New Evidences of Glass Transitions and Microstructures of Soy Protein Plasticized with Glycerol

Structural, material and antibacterial properties of quercetin incorporated soy protein isolate films and its binding behavior through molecular docking

This study aimed to investigate the three different methods for the fabrication of quercetin (1%-3% w/w of protein) incorporated soy protein isolate (SPI) films and their effect on material properties. The quercetin incorporated SPI films prepared by these methods were characterized by Fourier transform infrared (FTIR) spectroscopy, UV-Vis spectrophotometer, tensile properties, and water uptake and leaching properties. The cross-linking pattern was revealed by the FTIR spectrum that showed formation of an ester group because of interaction between the quercetin hydroxyl group and the carboxyl side chain of SPI amino acids. The tensile strength of SPI films were enhanced with the addition of quercetin as it increased to a maximum of 6.17 MPa while neat SPI film had tensile strength 4.13 MPa. The prepared films exhibit significant antibacterial activity against Listeria monocytogenes and Escherichia coli. The In-silico docking analysis demonstrates that covalent and non-covalent forces play crucial roles in binding interaction. It shows the formation of four hydrogen bonds, two salt bridges along with one pi-alkyl interaction. The simulation studies reflect the crucial amino acid residues involved in SPI-quercetin binding. The effect of quercetin binding with SPI on its stability and compactness is revealed by Root mean square deviation (RMSD) and radius of gyration studies.

Statistical optimization of a sustainable fertilizer composition based on black soldier fly larvae as source of nitrogen

In the present work, a statistical optimization of a sustainable coating for core-shell NPK (Nitrogen-Phosphorus-Potassium) fertilizers was investigated. The environmental green coating was enriched in nitrogen using a biomass and renewable source, namely the nitrogen rich fraction of black soldier fly larvae (BSFL) (Hermetia Illucens, Diptera: Stratiomyidae) reared on vegetable waste. A rational approach was proposed with the aim of calculating the best formulation of the coating, considering both its manufacturing behavior, such as adhesion to the core, and its physical properties, such as homogeneity or plasticity. From a circular economy perspective, together with the nitrogen-rich fraction from BSFL (from 51 to 90 wt.%), water and glycerol were considered for the coating formulation in different proportion: from 10 to 32 wt.% and from 0 to 17 wt.% respectively. The Design of Experiments technique was implemented to limit the total number of tests for the coating formulation (18 tests). ANOVA was employed, with the aim of obtaining mathematical models to derive a better precise and objective formulation. The results show that the use of glycerol can be avoided, as well as only a limited amount of water (11 wt.%) is necessary to obtain an optimized coating formulation, thereafter, satisfying the more relevant technological and physical properties for the coating manufacturing.

Tunable surface wettability and pH-responsive 2D structures from amphiphilic and amphoteric protein microfibrils

Two dimensional films and paper-like structures (60–170 μm thick) have been facilely fabricated by casting ethanolic dispersions of amphiphilic and amphoteric protein microfibrils (ca. 1.3 μm width; 53 μm length) under controlled temperatures and moisture levels. Surface hydrophilicity or hydrophobicity can be easily tuned by the abillity of the highly responsive microfibers to self-organize at the interface to mimic the hydrophilicity or hydrophobicity of cast substrates. For instance, surfaces cast on hydrophobic polystyrene or Teflon were moderately hydrophobic with water contact angles (WCAs) of 54°–71° while those on hydrophilic glass or exposed to air were hydrophilic (WCAs: 5°–10°). Thin film dried in the presence of moisture (60% RH) at 65 °C had the highest crystallinity (CrI: 56%) and β structure (64%), including 48% β-sheet form, and exhibited moisture-responsive T_g, pH-responsive planar swelling, and excellent wet resiliency in extremely acidic (pH = 0) to basic (pH = 10) conditions. The pH-dependent release of highly water-soluble cationic methylene blue bound to protein microfibril (SPMF) films attests to their amphoterism and demonstrates the applicability of such 2D structures for pH-dependent controlled release of other cationic and anionic species. Such versatility of amphiphilic and amphoteric protein microfibrils can be engineered into 2D structures with tunable surface hydrophilicity and hydrophobicity, moisture- and pH-responsive behaviors and controlled release capabilities.

2D structures from amphiphilic and amphoteric protein microfibrils with tunable surface amphiphilicity, pH-responsive controlled release of cationic and anionic species.

