Lysine-Grafted MCM-41 Silica as An Antibacterial Biomaterial

Abstract: A facile strategy for zwitterionization of bioceramics based on direct incorporation of L-lysine amino acid via the ε-amino group onto mesoporous MCM-41 materials is proposed. FTIR studies of lysine-grafted MCM-41 (MCM-LYS) showed simultaneously bands at 3080 and 1540 cm−1 and bands at 1625 and 1415 cm−1 corresponding to -NH3+/COO− pairs, demonstrating the incorporation of the amino acid on the material surface keeping its zwitterionic character. Both elemental and thermogravimetric analyses showed that the amount of grafted lysine was 8 wt % based on the bioceramic total weight. Moreover, MCM-LYS material exhibited a reduction of adhesion of S. aureus and E. coli bacteria in 33 and 50%, respectively at physiological pH, as compared with pristine MCM-41. Biofilm studies onto surfaces showed that lysine functionalization elicited a reduction of the area covered by S. aureus biofilm from 42% to only 5% (88%). This research shows a simple and effective approach to chemically modify bioceramics using single amino acids that provide zwitterionic functionality, useful to develop new biomaterials able to resist bacterial adhesion

Structural characterization of the family GH115 alpha-glucuronidase from Amphibacillus xylanus yields insight into its coordinated action with alpha-arabinofuranosidases

The coordinated action of carbohydrate-active enzymes has mainly been evaluated for the purpose of complete saccharification of plant biomass (lignocellulose) to sugars. By contrast, the coordinated action of accessory hemicellulases on xylan debranching and recovery is less well characterized. Here, the activity of two family GH115 alpha-glucuronidases (SdeAgu115A from Saccharophagus degradans, and AxyAgu115A from Amphibacillus xylanus) on spruce arabinoglucuronoxylan (AGX) was evaluated in combination with an alpha-arabinofuranosidase from families GH51 (AniAbf51A, aka E-AFASE from Aspergillus niger) and GH62 (SthAbf62A from Streptomyces thermoviolaceus). The alpha-arabinofuranosidases boosted (methyl)-glucuronic acid release by SdeAgu115A by approximately 50 % and 30 %, respectively. The impact of the alpha-arabinofuranosidases on AxyAgu115A activity was comparatively low, motivating its structural characterization. The crystal structure of AxyAgu115A revealed increased length and flexibility of the active site loop compared to SdeAgu115A. This structural difference could explain the ability of AxyAgu115A to accommodate more highly substituted arabinoglucuronoxylan, and inform enzyme selections for improved AGX recovery and use.Peer reviewe

Una estructura química propuesta para fructanos de la planta de agave azul (Tequilana Weber var. azul)

La estructura química de fructanos de agave Tequilana propuesta se basa en los resultados combinados de permetilación y fragmentación reductora, así como cromatografía de exclusión molecular acoplada a cromatografía de gas-líquido (GLC) y la dispersión de la luz técnica.

Effect of xylan content on mechanical properties in regenerated cellulose/xylan blend films from ionic liquid

We report of cellulose and arabinoglucuronoxylan (AGX) blend films made from wood polymers extracted from one and the same tree. Blends were prepared by dissolution of wood polymers in 1-ethyl-3-methylimidazolium acetate (EmimAc). Films were produced by casting EmimAc solution followed by coagulation in ethanol. The films were optically transparent, fully amorphous as shown by wide angle X-ray scattering, and free from EmimAc residues as shown by Fourier transform infrared spectroscopy. Mechanical properties were analyzed as a function of water content. The plasticizing effect of water on the films was evidenced by both tensile and dynamical mechanical analysis measurements with humidity scans. Equilibrium moisture content (w/w) was measured at different relative humidities and the proportional water uptake was clearly related to the mechanical properties. We found good mechanical properties independent of the polysaccharide composition and an increased Young\u27s modulus at low humidities with a maximum at approximately 20 % AGX content. The strengthening effect was removed after leaching the AGX from the films This study shows potential applications of biopolymer extracted from trees as future packaging

Moisture induced plasticity of amorphous cellulose films from ionic liquid

Amorphous cellulose films were created by regeneration from 1-Ethyl-3-methylimidazolium acetate (EmimAc) solutions. Their mechanical properties were analyzed as a function of water content. Cellulose with different molecular weights, i.e. microcrystalline cellulose (Avicel), Spruce cellulose and bacterial nanocellulose (BNC), were used for film preparation. All the regenerated films were free from EmimAc residues as shown by Fourier transform infrared spectroscopy (FTIR), amorphous as shown by wide angle X-ray spectroscopy (WAXS) and optical transparent. The equilibrium water content (w/w) was measured at different relative humidities. The plasticizing effect of water on the films was evidenced by both tensile tests and dynamical mechanical analysis (DMA) with humidity scans. The mechanical properties were clearly related to the proportional water uptake of the films. The sample with the longest cellulose chains, i.e. BNC, showed significantly larger elongation to brake at high moisture content which was owed to chain entanglements. (C) 2013 Elsevier Ltd. All rights reserved