This document discusses biodegradable plastics and polyhydroxybutyrate (PHB). It provides background on biodegradable plastics, including their production from renewable biomass sources and ability to break down naturally. It then focuses on PHB, describing its discovery in bacteria in the 1920s, how it is synthesized intracellularly through three enzymatic reactions, and its properties. Factors that influence biodegradation rates and some commercial producers of PHB are also mentioned.

1. TOPIC:-BIO-DEGRADABLE
PLASTICS
Presentation By-
GAGAN KUMAR JANGHEL [M.Sc.III-Sem.]

2. • Biodegradable plastics are plastics that can be decomposed by the action of
living organisms, usually microbes, into water, carbon dioxide, and biomass.
• On the other hand, petroleum-based plastics that are combined with an
additive that makes them break down quickly.
• Biodegradable or compostable plastics are those that meet all the scientifically
recognized standards of biodegradability of plastics and plastic products
independent of their carbon origin.
• Biodegradability is measured on mineralization, disintegration and Safety of
the material.
• At least 90% conversion to CO2, water and biomass via microbial
assimilation.should occur within a time period of 180 days or less.
• No impacts on plants.

3. • In 1862 -The first ever man made plastic was a bio-plastic. It was made from
cellulose nitrate By Wascalles Parkesine.
• In 1888-Polyhydroxyalkanoate (PHA) was first observed in bacteria by
Martinus Beijerinck.
• In 1926-French microbiologist Maurice Lemoigne chemically identified the
polymer after extracting it from Bacillus megaterium.
• In 1983-Imperial Chemical Industries [ICI] manufacture the first broad-
application biodegradable plastic,PHBV, named -Biopol. that was biodegradable
• In 1996, Monsanto discovered a method of producing one of the two polymers in
plants and acquired Biopol with Zeneca, a spinout of ICI, as a result of the
potential for cheaper production.

4. Bioplastics are plastics derived from, corenewable biomass
sources, such as vegetable Fats and oilsrn ,starch,
or micro organism.
Bioplastics can be made from and also from used agricultural
by products plastic bottles and other containers using
microorganisms.
Common plastics, such as fossil-fuel plastics, are derived from
petroleum or natural gas.
Production of such plastics tends to require more fossil fuels
and to produce more greenhouse gases than the production of
biobased polymers (bioplastics).

5. Degradable polymers that are naturally degraded by the action of
microorganisms such as bacteria, fungi and algae
Biodegradable plastics is plastic that decompose naturally in the
environment.This is achieved when microorganism in the environment
metabolize and breakdown the structure of biodegradable plastics.
The end result is one which is less harmful to the
environment then traditional plastics.
A polymer derived from natural sources,e.g corn or
sugars.

6. Reason
Conventional
plastic use fossil
fuels, decreasing
fossil fuels
reserves
consumers and governments
demand cleaner alternatives
to petroleum based
technologies and their
reckless production of the
greenhouse gas CO2.
Bio-plastics also offer an
opportunity to get a double return
for the energy used in their
manufacture-first as a useful item
and secondly as a fuel source.

7. 1.Bio-based plastics
a) Polyhydroxyalkanoates (PHAs)
b) Polylactic acid (PLA)
c) Starch blends
d) Cellulose-based plastics
2.Petroleum-based plastics
a) Polyglycolic acid (PGA)
b) Polybutylene succinate (PBS)
c) Polycaprolactone (PCL)
d) Poly(vinyl alcohol) (PVA, PVOH)
e) Polybutylene adipate terephthalate
(PBAT)
3.Thermal Plastic
acrylic, polyester, polypropylene,
polystyrene, nylon and Teflon.
4.Oxo-biodegradable plastic-High
Density Polyethylene (HDPE),
commonly used in carrier bags.
5.Microbial Biodegrdation-
bio-polyethylene terephthalate (bio-
PET), bio-polyethylene (bio-PE), or
bio-polyamides (bio-PA or nylon).

