Animal derived biopolymers for food packaging applications: A review

It is essential to use environment-friendly, non-toxic, biodegradable and sustainable materials for various applications. Biopolymers are derived from renewable sources like plants, microorganisms, and agricultural wastes. Unlike conventional polymers, biopolymer has a lower carbon footprint and contributes less to greenhouse gas emission. All biopolymers are biodegradable, meaning natural processes can break them down into harmless products such as water and biomass. This property is of utmost importance for various sustainable applications. This review discusses different classifications of biopolymers based on origin, including plant-based, animal-based and micro-organism-based biopolymers. The review also discusses the desirable properties that are required in materials for their use as packaging material. It also discusses the different processes used in modifying the biopolymer to improve its properties. Finally, this review shows the recent developments taking place in using specifically animal origin-based biopolymer and its use in packaging material. It was observed that animal-origin-based biopolymers, although they possess unique properties however, are less explored than plant-origin biopolymers. The animal-origin-based biopolymers covered in this review are chitosan, gelatin, collagen, keratin, casein, whey, hyaluronic acid and silk fibroin. This review will help in renewing research interest in animal-origin biopolymers. In summary, biopolymer offers a sustainable and environment-friendly alternative to conventional polymers. Their versatility, biocompatibility will help create a more sustainable future.

Challenges and issues with the performance of boron nitride rooted membrane for gas separation

Various fillers such as zeolites, metal-organic framework, carbon, metal framework, graphene, and covalent organic framework have been incorporated into the polymers. However, these materials are facing issues such as incompatibility with the polymer matrix, which leads to the formation of non-selective voids and thus, reduces the gas separation properties. Recent studies show that hexagonal boron nitride (h-BN) possesses attractive characteristics such as high aspect ratio, good compatibility with polymer materials, enhanced gas barrier performance, and improved mechanical properties, which could make h-BN the potential candidate to replace conventional fillers. The synthesis of materials and membranes is the subject of this review, which focuses on recent developments and ongoing problems. Additionally, a summary of the mathematical models that were utilised to forecast how well polymer composites would perform in gas separation is provided. It was found in the previous studies that tortuosity is the governing factor for the determination of the effectiveness of a nanofiller as a gas barrier enhancer in polymer matrices. The shape of the nanofiller particles and sheets, disorientation and distribution of the nanofillers within the polymer matrix, state of aggregation and rate of reaggregation of the nanofiller particles, as well as the compatibility of the nanofiller with the polymer matrix all played a significant role in determining how well a particular nanofiller will perform in enhancing the gas barrier properties of the nanocomposites. For this purpose, this review has been focused not only on the experimentation work but also on the effect of tortuosity, exfoliation quality, compatibility, disorientation, and reaggregation of nanofillers.

Established and Emerging Producers of PHA: Redefining the Possibility

The polyhydroxyalkanoate was discovered almost around a century ago. Still, all the efforts to replace the traditional non-biodegradable plastic with much more environmentally friendly alternative are not enough. While the petroleum-based plastic is like a parasite, taking over the planet rapidly and without any feasible cure, its perennial presence has made the ocean a floating island of life-threatening debris and has flooded the landfills with toxic towering mountains. It demands for an immediate solution; most resembling answer would be the polyhydroxyalkanoates. The production cost is yet one of the significant challenges that various corporate is facing to replace the petroleum-based plastic. To deal with the economic constrain better strain, better practices, and a better market can be adopted for superior results. It demands for systems for polyhydroxyalkanoate production namely bacteria, yeast, microalgae, and transgenic plants. Solely strains affect more than 40% of overall production cost, playing a significant role in both upstream and downstream processes. The highly modifiable nature of the biopolymer provides the opportunity to replace the petroleum plastic in almost all sectors from food packaging to medical industry. The review will highlight the recent advancements and techno-economic analysis of current commercial models of polyhydroxyalkanoate production. Bio-compatibility and the biodegradability perks to be utilized highly efficient in the medical applications gives ample reason to tilt the scale in the favor of the polyhydroxyalkanoate as the new conventional and sustainable plastic.

