Seaweed as Basis of Eco-Sustainable Plastic Materials: Focus on Alginate.

Seaweed, a diverse and abundant marine resource, holds promise as a renewable feedstock for bioplastics due to its polysaccharide-rich composition. This review explores different methods for extracting and processing seaweed polysaccharides, focusing on the production of alginate plastic materials. Seaweed emerges as a promising solution, due to its abundance, minimal environmental impact, and diverse industrial applications, such as feed and food, plant and soil nutrition, nutraceutical hydrocolloids, personal care, and bioplastics. Various manufacturing techniques, such as solvent casting, injection moulding, and extrusion, are discussed for producing seaweed-based bioplastics. Alginate, obtained mainly from brown seaweed, is particularly known for its gel-forming properties and presents versatile applications in many sectors (food, pharmaceutical, agriculture). This review further examines the current state of the bioplastics market, highlighting the growing demand for sustainable alternatives to conventional plastics. The integration of seaweed-derived bioplastics into mainstream markets presents opportunities for reducing plastic pollution and promoting sustainability in material production.

Properties of biopolymer blends based on Rugulopteryx okamurae and hydrophobic polycaprolactone (PCL) and hydrophilic acylated soy protein isolated (SPIa).

The present study explored the utilization of Rugulopteryx okamurae (RO), an invasive brown seaweed, as a renewable raw material for plastic materials based on biopolymer blends. The goal of this study was to improve the previously observed poor mechanical properties of materials based on single biopolymer RO. To enhance these properties, two polymers with distinct hydrophobicities were incorporated into the formulation of different blends: hydrophobic polycaprolactone (PCL) and hydrophilic acylated soy protein isolate (SPIa). SPIa was derived from soy protein through a chemical modification process, introducing hydrophilic carboxyl groups. The addition of PCL significantly strengthened the blend, increasing the storage modulus (E'1 Hz) from ~ 110 to ~ 250 MPa. Conversely, SPIa incorporation resulted in softening, with E' values around 40 MPa. Both additives enhanced deformability proportionally to their concentrations, with SPIa exhibiting notably higher deformability, reaching a maximum deformation of ~ 23% for a RO/SPIa ratio of 25/75. In summary, the study demonstrates the feasibility of producing environmentally friendly blend materials based on RO, tailored for specific applications by incorporating suitable additives into the formulation. Therefore, PCL is recommended for applications susceptible to moisture effects, such as packaging, while SPIa is suggested for highly absorbent applications such as personal care or horticulture.

Optimization of Ink Composition and 3D Printing Process to Develop Soy Protein-Based Scaffolds.

Inks based on soybean protein isolate (SPI) were developed and their formulations were optimized as a function of the ink heat treatment and the content of other biopolymers to assess the effects of protein-polysaccharides and protein-protein interactions. First, the rheological behavior of the inks was analyzed in relation to the polyvinyl alcohol (PVA) concentration employed (20, 25, and 30 wt%) and, as a result of the analysis, the ink with 25 wt% PVA was selected. Additionally, sodium alginate (SA) and gelatin (GEL) were added to the formulations to improve the viscoelastic properties of the inks and the effect of the SA or GEL concentrations (1, 2, and 3 wt%) was studied. All inks showed shear thinning behavior and self-supporting abilities. Among all the 3D printed scaffolds, those with higher SA (3 wt%) or GEL (2 and 3 wt%) content showed higher shape fidelity and were selected for further characterization. Texture profile analysis demonstrated that the scaffolds prepared with previously heat-treated inks containing 3 wt% GEL showed the highest strength. Additionally, these scaffolds showed a higher water-uptake capacity profile.

Feasibility of Invasive Brown Seaweed Rugulopteryx okamurae as Source of Alginate: Characterization of Products and Evaluation of Derived Gels.

