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

Abstract

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.

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

“…In fact, the native structure of lignin degrades during its extraction from the original lignocellulosic material and smaller polymer molecules endowed with new functional groups are formed. Lignin fraction (LF) obtained from egagropili by sodium chlorite oxidation technique [37] was water soluble and exhibited a brownish-to-black color, probably due to the presence of unsaturated functional groups, including conjugated carbonyl groups, aromatic rings and carbon-carbon double bonds, produced during such harsh chemical treatment [46][47][48]. As shown in Figure 3, the highest absorbance of the extensively dialyzed LF is in the range of 250-400 nm that could be attributed to the different chromophore functional groups present in the extracted phenylpropane-based polymer.…”

“…The effect of different concentrations of egagropili LF on the mechanical and barrier properties of hemp-protein (HP)-based films has been previously investigated [37]. Since it was demonstrated that the presence of 6% LF (w/w protein) in the film-forming solution (FFS) gave rise to films with improved performances, the antioxidant activity of both FFSs and derived films was studied by measuring their DPPH radical scavenging activity in the presence of the same amount of egagropili LF (Figure 9).…”

“…As is shown in Figure 10, the control films prepared in the absence of egagropili LF were not able to release into DPPH solution any antioxidant agent, since no DPPH As is shown in Figure 10, the control films prepared in the absence of egagropili LF were not able to release into DPPH solution any antioxidant agent, since no DPPH scavenging activity was detected at all over time. Therefore, taking also into account the increased barrier effect of LF-containing protein-based films [37], egagropili LF might be considered a suitable candidate as an antioxidant additive for reinforced packaging of food products with high susceptibility to be deteriorated in aerobic conditions.…”

“…In the present study, LCCs were extracted from egagropili (fibrous balls from Posidonia oceanica detritus), considered as a waste since they accumulate in huge numbers along sandy shores, by using a sodium chlorite extraction procedure at acidic pH [37]. With this procedure, as shown in Figure 1B, coniferyl aldehyde and aromatic ketones present in the lignin originally linked to hemicellulose undergo to oxidative and ring-opening reactions to form acidic groups, making lignin fragments more soluble in water [38].…”

“…Around 85% of the produced lignin is obtained through the "kraft pulping process", able to break down the majority of hemicellulose covalently bound to lignin and to give rise to LCCs that are different depending on the specific lignocellulosic biomass used [35,36] (Figure 1A). In the present study, LCCs were extracted from egagropili (fibrous balls from Posidonia oceanica detritus), considered as a waste since they accumulate in huge numbers along sandy shores, by using a sodium chlorite extraction procedure at acidic pH [37] With this procedure, as shown in Figure 1B, coniferyl aldehyde and aromatic ketones present in the lignin originally linked to hemicellulose undergo to oxidative and ring opening reactions to form acidic groups, making lignin fragments more soluble in wate…”