Comparison of miscibility and structure of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/poly(l-lactic acid) blends with those of poly(3-hydroxybutyrate)/poly(l-lactic acid) blends studied by wide angle X-ray diffraction, differential scanning calorimetry, and FTIR microspectroscopy

Modification of poly(lactate) via polymer blending with microbially produced poly[(R)-lactate-co-(R)-3-hydroxybutyrate] copolymers

This study investigated the effect of polymer blending of microbially produced poly[(R)-lactate-co-(R)-3-hydroxybutyrate] copolymers (LAHB) with poly(lactate) (PLA) on their mechanical, thermal, and biodegradable properties. Blending of high lactate (LA) content and high molecular weight LAHB significantly improved the tensile elongation of PLA up to more than 250 % at optimal LAHB composition of 20-30 wt%. Temperature-modulated differential scanning calorimetry and dynamic mechanical analysis revealed that PLA and LAHB were immiscible but interacted with each other, as indicated by the mutual plasticization effect. Detailed morphological characterization using scanning probe microscopy, small-angle X-ray scattering, and solid-state NMR confirmed that PLA and LAHB formed a two-phase structure with a characteristic length scale as small as 20 nm. Because of mixing in this order, the polymer blends were optically transparent. The biological oxygen demand test of the polymer blends in seawater indicated an enhancement of PLA biodegradation during biodegradation of the polymer blends.

Characterization of P(3HB) from untreated raw palm oil mill effluent using Azotobacter vinelandii ΔAvin_16040 lacking S-layer protein

The production of poly(3-hydroxybutyrate) [P(3HB)] from untreated raw palm oil mill effluent (urPOME), the first wastewater discharge from crude palm oil extraction, is discussed. The mutant strain Azotobacter vinelandii ΔAvin_16040, which lacks the S-layer protein but has a better P(3HB) synthesis capability than the wild type strain ATCC 12,837, was chosen for this study. UrPOME substrate, with high biological oxygen demand (BOD), chemical oxygen demand (COD) and suspended solids, was used without pre-treatment. DSMZ-Azotobacter medium which was devoid of laboratory sugar(s) was used as the basal medium (BaM). Initially, Azotobacter vinelandii ΔAvin_16040 generated 325.5, 1496.3, and 1465.7 mg L^-1 of P(3HB) from BaM with 20% urPOME, 2BaM with 20% urPOME and 20 g L^-1 sucrose, and 2BaM with 20% urPOME and 2 mL L^-1 glycerol, respectively. P(3HB) generation was enhanced by nearly tenfold using statistical optimization, resulting in 13.9 g L^-1. Moreover, the optimization reduced the compositions of mineral salts and sugar in the medium by 48 and 97%, respectively. The urPOME-based P(3HB) product developed a yellow coloration most possibly attributed to the aromatic phenolics content in urPOME. Despite the fact that both were synthesised by ΔAvin_16040, thin films of urPOME-based P(3HB) had superior crystallinity and tensile strength than P(3HB) produced only on sucrose. When treated with 10 and 50 kGy of electron beam irradiation, these P(3HB) scissioned to half and one-tenth of their original molecular weights, respectively, and these cleavaged products could serve as useful base units for specific polymer structure construction.

Blends of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) with Fruit Pulp Biowaste Derived Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate-co-3-Hydroxyhexanoate) for Organic Recycling Food Packaging

In the present study, a new poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) [P(3HB-co-3HV-co-3HHx)] terpolyester with approximately 68 mol% of 3-hydroxybutyrate (3HB), 17 mol% of 3-hydroxyvalerate (3HV), and 15 mol% of 3-hydroxyhexanoate (3HHx) was obtained via the mixed microbial culture (MMC) technology using fruit pulps as feedstock, a processing by-product of the juice industry. After extraction and purification performed in a single step, the P(3HB-co-3HV-co-3HHx) powder was melt-mixed, for the first time, in contents of 10, 25, and 50 wt% with commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Thereafter, the resultant doughs were thermo-compressed to obtain highly miscible films with good optical properties, which can be of interest in rigid and semirigid organic recyclable food packaging applications. The results showed that the developed blends exhibited a progressively lower melting enthalpy with increasing the incorporation of P(3HB-co-3HV-co-3HHx), but retained the PHB crystalline morphology, albeit with an inferred lower crystalline density. Moreover, all the melt-mixed blends were thermally stable up to nearly 240 °C. As the content of terpolymer increased in the blends, the mechanical response of their films showed a brittle-to-ductile transition. On the other hand, the permeabilities to water vapor, oxygen, and, more notably, limonene were seen to increase. On the overall, this study demonstrates the value of using industrial biowaste derived P(3HB-co-3HV-co-3HHx) terpolyesters as potentially cost-effective and sustainable plasticizing additives to balance the physical properties of organic recyclable polyhydroxyalkanoate (PHA)-based food packaging materials.