Rugulopteryx okamurae (RO) is an invasive brown seaweed that causes severe environmental problems in the Mediterranean Sea. This work proposed an extraction method that enables their use as a raw material for producing sodium alginate. Alginate was successfully extracted from this invasive seaweed, with its gelling performance in the presence of Ca2+ ions comparable to existing commercial alginates. The mannuronic acid (M)-to-guluronic (G) acid ratio in the 1H-NMR profile indicated a higher percentage of G in the RO-extracted alginate, which implies a greater formation of so-called egg box structures. These differences resulted in their different rheological behaviour, as sodium alginate aqueous solutions exhibited a greater viscosity (η at 1 s-1 = 3.8 ± 0.052 Pa·s) than commercial alginate (2.8 ± 0.024 Pa·s), which is related to the egg box structure developed. When gelled in the presence of calcium, an increase in the value of the elastic modulus was observed. However, the value of the tan δ for the extracted alginate was lower than that of commercial alginate gels, confirming a structure more densely packed, which implies a different restructuring of the alginate chain when gelling. These results confirm the suitability of using invasive Rugulopteryx okamurae as a source of calcium alginate gels. In this way, sustainable bio-based materials may be produced from undesired biomass that currently poses a threat to the ecosystem.

Three-Dimensional Printing of Red Algae Biopolymers: Effect of Locust Bean Gum on Rheology and Processability.

Seaweeds, rich in high-value polysaccharides with thickening/gelling properties (e.g., agar, carrageenan, and alginate), are extensively used in the food industry for texture customization and enhancement. However, conventional extraction methods for these hydrocolloids often involve potentially hazardous chemicals and long extraction times. In this study, three red seaweed species (Chondrus crispus, Gelidium Corneum, and Gracilaria gracilis) commercialized as food ingredients by local companies were chosen for their native gelling biopolymers, which were extracted using water-based methodologies (i.e., (1) hydration at room temperature; (2) stirring at 90 °C; and (3) centrifugation at 40 °C) for production of sustainable food gels. The potential use of these extracts as bioinks was assessed employing an extrusion-based 3D printer. The present work aimed to study the gelation process, taken place during printing, and assess the effectiveness of the selected green extraction method in producing gels. To improve the definition of the printed gel, two critical printing parameters were investigated: the addition of locust bean gum (LBG) at different concentrations (0, 0.5, 1, 1.5, 2, and 2.5%) and printing temperature (30, 40, 60, and 80 °C). Rheological results from a controlled-stress rheometer indicated that gels derived from G. corneum and G. gracilis exhibited a lower gel strength (lower G' and G″) and excessive material spreading during deposition (lower viscosity) than C. crispus. Thus, G' was around 5 and 70 times higher for C. crispus gels than for G. corneum and G. gracilis, respectively. When increasing LBG concentration (0.5 to 2.5% w/w) and lowering the printing temperature (80 to 30 °C), an enhanced gel matrix definition for G. corneum and G. gracilis gels was found. In contrast, gels from C. crispus demonstrated greater stability and were less influenced by these parameters, showcasing the potential of the seaweed to develop sustainable clean label food gels. Eventually, these results highlight the feasibility of using algal-based extracts obtained through a green procedure as bioinks where LBG was employed as a synergic ingredient.

Development and Characterization of Edible Films Based on Cassava Starch Modified by Corona Treatment.

Corona treatment (CT), a surface treatment widely used in the plastic industry, can be used to alter the properties of cassava starch. In the present work, CT was performed on dry granular starch (DS), water-suspended humid granular starch (HS), and gelatinized starch (GS). Different properties and structural characteristics of treated starches were studied. A lowering in pH was generally observed after CT and the rheological properties depended on the starch presentation. A reinforcement of DS and HS samples after CT was deduced from higher viscosity values in flow assays and viscoelastic moduli, but weak gels were obtained when CT was applied to GS. Changes in the A-type polymorphic structure, as well as a drop in relative crystallinity, were produced by CT for DS and HS. Additionally, changes in O-H and C-O-C FTIR bands were observed. Therefore, CT can be applied for starch modification, producing predominantly cross-linking in the DS and de-polymerization in the HS. Casting films made from the modified DS showed higher tensile strength and lower hydrophilicity, solubility, water absorption capacity, and water vapor permeability. Thus, the DS cross-linking induced by CT improved mechanical characteristics and hydrophobicity in edible films, which can be better used as packaging materials.