Production and characterization of poly 3-hydroxybutyrate-co-3-hydroxyvalerate in wheat starch wastewater and its potential for nanoparticle synthesis

Polyhydroxyalkanoates (PHAs) are polymers with biodegradable and biocompatible properties accumulated in a wide variety of bacterial strains. In the present study, active sludge, wheat starch wastewater (WSW), and oil wastewater were used for the isolation and screening of PHA-accumulating bacteria. WSW was then implemented as a cheap and economical culture medium for the production of PHAs by the selected isolate. The extracted PHA was characterized, and the capability of produced biopolymer for preparing nanoparticles was evaluated. Based on the results, 96 different bacterial isolates were obtained, of which the strains isolated from WSW demonstrated the highest PHA-accumulation capability. The maximum PHA content of 3.07 g/l (59.50% of dry cell weight) was obtained by strain N6 in 21 h. The selected strain was identified by molecular approaches as Bacillus cereus. Afterward, the physicochemical characterization of an accumulated biopolymer was specified as a PHBV copolymer. Finally, spherical homogenous PHBV nanoparticles with a size of 137 nm were achieved. The PHBV nanoparticles showed a suitable small size and good zeta potential for medical applications. Hence, it can be concluded that isolated wild strain (B. cereus) has the potential exploitation capability for cost-effective PHBV production using the WSW.

In vivo and Post-synthesis Strategies to Enhance the Properties of PHB-Based Materials: A Review

The transition toward "green" alternatives to petroleum-based plastics is driven by the need for "drop-in" replacement materials able to combine characteristics of existing plastics with biodegradability and renewability features. Promising alternatives are the polyhydroxyalkanoates (PHAs), microbial biodegradable polyesters produced by a wide range of microorganisms as carbon, energy, and redox storage material, displaying properties very close to fossil-fuel-derived polyolefins. Among PHAs, polyhydroxybutyrate (PHB) is by far the most well-studied polymer. PHB is a thermoplastic polyester, with very narrow processability window, due to very low resistance to thermal degradation. Since the melting temperature of PHB is around 170-180°C, the processing temperature should be at least 180-190°C. The thermal degradation of PHB at these temperatures proceeds very quickly, causing a rapid decrease in its molecular weight. Moreover, due to its high crystallinity, PHB is stiff and brittle resulting in very poor mechanical properties with low extension at break, which limits its range of application. A further limit to the effective exploitation of these polymers is related to their production costs, which is mostly affected by the costs of the starting feedstocks. Since the first identification of PHB, researchers have faced these issues, and several strategies to improve the processability and reduce brittleness of this polymer have been developed. These approaches range from the in vivo synthesis of PHA copolymers, to the enhancement of post-synthesis PHB-based material performances, thus the addition of additives and plasticizers, acting on the crystallization process as well as on polymer glass transition temperature. In addition, reactive polymer blending with other bio-based polymers represents a versatile approach to modulate polymer properties while preserving its biodegradability. This review examines the state of the art of PHA processing, shedding light on the green and cost-effective tailored strategies aimed at modulating and optimizing polymer performances. Pioneering examples in this field will be examined, and prospects and challenges for their exploitation will be presented. Furthermore, since the establishment of a PHA-based industry passes through the designing of cost-competitive production processes, this review will inspect reported examples assessing this economic aspect, examining the most recent progresses toward process sustainability.

PHBV/PLGA nanoparticles for enhanced delivery of 5-fluorouracil as promising treatment of colon cancer

5-Fluorouracil (5-FU) is one of the most widely used agents in the first-line chemotherapy for colon cancer. However, clinical use of 5-FU is limited because of the low efficacy of drug uptake and systemic toxic effects. Therefore, there is a critical need to find better drug delivery systems in order to improve the efficacy of the drug. In the present study, we have developed a novel combination drug delivery system based on PHBV/PLGA NPs for delivery of 5-FU to cancer cells. NPs were prepared by the double emulsion method and their optimization of preparation was evaluated using Box-Behnken design (BBD) of response surface methodology (RSM). 5-FU loaded NPs were characterized by scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and Fourier transformed infra-red spectroscopy (FT-IR). SEM image implied that NPs were spherical in shape and the results of DSC, TGA, and FT-IR suggest that 5-FU was encapsulated into NPs. The obtained results revealed that 5-FU loaded PHBV/PLGA NPs induced significant higher cell death at concentration much lower than free 5-FU. Results of hemolysis assay indicated that the NPs were hemo-compatible. In vivo anti-tumor studies showed that 5-FU loaded NPs reduced tumor volume significantly in comparison with free 5-FU. As the first example of using PHBV/PLGA as nano-drug delivery system with enhanced anti-tumor activities, this study establishes PHBV/PLGA as a novel promising drug delivery platform for treatment of colon cancer.

