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The effect of accelerated weathering exposure time on the bioplastic, poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) was studied. The chemical structure and thermophysical property changes of solvent cast PHBV films were examined by a combination of optical microscopy, size exclusion chromatography, FTIR and 1 H NMR spectroscopies, tensile testing, and differential scanning calorimetry (DSC). The exposed PHBV surfaces experienced surface crazing upon weathering. The molar mass of weathered PHBV was shown to decrease due to chain scission which was dominant over the crosslinking reaction mechanism, and compositional analysis showed the polymer degradation was non-random between the hydroxybutyrate-hydroxyvalerate units. The degree of crystallinity for PHBV was shown to increase significantly (by about 20%) upon weathering. Tensile tests showed that the weathered PHBV exhibited reduced ultimate strength and elongation to break, while the Young's modulus increased ascribing to an increase in crystallinity. Different degradation mechanisms (Norrish I/II, radical initiation, crosslinking, and hydrolysis) of PHBV are proposed and confirmed based on the experimental findings. This study provides degradation insight for PHBV exposed to both UV radiation and moisture. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) was grafted onto cellulose fiber by dicumyl peroxide (DCP) radical initiation via in situ reactive extrusion. The yield of the grafted (cellulose-g-PHB) copolymer was recorded and grafting efficiency was found to be dependent on the reaction time and DCP concentration. The grafting mechanism was investigated by electron spin resonance (ESR) analysis and showed the presence of radicals produced by DCP radical initiation. The grafted copolymer structure was determined by nuclear magnetic resonance (NMR) spectroscopy. Scanning electronic microscopy (SEM) showed that the cellulose-g-PHB copolymer formed a continuous phase between the surfaces of cellulose and PHB as compared to cellulose-PHB blends. The relative crystallinity of cellulose and PHB were quantified from Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) results, while the absolute degree of crystallinity was evaluated by differential scanning calorimetry (DSC). The reduction of crystallinity indicated the grafting reaction occurred not just in the amorphous region but also slightly in crystalline regions of both cellulose and PHB. The smaller crystal sizes suggested the brittleness of PHB was decreased. Thermogravimetric analysis (TGA) showed that the grafted copolymer was stabilized relative to PHB. By varying the reaction parameters the compositions (%PHB and %cellulose) of resultant cellulose-g-PHB copolymer are expected to be manipulated to obtain tunable properties. [ABSTRACT FROM AUTHOR]

In this study, the target was the generation of fermentable monosaccharides from hardwoods that can be converted into value-added chemicals, such as polyhydroxybutyrates (PHB). Poplar flour was subjected to a hot-water pretreatment. The pretreatment conditions were optimized using a response surface methodology (RSM) on a 2 3 full central composites design by varying temperature, reaction time and solid loading. The optimal pretreatment condition for producing sugars was 200 °C, 22 min and 20% solid loading. After pretreatment the solid residue was treated with a commercial cellulase/xylanase preparation and released sugars quantified. The total sugars yield was applied as response variable to the RSM. A maximum yield of 96% sugars was obtained. Potential fermentation inhibitors were also detected at low concentrations (acetic acid, furfural, hydroxymethylfurfural). A preliminary trial using wood hydrolysates in a fed-batch bioreactor using a mixed microbial consortia afforded PHB (14% on biomass basis) and maximum PHB productivity of 0.18 g/L/h. [ABSTRACT FROM AUTHOR]

ABSTRACT The bioplastic poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV), was isolated from a bioreactor using mixed microbial consortia fed volatile fatty acids (VFA), from fermented dairy manure, as the carbon source. The molar fraction of 3-hydroxyvalerate (3HV) amounted to 0.33 mol mol−1 for two isolated PHBV samples as determined by GC-MS and 1H-NMR spectroscopy. The chemical, thermal, and mechanical properties were determined. The PHBVs had relatively high Mw (∼790,000 g mol−1). Only a single glass transition temperature ( Tg) and melting point ( Tm) were observed. Isolated PHBVs exhibited good flexibility and elongation to break as compared with commercial PHBVs with lower HV. The diad and triad sequence distributions of the monomeric units were determined by 13C-NMR spectroscopy and followed Bernoullian statistics suggesting that the PHBVs were random. The PHBV sequence distribution was also characterized by electrospray ionization-mass spectrometry (ESI-MSn) after partial alkaline hydrolysis to oligomers showing a random 3HV distribution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40333. [ABSTRACT FROM AUTHOR]

