Poly P-hydroxybutyrate

Poly-P-hydroxybutyrate (PHB) is a biodegradable thermoplastic that is produced by several microorganism. The PHB synthesis has been characterized eutrophus and the operon iavolved ia PHB productioa has beea cloaed. Recombiaant E. coli straias that can produce high levels of... 

Incorporation of C02 into poly-p-hydroxybutyrate by a strain of Xanthomonas sp. that metabolizes propene or its oxide (Small and Ensign 1995 Allen and Ensign 1996)... 

I.H. Lee, J.Y. Park, D.H. Kho, M.S. Kim and J.K. Lee (2002) Reductive effect of H2 uptake and poly-P-hydroxybutyrate formate on nitrogenase-mediated H2 accumulation of Rhodobacter sphaeroides according to light intensity. Appl. Microbiol. Biotechnol. 

PolyCy-benzyl L-glutamate) (PBLG), 15 109 Poly(y-ketosulfide)s, optically active, 23 711 Poly(P-alanine), 1 292 Poly-P-hydroxybutyrate (PHB), 12 482 Polybetaines, 20 479-482 applications of, 20 482 preparation of, 20 480-481 solution properties of, 20 481-482 synthesis of, 20 479-481 Polyborates, 4 256-258 Polyborosiloxanes, in silicon carbide manufacture and processing, 22 533 Polybrominated diphenyl ethers (PBDEs), 13 142-143 20 56... 

Another example where metabolic pathway engineering has made a dramatic impact is in the biodegradable polymer field. One of the most widely studied polymers in this family is poly-P-hydroxybutyrate (PHB) (64). A related member of the poly-P-hydroxyalkanoate (PHA) family commercialized by Imperial Chemical Industries (ICI), which later became Zeneca Bio Products,... 

Figure 2.20 Asymmetric unit of complexes Tb(L )3(H20)2, thermal ellipsoids drawn with 30% probability and hydrogen atoms omitted for clarity [51a], (Reproduced from S. Iju, M.L.P. Reddy, A.H. Cowley and K.V. Vasudevan, 3-Phenyl-4-acyl-5-isoxazolonate complex of Tb + doped into poly-P-hydroxybutyrate matrix as a promising light-conversion molecular device, Journal of Materials Chemistry, 19, 5179-5187, 2009, by permission of the Royal Society of Chemistry.)...

Answers to these questions can be obtained if one performs small angle scattering measurements during isothermal crystallization. Such measurements have been performed on different materials. The results were observed to depend strongly on the material used. So, for example, with increasing crystallization time, the long period increased with polyethylene, it decreased with polyethylene terephthalate and it stayed constant with poly-P-hydroxybutyrate. 

Poly-P-hydroxybutyrate Aliphatic polyesters of 3-hydroxybutyric Prepared by fermentation most pol5miers are... 

Figure 1-3 A cell of a Spirillum negatively stained with phosphotungstic acid. Note the tufts of flagella at the ends, the rough appearance of the outer surface, the dark granules of poly-p-hydroxybutyric acid and the light-colored granules of unknown nature. Courtesy of F. D. Williams, Call E. VanderMolen, and C. F. Amstein.

Polysaccharide Nucleic acid Teichoic acid Poly-P-hydroxybutyrate... 

Storage compounds Poly-p-hydroxybutyrate absent Poly-p-hydroxybutyrate often present... 

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. 

Abbreviations A, acetone ASES, aerosol solvent extraction system DM, dichloromethane DMF, A/,A/-dimethyl-formamide E, ethanol GAS, gas antisolvent process H, hexane HYAFF-11, hyaluronic acid benzylic ester I, isopropanol PAN, polyacrylonitrile PCA, precipitation with compressed antisolvent PCL, polycaprolactone PHB, poly(p-hydroxybutyric acid) PLA, polylactic acid PLGA, poly(lactic-co-glycolic acid) SAS, supercritical antisolvent process SEDS, solution enhanced dispersion by supercritical fluids TFE, 2,2,2-trifluoroethanol Triblock polymer, p poly(L-lactide-CO-D,L-lactide-co-glycolide)(62.5 1 2.5 25). 

AcetylCoA is also involved in the biosynthesis of poly-P-hydroxybutyrate (Fig. 14.4-2, x = 0). Many whole cell systems have been used to synthesize this polymer and other interesting materials in this class 246. For example, copolymers consisting of (J )-3-hydroxybutyl and (R)-3-hydroxyvaleryl units (Fig. 14.4-2, x=0 and 1, respectively) were prepared by feeding propionate to whole cells of A. eutrophus[246l... 

Poly-P-hydroxybutyrate (PHB) crystallizes in a low temperature modification (LTM), which is transformed into a high temperature modification (HTM) when heated above 320 °C. Both modifications exhibit distinct WAXS patterns, thus a quantitative determination of the two fractions is possible. However, measurements at the HTM are only feasible with S.R., since the molecules quickly decompose at the high temperatures. Figure 23 shows the fraction of the HTM during heating the PHB sample from 280 °C to 340 °C at a rate of 2 °C/min and subsequent cooling to 280 °C at the same rate [49], A reversible transformation is observed. But the transition from the LTM to the HTM occurs at a temperature, which lies about 20 °C higher than the transition in the opposite direction. This indicates, that each modification is formed by its own nucleation process. 

The enzymatic hydrolysis of poly-p-hydroxybutyrate, PHB, by several different bacteria, which are known to secrete active esterases, has been studied in some detail by several research groups [7, 8]. As with the polysaccharides, the final products of these degradation reactions are the monomers, dimers and trimers, which are removed by hydrolysis only from hydroxyl-end of the polymer chain, as follows ... 

Poly(p-hydroxybutyrate) occurs naturally as the optically active high-molecular-weight polyester in some bacteria (e.g. Bacterium megaterium) ... 

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