Mechanical properties and biodegradation characteristics of PHB-based films

Savenkova, Ludmila; Gercberga, Z; Nikolaeva, V. G.; Dzene, Anda; Bibers, I.; Kalnin, M. M.

doi:10.1016/s0032-9592(99)00107-7

Cited by 155 publications

(86 citation statements)

References 12 publications

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“…Physical characteristics of the PHB produced by the recombinant strains. In order to be suitable for industrial processing, the polymer must have a high molecular weight that enables it to retain its strength (28,34). The physical characteristics of PHB obtained from E. coli K24 and E. coli K24K were compared with those of the polymer purified from C. necator and Azotobacter sp.…”

Section: Resultsmentioning

confidence: 99%

New Recombinant Escherichia coli Strain Tailored for the Production of Poly(3-Hydroxybutyrate) from Agroindustrial By-Products

Nikel

Almeida

Melillo

et al. 2006

Appl Environ Microbiol

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A recombinant E. coli strain (K24K) was constructed and evaluated for poly(3-hydroxybutyrate) (PHB) production from whey and corn steep liquor as main carbon and nitrogen sources. This strain bears the pha biosynthetic genes from Azotobacter sp. strain FA8 expressed from a T5 promoter under the control of the lactose operator. K24K does not produce the lactose repressor, ensuring constitutive expression of genes involved in lactose transport and utilization. PHB was efficiently produced by the recombinant strain grown aerobically in fed-batch cultures in a laboratory scale bioreactor on a semisynthetic medium supplemented with the agroindustrial by-products. After 24 h, cells accumulated PHB to 72.9% of their cell dry weight, reaching a volumetric productivity of 2.13 g PHB per liter per hour. Physical analysis of PHB recovered from the recombinants showed that its molecular weight was similar to that of PHB produced by Azotobacter sp. strain FA8 and higher than that of the polymer from Cupriavidus necator and that its glass transition temperature was approximately 20°C higher than those of PHBs from the natural producer strains.Polyhydroxyalkanoates (PHAs) are a group of polyesters produced by a large number of bacteria, which accumulate them in intracellular granules as a response to environmental stress and nutrient imbalance (7, 10). These thermoplastics have properties that vary according to their monomer compositions. A copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate was commercialized in the 1980s, but high production costs have hindered the use of PHAs as commodity plastics, since their final price is considerably higher than that of petrochemical-based synthetic plastic materials (16). Growing concern about environmental pollution has renewed interest in the development of PHAs, which are totally biodegraded by microorganisms present in most environments (11). Also, these polymers can be produced from different renewable carbon sources (11).Poly(3-hydroxybutyrate) (PHB) production costs can be reduced by several means, including the use of cheap substrates, such as whey, favored in countries with important dairy industries, or the enhancement of product yield, e.g., by using recombinant Escherichia coli (11,18). E. coli is a suitable host as a heterologous expression background for foreign genes that can be easily manipulated and improved by means of recombinant DNA methodologies. Also, high-cell-density cultivation strategies for numerous E. coli strains are well established (15,32). E. coli cells that accumulate large amounts of PHB become fragile, facilitating the isolation and purification of the biopolymer, and the bacterium does not express PHA-degrading enzymes (2).PHB is the best known PHA and has been studied most often as a model product in the development of fermentation strategies. In the majority of PHB-accumulating species, it is synthesized in three sequential enzymatic steps: a 3-ketothiolase condenses two acetyl-coenzyme A (CoA) moieties to form acetoacetyl-CoA; a NADPH-dependent a...

