Polyhydroxybutyrate PHB Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class. Progress Analysis: - Bacteria first used to make PHB in 1925 at Pastuer Institute in Paris. - In 1970’s adopted by Imperial Chemical Industries (ICI) – Alcaligenes Eutrophus grown in fermentation vats with Molasses - The bacteria is then starved of nutrients (glucose and nitrogen) – PHB is produced as an energy store for the bacteria. In 1980’s Maddison University (Virgina) successfully cloned the 3 genes of A. Eutrophus that control PHB production and transferred them to Escherichia coli – an easier bacteria to work with allowing easier manipulation of the polymer depended on the need. - In 1990’s the 3 genes were cloned into sugar beets and turnips – much larger scale production of polymer. Work continuing (with Monsanto – company bought patent) into cloning genes to corn. Production: The manufacturing process of PHB begins with sunlight.
Through photosynthesis carbon dioxide from the atmosphere is converted to carbohydrates via sugar beets or sugar cane. These carbohydrates (like Lactose, Fructose and Glucose) are the raw material for the manufacturing of PHB. Uses: •In medicine, PHB is compatible with the blood and tissues of mammals. The monomer of PHB is a normal metabolic in the human blood. As the body reabsorbs PHB it might be used as a surgical implant, in surgery, as seam threads for the healing of wounds and blood vessels. In pharmacology, PHB can be used as microcapsules in therapy or as materials for cell and tablet packaging. •In packaging for deep drawing articles in the food industry, for example, bottles, laminated foils, fishnets, potted flower, hygiene, fast food, one-way cups, agricultural foils and fibres in textile. Advantages of PHB: •Good mechanical properties, especially when low density and price are taken into account. •Recyclable, renewable and non-abrasive to manufacturing equipment. •PHB is hydrophobic, therefore protects natural ? res from moisture sensitivity. •Mechanical properties are comparable to other polymers used (e. g. PP). •PHB has a fast degradation rate compared to other plastics. (months in sewage and years in sea water) yet ultra violet light can speed up this process. •The main advantage in the medical field is that PHB is a biodegradable plastic which can be inserted into the human body and does not have to be removed again. •Can be manipulated genically therefore can be used for many things Disadvantages of PHB: •It has a tendency to be brittle. Costs four times as much as polyethylene (it’s major competitor) •Cheaper to produce necessary materials from petrochemical industry. •Large scale production in early stages. •Uses sugarcane which can decrease biodiversity such as in Brazil. Evaluative Conclusion: PHB has huge potetial as polymer for future,this is due to its main advantages such as being biodegradable and it has an ease of manipulation. This is good although work must be done to make it cheaper. Also work must be done to reduce the very large scale production in the early stages of production.
There needs to be a way to make this plastic from cellulose in plant cell walls rather than from sugarcane alone. As the petrochemical industry supplies become scarce the price of PHB will go down, which is good for future use. Links Used: http://sundoc. bibliothek. uni-halle. de/diss-online/02/02H017/t2. pdf http://en. wikipedia. org/wiki/Poly-3-hydroxybutyrate http://en. wikipedia. org/wiki/Biopolymer http://www. gotessays. com/essays/543/index. php http://umpir. ump. edu. my/696/1/Aimi_Salma_Awalludin. pdf
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