Some structural and mechanical properties of bacterially produced poly-?-hydroxybutyrate-co-?-hydroxyvalerate

Bauer, H. J.; Owen, A. J.

doi:10.1007/bf01452586

Cited by 84 publications

(37 citation statements)

References 6 publications

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“…(PHB) and copolymers poly(3-hydroxybutyrate-When propionic acid is added to the growth medium co-3-hydroxyvalerate) (PHB/HV). [2][3][4][5][6][7][8][9][10][11] Although during conditions of nitrogen limitation, the poly-PHAs are biodegradable-microorganisms are mer produced is PHB/HV copolymer. Bacterially able to rapidly degrade PHB and PHB/HV to carproduced PHB/HV copolymers have been demonstrated to be randomly sequenced.…”

Section: Introductionmentioning

confidence: 99%

Crystallization of poly(hydroxybutrate-co-hydroxyvalerate) in wood fiber-reinforced composites

Reinsch

Kelley

1997

J. Appl. Polym. Sci.

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Wood fiber-reinforced composites were prepared from poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHB/HV) copolymers containing 9 and 24% valerate. The effects of fibers on crystallization were investigated. Thermomechanical pulp, bleached Kraft fibers, and microcrystalline cellulose filler were used as the reinforcing phase. The crystallization of PHB/HV in composite materials was examined using Modulated Differential Scanning Calorimetry (MDSC) and hotstage microscopy. Hot-stage microscopy showed that polymer crystallites are nucleated on the fiber surface and that the density of nuclei was greater in fiber-reinforced composites than in unfilled material. Dynamic crystallization experiments showed that bleached Kraft, thermomechanical pulp, and microcrystalline cellulose increased the crystallization rate of PHB and PHB/HV both from the glass and melt. However, ultimate crystallinity determined from the heat of crystallization was the same in unreinforced and reinforced materials. The kinetics of PHB/HV crystallization were examined using nonisothermal Avrami-type analysis. Unreinforced and Kraft-reinforced PHB were characterized and compared with unreinforced PHB/9%HV. The Avrami exponent of crystallization, related to nucleation mechanism and growth morphology, is 2.0 for unreinforced PHB, 2.8 for kraft-reinforced PHB, and 3.0 for unreinforced PHB/9%HV.

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Section: Introductionmentioning

confidence: 99%

Crystallization of poly(hydroxybutrate-co-hydroxyvalerate) in wood fiber-reinforced composites

Reinsch

Kelley

1997

J. Appl. Polym. Sci.

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“…The PHA accumulated by H. mediterranei was reported to be poly(3-hydroxybutyrate) (PHB) originally (8,23) but has been reevaluated as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) recently (5,17). PHBV has much better mechanical properties than PHB and hence is more promising for commercial production and application (1,19). Unlike PHBV production in bacteria, where costly and cellular toxic carbons, such as propionic acid or valeric acid, would be provided as the precursors of the 3-hydroxyvalerate (3HV) unit (36), H. mediterranei can accumulate PHBV up to ϳ60% (wt/wt) from starch, glucose, or other cheaper carbon sources, including industrial by-products (17,23).…”

mentioning

confidence: 99%

Genetic and Biochemical Characterization of the Poly(3-Hydroxybutyrate- co -3-Hydroxyvalerate) Synthase in Haloferax mediterranei

et al. 2008

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The haloarchaeon Haloferax mediterranei has shown promise for the economical production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a desirable bioplastic. However, little is known at present about the genes involved in PHBV synthesis in the domain Archaea. In this study, we cloned the gene cluster (phaEC Hme ) encoding a polyhydroxyalkanoate (PHA) synthase in H. mediterranei CGMCC 1.2087 via thermal asymmetric interlaced PCR. Western blotting revealed that the phaE Hme and phaC Hme genes were constitutively expressed, and both the PhaE Hme and PhaC Hme proteins were strongly bound to the PHBV granules. Interestingly, CGMCC 1.2087 could synthesize PHBV in either nutrient-limited medium (supplemented with 1% starch) or nutrient-rich medium, up to 24 or 18% (wt/wt) in shaking flasks. Knockout of the phaEC Hme genes in CGMCC 1.2087 led to a complete loss of PHBV synthesis, and only complementation with the phaEC Hme genes together (but not either one alone) could restore to this mutant the capability for PHBV accumulation. The known haloarchaeal PhaC subunits are much longer at their C termini than their bacterial counterparts, and the C-terminal extension of PhaC Hme was proven to be indispensable for its function in vivo. Moreover, the mixture of purified PhaE Hme /PhaC Hme (1:1) showed significant activity of PHA synthase in vitro. Taken together, our results indicated that a novel member of the class III PHA synthases, composed of PhaC Hme and PhaE Hme , accounted for the PHBV synthesis in H. mediterranei.

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“…However, when the crystallized sample is cooled fast (above 80°C/min), the circle lines could not form. Some previous research works [29][30][31][32] also found the homocentric lines in different polymer spherulites; they believe that these lines are cracks, but there are no detailed characterizations of these cracks. We will study these lines in next part in detail.…”

Section: Effect Of the Film Thickness On Spherulitesmentioning

confidence: 90%

“…(2) No cracks will form in pure PTT with any film thickness. PTT is different to PLLA although similar cracks are also widely reported in poly(L-lactic acid) (PLLA) with no fibers or other polymers [29][30][31][32]. The film strength and the constriction difference of these polymers are all different to PTT.…”

Section: Surface Topography Of the Composite's Spherulitesmentioning

confidence: 92%

Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)

Run

Song

Hao

2009

Front. Chem. Eng. China

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The spherulites of the short carbon fiber(SCF)/ poly (trimethylene terephthalate) (PTT) composites formed in limited space at designed temperatures, and their melting behaviors were studied by the polarized optical microscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. The results suggest that SCF content, isothermal crystallization temperatures, and the film thicknesses influence the crystal morphology of the composites. The dimension of the spherulites is decreased with increasing SCF content, but whether banded or nonbanded spherulites will form in the composites is not dependent on SCF content. However, the crystal morphology of the composites depends strongly on the temperature. When the isothermal crystallization temperatures increase from 180°C to 230°C, the crystal morphology of SCF/PTT composites continuously changes in the following order: nonbanded ! banded ! nonbanded spherulites. Discontinuous circle lines form in the film when the film thickness increases from 30 to 60 μm. Basing on the SEM observation, it is found that these circle lines are cracks formed due to the constriction difference of the different parts of the spherulites. These cracks are formed when the film is cooled from the isothermal crystallization temperature to the room temperature at a slow cooling rate; while they will disappear gradually at different temperatures in the heating process. The crack will appear/disappear first around the center of the spherulite when the film was cooled/heated. The nontwisted or slightly twisted lamellas will reorganize to form highly twisted lamellas inducing apparent banded texture of the spherulites.

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Some structural and mechanical properties of bacterially produced poly-?-hydroxybutyrate-co-?-hydroxyvalerate

Cited by 84 publications

References 6 publications

Crystallization of poly(hydroxybutrate-co-hydroxyvalerate) in wood fiber-reinforced composites

Crystallization of poly(hydroxybutrate-co-hydroxyvalerate) in wood fiber-reinforced composites

Genetic and Biochemical Characterization of the Poly(3-Hydroxybutyrate- co -3-Hydroxyvalerate) Synthase in Haloferax mediterranei

Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)

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