Browsing by Author "Pinchetti, Juan Luis Gómez"
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- Characterization of biodegradable films based on extracellular polymeric substances extracted from the thermophilic microalga Graesiella spPublication . Gongi, Wejdene; Pinchetti, Juan Luis Gómez; Cordeiro, Nereida; Sadok, Saloua; Ouada, Hatem BenIn this research, a new type of biodegradable film based on the extracellular polymeric substances (EPS) and isolated from the thermophilic microalga Graesiella sp., was formulated and characterized. The EPS film was 0.221 mm thick. Atomic force microscopy and scanning electron microscopy images revealed a homogeneous character with a lamellar microstructure. The EPS film displayed yellowish color, high transparency, high ul traviolet barrier properties, and low oxygen (0.008 SI), and water-vapor permeability (0.037 SI). Film tensile strength (16.24 MPa) and elongation at break (4.76%) were in the range of common biofilms and the thermal analyses showed high transition temperature (126 ◦C) and high thermal stability (up to 800 ◦C). Compared to ascorbic acid, results indicated that the EPS film shows a higher antioxidant activity, mainly as β-carotene anti bleaching (84%), DPPH- free radical scavenging ability (80%), and ferrous iron-chelating (55%). Graesiella sp., EPS film effects on beef meat packaging were studied during nine days of cold storage. Compared to polyvinylchloride-packed meat, EPS-packed meat samples showed higher stability of color (redness = 13.6) and pH (5.85) during storage and low proliferation of total viable counts (4.04 CFU⋅g− 1 ) and Pseudomonas bacteria (4.09 CFU⋅g− 1 ). They also exhibit lower drip loss (9%) and less metmyoglobin (32%), heme iron (4.87 μg⋅g− 1 ) total volatile basic nitrogen (TVB-N = 22.96 mg⋅kg− 1 ), and lipid oxidation (MDA = 0.025 mg⋅kg− 1 ). The obtained results highlight the potential for use of microalgae EPS as a new film forming material that could be applied in beef meat preservation.
- Production of exopolymer substances from the thermophilic chlorophyte Graesiella: industrial and ecological applicationsPublication . Gongi, Wejdene; Cordeiro, Nereida; Pinchetti, Juan Luis Gómez; Ben Ouada, HatemMicroalgal extracellular polymeric substances (EPSs) are heteropolysaccharides that have characteristics suitable for industrial and biotechnological applications. Notably, they have strong anionic nature and high hydrophobicity. Nevertheless, systematic studies to demonstrate the viability of the production of EPSs on an industrial scale are still crucial. In this research, the chlorophyte Graesiella was grown on a raceway pond to view its EPS valorization. The biomass production achieved a maximum of 1.98 g L−1 and an EPS production of 1.6 g L−1 after six production days. The Graesiella EPSs with a molecular weight above 100 kDa are sulfated exopolymers containing mainly polysaccharide (70%) and protein (16%). The EPSs produced more stable emulsions with hydrocarbons and oils than Tween-20. The emulsification indices with n-hexane (88%) and maize oil (28%) indicate the EPSs’ strong emulsion-stabilizing capacity. The EPSs showed a peak flocculating percentage of 95% to kaolin suspension, with better flocculation performance than Al2(SO4)3 and alginate. Moreover, Graesiella EPSs had a significant effect on antimicrobial activity, significantly inhibiting fungal growth (71% for Botytis cinerea and 87% for Fusarium oxysporum), spore germination (100% of inhibition at a concentration of 1.8 g L−1), and mycelium growth (68% of inhibition). Also, Graesiella EPSs acted as a bactericide against Vibrio anguilaruim and Listonella anguilaruim (100% inhibition). EPSs were also found to have potent antioxidant activity compared with L-ascorbic acid. The obtained results open new perspectives to the further exploration of Graesiella sp. as a potential EPS producer, making it a promising candidate for numerous industrial applications.