Gamma radiation-induced grafting of n-hydroxyethyl acrylamide onto poly(3-hydroxybutyrate): A companion study on its polyurethane scaffolds meant for potential skin tissue engineering applications

This study aimed at investigating the synthesis, characterization, and search for a biotechnological application proposal for poly [(R)-3-hydroxybutyric acid] (PHB) grafted with the n-hydroxyethyl acrylamide (HEAA) monomer. The novel copolymer was prepared by ⁶⁰Co gamma radiation-induced-graft polymerization. The effect of different solvents in the graft polymerization; the degree of grafting, crystallinity, and hydrophilicity; the morphology and the thermal properties were evaluated. The polyurethane fabricated from the grafted PHB was suggested as a scaffold. The enzymatic degradation behavior and the spectroscopic, morphological, mechanical, and biological properties of the composites were assessed. According to the results, the successful grafting of HEAA onto PHB was verified. The grafting was significantly affected by the type of solvent employed. A decreased crystallinity and increased hydrophilicity of the graft copolymer, concerning the PHB, was found. An increased roughness was observed in the morphology of the polymer after grafting. The thermodynamic parameters, except for the glass transition temperature, also decreased for the synthetic biopolymer. The intended use of these scaffolds for skin tissue engineering was supported by a proper degradability and degree of porosity, improved mechanical properties, the optimal culture of human fibroblasts, and its transfection with a plasmid vector containing an enhanced green fluorescent protein.

Shape Memory and Osteogenesis Capabilities of the Electrospun Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Modified Poly(l-Lactide) Fibrous Mats

Poly(l-lactide) (PLLA) as one of the most well-known biodegradable polyesters has been studied extensively for bone tissue engineering. If being properly programmed, scaffolds from PLLA can also be endowed with the capability of shape memory. However, several noted issues, for example, mechanical brittleness, high glass transition temperature T_g, and relatively poor shape retention and recovery properties, necessitate modification of the PLLA to improve its application efficacy in physiological conditions. This study is proposed to modify PLLA by having the biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) incorporated to form ultrafine composite fibers (i.e., PLLA-PHBV) through electrospinning. Different pairs of PLLA-PHBV at the varying mass ratios of 10:0, 9:1, 8:2, 7:3, 6:4, and 0:10 can be successfully electrospun into fibrous form with the fineness of 2-3 μm. Incorporation of PHBV enables to give rise to desired T_g decreases and also, interestingly, increases in the Young's modulus of the PLLA-PHBV blends, while gradually increasing the PHBV mass ratios up to 30%. The PLLA-PHBV (7:3) formulation is identified to present excellent shape memory properties with high shape fixing ratio (>98%) and shape recovery ratio (>96%) compared to the unmodified PLLA fiber counterpart. Moreover, the PLLA-PHBV (7:3) fibers also show enhanced osteogenesis-inducing ability in the mouse bone mesenchymal stem cells, even under nonosteoinductive conditions. Collectively, for the first time this study demonstrates the enhanced shape memory and osteogenesis capabilities of the electrospun PLLA-PHBV composite fibers, and the researched PLLA-PHBV (7:3) fiber system could be potentially applied as a multifunctional scaffolding material for applications in bone tissue repair and regeneration. Impact statement By first converting the poly(l-lactide) (PLLA)-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) hybrids into fibrous form at varied mass ratios followed by a thorough characterization, we reasonably demonstrated that incorporation of an appropriate amount of PHBV (i.e., 30%) into the PLLA fibers could give rise to significant improvement on the shape memory capability of the PLLA, along with the desired decreases in the transition temperature (T_g). Moreover, the fibrous PLLA-PHBV (7:3) scaffold was also found to significantly promote the osteogenic commitment in bone mesenchymal stem cells with osteoinductive factors in a synergistic manner. Our biomimicking and shape memory enabled fibrous scaffold of PLLA-PHBV could be used to construct multifunctional three-dimensional scaffold with shape memory effect for bone regeneration.

