management system.

Page 28: Prospects of microorganisms in detoxifying environmental pollutants

Thank You