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Section: Resultsmentioning

confidence: 99%

New Recombinant Escherichia coli Strain Tailored for the Production of Poly(3-Hydroxybutyrate) from Agroindustrial By-Products

Nikel

Almeida

Melillo

et al. 2006

Appl Environ Microbiol

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“…polylactic acid, poly (ɛ-caprolactone) (PCL), poly(3-hydroxybutyrate) (PHB), and thermoplastic proteins] are the important issues. The PHB, whose mechanical properties are similar to those of isotactic polypropylene, has attracted an industrial attention as environmentally degradable plastics for a wide range of agricultural, marine, and medical applications because it is 100% biodegradable and it can be produced from renewable resource [1,2]. Besides the higher cost as compared to petroleum-based plastics, the main drawbacks of PHB are its brittleness and thermal instability.…”

Section: Introductionmentioning

confidence: 99%

Poly(3-hydroxybutyrate)/multi-walled carbon nanotubes nanocomposites: preparation and characterizations

Liao

2012

Designed Monomers and Polymers

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In this study, the poly(3-hydroxybutyrate)/multi-walled carbon nanotubes (PHB/MWNTs) nanocomposite was prepared by means of a melt blending method. To improve the compatibility/dispersability of MWNTs within the PHB matrix, the acrylic acid grafted poly(3-hydroxybutyrate) (PHB-g-AA) and the multihydroxyl functionalized MWNTs (MWNTs-OH) were used as alternatives. Based on the results of TEM micrographs, FTIR spectra, 13 C solid-state NMR spectra, XRD patterns, and thermal and mechanical characterizations, the PHB-g-AA/MWNTs-OH blend demonstrated dramatic enhancement in thermal and mechanical properties of PHB due to the formation of ester carbonyl groups through the reaction between carboxylic acid groups of PHB-g-AA and hydroxyl groups of MWNTs-OH. For example, with an addition of 1 wt.% MWNTs-OH, the increases in the initial decomposition temperature and the tensile strength at break were 75°C and 15.1 MPa, respectively. Finally, the optimal amount of MWNTs-OH was 1 wt.% because excess MWNTs-OH caused separation of the organic and inorganic phases and reduced their compatibility.

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“…Plasticizers such as laprol, dibutylsebacate, dioctylsebacate, polyisobutylene and polyethylene glycol have been used to alter the mechanical properties and biodegradation character of PHA from Azotobacter sp. [6]. For such assessment, the fi lms are prepared by solution casting technique and then analyzed, which requires sizable quantity of polymer.…”

Section: Introductionmentioning

confidence: 99%

Production and characterization of bacterial polyhydroxyalkanoate copolymers and evaluation of their blends by fourier transform infrared spectroscopy and scanning electron microscopy

et al. 2009

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Rhizobium meliloti produced a copolymer of short chain length polyhydroxyalkanoate (scl-PHA) on sucrose and rice bran oil as carbon substrates. Recombinant Escherichia coli (JC7623ABC1J4), bearing PHA synthesis genes, was used to synthesize short chain length-co-medium chain length PHA (scl-co-mcl-PHA) on glucose and decanoic acid. Fourier transform infrared spectroscopy (FTIR) spectra of the PHAs indicated strong characteristic bands at 1282, 1723, and 2934 cm -1 for scl-PHA and at 2933 and 2976 cm -1 for scl-co-mcl-PHA polymer. Differentiation of polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-hydroxyvalerate-P(HB-co-HV) copolymer was obseverd using FTIR, with absorption bands at 1723 and 1281 for PHB, and at 1738, 1134, 1215 cm -1 for HV-copolymer. The copolymers were analyzed by GC and 1 H NMR spectroscopy. Films of polymer blends of PHA produced by R. meliloti and recombinant E. coli were prepared using glycerol, polyethylene glycol, polyvinyl acetate, individually (1:1 ratio), to modify the mechanical properties of the fi lms and these fi lms were evaluated by FTIR and scanning electron microscopy.

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Mechanical properties and biodegradation characteristics of PHB-based films

Cited by 155 publications

References 12 publications

New Recombinant Escherichia coli Strain Tailored for the Production of Poly(3-Hydroxybutyrate) from Agroindustrial By-Products

New Recombinant Escherichia coli Strain Tailored for the Production of Poly(3-Hydroxybutyrate) from Agroindustrial By-Products

Poly(3-hydroxybutyrate)/multi-walled carbon nanotubes nanocomposites: preparation and characterizations

Production and characterization of bacterial polyhydroxyalkanoate copolymers and evaluation of their blends by fourier transform infrared spectroscopy and scanning electron microscopy

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