Zein as a Basis of Recyclable Injection Moulded Materials: Effect of Formulation and Processing Conditions.

The growing concern about reducing carbon footprint has led to the progressive replacement of traditional polymeric materials by natural-based biodegradable materials. However, materials from natural sources (i.e., plants) typically possess poorer mechanical properties when compared to conventional plastics. To counterbalance this, they need to be adequately formulated and processed to eventually meet the standards for certain applications. Zein is the major storage protein from corn and can be obtained as a by-product from the corn-oil industry. It is an excellent candidate for producing green materials due to its stability, biodegradability, renewability, and suitable mechanical and technical-functional properties. In the present work, zein was blended with a plasticizer (i.e., glycerol) at three different zein/glycerol ratios (75/25, 70/30, and 65/25) and then injection moulded at three different processing temperatures (120, 150, and 190 °C). The properties of both blends and bioplastics were evaluated using dynamic mechanical analysis (DMA), tensile tests, and water absorption capacity (WUC). The properties-structure interrelation was assessed through a scanning electron microscope. Generally, a higher zein content and processing temperature led to a certain reinforcement of the samples. Moreover, all bioplastics displayed a thermoplastic behaviour finally melting at temperatures around 80 °C. The lack of massive crosslinking enabled this melting, which finally could be used to confirm the ability of zein based materials to be recycled, while maintaining their properties. The recyclability of thermoplastic zein materials widens the scope of their application, especially considering its biodegradability.

Functionalization Routes for Keratin from Poultry Industry Side-Streams-Towards Bio-Based Absorbent Polymers.

Keratin is a largely available protein that can be obtained from the ca. 3 million tons of feathers that the European poultry industry produces as a side-stream. Here, the functionalization of keratin from poultry feathers was evaluated using a one- versus two-stage process using two functionalization agents (succinic anhydride-SA and ethylene dianhydride-EDTAD). The functionalization resulted in the keratin having improved liquid swelling capacities, reaching up to 400%, 300%, and 85% increase in water, saline, and blood, respectively, compared to non-functionalized keratin. The highest swelling was obtained for samples functionalized with EDTAD (one-stage process), while the highest saline uptake was noted for samples processed with 25 wt% SA (two-stage process). Swelling kinetics modeling indicated that the water uptake by the functionalized samples takes place in two steps, and the EDTAD samples showed the highest diffusivity. It is demonstrated that the one-stage functionalization of keratin utilizing EDTAD results in better performance than two-stages, which allows for resource-saving and, thereby, protecting the environment. The results show some potential for the keratin to be utilized as liquid absorbent materials in water, saline, and blood uptake applications. Using keratin from side-streams is an advantage from a sustainability perspective over biomacromolecules that need to be extracted from virgin biomass.

Eco-Composites from Silkworm Meal and Polycaprolactone: Effect of Formulation and Processing Conditions.

The production of green plastic materials from defatted silkworm meal (SW) through a scalable technique (e.g., injection moulding) would permit the revalorization of a by-product of the textile industry. The textile by-product contains an estimable protein content (~50%) which can justify its applicability in the field of eco-materials. Thus, SW-based materials have been processed and characterized, sometimes requiring the addition of another biodegradable polymer, such as polycaprolactone (PCL), in the formulation. Thermomechanical, tensile and water uptake properties have been assessed at different PCL contents (from 0 to 20%). The viscoelasticity of the plastic composites when heated was greatly affected by the melting point of PCL, which also led generally to an increase in their extensibility and resistance. However, this effect of PCL was diminished when composites were processed at higher moulding temperatures. As PCL possesses a hydrophobic character, a decrease in the water uptake was generally detected as PCL content increased, which could also be related to the lower plasticizer content in the formulation. Silkworm meal is an adequate ingredient to consider in the production of green plastic materials that would eventually add value to a main by-product of the sericulture industry.

