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An Insight Into Bioremediation of Synthetic Polymers (Plastics)
Dr. Alok Kumar SilDepartment of Microbiology
University of Calcutta
Plastics are widely used in daily life and industrial sectors
Merits :High tensile strengthLight weightLong lasting
Demerits :Non-biodegradabilityRetention of plastic in soil and water leads to major environmental hazard
Measures
Say NO to indiscriminate use of plastic
Recycling of plastic waste
Demerits Recycling of plastic waste
Recycling is labor intensive and not cost effective
Often the bi-product or end-product of recycling may be toxic or hazardous
Burning releases a host of poisonous chemicals
into the air
Burning
Bioremediation
If properly identified, microbe-mediated degradation can be applied in situ making the process cost effective and non-
laborious In most cases microbial degradation
of plastics is hazard free and yields non-toxic breakdown products
Biodegradable Polymers
Polymers containing bonds susceptible to enzymatic degradation
Naturally accumulated by bacteria
Eg.
Polyhydroxyalkanoates (PHA) such as polyhydroxybutyrate (PHB)
Chemically synthesizedby including some bonds susceptible to enzymatic degradation
Eg. PolylactidesPolyglycolic acids
Polyethylenesuccinate (PES)Polyurethane (PUR)
Incubation at 30 °C for 3 to 6 days
Collection of soil sample from the solid waste ground
Spreading of the diluted soil samples on agar plates containing PES as the sole carbon source
Selection strategy
Serial dilutions
WEIGHT LOSS-23mgRATE OF
DEGRADATION-1.15mg/day
Degradation
CONCLUSION
Cell surface hydrophobicity of the bacteria is responsible for itsenhanced attachment to the polymer surface that leads to better degradation thorough biofilm formation
Additive Concentration (in %)
Weight loss (in %) after 45
days of incubation
None 0 5±1
Tween 800.01 2±1 0.05 2±1
Mineral oil0.01 8±2 0.05 14±2
Effects of Tween 80 and mineral oil on LDPE-degradation by Pseudomonas sp AKS2.
Better attachment leads to formation of biofilm that provides the organism a milieu conducive for better execution of biodegradation.
AKS2 cells develops viable microbial population in biofilm on polyethylene surface
Biofilm harvested cells have higher reproduction ability
Biofilm-harvested cells exhibit increased functional diversity and metabolic activity
Biofilm cells exhibited increased hydrolytic activity and functional homogeneity in biofilm
Biofilm-harvested cells exhibit higher level of cell surface hydrophobicity
Biofilm cells exhibited •higher metabolic activities•higher functional diversities•higher level of functional homogeneity •higher surface hydrophobicity and thus increased fitness
Taken together, degradation of polymer by biofilm cellscan be attributed to the adaptiveness resulting
in the modulation enzymatic activities and surface hydrophobicity.
Thank you
Increased colonization and reproduction efficiency for biofilm-harvested cells