Feasibility of attenuated total reflection-fourier transform infrared (ATR-FTIR) chemical imaging and partial least squares regression (PLSR) to predict protein adhesion on polymeric surfaces

PLSR with ATR-FTIR chemical imaging predicts protein adhesion on polymeric surfaces well (R² = 0.99, RMSECV = 0.16).

Crystallization of ultrathin poly(3-hydroxybutyrate) films in blends with small amounts of poly(l-lactic acid): correlation between film thickness and molecular weight of poly(l-lactic acid)

The crystallization behavior of poly(3-hydroxybutyrate) (PHB) films in blends with small amounts of poly(l-lactic acids) (PLLAs) was investigated by grazing incidence X-ray diffraction (GIXD) and infrared-reflection absorption spectroscopy (IRRAS).

Production and characterization of poly(3-hydroxybutyrate) generated by Alcaligenes latus using lactose and whey after acid protein precipitation process

Whey after acid protein precipitation was used as substrate for PHB production in orbital shaker using Alcaligenes latus. Statistical analysis determined the most appropriate hydroxide for pH neutralization of whey after protein precipitation among NH4OH, KOH and NaOH 10%w/v. The results were compared to those of commercial lactose. A scale-up test in a 4L bioreactor was done at 35°C, 750rpm, 7L/min air flow, and 6.5 pH. The PHB was characterized through Fourier Transform Infrared Spectroscopy, thermogravimetry and differential scanning calorimetry. NH4OH provided the best results for productivity (p), 0.11g/L.h, and for polymer yield, (YP/S), 1.08g/g. The bioreactor experiment resulted in lower p and YP/S. PHB showed maximum degradation temperature (291°C), melting temperature (169°C), and chemical properties similar to those of standard PHB. The use of whey as a substrate for PHB production did not affect significantly the final product quality.

Modification and Potential Application of Short-Chain-Length Polyhydroxyalkanoate (SCL-PHA)

As the only kind of naturally-occurring biopolyester synthesized by various microorganisms, polyhydroxyalkanoate (PHA) shows a great market potential in packaging, fiber, biomedical, and other fields due to its biodegradablity, biocompatibility, and renewability. However, the inherent defects of scl-PHA with low 3HV or 4HB content, such as high stereoregularity, slow crystallization rate, and particularly the phenomena of formation of large-size spherulites and secondary crystallization, restrict the processing and stability of scl-PHA, as well as the application of its products. Many efforts have focused on the modification of scl-PHA to improve the mechanical properties and the applicability of obtained scl-PHA products. The modification of structure and property together with the potential applications of scl-PHA are covered in this review to give a comprehensive knowledge on the modification and processing of scl-PHA, including the effects of physical blending, chemical structure design, and processing conditions on the crystallization behaviors, thermal stability, and mechanical properties of scl-PHA.

Microbial production of polyhydroxyalkanoates (PHAs) and its copolymers: A review of recent advancements

Traditional mineral oil based plastics are important commodity to enhance the comfort and quality of life but the accumulation of these plastics in the environment has become a major universal problem due to their low biodegradation. Solution to the plastic waste management includes incineration, recycling and landfill disposal methods. These processes are very time consuming and expensive. Biopolymers are important alternatives to the petroleum-based plastics due to environment friendly manufacturing processes, biodegradability and biocompatibility. Therefore use of novel biopolymers, such as polylactide, polysaccharides, aliphatic polyesters and polyhydroxyalkanoates is of interest. PHAs are biodegradable polyesters of hydroxyalkanoates (HA) produced from renewable resources by using microorganisms as intracellular carbon and energy storage compounds. Even though PHAs are promising candidate for biodegradable polymers, however, the production cost limit their application on an industrial scale. This article provides an overview of various substrates, microorganisms for the economical production of PHAs and its copolymers. Recent advances in PHAs to reduce the cost and to improve the performance of PHAs have also been discussed.

