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Zucca P.,Consortium University of Oristano | Zucca P.,Complesso Universitario | Rescigno A.,Complesso Universitario | Rinaldi A.C.,Complesso Universitario | Sanjust E.,Complesso Universitario
Journal of Molecular Catalysis A: Chemical | Year: 2014

Lignin is a recalcitrant polymer arising from addition polymerization of phenylpropanoid units via an oxidative, enzyme-catalyzed radical mechanism. Lignin removal is a serious technological challenge in wood-related industries such as pulping for paper production. In this review, some outstanding aspects in lignin biosynthesis and structure are depicted; also the commonly used industrial protocols for pulp delignification are described, with special emphasis on their molecular aspects. A discussion is presented concerning the known chemical mechanisms of enzyme-catalyzed delignification by white-rot fungi. Biomimetic and bioinspired synthetic metalloporphines show monooxygenase/peroxygenase-like catalytic activity, being quite more versatile catalysts than ligninolytic enzymes (being capable only of one-electron oxidations). The advantages of this behavior are encompassed with an in-depth discussion about the molecular aspects of their action mechanisms, the possible oxygen donors, and the known oxidizable substrates. Limitations and perspectives about their practical use at an industrial scale in delignification processes are discussed. © 2013 Elsevier B.V.

Zucca P.,Consortium University of Oristano | Zucca P.,University of Cagliari | Sanjust E.,University of Cagliari
Molecules | Year: 2014

Several inorganic materials are potentially suitable for enzymatic covalent immobilization, by means of several different techniques. Such materials must meet stringent criteria to be suitable as solid matrices: complete insolubility in water, reasonable mechanical strength and chemical resistance under the operational conditions, the capability to form manageable particles with high surface area, reactivity towards derivatizing/functionalizing agents. Non-specific protein adsorption should be always considered when planning covalent immobilization on inorganic solids. A huge mass of experimental work has shown that silica, silicates, borosilicates and aluminosilicates, alumina, titania, and other oxides, are the materials of choice when attempting enzyme immobilizations on inorganic supports. More recently, some forms of elemental carbon, silicon, and certain metals have been also proposed for certain applications. With regard to the derivatization/functionalization techniques, the use of organosilanes through silanization is undoubtedly the most studied and the most applied, although inorganic bridge formation and acylation with selected acyl halides have been deeply studied. In the present article, the most common inorganic supports for covalent immobilization of the enzymes are reviewed, with particular focus on their advantages and disadvantages in terms of enzyme loadings, operational stability, undesired adsorption, and costs. Mechanisms and methods for covalent immobilization are also discussed, focusing on the most widespread activating approaches (such as glutaraldehyde, cyanogen bromide, divinylsulfone, carbodiimides, carbonyldiimidazole, sulfonyl chlorides, chlorocarbonates, N-hydroxysuccinimides). © Molecules 2014.

Zucca P.,University of Cagliari | Zucca P.,Consortium University of Oristano | Rosa A.,University of Cagliari | Tuberoso C.I.G.,University of Cagliari | And 5 more authors.
Nutrients | Year: 2012

Cynomorium coccineum is an edible, non-photosynthetic plant widespread along the coasts of the Mediterranean Sea. The medicinal properties of Maltese mushroom-one of the oldest vernacular names used to identify this species-have been kept in high regard since ancient times to the present day. We evaluated the antioxidant potential of fresh specimens of C. coccineum picked in Sardinia, Italy. Both aqueous and methanolic extracts were tested by using multiple assay systems (DPPH, FRAP, TEAC, ORAC-PYR). Total phenolics and flavonoids were also determined. Gallic acid and cyanidin 3-O-glucoside were identified as the main constituents and measured. Both extracts showed antioxidant capacities; ORAC-PYR assay gave the highest antioxidant value in both cases. The methanolic extract was further investigated with in vitro biological models of lipid oxidation; it showed a significant activity in preventing cholesterol degradation and exerted protection against Cu2+-mediated degradation of the liposomal unsaturated fatty acids. Results of the present study demonstrate that the extracts of C. coccineum show a significant total antioxidant power and also exert an in vitro protective effect in different bio-assays of oxidative stress. Therefore, Maltese mushroom can be considered a valuable source of antioxidants and phytochemicals useful in the preparation of nutraceuticals and functional foods. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

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