Utilisation of lignin in plastic based blends offers a sustainable alternative to non-renewable materials as well as value-added use of technical lignin obtained from pulping operations. To overcome poor compatibility between lignin and plastic, in this study, two industrial lignins (softwood Kraft and agricultural fiber soda) were esterified (with acetic, propionic, butyric, and hexanoic anhydrides) and subsequently blended with poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) or polypropylene (PP) at a weight ratio of 3:7. This paper systematically characterized C 2 –C 6 anhydrides esterified lignins (molar mass, glass transition temperature (T g ), hydrophobicity, and polarity), and provides a comprehensive evaluation of the effect of different lignin esters in the blends on tensile properties, water absorption, thermal transitions, for the first time, spherulite morphology, and dynamic rheological behaviour. Generally, compared to blends with unmodified lignin, a progressive increase of tensile strength (25%) and elongation at break (26%) could be observed with increasing ester carbon chain length in PHBV based systems, while no improvement was seen in PP based systems. Water absorption of PHBV and PP blends decreased by about 50% after lignin esterification. The effect of lignin esterification on the crystallization process was matrix dependent: depression of melting crystallization and occurrence of cold crystallization was observed in PHBV based blends, while the melting crystallization shifted to higher temperature in PP based blends. The lignin acetate and propionate blends were partially miscible showing two-stage glass transitions by thermal mechanical analysis. Esterification led to more uniform dispersion of lignin in the plastic matrix. The frequency of PHBV spherulites increased and their size decreased from 700 μm to less than 100 μm with addition of lignin acetate and propionate. Lignin hexanoate blends showed a T g depression and smaller dynamic elastic and viscous moduli than the other lignin esters, suggesting that it acted as a plasticizer. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is a bioplastic biosynthesized by microorganisms as an intracellular granule. In this study, PHB was produced by a mixed microbial culture fed crude glycerol in a sequencing batch bioreactor. Bioreactor operations were monitored by near infrared (NIR) spectroscopy (908–1708 nm) with a direct insertion probe to develop a model for predicting microbial PHB concentration. Multivariate statistical methods, principal component analysis (PCA) and partial least squares (PLS), were applied for modeling of the NIR spectral data. The results showed that NIR spectra can (i) be used to predict PHB content in-situ, with a calibration model and prediction model exhibiting a good fit (R 2 = 0.88 and R 2 = 0.89, respectively) and (ii) also be used to monitor substrate, glycerol, concentration. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is one of most biodegradable bioplastic, but its high cost and brittleness limits its applications. In this study, low-value waste byproduct from a fermentation process of potato peel waste, called the potato peel waste fermentation residue (PPW-FR) fibers, were recovered and compounded with PHB to form biocomposites of tunable properties. The mechanical and thermal properties of pure PHB and biocomposites were investigated by thermogravimetric analysis (TGA), tensile and flexural tests, and dynamic mechanical analysis (DMA). Fiber content was shown to have a significant effect on the surface hydrophobicity and water absorption of the biocomposites. All absolute and specific mechanical properties and water absorption (by normalizing the measured parameters against the measured density ( ρ )) were investigated. The biodegradability of PHB and biocomposites were evaluated in soil over 8 months. The surface morphology, chemistry and melting/crystallization behavior were monitored and characterized by microscopy, FTIR spectroscopy and differential scanning calorimetry (DSC), respectively. The biocomposites showed poor mechanical properties but extremely higher biodegradation rate as compared with pure PHB, especially when the fiber content was >15%. The degradation rate increased with increasing fiber content and positively correlated to the water absorption showing more cracks and deeper pits. FTIR spectroscopic analysis showed that the plant polysaccharides and PHB within the biocomposite were degraded with exposure time. At 50% fiber content the biocomposites were completely degraded by 8 months. These PPW-FR based biocomposites offer new opportunities for fast degrading biomaterials in agricultural and horticultural applications. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the potential of using wood hydrolysates (enzymatically hydrolyzed from hybrid poplar) as substrate to produce polyhydroxybutyrate (PHB) using mixed microbial cultures. The optimal operational conditions for fed-batch bioreactors were 4 d solid retention time with an organic loading rate of 2.5 g/Ld. The maximum PHB accumulated was 27% of cell dry weight with a yield of 0.32 g/g (g PHB produced per g sugars consumed). Microbial community analysis was done at the genus level by 16S rRNA sequencing on an Illumina system and community evolution was observed among different samples and initial seed. Actinobacteria , Alpha- and Beta-proteobacteria were found to be the dominant groups in all the bioreactors. Several PHB-storing microorganisms were characterized belonging to Alpha- and Beta-proteobacteria . [ABSTRACT FROM AUTHOR]

Abstract: Crude glycerol (CG), a by-product of biodiesel production, is an organic carbon-rich substrate with potential as feedstock for polyhydroxyalkanoate (PHA) production. PHA is a biodegradable thermoplastic synthesized by microorganisms as an intracellular granule. In this study we investigated PHA production on CG using mixed microbial consortia (MMC) and determined that the enriched MMC produced exclusively polyhydroxybutyrate (PHB) utilizing the methanol fraction. PHB synthesis appeared to be stimulated by a macronutrient deficiency. Intracellular concentrations remained relatively constant over an operational cycle, with microbial growth occurring concurrent with polymer synthesis. PHB average molecular weights ranged from 200–380kDa, while thermal properties compared well with commercial PHB. The resulting PHB material properties and characteristics would be suitable for many commercial uses. Considering full-scale process application, it was estimated that a 38million L (10million gallon) per year biodiesel operation could potentially produce up to 19metric ton (20.9ton) of PHB per year. [ABSTRACT FROM AUTHOR]