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Browsing by Author "Pinchetti, Juan Luis Gomez"

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  • Extracellular polymeric substances with high radical scavenging ability produced in outdoor cultivation of the thermotolerant chlorophyte Graesiella sp
    Publication . Gongi, Wejdene; Cordeiro, Nereida; Pinchetti, Juan Luis Gomez; Sadok, Saloua; Ben Ouada, Hatem
    The present study developed a two-step strategy to enhance the production of extracellular polymeric substances (EPSs) by a thermotolerant chlorophyte, Graesiella sp., in view to their industrial valorisation. In the first step, Graesiella sp. was grown in outdoor conditions in pilot-scale photobioreactors of 100 L culture volumes. In the second step, the biomass collected in the exponential growth phase was submitted to heat stress (50 °C). A joint production of biomass reaching 0.50 gdw L−1 day−1 and of EPS production reaching 1.30 gdw L−1 in 2 days was obtained. EPSs mainly contained polysaccharides (80%) and proteins (14%). FTIR and 1HNMR revealed the presence of primary amine and sulfated groups. The EPSs contained antioxidant enzymes (SOD, CAT, and APX) maintained in an active state by the microenvironment offered by the EPSs. The EPSs were found to have a potent antioxidant activity via directly scavenging free radicals when compared to L-ascorbic acid.
    2020Journal article Open access Show more
  • Functional, rheological, and antioxidant properties of extracellular polymeric substances produced by a thermophilic cyanobacterium Leptolyngbya sp
    Publication . Gongi, Wejdene; Cordeiro, Nereida; Pinchetti, Juan Luis Gomez; Ouada, Hatem Ben
    Extracellular polymeric substances (EPSs) produced by the flamentous cyanobacterium identifed as Leptolyngbya sp. IkmLPT16 were isolated and characterized chemically, and their antioxidant, functional, and rheological properties were studied. The strain produces a signifcant amount of EPSs (2.15 g L−1) conjointly with a biomass production achieved at a maximum of 1.35 g L−1 after nine production days. Chemical analysis of EPSs revealed the presence of mannose (35%), arabinose (24%), glucose (15%), rhamnose (2%), and one uronic acid (8%). Fourier transformed infrared spectrum of EPSs further revealed the presence of νC-N groups indicating the presence of peptide moieties. Elemental analysis of EPSs showed the presence of sulfate groups (S=0.59%) as inorganic substituents. Functional properties of Leptolyngbya EPSs were determined based on water holding capacity, oil holding capacity, foaming ability, and metal sorption ability. Experimental results showed high water holding capacity (119%), water solubility index (97.43%), and oil holding ability (87.52%), with a strong metal sorption ability and consequent foam stability (22%). The rheological properties of EPSs were comparable with commercial xanthan gum with higher resistance to Temperature. Leptolyngbya sp. EPSs displayed an efective antioxidant activity via directly scavenging free radicals particularly DDPH• (IC50=4 mg. mL−1 against 10 mg. mL−1 for l-ascorbic acid) and •OH (IC50=10 mg. mL−1 against 20 mg. mL−1 for l-ascorbic acid) and as an iron-chelating agent (IC50=40 mg. mL−1 against 60 mg.mL−1 for EDTA). The outcomes of this study demonstrate the potential use of Leptolyngbya sp. EPSs in several food and pharmaceutical applications.
    2022Journal article Open access Show more