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Low Temperature Dissolution of Yeast Chitin-Glucan Complex and Characterization of the Regenerated Polymer
Publication . Araújo, Diana; Delgado Alves, Vitor; Marques, Ana C.; Fortunato, Elvira; Reis, Maria A.M.; Freitas, Filomena
Chitin-glucan complex (CGC) is a copolymer composed of chitin and glucan moieties
extracted from the cell-walls of several yeasts and fungi. Despite its proven valuable properties, that
include antibacterial, antioxidant and anticancer activity, the utilization of CGC in many applications
is hindered by its insolubility in water and most solvents. In this study, NaOH/urea solvent systems
were used for the first time for solubilization of CGC extracted from the yeast Komagataella pastoris.
Di erent NaOH/urea ratios (6:8, 8:4 and 11:4 (w/w), respectively) were used to obtain aqueous
solutions using a freeze/thaw procedure. There was an overall solubilization of 63–68%, with the
highest solubilization rate obtained for the highest tested urea concentration (8 wt%). The regenerated
polymer, obtained by dialysis of the alkali solutions followed by lyophilization, formed porous
macrostructures characterized by a chemical composition similar to that of the starting co-polymer,
although the acetylation degree decreased from 61.3% to 33.9–50.6%, indicating that chitin was
converted into chitosan, yielding chitosan-glucan complex (ChGC). Consistent with this, there was
a reduction of the crystallinity index and thermal degradation temperature. Given these results, this
study reports a simple and green procedure to solubilize CGC and obtain aqueous ChGC solutions
that can be processed as novel biomaterials
Demonstration of the ability of the bacterial polysaccharide FucoPol to flocculate kaolin suspensions
Publication . Araújo, Diana; Concórdio-Reis, Patrícia; Marques, Ana C.; Sevrin, Chantal; Grandfils, Christian; Delgado Alves, Vitor
In this study, the flocculation properties of FucoPol, a bacterial extracellular polysaccharide, were investigated. FucoPol is a high molecular weight polymer and negatively charged due to the presence of glucuronic acid and the acyl groups succinyl and pyruvyl. High flocculation rate values (>70%) were achieved with a low bioflocculant dosage of 1 mg/L, for pH values in the range 3–5 and temperature within 15–20°C. The bioflocculant was also shown to be stable after freezing/thawing and heating up to 100°C. Given the polymer’s anionic character, the size of flocs formed and their surface profile, bridging seems to be the main flocculation mechanism of FucoPol. This study demonstrated that FucoPol is a promising natural, biodegradable and biocompatible alternative to the currently used synthetic or inorganic hazardous products, with potential to be used as a novel flocculation agent in several applications, such as water treatment, food or mining. Further studies will involve evaluating the reduction of cation dosage on flocculation efficiency, as well as testing the applicability of FucoPol to flocculate different types of suspended solids, such as, for example, activated carbons, soil solids or yeast cells
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Fundação para a Ciência e a Tecnologia
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Orçamento de Funcionamento/POSC
Número da atribuição
POSC/EEA-SRI/61911/2004