Plasticization of poly(hydroxybutyrate) in vivo

Harrison, Susan T.L.; Chase, Howard A.; Amor, Stuart R.; Bonthrone, Karen M.; Sanders, Jeremy K. M.

doi:10.1016/s0141-8130(05)80020-0

Cited by 52 publications

(17 citation statements)

References 13 publications

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“…Because, in vivo, non-covalently attached phasins as structural proteins stabilizing the PHA granules (30, 141) and inhibiting individual granules from coalescing and agglutinating with other granules (123,145). In addition, water is a minor component of PHA inclusions and therefore it was suggested that water could act as a plasticizer (218,219). About 5-10% of water was estimated to be present in the nascent PHB inclusions which upon removal allows for the polymer chains to rearrange into lamellar crystals (220).…”

Section: Physical Propertiesmentioning

confidence: 99%

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

Muhammadi

Shabina

Afzal

et al. 2015

Green Chemistry Letters and Reviews

270

139

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Polyhydroxyalkanoates (PHAs) are intracellular aliphatic polyesters synthesized as energy reserves, in the form of water-insoluble, nano-sized discrete and optically dense granules in cytoplasm by a diverse bacteria and some archae under conditions of limiting nutrients in the presence of excess carbon source. Bacteria synthesize different PHAs from coenzyme A thioesters of respective hydroxyalkanoic acid, and degrade intracellularly for reuse and extracellularly in natural environments by other microorganisms. In vivo, PHAs exist as amorphous mobile liquid and water-insoluble inclusions but in vitro, exhibit material and mechanical properties, ranging from stiff and brittle crystalline to elastomeric and molding, similar to petrochemical thermoplastics. Further, they are hydrophobic, isotactic, biocompatible and exhibit piezoelectric properties. But as commodity plastics their applications are limited by high production cost, low yield, in vivo degradation, complexity of technology and difficulty of extraction. Therefore, to replace the conventional plastic with PHAs, it is prerequisite to standardize the PHA production systems.

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Section: Physical Propertiesmentioning

confidence: 99%

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

Muhammadi

Shabina

Afzal

et al. 2015

Green Chemistry Letters and Reviews

270

139

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“…More recently, nuclear magnetic resonance studies of whole cells have provided the first evidence that the "granule" is in fact in a mobile, amorphous state in vivo (3,4). Both the presence of plasticizers including water (4,18) or lipid (22) and the kinetics of the crystallization process (6,10) have been proposed to describe how the granules are maintained in the amorphous state inside the cell. Additional studies have concluded that the PHB granules inside the cell are surrounded by a membrane containing the synthase enzyme and that the D-3-hydroxybutyryl-CoA monomers are transported across the membrane in conjunction with polymerization (5,13,24,32).…”

mentioning

confidence: 99%

Immunocytochemical analysis of poly-beta-hydroxybutyrate (PHB) synthase in Alcaligenes eutrophus H16: localization of the synthase enzyme at the surface of PHB granules