Enhanced visible light photocatalysis by TiO2-BN enabled electrospinning of nanofibers for pharmaceutical degradation and wastewater treatment

Boron nitride (BN) nanosheets are promising support materials for catalysts. A series of TiO₂-BN enabled electrospun nanofibers were synthesized for the photocatalytic treatment of ibuprofen and secondary wastewater effluent under visible light. X-ray photoelectron spectroscopy confirmed the existence of B-O-Ti bonds between the BN nanosheets and TiO₂ nanofibers, resulting in energy rearrangement, narrowed band gaps, and enhanced light utilization efficiency of the TiO₂-BN nanocomposites in the visible light spectrum. Transient photocurrent measurements revealed that the BN enhanced the transport of photogenerated holes from the bulk TiO₂ nanofibers to its surface, resulting in more efficient separation and less recombination of the charge carriers. A kinetic study of ibuprofen degradation indicated the enhanced photocatalytic performance of TiO₂-BN catalysts with a higher BN content in the nanocomposites. The kinetic rate constant of the TiO₂-10% BN catalysts was 10 times higher than that of the pure TiO₂ nanofibers. The degradation of organic contaminants in wastewater followed the same trend as ibuprofen and improved with increasing BN content. The stability of the TiO₂-BN nanocomposites as an effective solar photocatalyst was demonstrated by multiple cycles of wastewater treatment. The results proved that TiO₂-BN is an appealing photocatalyst under visible light.

Enhancement of the properties of biosourced poly(3-hydroxybutyrate-co-4-hydroxybutyrate) by the incorporation of natural orotic acid

The aim of this study is to use natural orotic acid (OA) as a sustainable, environmentally friendly additive to improve the crystallization, rheological, thermal, mechanical, and biodegradation properties of bacterially synthesized poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB). OA was found to be an efficient nucleating agent for P34HB, and dramatically enhanced both non-isothermal and isothermal crystallization rates. The incorporation of OA increased nucleation density and decreased spherulite size, but had little effect on the crystalline structure. The rheological properties of the P34HB were greatly improved by the solid filler OA, particularly when a percolation network structure was formed in the blends. The thermal stability of P34HB was strongly enhanced, as exemplified by the ~23 °C increase in the onset thermal decomposition temperature (T_o) for the blend loaded with 5 wt% OA compared to that of pure P34HB. Moreover, the yield strength and elongation at break of P34HB containing 0.5 wt% OA increased by 25% and 119%, respectively. The most intriguing result was the clear enhancement in the enzymatic hydrolysis rates of the P34HB/OA blends compared to that of neat P34HB. The synergetic improvement in these properties may be of significant importance for the wider practical application of biosourced P34HB.

The Effect of Boron Nitride on the Thermal and Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The thermal and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV) composites filled with boron nitride (BN) particles with two different sizes and shapes were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermal gravimetric analysis (TGA) and mechanical testing. The biocomposites were produced by melt extrusion of PHBV with untreated BN and surface-treated BN particles. Thermogravimetric analysis (TGA) showed that the thermal stability of the composites was higher than that of neat PHBV while the effect of the different shapes and sizes of the particles on the thermal stability was insignificant. DSC analysis showed that the crystallinity of the PHBV was not affected significantly by the change in filler concentration and the type of the BN nanoparticle but decreasing of the crystallinity of PHBV/BN composites was observed at higher loadings. BN particles treated with silane coupling agent yielded nanocomposites characterized by good mechanical performance. The results demonstrate that mechanical properties of the composites were found to increase more for the silanized flake type BN (OSFBN) compared to silanized hexagonal disk type BN (OSBN). The highest Young's modulus was obtained for the nanocomposite sample containing 1 wt.% OSFBN, for which increase of Young's modulus up to 19% was observed in comparison to the neat PHBV. The Halpin⁻Tsai and Hui⁻Shia models were used to evaluate the effect of reinforcement by BN particles on the elastic modulus of the composites. Micromechanical models for initial composite stiffness showed good correlation with experimental values.

Cationic Cyclopentadienyliron Complex as a Novel and Successful Nucleating Agent on the Crystallization Behavior of the Biodegradable PHB Polymer

