Bacterial polyesters poly

Poly(3-hydroxybutyrate) (1.8) is a bacterial polyester that behaves as an acceptable thermoplastic, yet can be produced from renewable agricultural feedstocks and is biodegradable. It is typically produced not in the pure state. 

Keywords. Bacterial polyester, Medium-chain-length poly(3-hydroxyalkanoates), Pseudomonas oleovorans, Pseudomonas putida, Functional poly(3-hydroxyalkanoates), Short-chain-length poly(3-hydroxyalkanoates)... 

The copolymer poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-co-PHV) produced by A eutrophus has generated more interest than poly-(R)-3-hydroxybutyrate (PHB) homopolymer. Since these bacterial polyesters are biodegradable thermoplastics, their mechanical and physical properties have received much attention. PHB is a relatively stiff and brittle material because of its high crystallinity. However, the physiochemi-cal and mechanical properties of [P(HB-HV)] vary widely and depend on the molar percentage of 3-hydroxyvalerate (HV) in the copolymer (4,5) as shown inTable 1. Propionic acid is converted by a synthetase to propionyl-CoA, and the biosynthetic P-ketothiolase catalyzes the condensation of propionyl-CoA with acetyl-CoA to 3-ketovaleryl-CoA by the acetoacetyl-CoA reductase. The hydroxyvaleryl moiety is finally covalently linked to the polyester by the PHA synthase (6). 

Poly(3-hydroxybutyrate) (1.8) is a bacterial polyester that behaves as an acceptable thermoplastic, yet can be prodticed from renewable agricultural feedstocks and is biodegradable. It is tyjiically produced not in the pure state, but formed alongside minor amounts of poly(3-hydroxyv alerate). The ratio of these two polymers in a given sample is determined by the ratio of glucose and propionic acid in the medium in which the bacteria live and carry out their metabolic processes. 

Bacterial polyesters (polyhydroxy alkanoates) Poly(3-hydroxy butyrate), poly(3-hydroxy valerate) Some micro-organisms, especially bacteria, can synthesise biocompatible aliphatic polyesters, which have potential in medical applications. 

Ewering C, Lutke-Eversloh T, Luftmann H, Steinbuchel A (2002) Identification of novel sulfur-containing bacterial polyesters Biosynthesis of poly(3-hydroxy-S-propyl-w-thioalkanoates) containing thioether linkages in the side chains. Microbiol Mol Biol Rev 148 1397-1406... 

Several types of bacterial polyesters that are produced by biosynthesis are poly-3-hydroxybutyrate, poly-4-hydroxybutyrate, poly-3-hydroxyvalerate, poly-3-hydroxyhexanoate, poly-3-hydroxy-heptanoate, etc., and their respective copolymer combinations. Due to their ability to degrade naturally in variety of environments, they will find a lot of applications in disposal items, short-term packaging, and also considered biocompatible in contact with living tissues and can be used for biomedical applications (e.g., drug encapsulation, tissue engineering) (Chauhan, 2012). 

Besides the common polyhydroxybutyrate (PHB), other polymers of this class are produced by a variety of organisms such as poly-4-hydroxybutyrate, PHV, and polyhy-droxyhexanoate. PHV is a naturally occurring bacterial polyester, which was first isolated by Wallen and coworkers [172,173]. Also, PHV/PHB copolymers have been studied to make a wide range of thermally processable polyesters, which exhibit the necessary long-term degradation profile required for a degradable fracture fixation device [174]. 

Fritsche, K., Lenz, R.W., and Fuller, R.C., 1990, Bacterial polyesters containing branched poly(p-hydroxyalkanoate) units. Int.J.Biol.Macromol. 12 92... 

As for poly(3-hydroxybutyrate), which is one of the representative bacterial polyesters, monomeric (butenoic) and oligomeric (mainly dimeric and trimeric) acids were reported to be observed in the pyrograms, which should be mostly formed through the six-membered transition state. Due to the presence of a methyl side chain, three types of isomeric structures can be produced for each oligomer, as shown in Figure 5.5. Among these, the trans type of inner olefinic products was usually dominant. 

Lee SY, Chang HN (1994) Effect of complex nitrogen source on the synthesis and accumulation of poly(3-hydroxybutyric acid) by recombinant Escherichia coU in flask and fed-batch cultures. J Environ Polym Degrad 2 169-176 Lee SY (1997) E. coU moves into the plastic age. Nat. Biotechnol 15 17-18 Lee SY, Lee Y, Wang E (1999) Chirtil compounds from bacterial polyesters sugars to plastics to fine chemicals. Biotechnol Bioeng 65 363-368... 

Fritzsche K, Lenz RW, FuUer RC (1990b) Bacterial polyesters containing branched poly()3-hydroxy-aUcanoate) units. Int J Biol Macromol 12 92-101 Fritzsche K, Lenz RW, Fuller RC (1990c) Production of unsaturated polyesters by Pseudomonas oleovorans. Int J Biol Macromol 12 85-91... 

Page WJ, Knosp O (1989) Hyperproduction of poly-P-hydroxybutyrate during exponential growth of Azotobacter vinelandii UWD. Appl Environ Microbiol 55 1334-1339 Park WH, Lenz RW, Goodwin S (1998a) Epoxidation of bacterial polyesters with unsaturated side chains. I. Production and epoxidation of polyesters from 10-undecenoic add. Macromolecules 31 1480-1486... 

Ravenelle F, Marchessault RH (2002) One-step synthesis of amphiphilic diblock copolymers from bacterial poly([/J]-3-hydroxybutyric acid). Biomacromolecules 3 1057-1064 Ravenelle F, Marchessault RH (2003) Self-assembly of poly([R]-3-hydroxybutyric aaA)-block-poly(ethylene glycol) diblock copolymers. Biomacromolecules 4 856-858 Renard E, Langlois V, Guerin P (2007) Chemical modifications of bacterial polyesters from stability to controlled degradation of resulting polymers. Corros Eng Sci Technol 42300-42310... 

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