Poly-3-hydroxybutyrate limitations

There are a limited number of oligomers that have been used in biodegradable PU soft segments. They are PLA, PGA, poly(hydroxybutyrate), poly(ethylene glycerol)... 

In Europe, interest has centered particularly on polyhydroxybutyr ate, which can be made into films for packaging as well as into molded items. The polymer degrades within 4 weeks in landfills, both by ester hydrolysis and by an elimination reaction of the oxygen atom (i to the carbonyl group. This elimination is similar to what occurs during the dehydration step in an aldol reaction (Section 23.4). The use of poly-hydroxybutyrate is limited at present, however, by its cost—about four times as much as polypropylene. 

Comeau et al. [46] have described a simple assay for separating and quantifying poly-beta-hydroxybutyrate and poly-beta-hydroxyvalerate in activated sludge samples involved sludge lyophilization, purification of the chloroform extract by re-extraction with water, and capillary gas liquid chromatography. The detection limit, estimated by using hydroxybutyric acid standards, was approximately lOug per litre. 

To perform the complete set of chemical analyses for macromolecular compounds is generally too labour intensive for routine process monitoring. Following the concentrations of selected compounds can, however, give interesting insights for example, Bley et al. [23] found that a phosphate - limited population differentiated into two sub-populations of different DNA - and PHB (poly-3-hydroxybutyrate) - content. The cell-cycle of baker s yeast could be followed by a fluorimetric dye reaction for DNA content in a sample stream from the bioreactor [24]. 

Ryu, H. W., Hahn, S. K., Chang, Y. K., and Chang, H. N. 1997. Production of poly(3-hydroxybutyrate) by high cell density fed-batch culture of Alcaligenes eutrophus with phosphate limitation. Biotech. Bioeng., 55, 28-32. 

Wang, F., and Lee, S. Y. 1997. Poly(3-hydroxybutyrate) production with high productivity and high polymer content by a fed-batch culture of Alcaligenes latus under nitrogen limitation. Appl. Env. Microbiol., 63, 3703-3706. 

Bacteria occasionally contain inclusion granules within their cytoplasm. These consist of storage material composed of carbon, nitrogen, sulphur or phosphorus and are formed when these materials are replete in the environment to act as repositories of these nutrients when limitations occur. Examples include poly-p-hydroxybutyrate, glycogen and polyphosphate. 

Biodegradable Polymers Properties, Possibilities, and Limits Considering the Synthesis, Processing, and Application of Poly(2-Hydroxypropionic Acid) and Poly(3-Hydroxybutyric Acid)... 

Kose GT, Kenar H, Hasirci N, Hasirci V (2003) Macroporous poly(3-hydroxybutyrate-co-3-hy-droxyvalerate) matrices for bone tissue engineering. Biomateiials 24 1949-1958 Kourmentza C, Ntaikou I, Kornaros M, Lyberatos G (2009) Production of PHAs from mixed and pure cultures of Pseudomonas sp. using short-chain fatty acids as carbon source under nitrogen limitation. Desalination 248 723-732... 

Ryu HW, Cho KS, Kim BS, Chang YK, Chang HN, Shim HJ (1999) Mass production of poly(3-hydroxybutyrate) by fed-batch cultures of Ralstonia eutropha with nitrogen and phosphate limitation. J Microbiol Biotechnol 9 751-756... 

Poly[3-hydroxybutyrate] was the first PHA to be produced on an industrial scale, but its brittle nature, its poor mechanical properties and its high production cost limited its application potential. In the early 1990s, Imperial Chemical Industries [ICI] started the production of poly[3-hydroxybutyrate-co-3-hydroxyvalerate] [P3HB3HV] under the trade name Biopol . This material showed lower degrees of crystallinity and superior mechanical properties. Later on, the production of Biopol was continued by Monsanto and subsequently followed up by Metabolix. PHAs were originally intended as bio-based alternatives for polyolefins used in plastic containers, films and bottles. Despite the large interest in PHAs, their application remains, however, limited due to their narrow processing window [84, 85]. 

Shang, L., Jiang, M., Chang, H. Poly(3-hydroxybutyrate) synthesis in fed-batch culture of Ralstonia eutropha with phosphate limitation under different glucose concentrations. Biotechnol. Lett. 25, 1415-1419 (2003)... 

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