Possible Applications of PHAS

Early investigations of PHA granules by electron microscopy after freeze-etching showed that the polymer in the granule underwent a cold drawing process indicating the plastic nature of polyester and suggesting that it can be processed as a conventional thermoplastic. In addition to its potential as plastic material PHA is useful source of stereoregular compounds which can serve as chiral precursors for the chemical synthesis of optical ly active compounds, particularly in synthesis of some drugs or insect pheromones. These substances are biologically active only in the correct stereochemical configeration.

PHAs can be easily depolymerised to a rich source of optically pure bifunctional hydroxy acids. PHB, for example can be readily hydrolysed to R-3-hydroxybutyric acid and is used in the synthesis of Merck's anti-glaucoma drug Truspot. Along with R-1,3-butanediol, it is also used to synthesise-lactams. PHBV received European approval for food contact use in 1996. This opens opportunities in food service and packaging industry. Plant-derived PHAs may in future be depolymerised and used for bulk chemical manufacture. Western Europe, for example produces several million tonnes of butanols , half of which are used directly, or following esterification, as solvents. Besides replacing existing solvents -hydroxy acid esters and related derivatives are likely to find growing use as green solvents similar to lactic acid esters.-hydroxy acids a re more resistant to hydrolysis and are therefore better suited to certain applications. Hydroxy acids may also be converted into crotonic acids, 1,3-butanediol, lactones etc. all of which have existing markets of thousands of tonnes.

PHB,

• is 100% biodegradable,
• can be processed like thermoplastic and
• is 100% water resistant, so that it could be used for similar applications as conventional commodity plastics.

Practical Applications of PHA -

• Packaging films (for food packages), bags, containers, paper coatings.
• Biodegradable carrier for long term dosage of drugs, medicines, insecticides, herbicides, insecticides or fertilizers.
• Disposable items such as razors, utensils, diapers, feminine hygiene products, cosmetics containers, shampoo bottles, cups etc.
• Starting material for chiral compounds.
• Medical applications - Surgical pins, sutures, staples, swabs, wound dressings, bone replacements & plates and blood vessel replacements, Stimulation of bone growth by piezoelectric properties.

Industrial production of PHAs and other biodegradable plastics -

No.	Company	Areas of interest
(1)	Berlin Packaging Corp. (USA)	Marketing
(2)	Bioscience Ltd. (Finland)	Medical applications
(3)	Bio Ventures Alberta Inc. (Canada)	Production in recombinant E.coli
(4)	Metabolix Inc. (USA)	Production in transgenic plants
(5)	Monsanto (USA)
(6)	Polyferm Inc. (Canada)	Production from cheap substrates
(7)	ZENECA Bio-Products (UK) (former ICI, UK)	Production by A.eutrophus
(8)	ZENECA Seeds (UK)	Production in transgenic plants
(9)	Petrochemia Danubia (PCD)	Production using A.lactus

It was shown that PBH-HV, 1 mm molding was completely degraded after 6, 75, 350 weeks in anaerobic sewage, soil & sea water respectively.