8. Bio-based plastics –
Biologically synthesized plastics,produced from
natural origins, such as plants, animals, or micro-
organisms or starch based plastics that are made from
soy, corn, or potatoes, breaking down 60 percent or
more, within 180 days or less. In order to do this, bio
based plastics need water, heat, and aeration. Bio-based
plastics can take longer to decompose in landfills
because of non-availability of aeration. The bio based
plastics are non-recyclable. An example of bio-based
plastic is the cellulose fiber plastic, which is made from
reconstituted cellulose, and zein plastic, which is made
from corn protein.

10. DISCOVERY:-
PHB was discovered in 1925 by French
scientist Maurice Lemoigne.
Found that PHB as the intracellular
inclusionsin many bacteria.

11. • Polyhydroxybutyrates (PHBS) are members from family of polyesters known as
Polyhydroxyalkanoates (PHAS).
• Accumulated in intracellular granules by Gram-positive and Gram-negative micro organisms.
• PHA monomer combine to form a biopolymer.
• Known as Biopolymers as they are produced from microorganisms and naturally synthezised.
• PHB are produced when there is excess carbon source with the limitation of one of the essential
nutrients.Produce under stress conditions lack of-02,N,P,S,Fe,Mg,Zn.
• When produced by bacteria they serve as both a source of energy and as a carbon store.
• Many different types of PHAS are available and PHB is the most common one use.
• The mechanical properties and biocompatibility of PHA can also be changed
by blending, modifying the surface or combining PHA with other polymers,
enzymes and inorganic materials, making it possible for a
wider range of applications.
.

12. • n=600-35,000
(no. of times monomer repeating to
produce 1 biopolymer)
• m=1-3
(no. of times CH2 repeated)
• R=acyl group
(C-atom1-13)
R=CH3(poly 3-hydroxybutyrate)

13. Thermoplastic
Water insoluble
(Hydrophobic)
Good oxygen
permeability
Good ultra-violet
resistance
Poor resistance to
acids and bases
Soluble in
chloroform and
other chlorinated
hydrocarbons
Biocompatible,
Biodegradable
Sinks in water Brittle to elastic Non toxic
Piezoelectrical
Can have
functional groups
Biodegradable

14. Important PHB producing bacteria:Ralstonia,Bacillus,Pseudomonas,
Alcaligenes,Azotobacter,Hydrogenomonas,Chromatium, Methylobacterium,Recombinant
Escherichia coli and many others.

16. phb-c/a/b OPERON IN R.EUTROPHA
PHB BIOSYNTHESIS
It consists of three enzymes
1) B-ketoacyl-CoA thiolase (phb A)
2) NADPH dependent Acetoacetyl-CoA dehydrogenase (phb B).
3) P(3HB) polymerase (phb C)
• Transferring the complete phb operon, consisting of the phbC,phbA and phbB genes from Ralstonia
eutropha.
• Polyhydroxybutyrates (PHBS) are polymers that bacteria produce under conditions of low
concentrations of important nutrients (typically nitrogen, but sometimes oxygen) and high
concentrations of carbon sources.
• This process occurs because the excess carbon leads to bacteria creating carbon reserves (PHAs) to
save for a time with more plentiful nutrients in which they need energy to carry out regular functions.
• Bacteria store PHBS in granules for later use.
• These polymers are accumulated intracellularly under conditions of nutrient stress and act as a carbon
and energy reserve.
• Poly-B-hydroxybutyrate (PHB) is synthesized as an intracellular storage material and accumulates
as distinct white granules during unbalanced growth in the cell, these are clearly visible in the
cytoplasm of the cell.

