Crystallisation and fractionation of selected polyhydroxyalkanoates produced from mixed cultures

Laycock, Bronwyn; Arcos-Hernández, Mónica V.; Langford, Alexandra; Pratt, Steven; Werker, Alan; Halley, P. J.; Lant, Paul

doi:10.1016/j.nbt.2013.05.005

Cited by 50 publications

(76 citation statements)

References 48 publications

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“…However, sample SYNTH 100% showed the highest T m 's. Laycock et al . reported that the T m 's of aged samples remained virtually the same, independent of the block copolymer or random copolymer structure and the HV content.…”

Section: Discussionsupporting

confidence: 87%

“…The T g 's reported in Table for the purified samples did not show the expected decrease with increasing HV content because the T g of sample CW 100% was between the T g 's measured for samples CW 100% and SYNTH 100%. The same remark holds true for T g 1 and T g 2 .…”

Section: Discussionmentioning

confidence: 73%

“…Note, however, that two T g 's were measured during the second heating of the MMC PHBVs produced with the pulse‐feed method, in contrast to the single T g 2 found for sample SYNTH 100%. The presence of two glass transitions was reminiscent of the nanoscopic phase separation in block copolymers of MMC PHBVs . We could not exclude any effect of the molecular mass of the HV or HB blocks on the glass transitions of the corresponding blocks.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, the copolymer structure of the MMC PHBVs and inherent thermal properties seemed to be very sensitive to the production and recovery methods. Similarly, it has been shown that the temperature of crystallization increased with the HV content and that at constant HV contents, a random copolymer structure gave a higher T c . The data in Table suggest the opposite.…”

Section: Discussionmentioning

confidence: 99%

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Impact of fermentation residues on the thermal, structural, and rheological properties of polyhydroxy(butyrate‐co‐valerate) produced from cheese whey and olive oil mill wastewater

Hilliou

Machado

Oliveira

et al. 2015

J of Applied Polymer Sci

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On the use of tris(nonylphenyl) phosphite as a chain extender in melt-blended poly(hydroxybutyrate-co-hydroxyvalerate)/ clay nanocomposites: Morphology, thermal stability, and mechanical properties Interaction and quantification of thymol in active PLA-based materials containing natural fibers I. S. M. A. Tawakkal, M.ABSTRACT: The effects of recovered residues on the characteristics of polyhydroxy(butyrate-co-valerate) (PHBV) produced from mixed microbial cultures (MMCs) fed with cheese whey, olive oil mill wastewater, or a synthetic mixture of acetic and propionic acid were investigated. The different types of MMC PHBVs were extracted and purified with different downstream routes; this enabled the recovery of polymers with different hydroxyvalerate contents and different residue types and levels, ranging from 0 to 11%. The results indicate overall that the recovery of residues together with the biopolymer brought benefits to the melt processability of these MMC PHBVs. Impurities triggered thermal degradation at smaller temperatures, promoted melting at lower temperatures, acted as thermal stabilizers, improved the melt viscosity, and enhanced the shear thinning. The degree of crystallinity of the aged samples was not affected by the impurities, but the crystallites size increased. MMC PHBVs recovered with residues containing more proteins showed better thermal stability, whereas MMC PHBVs containing more inorganic residues showed better melt viscoelastic properties. The results of this study show that impurities recovered together with the MMC PHBVs introduced changes to their thermal, semicrystalline, and rheological properties; these changes, in some cases, were detrimental, but they were also potentially advantageous to the processing and conversion of these materials into products such as packages.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Impact of fermentation residues on the thermal, structural, and rheological properties of polyhydroxy(butyrate‐co‐valerate) produced from cheese whey and olive oil mill wastewater

Hilliou

Machado

Oliveira

et al. 2015

J of Applied Polymer Sci

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“…For these reasons, it is necessary to monitor periodically the population in order to identify the different groups of microorganisms and relate them with the storage capacity and kinetics of the MMC. Extensive studies have been done on the process engineering to understand the impact of the different SBR-operating conditions on PHA production rates, yields, and final composition (Dionisi et al 2007;Serafim et al 2008b;Villano et al 2010a;Moralejo-Gárate et al 2013;Laycock et al 2014;MontanoHerrera et al 2014;Valentino et al 2014). However, ecological understanding has been consigned to a second plan hindering the development of strategies that cover high selective pressure and high biomass production rate (Reis et al 2011;Albuquerque et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Unveiling PHA-storing populations using molecular methods

Queirós

Lemos

Rossetti

et al. 2015

Appl Microbiol Biotechnol

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Enrichment of mixed microbial cultures (MMCs) in polyhydroxyalkanoate (PHA)-storing microorganisms must take place to develop a successful PHA production process. Moreover, throughout the operational period of a MMC system, the population needs to be checked in order to understand the changes in the performance that eventually occurred. For these reasons, it is necessary to monitor the population evolution, in order to identify the different groups of microorganisms and relate them with the storage capacity and kinetics of the MMC. Regarding this particular process, several culture-independent molecular techniques were already applied, with the use of hybridization techniques such fluorescence in situ hybridization and also PCR-based methods like denaturing gradient gel electrophoresis, terminal restriction fragment length polymorphism, pyrosequencing, and quantitative PCR standing out. This review intends, thus, to look at the molecular methods currently applied in monitoring the PHA-storing population evolution and how they can be combined with the evolutionary engineering step in order to optimize the overall process.

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Thermal properties and crystallization behavior of fractionated blocky and random polyhydroxyalkanoate copolymers from mixed microbial cultures

Laycock

Arcos-Hernández²,

Langford

et al. 2014

J of Applied Polymer Sci

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This study represents the first detailed analysis of the thermal, morphological, and crystallization properties of the blend components within a range of mixed-culture polyhydroxyalkanoates (PHAs), with 3-hydroxyvalerate content in the as-produced materials and in the fractions ranging from low (12 mol %) to high (91 mol %). Both coarse and fine fractionation of the asproduced copolymers confirmed that they were blends of nominally blocky and/or random copolymers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), with very broad compositional distributions as governed by the PHA accumulation strategy. The crystallization kinetics and thermal properties of the fractions were found to be very significantly different from each other, consistent with the hypothesis that the overall mechanical properties were primarily controlled by the more rapidly crystallizing components. Two materials produced using an alternating feeding strategy demonstrated unique crystallization and thermal properties in their fractions, which are considered to have contributed to distinctly more elastic mechanical properties in these particular samples. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40836.

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Crystallisation and fractionation of selected polyhydroxyalkanoates produced from mixed cultures

Cited by 50 publications

References 48 publications

Impact of fermentation residues on the thermal, structural, and rheological properties of polyhydroxy(butyrate‐co‐valerate) produced from cheese whey and olive oil mill wastewater

Impact of fermentation residues on the thermal, structural, and rheological properties of polyhydroxy(butyrate‐co‐valerate) produced from cheese whey and olive oil mill wastewater

Unveiling PHA-storing populations using molecular methods

Thermal properties and crystallization behavior of fractionated blocky and random polyhydroxyalkanoate copolymers from mixed microbial cultures

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