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.

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.

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 ($\eta$ 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.

The development of plastic materials based on cassava reduces the dependence on non-biodegradable petroplastics, and enhances the sustainability of the cassava value chain. In this sense, cassava starch (CS) is used as a reinforcer of biocomposites that also contain brown seaweed Rugulopteryx okamurae (RO). RO is an invasive species whose accumulation poses a strong environmental burden in the strait of Gibraltar. Because it can be used as a biopolymer, its use in the plastics industry would promote a healthy ecosystem. Thus, RO/CS mixtures with different RO/CS ratios (from 100/0 to 30/70) were processed through injection moulding at 140 °C. The thermal properties of plastic samples have been analysed through calorimetric, thermogravimetric and rheological techniques. Moreover, the mechanical properties, hydrophilicity, and microstructure of samples have also been studied. Thus, biopolymer degradation of the composites seems to happen at 213–303 °C, as revealed by thermal gravimetric analysis (TGA) of the samples, whereas an exothermic peak observed in DSC at 350–500 °C would be related to the degradation of organic compounds in anaerobic conditions. Rheological tests evidenced a softening of the RO/CS biocomposites when CS content increased in the formulation, so that elastic moduli dropped from 23.72 MPa in the 70/30 to 5.69 MPa for 30/70. However, RO/CS biocomposites became more resistant and deformable as CS content increased: maximum stress and strain at break increased from 78.2 kPa and 0.14% (70/30 system) to 580 kPa and 25.2% (30/70), respectively. Finally, no important differences were observed in their water uptake capacities or microstructures when increasing CS ratio in the mixture. As cassava starch can be extracted from agro-industrial wastes (i.e., cassava peel and bagasse), its use in biocomposites could be of great use for a more sustainable approach for plastic materials.

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.