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The present work reports on the production and characterization of polyhydroxyalkanoates (PHAs) with different valerate contents, which were synthesized from microbial mixed cultures, and the subsequent development of nanocomposites incorporating bacterial cellulose nanowhiskers (BCNW) via solution casting processing. The characterization of the pure biopolyesters showed that the properties of PHAs may be strongly modified by varying the valerate ratio in the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer, as expected. Increasing the valerate content was seen to greatly decrease the melting temperature and enthalpy of the material, as well as its rigidity and stiffness, resulting in a more ductile behaviour. Additionally, the higher valerate PHA displayed higher permeability to water and oxygen and higher moisture sensitivity. Subsequently, BCNW were incorporated into both PHA grades, achieving a high level of dispersion for a 1 wt.-% loading, whereas some agglomeration took place for 3 wt.-% BCNW. As evidenced by DSC analyses, BCNW presented a nucleating effect on the PHA matrices. BCNW also increased the thermal stability of the polymeric matrices when properly dispersed due to strong matrix-filler interactions. Barrier properties were seen to depend on relative humidity and improved at low nanofiller loadings and low relative humidity.

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

UV/titanium dioxide (TiO(2)) degradation of two xanthene dyes, erythrosine B (Ery) and eosin Y (Eos), was studied in a photocatalytic reactor. Photocatalysis was able to degrade 98% of Ery and 73% of Eos and led to 65% of chemical oxygen demand removal. Experiments in buffered solutions at different initial pH values reveal the pH dependence of the process, with better results obtained under acidic conditions due to the electrostatic attraction caused by the opposite charges of TiO(2) (positive) and of anionic dyes (negative). Batch activity tests under methanogenic conditions showed the high toxicity exerted by the dyes even at low concentrations (~85% with initial concentration of 0.3 mmol L(-1)), but the end products of photocatalytic treatment were much less toxic toward methanogenic bacteria, as detoxification of 85 ± 5% for Eos and 64 ± 7% for Ery were obtained. In contrast, the dyes had no inhibitory effect on the biogenic-carbon biodegradation activity of aerobic biomass, obtained by respirometry. The results demonstrate that photocatalysis combining UV/TiO(2) as a pretreatment followed by an anaerobic biological process may be promising for the treatment of wastewaters produced by many industries.

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) produced by mixed bacterial cultures derived from a cheese whey (CW) industrial by‐product (unpurified PHBV; u‐PHBV) was incorporated into commercial PHBV without previous purification or isolation processes. The presence of certain impurities was evident as investigated by scanning electron microscopy. The crystallinity of the polymer fraction was decreased by about 3% compared to the commercial PHBV. The onset of thermal degradation was not substantially affected by the incorporation of the u‐PHBV fraction. A higher flexibility and elongation at break was mostly attributed to the increased contents in 3‐hydroxyvalerate in the blends with increasing u‐PHBV content. Water and D‐limonene vapor permeability were not affected up to u‐PHBV contents of 15 wt %. This study puts forth the potential use of unpurified PHBV obtained from mixed microbial cultures and grown from industrial by‐products as a cost‐effective additive to develop more affordable and waste valorized packaging articles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42633.

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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