Sustainable Exploitation of Posidonia oceanica Sea Balls (Egagropili): A Review.

Posidonia oceanica (L.) Delile is the main seagrass plant in the Mediterranean basin that forms huge underwater meadows. Its leaves, when decomposed, are transported to the coasts, where they create huge banquettes that protect the beaches from sea erosion. Its roots and rhizome fragments, instead, aggregate into fibrous sea balls, called egagropili, that are shaped and accumulated by the waves along the shoreline. Their presence on the beach is generally disliked by tourists, and, thus, local communities commonly treat them as waste to remove and discard. Posidonia oceanica egagropili might represent a vegetable lignocellulose biomass to be valorized as a renewable substrate to produce added value molecules in biotechnological processes, as bio-absorbents in environmental decontamination, to prepare new bioplastics and biocomposites, or as insulating and reinforcement materials for construction and building. In this review, the structural characteristics, and the biological role of Posidonia oceanica egagropili are described, as well as their applications in different fields as reported in scientific papers published in recent years.

Argan (Argania spinosa L.) Seed Oil Cake as a Potential Source of Protein-Based Film Matrix for Pharmaco-Cosmetic Applications.

Various different agri-food biomasses might be turned into renewable sources for producing biodegradable and edible plastics, potentially attractive for food, agricultural and cosmeceutical sectors. In this regard, different seeds utilized for edible and non-edible oil extraction give rise to high amounts of organic by-products, known as seed oil cakes (SOCs), potentially able to become protein-rich resources useful for the manufacturing of biodegradable films. This study reports the potential of SOC derived from Argania spinosa (argan), a well-known plant containing valuable non-refined oil suitable for food or cosmetic use, to be a promising valuable source for production of a protein-based matrix of biomaterials to be used in the pharmaco-cosmetic sector. Thus, glycerol-plasticized films were prepared by casting and drying using different amounts of argan seed protein concentrate, in the presence of increasing glycerol concentrations, and characterized for their morphological, mechanical, barrier, and hydrophilicity properties. In addition, their antioxidant activity and effects on cell viability and wound healing were investigated. The hydrophobic nature of the argan protein-based films, and their satisfying physicochemical and biological properties, suggest a biorefinery approach for the recycling of argan SOC as valuable raw material for manufacturing new products to be used in the cosmeceutical and food industries.

Lignin/Carbohydrate Complex Isolated from Posidonia oceanica Sea Balls (Egagropili): Characterization and Antioxidant Reinforcement of Protein-Based Films.

A lignin fraction (LF) was extracted from the sea balls of Posidonia oceanica (egagropili) and extensively dialyzed and characterized by FT-IR and NMR analyses. LF resulted water soluble and exhibited a brownish-to-black color with the highest absorbance in the range of 250-400 nm, attributed to the chromophore functional groups present in the phenylpropane-based polymer. LF high-performance size exclusion chromatography analysis showed a highly represented (98.77%) species of 34.75 kDa molecular weight with a polydispersity index of 1.10 and an intrinsic viscosity of 0.15. Quantitative analysis of carbohydrates indicated that they represented 28.3% of the dry weight of the untreated egagropili fibers and 72.5% of that of LF. In particular, eight different monosaccharides were detected (fucose, arabinose, rhamnose, galactose, glucose, xylose, glucosamine and glucuronic acid), glucuronic acid (46.6%) and rhamnose (29.6%) being the most present monosaccharides in the LF. Almost all the phenol content of LF (113.85 ± 5.87 mg gallic acid eq/g of extract) was water soluble, whereas around 22% of it consisted of flavonoids and only 10% of the flavonoids consisted of anthocyanins. Therefore, LF isolated from egagropili lignocellulosic material could be defined as a water-soluble lignin/carbohydrate complex (LCC) formed by a phenol polymeric chain covalently bound to hemicellulose fragments. LCC exhibited a remarkable antioxidant activity that remained quite stable during 6 months and could be easily incorporated into a protein-based film and released from the latter overtime. These findings suggest egagropili LCC as a suitable candidate as an antioxidant additive for the reinforcement of packaging of foods with high susceptibility to be deteriorated in aerobic conditions.

Amylose/cellulose nanofiber composites for all-natural, fully biodegradable and flexible bioplastics.