Processing and Characterization of Bioplastics from the Invasive Seaweed Rugulopteryx okamurae.

The seaweed Rugulopteryx okamurae, from the Pacific Ocean, is considered an invasive species in the Mediterranean Sea. In this work, the use of this seaweed is proposed for the development of bio-based plastic materials (bioplastics) as a possible solution to the pollution produced by the plastic industry. The raw seaweed Rugulopteryx okamurae was firstly blended with glycerol (ratios: 50/50, 60/40 and 70/30), and subsequently, they were processed by injection molding at a mold temperature of 90, 120 and 150 °C. The rheological properties (frequency sweep tests and temperature ramp tests) were obtained for blends before and after processing by injection molding. The functional properties of the bioplastics were determined by the water uptake capacity (WUC) values and further scanning electron microscopy (SEM). The results obtained indicated that E' was always greater than E", which implies a predominantly elastic behavior. The 70/30 ratio presents higher values for both the viscoelastic moduli and tensile properties than the rest of the systems (186.53 ± 22.80 MPa and 2.61 ± 0.51 MPa, respectively). The WUC decreased with the increase in seaweed in the mixture, ranging from 262% for the 50/50 ratio to 181% for the 70/30 ratio. When carrying out the study on molded bioplastic 70/30 at different temperatures, the seaweed content did not exert a remarkable influence on the final properties of the bioplastics obtained. Thus, this invasive species could be used as raw material for the manufacture of environmentally friendly materials processed by injection molding, with several applications such as food packaging, control-release, etc.

3D Printed Chitosan-Pectin Hydrogels: From Rheological Characterization to Scaffold Development and Assessment.

Chitosan-pectin hydrogels were prepared, and their rheological properties were assessed in order to select the best system to develop scaffolds by 3D printing. Hydrogels showed a weak gel behavior with shear thinning flow properties, caused by the physical interactions formed between both polysaccharides, as observed by FTIR analysis. Since systems with high concentration of pectin showed aggregations, the system composed of 2 wt% chitosan and 2 wt% pectin (CHI2PEC2) was selected for 3D printing. 3D printed scaffolds showed good shape accuracy, and SEM and XRD analyses revealed a homogeneous and amorphous structure. Moreover, scaffolds were stable and kept their shape and size after a cycle of compression sweeps. Their integrity was also maintained after immersion in PBS at 37 °C, showing a high swelling capacity, suitable for exudate absorption in wound healing applications.

Rheology and Water Absorption Properties of Alginate-Soy Protein Composites.

Composite materials based on proteins and carbohydrates normally offer improved water solubility, biodegradability, and biocompatibility, which make them attractive for a wide range of applications. Soy protein isolate (SPI) has shown superabsorbent properties that are useful in fields such as agriculture. Alginate salts (ALG) are linear anionic polysaccharides obtained at a low cost from brown algae, displaying a good enough biocompatibility to be considered for medical applications. As alginates are quite hydrophilic, the exchange of ions from guluronic acid present in its molecular structure with divalent cations, particularly Ca2+, may induce its gelation, which would inhibit its solubilization in water. Both biopolymers SPI and ALG were used to produce composites through injection moulding using glycerol (Gly) as a plasticizer. Different biopolymer/plasticizer ratios were employed, and the SPI/ALG ratio within the biopolymer fraction was also varied. Furthermore, composites were immersed in different CaCl2 solutions to inhibit the amount of soluble matter loss and to enhance the mechanical properties of the resulting porous matrices. The main goal of the present work was the development and characterization of green porous matrices with inhibited solubility thanks to the gelation of alginate.

