Biodegradable plastic plant biotech.

BIODEGRDABLE PLASTIC
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

•Introduction
•Types of Biodegradable plastic
Renewable resources
Non-renewable
Other biodegradable plastics
•Properties of biodegradable plastics
•Mechanism of Biodegradation of plastics
•Factors affecting biodegradation
•Applications of Biodegradable plastics
•Advantage of biodegradable plastic
•Disadvantage of biodegradable plastic
•Conclusion
•References
BIODEGRADABLE PLASTIC

Introduction
Plastics
Plastics are polymerized products that have been
used extensively and can be molded into objects.
Although nobody can deny the significance of plastic
and its products in our lives.
Plastic-:
-hydrophobic
-resistant to household chemical
-Cheap

-Take centuries to degrade
-Major cause of pollution
-Non-renewable resources
Why the conventional plastics is non-biodegradable
The term biodegradable means that a substance is able to be broken
down into simpler substances by the activities of living organisms.
*Because their long polymer molecules are too large and too tightly
bonded together to be broken apart and assimilated by decomposer
organisms
* inhibits the enzymes activity.
*high molecular weight.

Biodegradable plastics
Biodegradable plastic have the potential to be the solution of
pollution, nonrenewable sources and issue of global worming.
Biodegradable plastics are a new generation of polymers,
which are degradable and so are environment friendly. This
means that they can be disintegrated into carbon dioxide,
water, and biomass, and do not release any toxic chemicals.
.
Biodegradable plastics are will decompose in natural
aerobic and anaerobic environments.

Biodegradation of plastics occurs when microorganisms
metabolize the plastics to either assimilable compounds or to
humus-like materials that are less harmful to the
environment.
Types of Biodegradable Plastics
#Renewable sources
Natural biodegradable plastic
Modified naturally biodegradable plastics
#Non renewable

Renewable sources
Natural biodegradable plastics
Polyhydroxyalkanoates (Bacterial Polyesters):
Polyhydroxyalkanoates (PHAs) are aliphatic polyesters.
synthesized by a variety of naturally occurring bacteria by the process of
fermentation of sugars and lipids.

PHB
Most common type of PHA.
Aliphatic poly esters,homopolymers of 3-
hydroxybutyric acid.
Stiff and less flexible.
The most common commercial PHA consist of a
copolymer PHB/PHV together &plasticiser (triacetine)
& inorganic additives (titanium dioxide).

Biosntheses of PHB
Glucose
↓
Pyruvate
↓
Acetyl CoA
↓ 3-ketothiolase
Acetoacetyl CoA
↓Acetoacetyl CoA reductase
3-Hydroxybutyryl CoA

Oragnism- Ralstonia eutrophia
Property of PHB
-Insoluble in water
-They have good oxygen permeability and UV resistance
-Degrade without leaving toxin
PHBH (Poly-hydroxybutyrate-co-polyhydroxyhexanoates)
. The PHBH resin is derived from carbon sources such as sucrose,
fatty acids or molasses via a fermentation process.

Chitin and chitosan : Chitin is a skeletal polysaccharide
making up a basic shell constituent of crabs, lobsters,
shrimps, and insects.
Chitin can be degraded by chitinase.
It is insoluble in its native form, although chitosan, a
partly deacetylated form of chitin, is water - soluble.
Proteins -The fibrous proteins wool, silk, and collagen
are used in natural form.

Gelatin , animal protein.
Gelatin is a water - soluble, biodegradable polymer with wide
industrial, pharmaceutical, and biomedical applications.
In addition, it is also used for production of coatings and for
microencapsulating various drugs.
Modified naturally biodegradable plastic
Starch based plastics
It’s a carbohydrate that is synthesized in the organs of plants as
reserve food supply for periods of dormancy, germination and
growth.
It’s a condensation polymer of glucose.

It is cheap ,abundant and renewable. These materials are
widely used in polymer blends and are available in
commercial grades suitable for extrusion, injection/blow
molding and thermoforming processes.
Starch is modified by grafting with vinyl monomer or with
polymer such as polyethelen(PE).

Thermoplastic like starch (TPS)
In the presence of a plasticizers and high temprature starch
melts ,fluidizes ,enabling its use in injection,extrusions and
blowing equvipment.
Some plasticizers used are –water,glycerol,sorbitol etc.
the water plays two roles: it is an agent that breaks the
structure of native granule, breaking the bond of hydrogen
chains and it is plasticizers.

Cellulosic plastic
The most abundant of naturally occurring polymers
Cellulose is readily biodegradable and is mineralized by
variety of microorganisms.