17. • The polyester PHB is derived from acetyl-CoA by a sequence of three enzymatic
reactions-
1) [Condensation Step]-First condensation of two molecules of acetyl-CoA is catalyzed
by ẞ-ketothiolase(phbA) to form acetoacetyl-CoA.
2) [Reduction Step]-Acetyl-CoA(phbB) reductase reduces acetoacetyl-CoA to D-ẞ-
hydroxybutyryl-CoA.
3) [Polymerization Step]-It is polymerized by PHA(phbC) synthase to PHB.
Glucose

18. RECOVERY OF PHAS FROM CELLS
1. PHA producing microorganisms stained with Sudan black or Nile blue (fluorescent dye).
2. Cells separated out by centrifugation or filtration.
3. PHA is recovered using solvents (chloroform) to break cell wall & extract polymer.
4. Purification of polymer

19. Poly-B-hydroxybutyrate (PHB) is synthesized as an intracellular storage material and accumulates as distinct white
granules during unbalanced growth in the cell, these are clearly visible in the cytoplasm of the cell.
white granules of PHB

20. PHB
GRANULES
Round granules-
0.1-0.2µm in diameter

21. POLYETHYLENE BIO-DEGRADATION BY CATERPILLARS OF THE
WAX MOTH GALLERIA MELLONELLA:-
The fast biodegradation of Polyethylene PE by the wax
worm, the caterpillar larva of the wax moth Galleria
mellonella of the snout moth (Pyralidae) family of
Lepidoptera. When a Polyethylene (PE) film was left in
direct contact with wax worms, holes started to appear
after 40 minutes, with an estimated 2.2±1.2 holes per
worm per hour. This meant that the wax worms had
chewed their way out of the plastic bags at a relatively
high speed.
Two species of waxworm, Galleria mellonella and
Plodia interpunctella have both been observed eating
and digesting polyethylene plastic.
The waxworms metabolize polyethylene plastic films
into ethylene glycol, a compound which biodegrades
rapidly. Source-Current biology magazine
Adult and Larvae of Indian waxworm,
Galleria mellonella (L).

22. FACTORS AFFECTING BIODEGRADATION:-
One of the challenges for the design and use of biodegradable plastics is that biodegradability is
a "system property". That is, whether a particular plastic item will biodegrade depends not only
on the intrinsic properties of the item, but also on the conditions in the environment in which it
ends up. The rate at which plastic biodegrades in a specific ecosystem depends on a wide range
of environmental conditions, including temperature and the presence of specific
microorganisms.
1.Intrinsic factors:-
A.Chemical composition:
Least to greatest resistance to biodegradation: n-alkanes > branched alkanes > low molecular
weight aromatics > cyclic alkanes > high molecular weight aromatics = polar polymers
B.Physical properties:
Shape,Exposed surface area,Thickness
2.Extrinsic factors:-
A.Abiotic factors:
Temperature,Atmospheric water/salt concentration,Photo-degradation,Hydrolysis
B.Biotic factors:
Presence of proper strains of microorganisms

23. COMPANIES PRODUCING PHB:-
1) Bioenvelop-Canada- BioP-food containers.
2) EarthShell-USA-utensils.
3) EverCom. Inc. - Japan - EverCorn-resin for
coating.
4) National Starch Company-UK-packaging films
and products.
5) Novamont-Italy-Mater-Bi-films and moulded
products.
6) VTT Chemical Technology-Finland COHPOL.
7) Plasto bag Industries – India-carry bag

24. Bio plastic products are used in:
Automobile interiors(toyota)
Electronics- flame retardant in
projector
Packaging- shopping bags, bottles.
Gardening- mulch foils, flower pots.
Sanitary products- disposable gloves.
Laboratory- pipette tips, centrifuge tips
Building and construction.
Medical and Health
Hydrogen fuel (mazda)
And many more…
APPLICATIONS

25. ADVANTAGE
Carbon emission reduction
Consumes less energy
Less landfill area needed
Easy to use (Recyclable)
Non Toxic
Take less time to breakdown
No greenhouse gas emission.
Not contain additives harmful to
health, such as phthalates or
bisphenol A.
DISADVANTAGE
Need for composter
Engineering issues or manufacturing
problems
Risk of contamination, Improper
disposal leads totoxicity, already
increasing landfill waste, non
biodegradable plastic contamination.
Water soluable
Melts at temp. above 300.C
Plants (generally genetically modified)
grown for bio plastics have negative
impacts of their own, eg. PLA (Poly
Lactic Acid) from GM corn