Cationic cyclopentadienyliron (CpFe⁺) is one of the most fruitful organometallic moieties that has been utilized to mediate the facile synthesis of a massive number of macromolecules. However, the ability of this compound to function as a nucleating agent to improve other macromolecule properties has not been explored. This report scrutinizes the influence of the cationic complex as a novel nucleating agent on the spherulitic morphology, crystal structure, and isothermal and non-isothermal crystallization behavior of the Poly(3-hydroxybutyrate) (PHB) bacterial origin. The incorporation of the CpFe⁺ into the PHB materials caused a significant increase in its spherulitic numbers with a remarkable reduction in the spherulitic sizes. Unlike other nucleating agents, the SEM imageries exhibited a good dispersion without forming agglomerates of the CpFe⁺ moieties in the PHB matrix. Moreover, according to the FTIR analysis, the cationic organoiron complex has a strong interaction with the PHB polymeric chains via the coordination with its ester carbonyl. Yet, the XRD results revealed that this incorporation had no significant effect on the PHB crystalline structure. Though the CpFe⁺ had no effect on the polymer’s crystal structure, it accelerated outstandingly the melt crystallization of the PHB. Meanwhile, the crystallization half-times (t_0.5) of the PHB decreased dramatically with the addition of the CpFe⁺. The isothermal and non-isothermal crystallization processes were successfully described using the Avrami model and a modified Avrami model, as well as a combination of the Avrami and Ozawa methods. Finally, the effective activation energy of the PHB/CpFe⁺ nanocomposites was much lower than those of their pure counterparts, which supported the heterogeneous nucleation mechanism with the organometallic moieties, indicating that the CpFe⁺ is a superior nucleating agent for this class of polymer.

Surface Modification of SPIONs in PHBV Microspheres for Biomedical Applications

Surface modification of superparamagnetic iron oxide nanoparticles (SPIONs) has been introduced with lauric acid and oleic acid via co-precipitation and thermal decomposition methods, respectively. This modification is required to increase the stability of SPIONs when incorporated in hydrophobic, biodegradable and biocompatible polymers such as poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). In this work, the solid-in-oil-in-water (S/O/W) emulsion-solvent extraction/evaporation method was utilized to fabricate magnetic polymer microspheres incorporating SPIONs in PHBV. The prepared magnetic PHBV microspheres exhibited particle sizes <1 µm. The presence of functional groups of lauric acid, oleic acid and iron oxide in the PHBV microspheres was confirmed by Fourier Transform Infrared spectroscopy (FTIR). X-ray diffraction (XRD) analysis was performed to further confirm the success of the combination of modified SPIONs and PHBV. Thermogravimetric analysis (TGA) indicated that PHBV microspheres were incorporated with SPIONs^Lauric as compared with SPIONs^Oleic. This was also proven via magnetic susceptibility measurement as a higher value of this magnetic property was detected for PHBV/SPIONs^Lauric microspheres. It was revealed that the magnetic PHBV microspheres were non-toxic when assessed with mouse embryotic fibroblast cells (MEF) at different concentrations of microspheres. These results confirmed that the fabricated magnetic PHBV microspheres are potential candidates for use in biomedical applications.

High photodegradation and antibacterial activity of BN–Ag/TiO2 composite nanofibers under visible light

To develop material with good photocatalytic properties for organic compound degradation and bacterial removal, we produced Ag/TiO₂ and BN–Ag/TiO₂ composite nanofibers that included controlled amounts of boron nitride (BN) nanosheets and silver (Ag).

Potential of polyhydroxyalkanoate (PHA) polymers family as substitutes of petroleum based polymers for packaging applications and solutions brought by their composites to form barrier materials

Today, there is an increasing concern about protection of ecological systems. Petro-based synthetic polymers are not biodegradable and cause environmental pollution. These polymers that are stuck in nature, affect wildlife adversely. Also, in future petrochemical materials will drain away and demand for eco-friendly plastics which can substitute synthetic plastics will increase. Biopolymers are products which can be degraded by enzymatic activities of various microorganisms, and the degradation products are nontoxic. They are attractive alternatives to non-degradable materials in short-term applications such as packaging. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a member of polyhydroxyalkanoate (PHA) family which is biodegradable and produced by microorganism. It has good gas barrier properties that make it convenient to use in different applications. The present paper gives an overview on PHAs and their composites, their main properties, with a specific focus on potential applications of PHBV in packaging.

Fabrication and evaluation of Rb2Co(H2P2O7)2·2H2O/waterborne polyurethane nanocomposite coating for corrosion protection aspects

Here we investigate the influence of new acidic pyrophosphate (Rb₂Co(H₂P₂O₇)₂·2H₂O) (DP) incorporation in waterborne polyurethane (WBPU) coatings on the corrosion protection efficiency of WBPU coatings for carbon steel in 3.5% NaCl solution.

Enhanced photocatalytic performance of novel electrospun BN/TiO2 composite nanofibers

We report the elaboration of novel BN/TiO₂ composite nanofibers with different amounts of BN sheets and their photocatalytic activity under UV irradiation.