Polyhydroxybutyrate properties

Table 31.3 Some selected properties of polyhydroxybutyrate-valerate copolymers (Biopol—Zeneca)...

Aliphatic polyesters based on monomers other than a-hydroxyalkanoic acids have also been developed and evaluated as drug delivery matrices. These include the polyhydroxybutyrate and polyhydroxy valerate homo- and copolymers developed by Imperial Chemical Industries (ICI) from a fermentation process and the polycaprolactones extensively studied by Pitt and Schindler (14,15). The homopolymers in these series of aliphatic polyesters are hydrophobic and crystalline in structure. Because of these properties, these polyesters normally have long degradation times in vivo of 1-2 years. However, the use of copolymers and in the case of polycaprolactone even polymer blends have led to materials with useful degradation times as a result of changes in the crystallinity and hydrophobicity of these polymers. An even larger family of polymers based upon hydroxyaliphatic acids has recently been prepared by bacteria fermentation processes, and it is anticipated that some of these materials may be evaluated for drug delivery as soon as they become commercially available. 

No. 16,2003, p.2685-93 PROTEIN ADSORPTION, FIBROBLAST ACTIVITY AND ANTIBACTERIAL PROPERTIES OF POLYHYDROXYBUTYRIC ACID-CO-... 

Specifically, 70-30 parts poly(hydroxy-butyrate-co-hydroxyvalerate) (4 mol% valerate) or polyhydroxybutyrate was mixed with 30-70 parts PCL in an internal mixer at 100° or 160°C in the presence of 0-0.5 parts DCP or DBP radical initiator. Blends were characterized by SEM, mechanical properties, selective solvent extraction, and FTIR. 

In the presence of limited nutrients, bacteria can be induced to make polyhydroxybutyrates and valerates, which are processed into a copolymer known as BiopoP. BiopoP has properties similar to polypropylene, but it is biodegradable and obtained from nonpetroleum sources. 

Polyhydroxybutyrate (PHB) is a polyhdroxyalkmioate polymer with pl tic-like properties that is synthesized by some soil bacteria (e.g. Alcaligenes eutrophus). The genes for the pathway have been cloned and inserted into plants with successful production of PHB. Additional research is required to optimize the properties the butyrate-valerate copolymer has superior functionality but it remains more difficult to express this material in plants compared to the pure polymer (75). Improved expression levels and localization would also assist in separations and in the economic cost to produce this renewable biodegradable plastic. 

Hezayen FF, Steinbiichel A, Rehm BH (2002) Biochemical and enzymological properties of the polyhydroxybutyrate synthase from the extremely halophiUc archaeon strain 56. Arch Biochem Biophys 403 284-291... 

Noda I, Green PR, Satkowski MM, Schechtman LA (2005) Preparation and properties of a novel class of polyhydroxyalkanoate copolymers. Biomacromolecules 6 580-586 Omidvar V, Akmar ASN, Marziah M, Maheran AA (2008) A transient assay to evaluate the expression of polyhydroxybutyrate genes regulated by oil palm mesocarp-spedfic promoter. Plant Cell Rep 27 1451-1459... 

Gordeyev SA, Nekrasov YPJ (1999) Processing and mechanical properties of oriented poly(beta-hyioxybutyrate) fibers. Mater Sd Lett 18 1691-1692 Hisano T, Kasuya K, Tezuka Y, Ishii N, Kobayashi T, Shiraki M, Oroudjev M, Hansma H, Iwata T, Doi Y, Saito T, Mild K (2006) The crystal structure of polyhydroxybutyrate depolymerase from Penicilliumjuniculosum provides insights into the recognition and degradation of biopolyesters. J Mol Biol 356 993-1004... 

Polyhydroxyalkanoates, Polyhydroxybutyrate, History, Bacterial synthesis. Chemical synthesis. Genetic engineering. Mechanical properties. Thermal transitions. Crystallization, Plasticizers, Thermal degradation. Processing, Applications... 

As a polymeric matrix in work used polyhydroxybutyrate (PHB) bio decomposed polymer. Thanking these properties PHB it is applied as packing, to the biomedical appointment, self-resolving fibers and films, etc. 

PolyhydroxyaUcanoates (PHAs) are the biopolymers possessing the material properties ranging from rigid and highly crystalline to flexible, amorphous, and elastomeric. Because of such properties and inherent biodegradability, PHAs have attracted the world-wide attention of scientists and researchers as environment-friendly alternative to the conventional petroleum-based polymers. Polyhydroxybutyrate (PHB) and polyhydroxyoctanoate (PHO) have been found to possess biocompatibility in mammalian systems. Such biomaterials have got great potential as medical implantation devices [78-81]. 

One of the early truly biodegradable polymers was polyhydroxybu-tyrate/valerate (PHBV). This is a member of the polyester family which is produced by certain types of bacteria when they have a diet which is carbon-rich but poor in some essential nutrient. Under these conditions, they produce polyhydroxybutyrate (PHB) as a food store to be called upon when carbon sources are less available. With manipulation of the diet, the bacteria can be induced to form a copolymer, PHBV, which has more useful properties than PHB. 

Polyhydroxybutyrate. Copolymers of hydroxybutyrate and hydroxyvaler-ate possess many mechanical properties in common with synthetic polyolefins, and so have attracted much attention as replacements for these materials in environments where biodegradability is an important parameter (see Poly(3-HYDROXYALKANOATES)). Carswell-Pomerantz and co-workers (217,218) have reported a detailed study of the radicals formed on irradiation of such materials. They found that the yield of radicals at 77 K was G(R) = 1.7 0.2, independent of copolymer composition, but that on irradiation at 300 K, the yield of radicals was reduced for the copol5mers because of their lower glass-transition temperatures compared with the homopolymer. At low temperatures a significant contribution to the ESR spectra from radical anions was noted. These radicals were observed to decay on warming to produce scission radicals. At still higher temperatures, radicals produced by abstraction of a methylene proton adjacent to the carbonyl group were detected. 

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