Browsing by Author "Parra, Carolina"

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    Fractional Factorial Design to Evaluate the Synthesis and Electrochemical Transfer Parameters of h-BN Coatings
    (2023) Figueroa, Helen; Aristizabal, Juliet; Reinoso-Guerra, Elias; Arce, Barbara; Vargas-Straube, Maria Jose; Gentil, Dana; Ramirez, Cristian; Cordero, Jose; Barrera, Nelson P.; Parra, Carolina
    In this study, we present a fractional factorial design approach for exploring the effects and interactions of key synthesis and electrochemical transfer parameters on the roughness and wettability of hexagonal boron nitride (h-BN) coatings, due to their essential role in biofilm formation. The studied parameters for the synthesis process include precursor mass, growth time, and substrate conditioning, whereas for the transfer process, applied voltage and aqueous medium concentration were studied. Through this polynomial model, we confirmed the strong influence of precursor mass and medium concentration parameters on h-BN surface roughness and its resulting antibiofilm properties.
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    Maximizing Bioethanol Production from Eucalyptus globulus Using Steam Explosion Pretreatment: A Multifactorial Design and Fermenter Development for High Solid Loads
    (2023) Troncoso-Ortega, Eduardo; Valenzuela, Roberto; Reyes-Contreras, Pablo; Castano-Rivera, Patricia; Schiappacasse, L-Nicolas; Parra, Carolina
    Steam explosion pretreatment is suitable for bioethanol production from Eucalyptus globulus wood. Multifactorial experiment designs were used to find the optimal temperature and residence time required to obtain the best glucose yield from the enzymatic hydrolysis of pretreated materials. The chemical composition, crystallinity index, morphology and polymerization degree of the pretreated materials were correlated with enzymatic accessibility. Simultaneous saccharification and fermentation (SSF) using a fed-batch strategy was applied to three different laboratory-scale fermenters. The optimization of the pretreatment was obtained at 208 degrees C and 11 min. However, the enzymatic hydrolysis performance did not show significant differences from the material obtained at 196 degrees C and 9.5 min, which was determined to be the real optimum, owing to its lower energy requirement. The vertical fermenter with type "G" blades and the horizontal fermenter with helical blades were both highly efficient for reaching ethanol yields close to 90% based on dry wood, and ethanol concentrations close to 9.0% v/v.
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    Sulfated Polysaccharide Extracted from the Green Algae Codium bernabei: Physicochemical Characterization and Antioxidant, Anticoagulant and Antitumor Activity
    (2022) Figueroa, Fabian A.; Abdala-Diaz, Roberto T.; Perez, Claudia; Casas-Arrojo, Virginia; Nesic, Aleksandra; Tapia, Cecilia; Duran, Carla; Valdes, Oscar; Parra, Carolina; Bravo-Arrepol, Gaston; Soto, Luis; Becerra, Jose; Cabrera-Barjas, Gustavo
    Codium bernabei is a green alga that grows on Chilean coasts. The composition of its structural polysaccharides is still unknown. Hence, the aim of this work is to isolate and characterize the hot water extracted polysaccharide fractions. For this purpose, the water extracts were further precipitated in alcohol (TPs) and acid media (APs), respectively. Both fractions were characterized using different physicochemical techniques such as GC-MS, GPC, FTIR, TGA, and SEM. It is confirmed that the extracted fractions are mainly made of sulfated galactan unit, with a degree of sulfation of 19.3% (TPs) and 17.4% (ATs) and a protein content of 3.5% in APs and 15.6% in TPs. Other neutral sugars such as xylose, glucose, galactose, fucose, mannose, and arabinose were found in a molar ratio (0.05:0.6:1.0:0.02:0.14:0.11) for TPs and (0.05:0.31:1.0:0.03:0.1:0.13) for ATs. The molecular weight of the polysaccharide samples was lower than 20 kDa. Both polysaccharides were thermally stable (Tonset > 190 degrees C) and showed antioxidant activity according to the ABTS(center dot+) and DPPH tests, where TPs fractions had higher scavenging activity (35%) compared to the APs fractions. The PT and APTTS assays were used to measure the anticoagulant activity of the polysaccharide fractions. In general, the PT activity of the TPs and APs was not different from normal plasma values. The exception was the TPs treatment at 1000 mu g mL(-1) concentration. The APTTS test revealed that clotting time for both polysaccharides was prolonged regarding normal values at 1000 mu g mL(-1). Finally, the antitumor test in colorectal carcinoma (HTC-116) cell line, breast cancer (MCF-7) and human leukemia (HL-60) cell lines showed the cytotoxic effect of TPs and APs. Those results suggest the potential biotechnological application of sulfate galactan polysaccharides isolated from a Chilean marine resource.