Proteins from Agri-Food Industrial Biowastes or Co-Products and Their Applications as Green Materials.

A great amount of biowastes, comprising byproducts and biomass wastes, is originated yearly from the agri-food industry. These biowastes are commonly rich in proteins and polysaccharides and are mainly discarded or used for animal feeding. As regulations aim to shift from a fossil-based to a bio-based circular economy model, biowastes are also being employed for producing bio-based materials. This may involve their use in high-value applications and therefore a remarkable revalorization of those resources. The present review summarizes the main sources of protein from biowastes and co-products of the agri-food industry (i.e., wheat gluten, potato, zein, soy, rapeseed, sunflower, protein, casein, whey, blood, gelatin, collagen, keratin, and algae protein concentrates), assessing the bioplastic application (i.e., food packaging and coating, controlled release of active agents, absorbent and superabsorbent materials, agriculture, and scaffolds) for which they have been more extensively produced. The most common wet and dry processes to produce protein-based materials are also described (i.e., compression molding, injection molding, extrusion, 3D-printing, casting, and electrospinning), as well as the main characterization techniques (i.e., mechanical and rheological properties, tensile strength tests, rheological tests, thermal characterization, and optical properties). In this sense, the strategy of producing materials from biowastes to be used in agricultural applications, which converge with the zero-waste approach, seems to be remarkably attractive from a sustainability prospect (including environmental, economic, and social angles). This approach allows envisioning a reduction of some of the impacts along the product life cycle, contributing to tackling the transition toward a circular economy.

Strengthening of Porcine Plasma Protein Superabsorbent Materials through a Solubilization-Freeze-Drying Process.

The replacement of common acrylic derivatives by biodegradable materials in the formulation of superabsorbent materials would lessen the associated environmental impact. Moreover, the use of by-products or biowastes from the food industry that are usually discarded would promote a desired circular economy. The present study deals with the development of superabsorbent materials based on a by-product from the meat industry, namely plasma protein, focusing on the effects of a freeze-drying stage before blending with glycerol and eventual injection molding. More specifically, this freeze-drying stage is carried out either directly on the protein flour or after its solubilization in deionized water (10% w/w). Superabsorbent materials obtained after this solubilization-freeze-drying process display higher Young's modulus and tensile strength values, without affecting their water uptake capacity. As greater water uptake is commonly related to poorer mechanical properties, the proposed solubilization-freeze-drying process is a useful strategy for producing strengthened hydrophilic materials.

Development of bioplastics from a microalgae consortium from wastewater.

Nowadays, as the world population is in need of creating alternative materials that can replace conventional plastics, microalgae biomass may be identified as a viable source for producing more environmentally friendly materials. Scenedesmus sp and Desmodesmus sp are the main components (~80%) of a microalgae consortium (MC) that first has been used to remove Nitrogen and Phosphorus from wastewater. The potential to develop bioplastic materials from MC considering its relatively high protein content (~48%) has been assessed in the present manuscript, using as a reference a commercial biomass rich an Arthrospira specie (AM) also present in the studied consortium. Bioplastics were obtained through injection moulding of blends obtained after mixing with different amounts of glycerol, and eventually characterized using Dynamic Mechanical Thermal Analysis (DMTA), water immersion and tensile tests. All bioplastics displayed a glass transition temperature around 60 °C, showing a thermoplastic behavior which is less pronounced in the CM based bioplastics. This would imply a greater thermal resistance of bioplastics produced from the biomass harvested in wastewater. Moreover, these bioplastics showed a lower ability to absorb water when immersed, due to the lower deformability displayed in the tensile tests. The mechanical properties of all samples, independently of the nature of the biomass, were improved when the presence of the biomass was higher. Therefore, results here presented prove the potential of valorisation of microalgae consortia used in the effective treatment of wastewater through the development of bioplastic materials.