Hybrid Bionanocomposites from Spent Hen Proteins

Spent hens, a poultry by-product, have little economic value for processing and mostly end up in landfills. However, there are concerns over disposal of spent hens; therefore, it is pertinent to find out alternative uses that are environmentally sound. On the other hand, single-use plastic packaging is leading to a global environmental crisis. In this study, proteins were extracted from spent hen, plasticized, and processed into films by compression molding. The hybrid bionanocomposite films were successfully prepared using glycerol as a plasticizer, chitosan as a cross-linker, and varying concentrations of nanoclay as a nanoreinforcement. The effects of nanoreinforcements, plasticization, and cross-linking were then evaluated on thermal, mechanical, and barrier properties of the prepared bionanocomposite films. Various concentrations of nanoclay and chitosan were dispersed in the protein matrix. However, with the same plasticizer loading, the optimum addition of chitosan and nanoclay led to almost twofold increase in the mechanical strength, compared to neat protein films. The results indicated that at optimal conditions, a good intercalation and/or exfoliation of the protein biopolymers into clay interlayer galleries was observed leading to improved thermal, thermomechanical, and barrier properties. These hybrid bionanocomposite films have great future potential to be used in packaging and other applications.

Fabrication, properties and applications of soy-protein-based materials: A review

The environmental crisis caused by the use of petroleum-based nondegradable polymers and the impending petroleum finite resources have directly threatened human being's sustainable development. Therefore, ecofriendly polymers based on natural renewable resources are attracting more and more attention. As the byproducts of soy oil industries, soy protein, is regarded as a viable alternative for petroleum-based polymeric products. In order to improve the physical properties, especially the mechanical properties and water resistance that limit their extensive applications, different modifications were adopted. Among these efforts, incorporating nanoparticles and blending with other polymers are proved to be effective ways. The properties of the resulting materials are highly dependent on the processing methods, nature of the components, dispersion status and the compatibility. This review intends to provide a clear overview on preparation, properties, and applications of soy-protein-based materials. These biodegradable materials will find more and more potential applications in biodegradable foams, edible films, packaging materials, biomedical materials, etc.

Chicken feathers as a natural source of sulphur to develop sustainable protein films with enhanced properties

In this work, the effect of hydrolyzed keratin on the properties of soy protein-based films was analyzed when different manufacture processes were employed. It is widely known that the processing method selected can affect the film properties as a function of the structure obtained during the film formation. Therefore, the assessment of hydrolyzed keratin/soy protein films processed by casting and compression moulding was carried out by means of the analysis of physicochemical, thermal, mechanical, optical and surface properties. It was observed that the incorporation of hydrolyzed keratin, obtained from a simpler, environmentally friendlier and more sustainable extraction method, resulted in the improvement of the thermal stability of the films, irrespective of the processing method employed. Moreover, the films processed by compression moulding showed enhanced tensile strength, which increased with the incorporation of hydrolyzed keratin due to the formation of disulfide bonds.

Protein-Based Bioproducts

Plant proteins can be used for the production of a variety of bioproducts, including films and coatings, adhesives, fibres and pharmaceuticals. Proteins derived from plant production systems have many advantages: they are safe, low-cost and rapidly deployable, allow for simple product storage and result in proteins that are properly folded, assembled and post-translationally modified. While plant-derived protein-based products are natural, renewable, biodegradable and environmentally friendly, they tend to be lower in strength and elasticity than their corresponding synthetic products. Current research in this area is focused on overcoming challenges in plant production platforms related to yield, purification, regulatory approval and customer acceptance.

Soy Protein Isolate and Glycerol Hydrogen Bonding Using Two-Dimensional Correlation (2D-COS) Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy

It is a trend to substitute bioplastics for petroleum-based plastics in food packaging. Glycerol-plasticized soy protein isolate (SPI) is promising as a replacement for traditional petroleum-based plastics. Hydrogen bonding (H-bonding) plays a key role in plasticization of SPI film. However, few publications are concerned with the interactions of SPI and glycerol at the molecular level. In this paper, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy was applied to investigate the effect of H-bonding on the secondary structures of glycerol-plasticized SPI films and thus on the plasticization. An "S" profile of the H-bonding between SPI and glycerol with an abrupt jump in the glycerol range of 10-30% was achieved. For more in-depth investigation of the H-bonding, two-dimensional correlation spectroscopy (2D-COS) and perturbation-correlation moving-window two-dimensional (PCMW2D) analyses were applied to the amide I and II bands of SPI films spectra series. The conformation change sequences under the effect of H-bonding were revealed. When glycerol was involved, it entered into the β-sheet and the H-bonds of the SPI peptide backbone (C = O···H-N-) were replaced by the new H-bonds between SPI and glycerol (C = O···H-O-). The transformations of parallel β-sheet to β-turn in the range of 0-20% and anti-parallel β-sheet to β-turn in the range of 20-35% were obtained. In the 35-60% concentration range, the β-sheet was first changed to a transition state conformation, then together with the β-turn, to the random coil. The 2D-COS results clearly suggest that the conformations of SPI gradually change from the ordered to the less ordered and disordered, which significantly improve the plasticity of SPI film.