et al. 1993

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Antibodies raised against the Alcaligenes eutrophus poly-1-hydroxybutyrate (PHB) synthase polypeptide were used for immunocytochemical localization of the synthase enzyme in whole cells and purified PHB granules. The data presented demonstrate for the first time that the synthase enzyme is located on the surface of the PHB granule rather than being incorporated inside the granule during its formation. From these basic observations and data from the recent literature, a model of granule assembly is proposed.Poly-p-hydroxybutyrate (PHB) accumulates as granular inclusions in the cells of a large number of bacterial species grown under conditions of nutrient limitation (2). In both Zoogloea ramigera (8,9,15,16,25,27,28) and Alcaligenes eutrophus (19,20), the condensation of two acetyl coenzyme A (CoA) units to form acetoacetyl-CoA by the enzyme 3-ketothiolase is followed by a stereospecific reduction step catalyzed by an NADP+-specific acetoacetyl-CoA reductase to form D-3-hydroxybutyryl-CoA, the substrate for PHB synthase. Both the 13-ketothiolase and acetoacetyl-CoA reductase are soluble cytosolic enzymes, whereas the PHB synthase is found attached to the PHB granules.Purified granules contain around 98% PHB by weight, with the remainder being made up of proteins and lipids (17,22). It was previously concluded that the physical state of the polymer inside the granules in vivo was that of a crystalline solid, similar to that of the extracted polymer (12,14,21). More recently, nuclear magnetic resonance studies of whole cells have provided the first evidence that the "granule" is in fact in a mobile, amorphous state in vivo (3,4). Both the presence of plasticizers including water (4, 18) or lipid (22) and the kinetics of the crystallization process (6, 10) have been proposed to describe how the granules are maintained in the amorphous state inside the cell. Additional studies have concluded that the PHB granules inside the cell are surrounded by a membrane containing the synthase enzyme and that the D-3-hydroxybutyryl-CoA monomers are transported across the membrane in conjunction with polymerization (5, 13, 24, 32).Our current research activities are focused on understanding the role of the PHB synthase in the biogenesis of the PHB granules in A. eutrophus. In this regard there are two main issues: (i) the mechanism by which the PHB synthase initiates and carries out the condensation of literally thousands of D-3-hydroxybutyryl-CoA units to form the polymer chains and (ii) the role of this mechanism and the PHB synthase protein in the assembly of the PHB granules. We report here the immunocytochemical localization of the PHB synthase on the surface of the granules and describe a working hypothesis for granule formation. * Corresponding author.Preparation and analysis of anti-PHB synthase antibodies. In order to obtain purified A. eutrophus PHB synthase protein for the purpose of preparing antibodies, the C-terminal region of the phbC gene from plasmid pAeT42 encoding residues 86 to 589 of the PHB synthase (26) was ...

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“…This method allows a larger throughput PHB production which was necessary for freeze drying procedures and is a modi®cation of [13]. Alcaligenes eutrophus cells were ruptured by high pressure homogenization using 4 passes at 600 bar (A.P.V.…”

Section: Freeze Dried Native Granule Preparationmentioning

confidence: 99%

“…In theory, the polyhydroxybutyrate could be recovered either before the oil extraction or afterwards. In practice, in spite of a number of reports of potential schemes for unconventional rapeseed fractionation, only the classical process with mechanical and hexane extraction is used commercially to yield oil and a protein meal [13,21]. Therefore, the present study concentrates on this process, the stages of which are indicated by Fig.…”

Section: Establishing An Ultra Scale-down Processmentioning

confidence: 99%

An ultra scale-down process study for the production of polyhydroxybutyrate from transgenic rapeseed

Mott

Hughes

Dunnill

2000

Bioprocess Engineering

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A study of the processing of 10 g quantities of wild-type and transgenic rapeseed is described to remove oil prior to PHB separation from meal. Processing of transgenic seed with 0.54% polyhydroxybutyrate (PHB) is compared with natural rapeseed containing zero, 0.5%, 5% and 20% PHB derived from a commercial microbial process. The 20% material was in the form of 1±2 lm particles and in the form of 80 lm aggregates of the smaller particles. An ultra scaled-down process was operated to match the conditions in commercial oil extraction involving mechanical and hexane extraction. The rapeseed extraction differed for the 20% PHB in the wild-type. This was evidently caused by entrappment of oil in the 80 lm aggregates and by loss to hexane of the 1±2 lm PHB particles. The transgenic seeds required a higher mechanical force to yield the same level of oil. Whereas natural seed with added microbial PHB released this to the oil during pressing and to the hexane during solvent extraction, the transgenic seed evidently did not which would be of importance during large-scale processing. Though with a scale-down of 10 8 from the likely industrial level the results cannot be quantitatively predictive of production performance, they de®ne process issues and do so several seasons before the quantities needed for pilot trials can be available or the ®nal concentrations of PHB attained.

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Plasticization of poly(hydroxybutyrate) in vivo

Cited by 52 publications

References 13 publications

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

Immunocytochemical analysis of poly-beta-hydroxybutyrate (PHB) synthase in Alcaligenes eutrophus H16: localization of the synthase enzyme at the surface of PHB granules

An ultra scale-down process study for the production of polyhydroxybutyrate from transgenic rapeseed

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