Citric acid modification of PLLA nano-fibrous scaffolds to enhance cellular adhesion, proliferation and osteogenic differentiation

Citric acid (CA) was used in a thermally induced phase separation (TIPS) process to improve the surface hydrophilicity and cell affinity of PLLA nano-fibrous scaffolds. The evolution of architecture, structure and physicochemical properties of the scaffold after modification has been investigated. Cell viability, adhesion, proliferation and osteogenic differentiation were characterized to evaluate the cytocompatibility and biological properties of PLLA nano-fibrous scaffolds. Citric acid interacted with PLLA through hydrogen bond association and the introduction of strong polar groups (-COOH) on the PLLA surface improved its hydrophilicity with the contact angle decreasing to a suitable range for cell adhesion and spreading. The cell exhibited extensive spreading on the CA modified PLLA scaffolds with many cellular protrusions interacting with nanofibers. Furthermore, such a modification significantly increased the cell proliferation rate, enhanced the alkaline phosphatase (ALP) activity and bone-related gene expression (ALP, OCN, COL I and Runx2) of mBMSCs along with cell development. The results demonstrate a promising modification method to promote applications of PLLA-based scaffolds.

Microscopic Fourier Transform Infrared Characterization on Two Types of Spherulite with Polymorphic Crystals in Poly(heptamethylene terephthalate)

FTIR microspectrometry with in situ temperature variation and IR-peak-mapping capability, and POM characterization were used to study the crystal distribution in dual spherulites in poly(heptamethylene terephthalate). By tracing the crystalline IR bands of the α-crystal and β-crystal to get the crystal distribution, the techniques resolve that the ringed and ringless spherulites comprise α- and β-crystals, respectively. In addition, temperature-dependent IR analyses on the spots related to the two crystals also reveal the α- and β-crystals melt at 98 and 104 °C, respectively. The ringed and ringless spherulites were proven to be correlated with the α- and β-crystal forms, respectively.

Biodegradação de filmes de polipropileno (PP), poli(3-hidroxibutirato) (PHB) e blenda de PP/PHB por microrganismos das águas do Rio Atibaia

O propósito deste estudo é investigar a biodegradação de filmes de PHB, PP e blenda de PP/PHB (1:1) por microrganismos de águas de rio poluído que recebeu vários tipos de descartes, inclusive de refinaria de petróleo. Os filmes poliméricos foram obtidos por fusão do pó do material a 175 ºC, prensados a 71,3 kgf.cm-2 e resfriados a 25 ºC. Estes filmes foram mantidos em amostras de águas do rio poluído, coletadas antes e após o descarte do efluente da refinaria de petróleo e mantidas em estufa bacteriológica a 28 ºC, durante 120 dias. As mudanças, causadas pela ação microbiana nos filmes, foram analisadas por medidas de perda de massa, infravermelho com transformada de Fourier (FTIR) e microscopia eletrônica de varredura (MEV). Os resultados provaram que a degradação do PHB ocorre tanto na sua fase amorfa como na cristalina, sendo mais significativa na água do rio que recebeu o efluente da refinaria de petróleo, contendo microrganismos reconhecidos como potencialmente capazes de degradar substâncias persistentes no meio ambiente.

Poly-3-hydroxy butyric acid interaction with the transgenic flax fibers: FT-IR and Raman spectra of the composite extracted from a GM flax

The FT-IR and FT-Raman studies have been performed on commercial 3-hydroxy-butyric acid, commercial poly-3-hydroxy butyric acid as well as poly-3-hydroxy butyric acid (PHB) produced by bacteria. The data were compared to those obtained for poly-3-hydroxy butyric acid extracted from natural and genetically modified flax. Genetically modified flax was generated by expression of three bacterial genes coding for synthesis of poly-3-hydroxy butyric acid. Thus transgenic flaxes were enhanced with different amount of the PHB. The discussion of polymer structure and vibrational properties has been done in order to get insight into differences among these materials. The interaction between the cellulose of flax fibers and embedded poly-3-hydroxybutyric acid has been also discussed. The spectroscopic data provide evidences for structural changes in cellulose and in PHB when synthesized in fibers. Based on this data it is suggesting that cellulose and PHB interact by hydrogen and ester bonds.

FTIR spectroscopic investigation of pyruvate electroreduction on copper in alkaline medium — On the mechanistic aspects

In this work some important aspects related to the electrocatalytic reduction of pyruvate on copper cathode were investigated in alkaline medium (0.5 mol/L NaOH). In situ IR reflectance spectroscopy (SPAIRS and SNIFTIRS techniques) was used to investigate the adsorbed intermediates and reaction products from the reduction of pyruvate. The results revealed that hydrogenation of the substrate to lactate occurred at the copper surface involving weakly adsorbed species. The identification of the different electroreactive species allowed to postulate a reaction mechanism for the transformation of pyruvate into lactate on copper.Key words: copper, electroreduction, pyruvate, lactate, in situ infrared reflectance spectroscopy, reaction mechanism.