Group – NOx, Joe & Lawrence

Describe the history and development of the biopolymer:

In the 1960’s, an American company called W.R Grace started manufacturing Biopol. This Biopolymer is a PHA; it is a co polymer as it consists of two PHB and PHV. PHB and PHV occur naturally in bacteria azobacter and pseudomonas. Biopol is a 2nd generation of PHB after it was discovered in 1920 by a scientist called M. Lemoigne. W.R Grace then began mass producing PHB in pellets. The bacteria used to make PHB is called Alcaligenes eutrophus but when W.R Grace found out how to make Biopol, another bacteria E. coli which is genetically modified, was used as it has faster growth and larger yield. From then on W.R grace has been mass producing Biopol as the need for biopolymers loom.

http://www.biomer.de/HistoryE.html

Group – Jamie, Mark, Alex, Daniel and Adrian

Anaylse the change in the nature of microorganisms used and synthesis of the biopolymer:

Microogranisms have been increasingly used in the synthesis of biopolymers in the petrochemical industry, this is due to the fact that certain microorganisms, such as the bacteria Azobacter, Pseudomonas and E.Coli, are able to naturally produce such biopolymers through their metabolisms, this is preferable to industry as the biopolymers have similar structure to the microorganisms and are able to easily breakdown the materials, allowing the disposal of such biopolymers much easier.

The nature of these organisms is changing due to increasing needs of consumer demand, this increase has lead to more efficient bacterium being utilised for the purpose of the production, and such changes to the bacterium being genetic engineering (which is used by BIOPOL manufacturers in the production of BIOPOL, through genetically engineered E.coli.

Group – Jason, Chris, Tony & Francis

Evaluate the potential use of biopolymer related to properties:

PHB have good oxygen permeability and good UV resistance.

It could be potentially used to replace a lot of synthetic fabrics used today. Umbrella’s could be made by biopol and so could clothing materials. This is provided that the degradation of the biopolymer can be controlled so that it will not degrade during it’s service life. It could also be used to make biodegradable ropes, fishing strings, fishing nets, water bottles. Other potential uses are the materials for diapers, computer parts, and condoms due to the fact that it is both insoluble in water and only degrades over a few decades, meaning that its service life is sufficient enough for it to be a viable replacement to modern day hydrocarbon plastics. However, due to its high production costs these products would become extremely expensive, and as such unless a more economically viable method of synthesis is discovered than the current method of production in genetically modified bacteria.

Group – Will, Ben & Campbell

Analyse the development of the biopolymer:

PHB was first isolated and characterized in 1925 by French microbiologist Maurice Lemoigne. To produce PHB, a culture of a microorganism such as Alcaligenes eutrophus is placed in a suitable medium and fed appropriate nutrients, so that it multiplies rapidly and grown into a large quantity. Then the ‘diet’ is changed to restrict the supply of one particular nutrient (such as nitrogen): under these conditions the organism is no loner able to increase in population but instead begins to make the desired polymer which it stores for later use as an energy source. The amount of PHB that the organism can produce is from 3080% of its own dry weight. The organism is then harvested and the polymer separated out. The technology to achieve this was developed in 1920s.

Recent developments of this may include genetically engineering bacteria such as E.coli and imprinting the genes of the bacteria with those of microorganisms that naturally produce Biopol (alcaligenes eutrophus from the top of my head). Also, other alternatives could include utilizing cheap substrates (food sources) to grow the bacteria required to produce Biopol.

The technology improvements and development from PHB to biopol have led to a number of social and environmental benefits. E.g. biopol can be used in bags, nappies, wrapping film, bottles and sutures. Due to its biodegradable nature. The technology has led to biopol being less expensive to produce than first generation PHB.

Biopolymers are non-toxic, renewable polymers that come from natural sources. They are usually biodegradable. The input material (monomers) for biopolymers can come directly from biological systems (such as animals, plants and microorganisms) or can be chemically synthesized by using biological materials as a starting point (such as natural fats, starch, oil or sugar). Some naturally occurring (non-synthesized) biopolymers include DNA, RNA and proteins.
The current focus in the research and development of biopolymers is to improve the properties of its products and to achieve large-scale production so as to lower costs and broaden availability, thus making it a more viable substitute for traditional polymer products. Different biopolymers have their own material-specific properties on which their possible applications are dependent. For example, bioplastics show much promise, especially for the packaging of products for in-flight catering and for dairy, as well as in pesticide soil pins.
Biopolymers are beneficial for a number of reasons, the first of which is their sustainability. They are also environment friendly, a characteristic that is becoming increasingly important to many consumers, and can prove useful in enhancing the image of a product. This biodegradability also means easier waste management, since it can be successfully composted.

