Polyhydroxyalkanoates types

These environmentally degradable polyolefins, because of their cost/ performance profiles are very competitive for the growing markets for such plastics. They will be strong competition for the polyester types such as poly(lactic acid) and polyhydroxyalkanoates so frequently publicized as the innovative solution to plastic waste management. 

An additional advantage of the polyhydroxyalkanoates is that the polymers can be produced by fermentation. Certain types of bacteria produce PHAs for energy storage when they are grown in glucose solution in the absence of specific nutrients. The polymer forms as discrete granules within the bacterial cell, and it is then removed by extraction to give a white powder that can be melted and modified into a variety of different products. 

Special types of purpose-built polymers can also be made with the intention of enabling more rapid direct microbiological attack and decomposition of these materials. Classes of both condensation and addition polymers among the polyesters, vinylic polymers, and polyhydroxyalkanoates typify current candidate materials being tested in these applications (e.g., Eq. 23.9), but as yet high costs have discouraged large scale exploitation. 

Qi, Q., Steinbtichel, A., and Rehm, B.H.A. (2000) In vitro synthesis of poly(3 -hydroxydecanoate) purification of type II polyhydroxyalkanoate synthases PhaCl and PhaC2 from Pseudomonas aeruginosa and development of an enzyme assay. Appl. Microbiol. Biotechnol., 54, 37-43. 

The Poly-3-hydroxybutyrate (P3HB) form of PHB [54, 55, 4, 56, 57] is probably the most common type of polyhydroxyalkanoate which is isolated from Azotobacter chroococcum. Pseudomonas putida. Pseudomonas oleovorans, Alcaligenes eutrophus, Zoogloea ramigera, and Alcaligenes sp. A-04 [ 58, 59, 55,60, 61,62,56]. 

Abstract Many types of fermentation feedstock have been studied for the production of polyhydroxyalkanoate (PHA). Several industrial-scale processes have been developed for PHA production from sugars. Sugars are attractive feedstock because of their abundant supply worldwide, market stability, and also because the metabolism of PHA from sugars is very well understood. Recently, plant oils have been gaining much interest as a potential feedstock for PHA production. Industrial-scale processes for the production of PHA from plant oils are currently being developed. This chapter looks at the challenges in using plant oils, especially pahn oil as feedstock for PHA production. 

Polyhydroxyalkanoates (PHAs) are very interesting polyesters synthesized by many types of bacteria. Numerous researchers from all over the world have carried out various smdies on PHAs. There is already a wealth of knowledge about all aspects of PHAs in the literatures. 

Polyhydroxybutyrate [PHB] is the most common type of polymer that falls in the category of polyhydroxyalkanoates. PHAs are generally classified into short-chain-length PHA (sCL-PHA) and medium-chain-length PHA (mCL-PHA) by the different number of carbons in their repeating units. 

Abstract The present chapter deals with a brief account on various types of natural polymers such as cellulose, chitin, starch, soy protein, casein, hemicellu-loses, alginates, polylactic acid and polyhydroxyalkanoates etc. Blends, composites and nanocomposites based on these polymers have been very briefly discussed. Finally the applications, new challenges and opportunities of these biomaterials are also discussed. 

Polyhydroxyalkanoates (PHAs) are polyesters formed by many prokaryotic micro-organisms-when unbalanced nutritional conditions are chosen for die (Hoducing cells Up to more than 90% of the cell dry weight can be accounted for as polymer. Besides the homopolyester poly-R-3-hydroxybutanoate, consisting of 3-hydroxybutanoate (3HB) only, two main types of copolyesters can be formed by different microorganisms. The first type of PHAs always contains C3 units in the polymer backbone, but the... 

Han, X., Satoh, Y., Satoh, T. et al. (2011) Chemo-enzymatic synthesis of polyhydroxyalkanoate (PHA)incorporating 2-hydroxybutyrate by wild-type class I PHA synthase from Ralstonia eutropha. Applied Microbiology ami Biotechrwlogy, 92, 509-517. 

In addition to bio-based polyesters such as poly(lactic acid) (PLA), polyhydroxyalkanoates (PHAs), and poly(ethylene furanoate) (PEE), all based upon biomass-derived building blocks that have a structure different from today s commercial petrochemical-based polyesters, biobased polyesters can be developed having an identical structure to well-known petrochemical based polyesters. A very important class of such drop-in type bio-based polyesters are represented by polyesters based upon either isophthalic acid or terephthalic acid, such as PET,... 

Polyhydroxyalkanoate(s) (PHA) are a group of polymers made up of a broad range of monomers. The variety of monomers and the percentage composition inflnence the material properties, contributing to the development of different applications. This highlights the importance of determining and quantifying the types and composition of the monomers. 

Fig. 1 General structure and three types of polyhydroxyalkanoates (PHAs), including short-chain-length (SCL) PHAs, medium-chain-length (MCL) PHAs, and SCL-MCL PHAs. Their characteristics are also summarized...

Fig. 2 Chemical structure of different types of usual (a) and unusual (b) polyhydroxyalkanoates (PHAs)...

Polyhydroxyalkanoates (PHAs) represent an important group of biodegradable plastics. They are produced by various bacteria in many grades, differing in composition, molecular weight and other parameters [1, 2]. The formation of a particular material, either homo or copolymra depends on the type of bacteria, but even more important are the conditions of polymer formation, mainly the substrate used for feeding the bacteria and the conditions of their growth. 

The four major types of biopolymer are frequently encountered in nature as closely linked units of considerable complexity, held together by covalent and other forces. These associated units are known as lipoproteins, glycoproteins, proteoglycans, glycolipids, nucleoproteins, and so on (Figure 10.1). Minor classes of biopolymers include (1) polyoxo esters, (2) polyhydroxyalkanoic esters, (3) polyisoprenoids, and (4) polyphenols. Some of these are referred to in Sections 10.1 and 10.3. 

In the present chapter, rayon and other man-made cellulose fibers wUl be introduced in terms of properties and stracture. The compounding method to obtain the composites will be described briefly. PP-rayon composites will be considered in more detail as the practically most relevant class of this type of material at present arousing interest from the automotive industry. In another section rayon composites with poly(lactic acid) (PLA) and polyhydroxyalkanoates (PHA) will be studied as a promising bio-based and biodegradable alternative to conventional materials in durable applications, transport, and automotive industry. Finally, some concluding remarks will be given concerning future prospects of rayon reinforced thermoplastics and the problems to be tackled in future work. 

Namral polyhydroxyalkanoates are typically produced by different types of microorganisms as an energy storage product. Different approaches have been developed... 

Ester bonds in polyester soft segments, such as poly(caprolactone) (PCL), jx)ly(lactide) (PLA), poly(glycolide) (PGA), their copolymers, and polyhydroxyalkanoates (PHAs) Carbonate bonds in polycarbonate soft segments Hydrolysis it can be catalysed by enzymes Degradation rate depends on the soft segment type e.g. the presence of poly(ethylene glycol) (PEG) units increases the hydrolysis rate... 

Figure 16.3 Global bioplastic packaging market by product type, 2010(%). AAC, aliphatic and aromatic copolyesters PLA, polylactic acid PHA, polyhydroxyalkanoate WSP, water-soluble polymers.

Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible polyesters with versatile structural compositions. Bacterial PHAs are produced using a combination of renewable feedstock and biological methods mostly via a fermentation process. Native and recombinant microorganisms have been generally used to produce different types of PHAs, such as homo-polymers and copolymers of diverse morphology. Alternative production schemes of PHAs in vitro based on cell-free enzymatic catalysis are gaining momentum and may become the preferred route to some specialty products. ... 

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