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