Effect of pH on the thermal gelation of carob protein isolate.

The specific aim of this work was to study the capability of a carob protein isolate (CPI) to produce self-supporting gels when subjected to a thermal treatment. CPI aqueous dispersions (10, 20 and 30 wt% protein basis) at three different pH values (2, 6 and 10) were subjected to a heating/cooling process (95 °C-30 min/4 °C-24 h) leading to the formation of self-supporting gels. Those gels were characterized for dynamic rheological properties; water holding capacity (WHC); textural properties; extractability in different media; scanning electron microscopy; and SDS-PAGE profiles of the soluble proteins. The results demonstrated that self-supporting CPI gels can only be obtained at concentrations higher than 20 wt%, being favoured at extreme pH values, especially at alkaline pH. At pH 10, gels with higher dynamic elastic and hardness properties and appropriate WHC were formed due to the promotion of disulphide bonds formation. Thus, if higher rheological properties and hardness are required for thermally treated CPI gels, alkaline pH conditions that favour hydrophobic interactions and disulphide bonding should be selected.

Influence of tragacanth gum in egg white based bioplastics: Thermomechanical and water uptake properties.

This study aims to extend the range of applications of tragacanth gum by studying its incorporation into bioplastics formulation, exploring the influence that different gum contents (0-20wt.%) exert over the thermomechanical and water uptake properties of bioplastics based on egg white albumen protein (EW). The effect of plasticizer nature was also evaluated through the modification of the water/glycerol ratio within the plasticizer fraction (fixed at 40wt.%). The addition of tragacanth gum generally yielded an enhancement of the water uptake capacity, being doubled at the highest content. Conversely, presence of tragacanth gum resulted in a considerable decrease in the bioplastic mechanical properties: both tensile strength and maximum elongation were reduced up to 75% approximately when compared to the gum-free system. Ageing of selected samples was also studied, revealing an important effect of storage time when tragacanth gum is present, possibly due to its hydrophilic character.

Shear and extensional properties of kefiran.

Kefiran is a neutral polysaccharide constituted by glucose and galactose produced by Lactobacillus kefiranofaciens. It is included into kefir grains and has several health promoting properties. In the present work, shear and extensional properties of different kefiran aqueous dispersions (0.5, 1 and 2% wt.) were assessed and compared to other neutral gums commonly used in food, cosmetic and pharmaceutics industries (methylcellulose, locust bean gum and guar gum). Kefiran showed shear flow characteristics similar to that displayed by other representative neutral gums, although it always yielded lower viscosities at a given concentration. For each gum system it was possible to find a correlation between dynamic and steady shear properties by a master curve including both the apparent and complex viscosities. When studying extensional properties of selected gums at 2% wt. by means of a capillary break-up rheometer, kefiran solutions did not show important extensional properties, displaying a behaviour close the Newtonian.

Influence of the presence of monoglyceride on the interfacial properties of wheat gluten.

BACKGROUND: The physical stability of several food systems depends strongly on their interfacial properties, which may be modified by adding proteins and low-molecular-weight surfactants to their formulation. This study deals with the possibility of using wheat gluten to alter the surface and interfacial properties of an aqueous system, considering the effects of protein concentration, pH and the presence of monostearin. RESULTS: It was generally found that the surface tension decreased as the protein concentration increased, reaching a minimum value at 0.5 g kg(-1). The influence of protein concentration on surface tension was much greater than the effect of pH owing to the low ionic character of wheat gluten protein. At acidic and alkaline pH values the interfacial viscosity of the protein system underwent a significant increase with time. The addition of monostearin either promoted the displacement of protein molecules at the interface or generated an interfacial mixed film with surface tension values lower than those of both single components, depending on the pH. CONCLUSION: The results obtained indicate that gluten can contribute to the stabilisation of air/water and oil/water interfaces in some food systems (emulsions, foams, etc.).