The mechanical property of cellulosic plastic differ with type
and amount of Plasticizers.Lower plasticizer content yields a
harder surface, higher heat resistance, greater rigidity, higher
tensile strength and better dimensional stability. High content of
plasticizer increases impact strength.
It is resistant to number of attack or change by a wide variety of
household,industrial and medical chemicals such as
toothpaste,detergent,salts, ethylene glycol,alcohol ,lipids etc.
PLA Polyesters
Polylactic acid (PLA) is a linear aliphatic polyester produced by poly-
condensation of naturally produced lactic acid.
The ester linkages in PLA are sensitive to both chemical hydrolysis and
enzymatic chain cleavage.

PLA is often blended with starch to increase biodegradability
and reduce costs.
However, the brittleness of the starch-PLA blend is a major
drawback in many applications. To remedy this limitation, a
number of low molecular weight plasticisers such as glycerol,
sorbitol and triethyl citrate are used.
PLA has high mechanical strength, thermal plasticity,
fabricability, biodegradability, and biocompatibility.

Non-renewable
PCL (Synthetic Aliphatic) Polyesters
Polycaprolactone (PCL) is a biodegradable synthetic aliphatic
polyester made by the ring-opening polymerization of
caprolactone.
PCL has a low melting-point, between 58-60°C, low viscosity
and is easy to process.
Commercially PCL and corn starch is used for production of
plastic.

PBS (Synthetic Aliphatic) Polyesters
Polybutylene succinate (PBS) is a aliphatic polyester .
PBS is generally blended with other compounds, such as
starch (TPS) and adipate copolymers (to form PBS-A), to make
its use economical.
Other biodegradable plastics
Water Soluble Polymers
Polyvinyl Alcohol (PVOH)
Ethylene Vinyl Alcohol (EVOH)

It is used as an oxygen barrier layer in multilayer film
packaging.
PVA has a melting point range of 190-230°C
It has excellent film forming, emulsifying and adhesive
properties
It is a strong polymer with high tensile strength and flexibility
as well as good oxygen barrier properties.

Photo-biodegradable Plastics
Photodegradable plastics are designed to become
weak and brittle when exposed to sunlight for
prolonged periods.
Photo sensitisers used include diketones, ferrocene
derivatives (aminoalkyferrocene) and carbonyl-
containing species.

Mechanism of Biodegradation of plastics
Biodegradation is the disintegration or degradation by the
action of microorganisms such as bacteria, fungi or algae and
may result in loss in some useful physical or mechanical
properties of polymers.
From chemical point of view, biological degradation of
polymers occurs either in
1)aerobic biodegradation or
2)anaerobic biodegradation

Generally, the mechanism occurs in two steps
Depolymerization
Polymer convert to their correspond oligomer or monomer.
1)Physical factors- Hydrolysis , photodegradation
2)Microbial enzyme
Mineralization
This is followed by mineralization in which monomers
and oligomers formed are of sufficiently smaller in
size and are transported to the cytoplasmic cells of
the microorganisms and get completely mineralized.

Factors affecting biodegradation
1). Property of plastic
2).Envoirnmental condition
3).Microbes
Applications of Biodegradable plastics
MEDICAL
Surgical Sutures
Bone - Fixation Devices,thread
Artificial Skin, Drug Delivery System
Hernia Repair Device

Food pakaging, Food service wears

Agricultural Application
Agricultural mulches ,
Controlled Release of Agricultural Chemicals

Advantage of biodegradable plastic
Disadvantage of biodegradable plastic
*Corn and soybeans are popular plants used in the
production of biodegradable plastic. These crops require
high doses of toxic pesticides that contribute to pollution
and may leech into the soil.
*Many of the farmed resources that are used to make
biodegradable plastics come from genetically modified
plants. There is a risk for cross-contamination associated
with farming genetically modified plants for non-food
purposes.

*Pollution in waterways due to high BOD concentrations resulting from
the breakdown of starch-based biodegradable plastic.
Conclusion
The biodegradable plastic are Eco-friendly and the main
advantage is that they are made by renewable sources. It is
used to overcome the environmental problem associated
with conventional plastic

References
www.grinningplanet.com/.../advantages-and-
disadvantages-of-biopla..
www.europeanplasticfilms.eu/.../AustralianReportonBio
degradablePlastics
www.polysciences.com
www.wikipedia.com
“Biotechnology” by U. Satyanarayana

Biodegradable plastic plant biotech.

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