Solution properties of D-xylans from corn cobs

Molecular modification, structural characterization, and biological activity of xylans

The differences in the source and structure of xylans make them have various biological activities. However, due to their inherent structural limitations, the various biological activities of xylans are far lower than those of commercial drugs. Currently, several types of molecular modification methods have been developed to address these limitations, and many derivatives with specific biological activity have been obtained. Further research on structural characteristics, structure-activity relationship and mechanism of action is of great significance for the development of xylan derivatives. Therefore, the major molecular modification methods of xylans are introduced in this paper, and the primary structure and conformation characteristics of xylans and their derivatives are summarized. In addition, the biological activity and structure-activity relationship of the modified xylans are also discussed.

Desenvolvimento de biofilmes à base de xilana e xilana/gelatina para produção de embalagens biodegradáveis

Resumo O objetivo deste trabalho foi desenvolver e caracterizar filmes biodegradáveis à base de xilana extraída de sabugo de milho com potencial uso como uma nova matéria-prima para embalagens biodegradáveis. Para tanto, os filmes foram produzidos através da secagem das dispersões filmogênicas com diferentes concentrações de xilana (150 mg, 300 mg, 600 mg), e glicerol (5%, 10%, 15%), com ou sem adição de gelatina (1000 mg). A caracterização avaliou a morfologia, espessura, solubilidade, biodegradabilidade e opacidade. Os filmes com melhores propriedades foram testados como biocobertura em uvas ‘Itália’ em duas condições de temperatura: ambiente (25 °C) e refrigerada (4 °C). Os parâmetros de perda de massa e acidez objetivaram avaliar sua eficácia. Os resultados mostraram que os filmes a base de xilana/gelatina apresentaram os melhores aspectos macroscópicos. Além disso, o aumento da concentração de xilana fez decrescer sua solubilidade. Conclui-se que a eficácia dos filmes como bioembalagem foi dependente da concentração de xilana na formulação e do período de avaliação.

An unconventional approach for improving the integrity and mechanical properties of xylan type hemicellulose based films

Inclusion of the salt KAcO into hemicellulose based polymeric films results in improved film formation and mechanical properties. Considering this beneficial effect of KAcO, its separation during the hemicellulose isolation process is not always a necessity for film production.

Extrusion of xylans extracted from corn cobs into biodegradable polymeric materials

Solvent casting technique, which comprises multiple energy demanding steps including the dissolution of a polymer in a solvent followed by the evaporation of the solvent from the polymer solution, is currently the main technique for the production of xylan based polymeric materials. The present study shows that sufficient water content renders arabinoglucuronoxylan (AGX) polymers extrudable, enabling the production of AGX based polymeric materials in a single step via extrusion, which is economically advantageous to solvent casting process for mass production. AGX polymers with water content of 27% were found to yield extrudates at an extrusion temperature of 90°C. The extruded strips showed very good mechanical properties with an ultimate tensile strength of 76 ± 6 MPa and elongation at break value of 35 ± 8%, which were superior to the mechanical properties of the strips obtained from polylactic acid.

In vitro antioxidant, anticoagulant and antimicrobial activity and in inhibition of cancer cell proliferation by xylan extracted from corn cobs

Xylan is one of most abundant polymer after cellulose. However, its potential has yet to be completely recognized. Corn cobs contain a considerable reservoir of xylan. The aim of this work was to study some of the biological activities of xylan obtained from corn cobs after alkaline extraction enhanced by ultrasonication. Physical chemistry and infrared analyses showed 130 kDa heteroxylan containing mainly xylose:arabinose: galactose:glucose (5.0:1.5:2.0:1.2). Xylan obtained exhibited total antioxidant activity corresponding to 48.5 mg of ascorbic acid equivalent/g of xylan. Furthermore, xylan displayed high ferric chelating activity (70%) at 2 mg/mL. Xylan also showed anticoagulant activity in aPTT test. In antimicrobial assay, the polysaccharide significantly inhibited bacterial growth of Klebsiella pneumoniae. In a test with normal and tumor human cells, after 72 h, only HeLa tumor cell proliferation was inhibited (p < 0.05) in a dose-dependent manner by xylan, reaching saturation at around 2 mg/mL, whereas 3T3 normal cell proliferation was not affected. The results suggest that it has potential clinical applications as antioxidant, anticoagulant, antimicrobial and antiproliferative compounds.