Thermoplastic, polysaccharide-based plastics are environmentally friendly. However, typical shortcomings include lack of water resistance and poor mechanical properties. Nanocomposite manufacturing using pure, highly linear, polysaccharides can overcome such limitations. Cast nanocomposites were fabricated with plant engineered pure amylose (AM), produced in bulk quantity in transgenic barley grain, and cellulose nanofibers (CNF), extracted from agrowaste sugar beet pulp. Morphology, crystallinity, chemical heterogeneity, mechanics, dynamic mechanical, gas and water permeability, and contact angle of the films were investigated. Blending CNF into the AM matrix significantly enhanced the crystallinity, mechanical properties and permeability, whereas glycerol increased elongation at break, mainly by plasticizing the AM. There was significant phase separation between AM and CNF. Dynamic plasticizing and anti-plasticizing effects of both CNF and glycerol were demonstrated by NMR demonstrating high molecular order, but also non-crystalline, and evenly distributed 20 nm-sized glycerol domains. This study demonstrates a new lead in functional polysaccharide-based bioplastic systems.

Valorisation of Posidonia oceanica Sea Balls (Egagropili) as a Potential Source of Reinforcement Agents in Protein-Based Biocomposites.

Nanocrystalline cellulose (NC) and a lignin-containing fraction (LF) were obtained from egagropili, the so called sea balls produced from rhizome and stem fragments of Posidonia oceanica that accumulate in large amounts along the coastal beaches in the form of tightly packed and dry materials of various dimensions. Both egagropili fractions have been shown to be able to improve the physicochemical properties of biodegradable films prepared from protein concentrates derived from hemp oilseed cakes. These materials, manufactured with a biodegradable industrial by-product and grafted with equally biodegradable waste-derived additives, exhibited an acceptable resistance with a still high flexibility, as well as they showed an effective barrier activity against water vapor and gases (O2 and CO2). Furthermore, both NC and LF decreased film moisture content, swelling ability and solubility, thus indicating that both additives were able to improve water resistance of the hydrocolloid films. The exploitation of egagropili, actually considered only an undesirable waste to be disposed, as a renewable source of reinforcing agents to blend with different kinds of polymers is suggested.

Hydrocolloid-Based Coatings with Nanoparticles and Transglutaminase Crosslinker as Innovative Strategy to Produce Healthier Fried Kobbah.

This study addresses the effect of coating solutions on fried kobbah. Coating solutions were made of pectin (PEC) and grass pea flour (GPF), treated or not with transglutaminase (TGase) and nanoparticles (NPs)-namely mesoporous silica NPs (MSN) or chitosan NPs (CH-NPs). Acrylamide content (ACR), water, oil content and color of uncoated (control) and coated kobbah were investigated. Zeta potential, Z-average and in vitro digestion experiments were carried out. Zeta potential of CH-NPs was stable from pH 2.0 to pH 6.0 around + 35 mV but decreasing at pH > 6.0. However, the Z-average of CH-NPs increased by increasing the pH. All coating solutions were prepared at pH 6.0. ACR of the coated kobbah with TGase-treated GPF in the presence nanoparticles (MSN or CH-NPs) was reduced by 41.0% and 47.5%, respectively. However, the PEC containing CH-NPs showed the higher reduction of the ACR by 78.0%. Water content was higher in kobbah coated by PEC + CH-NPs solutions, while the oil content was lower. The color analysis indicated that kobbah with lower browning index containing lower ACR. Finally, in vitro digestion studies of both coating solutions and coated kobbah, demonstrated that the coating solutions and kobbah made by means of TGase or nanoparticles were efficiently digested.

Cross-Linked Amylose Bio-Plastic: A Transgenic-Based Compostable Plastic Alternative.

Bio-plastics and bio-materials are composed of natural or biomass derived polymers, offering solutions to solve immediate environmental issues. Polysaccharide-based bio-plastics represent important alternatives to conventional plastic because of their intrinsic biodegradable nature. Amylose-only (AO), an engineered barley starch with 99% amylose, was tested to produce cross-linked all-natural bioplastic using normal barley starch as a control. Glycerol was used as plasticizer and citrate cross-linking was used to improve the mechanical properties of cross-linked AO starch extrudates. Extrusion converted the control starch from A-type to Vh- and B-type crystals, showing a complete melting of the starch crystals in the raw starch granules. The cross-linked AO and control starch specimens displayed an additional wide-angle diffraction reflection. Phospholipids complexed with Vh-type single helices constituted an integrated part of the AO starch specimens. Gas permeability tests of selected starch-based prototypes demonstrated properties comparable to that of commercial Mater-Bi© plastic. The cross-linked AO prototypes had composting characteristics not different from the control, indicating that the modified starch behaves the same as normal starch. The data shows the feasibility of producing all-natural bioplastic using designer starch as raw material.

All-natural bio-plastics using starch-betaglucan composites.

