Transcript alok-k-sil-university-of-calcutta

An Insight Into Bioremediation of
Synthetic Polymers (Plastics)
Dr. Alok Kumar Sil
Department of Microbiology
University of Calcutta
Plastics are widely used in daily life
and industrial sectors
Merits :
High tensile strength
Light weight
Long lasting
Demerits :
Non-biodegradability
 Retention 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
Burning releases a host of poisonous chemicals
into the air
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 synthesized
by including some bonds
susceptible to enzymatic
degradation
Eg.
Polylactides
Polyglycolic acids
Polyethylenesuccinate
(PES)
Polyurethane (PUR)
Selection strategy
Collection of soil sample from the solid waste ground
Serial dilutions
Spreading of the diluted soil samples on agar plates containing
PES as the sole carbon source
Incubation at 30 °C for 3 to 6 days
WEIGHT LOSS-23mg
RATE OF
DEGRADATION-1.15mg/day
Degradation
CONCLUSION
Cell surface hydrophobicity of the bacteria is responsible for its
enhanced attachment to the polymer surface that leads to better
degradation thorough biofilm formation
Effects of Tween 80 and mineral oil on LDPE-degradation
by Pseudomonas sp AKS2.
Additive
None
Tween 80
Mineral oil
Concentration Weight loss (in
(in %)
%) after 45
days of
incubation
0
5±1
0.01
2±1
0.05
2±1
0.01
8±2
0.05
14±2
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 cells
can 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