Glass transitions in native silk fibres studied by dynamic mechanical thermal analysis

Silks are a family of semi-crystalline structural materials, spun naturally by insects, spiders and even crustaceans. Compared to the characteristic β-sheet crystalline structure in silks, the non-crystalline structure and its composition deserves more attention as it is equally critical to the filaments' high toughness and strength. Here we further unravel the structure-property relationship in silks using Dynamic Mechanical Thermal Analysis (DMTA). This technique allows us to examine the most important structural relaxation event of the disordered structure the disordered structure, the glass transition (GT), in native silk fibres of the lepidopteran Bombyx mori and Antheraea pernyi and the spider Nephila edulis. The measured glass transition temperature Tg, loss tangent tan δ and dynamic storage modulus are quantitatively modelled based on Group Interaction Modelling (GIM). The "variability" issue in native silks can be conveniently explained by the different degrees of structural disorder as revealed by DMTA. The new insights will facilitate a more comprehensive understanding of the structure-property relations for a wide range of biopolymers.

Determination and Quantification of Molecular Interactions in Protein Films: A Review

Protein based films are nowadays also prepared with the aim of replacing expensive, crude oil-based polymers as environmentally friendly and renewable alternatives. The protein structure determines the ability of protein chains to form intra- and intermolecular bonds, whereas the degree of cross-linking depends on the amino acid composition and molecular weight of the protein, besides the conditions used in film preparation and processing. The functionality varies significantly depending on the type of protein and affects the resulting film quality and properties. This paper reviews the methods used in examination of molecular interactions in protein films and discusses how these intermolecular interactions can be quantified. The qualitative determination methods can be distinguished by structural analysis of solutions (electrophoretic analysis, size exclusion chromatography) and analysis of solid films (spectroscopy techniques, X-ray scattering methods). To quantify molecular interactions involved, two methods were found to be the most suitable: protein film swelling and solubility. The importance of non-covalent and covalent interactions in protein films can be investigated using different solvents. The research was focused on whey protein, whereas soy protein and wheat gluten were included as further examples of proteins.

Improvement of the Mechanical Properties of Soy Protein Isolate Based Plastics through Formulation and Processing

This paper reviews the characterization of the base strength and impact of water absorption on biodegradable, namely, soy protein-based plastics prepared by different methods. The initial approach included using different quantities of soy hydrolysate plasticized with glycerol, which is widely known for its plasticizing effect. With the second approach, the raw polymer was which plasticized with glycerol compounded with different additives such as polycaprolactone or zinc sterate, and was also heat-treated at various temperatures after injection molding. The results indicated the polycaprolactone and, respectively, a medium to high heat treatment significantly enhanced tensile strength and greatly decreased water absorption. The soy hydrolysate formulations that were studied enhanced tensile strength but didn not significantly improve elongation or water absorption.

Mechanical and Thermal Behaviour of Ecofriendly Composites Reinforced byKenafandCaroàFibers

Two kinds of environmental friendly composites were prepared based on sustainable matrices, respectively, defatted cross-linked soy flour and thermoplastic polyhydroxybutyrate cohydroxyvalerate, reinforced by natural fibers fromCaroàandKenafplants. The obtained composites were compared in terms of moisture tolerance, thermal and mechanical properties, and thermoregulation ability. It was found that this ecofriendly systems have suitable properties for indoor applications in housing and transportation.

Effects of plasticization and shear stress on phase structure development and properties of soy protein blends

In this study, soy protein concentrate (SPC) was used as a plastic component to blend with poly(butylene adipate-co-terephthalate) (PBAT). Effects of SPC plasticization and blend composition on its deformation during mixing were studied in detail. Influence of using water as the major plasticizer and glycerol as the co-plasticizer on the deformation of the SPC phase during mixing was explored. The effect of shear stress, as affected by SPC loading level, on the phase structure of SPC in the blends was also investigated. Quantitative analysis of the aspect ratio of SPC particles was conducted by using ImageJ software, and an empirical model predicting the formation of percolated structure was applied. The experimental results and the model prediction showed a fairly good agreement. The experimental results and statistic analysis suggest that both SPC loading level and its water content prior to compounding had significant influences on development of the SPC phase structure and were correlated in determining the morphological structures of the resulting blends. Consequently, physical and mechanical properties of the blends greatly depended on the phase morphology and PBAT/SPC ratio of the blends.

Protein substitution affects glass transition temperature and thermal stability

When proteins are removed from their native state they suffer from two deficiencies: (1) glassy behavior with glass transition temperatures (Tg) well above room temperature and (2) thermal instability. The glassy behavior originates in multiple hydrogen bonds between amino acids on adjacent protein molecules. Proteins, like most biopolymers, are thermally unstable. Substituting ovalbumin with linear and cyclic substituents using a facile nucleophilic addition reaction can affect Tg and thermal stability. More hydrophobic linear substituents lowered Tg by interrupting intermolecular interactions and increasing free volume. More hydrophilic and cyclic substituents increased thermal stability by increasing intermolecular interactions. In some cases, substituents instituted cross-linking between protein chains that enhanced thermal stability. Internal plasticization using covalent substitution and external plasticization using low molecular weight polar liquids show the same protein structural changes and a signature of plasticization is identified.