Grain polysaccharides represent potential valuable raw materials for next-generation advanced and environmentally friendly plastics. Thermoplastic starch (TPS) is processed using conventional plastic technology, such as casting, extrusion, and molding. However, to adapt the starch to specific functionalities chemical modifications or blending with synthetic polymers, such as polycaprolactone are required (e.g. Mater-Bi). As an alternative, all-natural and compostable bio-plastics can be produced by blending starch with other polysaccharides. In this study, we used a maize starch (ST) and an oat ß-glucan (BG) composite system to produce bio-plastic prototype films. To optimize performing conditions, we investigated the full range of ST:BG ratios for the casting (100:0, 75:25, 50:50, 25:75 and 0:100 BG). The plasticizer used was glycerol. Electron Paramagnetic Resonance (EPR), using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a spin probe, showed that the composite films with high BG content had a flexible chemical environment. They showed decreased brittleness and improved cohesiveness with high stress and strain values at the break. Wide-angle X-ray diffraction displayed a decrease in crystallinity at high BG content. Our data show that the blending of starch with other natural polysaccharides is a noteworthy path to improve the functionality of all-natural polysaccharide bio-plastics systems.

Transglutaminase-mediated modification of ovomucoid: effects on its trypsin inhibitory activity and antigenic properties.

Hen egg can cause food hypersensitivity in infants and young children, and ovomucoid is the most allergenic factor among proteins contained in egg white. Since proteinase treatment, a well-recognized strategy in reducing food allergenicity, is ineffective when applied to ovomucoid because of its ability to act as trypsin inhibitor, we investigated the possibility of reducing the ovomucoid antiprotease activity and antigenic properties by covalently modifying its structure. The present paper reports data showing the ability of the Gln115 residue of ovomucoid to act as an acyl donor substrate for the enzyme transglutaminase and, as a consequence, to give rise to a covalent monodansylcadaverine conjugate of the protein in the presence of both enzyme and the diamine dansylated derivative. Moreover, we demonstrated that the obtained structural modification of ovomucoid significantly reduced the capability of the protein to inhibit trypsin activity, also having impact on its anti-ovomucoid serum-binding properties.

Higher susceptibility to amyloid fibril formation of the recombinant ovine prion protein modified by transglutaminase.

Prion proteins are known as the main agents of transmissible spongiform encephalopathies affecting humans as well as animals. A recombinant ovine prion protein was found to be in vitro able to act as an effective substrate for a microbial isoform of transglutaminase, an enzyme catalyzing the formation of isopeptide bonds inside the proteins. We proved that transglutaminase modifies the structure of the prion protein by leading to the formation of three intra-molecular crosslinks and that the crosslinked protein form is more competent in amyloid formation compared to the unmodified one. In addition, the crosslinked prion protein was shown also to be more resistant to proteinase K digestion. Our findings suggest a possible use of transglutaminase in stabilizing the prion protein three-dimensional structure in order to investigate the molecular basis of the conversion of the protein into its pathological form.

Transglutaminase crosslinked pectin- and chitosan-based edible films: a review.

The production of biodegradable and edible films with desired mechanical characteristics and gas barrier properties represents one of the most advanced challenges in the field of food wrapping and coating. New edible films can serve not only to provide food with physical protection but also to reduce loss of their moisture, to restrict absorption of oxygen, to lessen migration of lipids, to improve their mechanical handling features, and as materials, to apply in direct contact with internal food to realize a multilayer food packaging. Polymers derived from natural products, like carbohydrates and proteins, offer the greatest opportunities as component of edible films since their biodegradability and environmental compatibility are assured and they can also supplement the nutritional value of specific foods. However, excessive water solubility and poor water vapor barrier properties, and often poor mechanical resistance, have their application limited until the present time. Numerous studies have been carried out to improve their properties by preparing composite and multi-component films or by physically and chemically crosslinking their natural components. In the present review we summarize the main results obtained by crosslinking with the enzyme transglutaminase different proteins contained in multi-component pectin- and chitosan-based edible films, having the aim to create environmentally-friendly "bioplastics" with mechanical and permeability properties similar to the ones exhibited by plastics of petrochemical origin.

Synthesis and resistance to in vitro proteolysis of transglutaminase cross-linked phaseolin, the major storage protein from Phaseolus vulgaris.

The ability of phaseolin to act as an acyl donor and acceptor substrate of transglutaminase was studied by using an enzyme isolated from Streptoverticillium mobarense. Phaseolin, a trimeric storage protein from Phaseolus vulgaris L., was shown to possess both glutamine and lysine residues reactive for the enzyme. The extent of transglutaminase-catalyzed cross-linking has been studied in function of both incubation time and enzyme concentration. Native- and SDS-PAGE demonstrated that phaseolin is intra- and intermolecularly cross-linked by transglutaminase and gives rise to different polymers as well as to modified forms of the protein having a similar molecular weight but lower Stokes radius if compared to unmodified phaseolin. Cross-linked phaseolin was found to be more resistant to proteolytic cleavage than the unmodified counterpart, as demonstrated by in vitro trypsin and pepsin digestion experiments. This behavior could suggest novel possible uses of the transglutaminase-modified phaseolin.