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Biodegradation Process
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Biodegradation – 6 x 106 chemicals synthesized
1000 new chemicals / year 60,000 to 95,000 commercial use Chemicals in the world Microbes used to treat synthetic contaminants Biodegradation used to treat sewage, solid waste, industrial residues & man made xenobiotics Biodegradation – Decomposition or destruction of contaminant molecule by the action of enzymes Microbes mineralize Organic contaminants to CO2 & carbon + energy & release inorganic forms of N, P, S Molecule enter inside the cell Biotransformation and bio-conversion less toxic form
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Agents for Biodegradation
Due to their catabolic versatility (good for all aspects), species composition, fast reaction Agents for Biodegradation Microbes (bacteria, algae, fungi) Biochemical reactions of microbes By step wise reaction Degrade macromolecule into smaller units
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Bioagumentation: addition of microbes
Macromolecules 고분자 Carbohydrates 탄수화물 Lipids Proteins Nucleic acids To increase Bioremediation process Bioagumentation: addition of microbes Microbial enzyme act as catalysts Conjugation: Transfer of metabolic capacities to indigenous bacteria to increase degradative microbes Breakdown of Complex organic substances by heterotrophs Oxidation of inorganic compounds by autotrophs Photosynthetic reaction of phototrophs Energy generated
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Enzymes for Biodegradation Common Enzymes produced by Microbes
Extracellular or intracellular Speed up reaction without alteration Extracellular breakdown large complex molecules & enable entry into cell Common Enzymes produced by Microbes Mono- & dioxygenases & dehydrogenases
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Optimal conditions for Biodegradation
This is lag period so microbes adjust the present of organic compounds Presence of microbes to decompose contaminants Pollutant induce the microbes to produce enzymes Number of microbes act one after other Each performing special function Microbes – contaminant contact makes biodegradation
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Depends on the nature of toxic compound
Detoxification or partial detoxification occur by several processes Depends on the nature of toxic compound After lag phase Favourable environmental factors to speedup biodegradation Water, pH & temperature
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More hazard due to movement in biological system Lipophilic compounds
Nature of Biodegradation Reactions Oxidation, Reduction, Hydrolysis & structural rearrangements Simple organic compounds (Carbohydrates, proteins, fats & nucleic acids) Molecules with branched chain (simple or fused aromatic ring, cyclo-paraffins) Quickly degrade Difficult to degrade Step wise removal of substituted atoms More hazard due to movement in biological system Lipophilic compounds
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Dynamism of Biodegradation Reaction Rate of biodegradation depends on
Capacity to adjust microbes activity based on contaminant concentration Process of biodegradation Ratio between “concentration required to saturated the system : contaminant concentration within a biological system” Rate of biodegradation depends on Below saturation Larger load of decomposition Reduced the concentration in system (diminishes) Constant decomposition per unit time Decompose faster Slow down decomposition Low pollutant concentration in soil High pollutant concentration in soil
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High concentration of pollutant Low pollutant concentration
When pollutant retention (half of original value) within a biological system “Half-life” High concentration of pollutant Low pollutant concentration
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Directly proportional Contaminant entry 4 g/12 hr
Small quantities of contaminants Microbes remove effectively Before 100% decomposition Concentration in media (Vs) degradation or elimination by microbes Accumulate in Microbial cells Entry of fresh dose of contaminants Microbes adjust Equilibrium between intake & rate of decomposition Directly proportional 직접 비례하는 Contaminant entry 4 g/12 hr
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Finally Reach Steady State
Contaminant half life time is 12 hrs (10 ppm reduced to 5 ppm after 12 hrs later by microbial degradation) or (100 ppm reduced to 50 ppm after 12 hrs later by microbial degradation) Time 0 Time 12 hr Time 24 hr Time 36 hr Time 48 hr Contaminant addition 4 g 4 g 4 g 4 g 4 g + 2 g + + + 6 g 3 g 7 g 3.5 g Microbial degradation 7.5 g 3.75 g 4 g 2 g 1 g 0.5 g After degradation conc raised by 0.25 g 0.125 g & so on.. Finally Reach Steady State
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State of contaminant with different half-lives
Half life & rate of uptake important for biodegradation Long half life pollutant more amount accumulate in environment if rate of input is same
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State of contaminant with different half-lives Contd…
Natural environment received small exposure & spread long duration Constant degradation affect simple arithmetic addition of contaminants As time increase contaminant reach lethal level but microbes adjust to this Reach above adjustable level mechanisms fail Rate of contaminant on biodegrading organisms Microbial biodegradation trying maintain the contaminant at safe level Bioremediation (self purification) is possible below self purification level Increase the contaminant level (beyond critical level) self purification lost & enfeeble (weak) decomposition
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