Renewability and sustainable development

Renewability is linked to the concept of sustainable development. The UN World commission on “Environment and Development in our Future” defines sustainability as the development, which meets the needs of the present without compromising the ability of future generations to meet their own needs. According to Narayan (2001) the manufactured products e.g., packaging, must be designed and engineered from “conception to reincarnation”, the so-called “cradle-to-grave” approach. The use of annually renewable biomass, like wheat, must be understood in a complete carbon cycle. This concept is based on the development and the manufacture of products based on renewable and biodegradable resources: starch, cellulose … By collecting and composting biodegradable plastic wastes, we can generate much-needed carbon-rich compost: humic materials. These valuable soil amendments can go back to the farmland and reinitiate the carbon cycle. Besides, composting is an increasingly key point to maintain the sustainability of the agricultural system by reducing the consumption of chemical fertilizers.

Source: http://discovery.kcpc.usyd.edu.au/9.2.2/9.2.2_Biosynthesis.html

(Aashray, Michael and Andrew)

Evaluate the current use of biopolymer related to properties .

PHB –

Properties :

Biodegradable polymers can be an alternative, since they have non-toxic residual products and low environmental permanence. Poly (hydroxybutyrate) is a biodegradable polymer with a strong potential for industrial purposes, but its thermal instability and fragility limit its applications.

Poly(hydroxybutyrate) - PHB is a biodegradable thermoplastic polyester produced by bacterial fermentation, whose biodegradation time is short. PHB has a very high potential for industrial applications3 due to its high crystallinity (50-70%), excellent gas barrier (water vapor permeability around 560 g.µm/m2/day) and physical properties similar to those of polypropylene4. PHB has an elasticity modulus of 3 GPa and tensile strength at break of 25 MPa. However, PHB has some disadvantages, such as high fragility5, showing 3-5% tensile elongation at break, and low thermal stability above its melting point6, with marked degradation starting at 200 °C.

Chemical Resistance
Acids - dilute / Fair
Alcohols / Fair
Alkalis / Poor
Greases and Oils / Good
Electrical Properties
Dielectric constant @1MHz / 3.0
Volume resistivity ( ohm.cm ) / 1016
Mechanical Properties
Izod impact strength ( J.m-1 ) / 35-60
Tensile modulus ( GPa ) / 3.5
Tensile strength ( MPa ) / 40
Physical Properties
Density ( g.cm-3 ) / 1.25
Resistance to Ultra-violet / Fair
Thermal Properties
Upper working temperature ( °C ) / 95

Uses:

Used in stiches or sutures .

Used in Plastic bags to increase the amount of land fill space available .

Used in disposable Nappies

Other information:

Polyhydroxybutyrate (PHB), a high molecular weight polyester, is accumulated as a storage carbon in many species of bacteria and is a biodegradable thermoplastic. To produce PHB by genetic engineering in plants, genes from the bacterium Alcaligenes eutrophus that encoded the two enzymes required to convert acetoacetyl—coenzyme A to PHB were placed under transcriptional control of the cauliflower mosaic virus 35S promoter and introduced into Arabidopsis thaliana. Transgenic plant lines that contained both genes accumulated PHB as electron-lucent granules in the cytoplasm, nucleus, and vacuole; the size and appearance of these granules were similar to the PHB granules that accumulate in bacteria.

http://www.sciencemag.org/content/256/5056/520

Background

Polyhydroxybutyrate (PHB) and its copolymers with polyhydroxyvalerate (PHV) are melt-processable semi-crystalline thermoplastics made by biological fermentation from renewable carbohydrate feedstocks. Polyhydroxybutyrate (PHB) have been described as “the first example of a true thermoplastic from biotechnology” and are also biodegradeable. Although quite stable under everyday conditions they degrade slowly in the body and when composted or in landfill sites. [The HB monomer unit is a normal constituent of human blood.]

Chemical Resistance

The chemical resistance of Polyhydroxybutyrate (PHB) is somewhat limited as they are attacked by acids and alkalis and dissolve in chlorinated solvents.

Optical Activity

Rather remarkably, Polyhydroxybutyrate (PHB) are optically active polymers with a chiral site in each molecular repeat unit, all of which are in the D- (or R) configuration.

Polyhydroxybutyrate ( PHB ) Homopolymers

Polyhydroxybutyrate (PHB) homopolymer is a stiff and rather brittle polymer of high crystallinity, whose mechanical properties are not unlike those of polystyrene, though it is less brittle and more temperature resistant. Also, its degradation rate is quite high at its normal melt processing temperature. Hence, Polyhydroxybutyrate (PHB) copolymers are preferred for general purposes. It is believed that the most likely area for the application of homopolymer is in the medical/biological fields.