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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Polysaccharides can be synthesized by polycondensation or ring-opening polymerization. Synthesis of polysaccharides by polycondensation stopped around 1965, in spite of long-term endeavors by many polymer synthesists, because the method cannot give polysaccharides with stereospecificity, regioselectivity, and the high molecular weight of natural polysaccharides. Synthetic dextran has the same backbone structure as that of natural dextran, (1-6)-a-d-glucopyranan. However, high molecular weight synthetic dextrans have almost no solubility in water because of their completely linear structure. Their viscosity measurements are carried out in dimethyl sulfoxide. Synthetic polysaccharides have no practical applications. Since sulfated ribofuranans and ribopyranans exhibit high anti-acquired immunodeficiency syndrome virus activity, their inhibitory effects on virus infection have been examined in vitro.
Polysaccharides
Published in Stanislaw Penczek, H. R. Kricheldorf, A. Le Borgne, N. Spassky, T. Uryu, P. Klosinski, Models of Biopolymers by Ring-Opening Polymerization, 2018
The principal basic structure of natural polysaccharides is a β-1,4- or α-1,4-pyranose structure and it has been one of the dreams of polymer chemists to synthesize cellulose, i.e., (1→4)-β-d-glucopyranan. After succeeding to prepare stereoregular dextran,1 the synthesis of cellulose was attempted by Micheel et al., using the ring-opening polymerization of anhydro sugars.7 Micheel first reported the synthesis of a poly(d-glucose) consisting of a cellulose-like backbone.122 However, Uryu and co-workers analyzed the polymer structures, obtained from the same monomer, namely 1,4-anhydro-2,3,6-tri-O-benzyl-α-d-glucopyranose, and found by using NMR spectroscopy, that the polymer obtained is an isomeric 2,3,6-tri-O-benzyl-(1→5)-α-d-glucofuranan rather than the reported 2,3,6-tri-O-benzyl(1→4)β-d-glucopyranan.8
Selected Conjugation Chemistries for Making Chemically or Biochemically Functionalized Colloidal Nanoparticles
Published in Nikhil Ranjan Jana, Colloidal Nanoparticles, 2019
Next, take 1–5 mL primary amine-terminated nanoparticle solution (1–10 mg/mL) in a phosphate buffer (pH 7.5) solution. Next, add activated dextran powder to the nanoparticle solution so that the dextran concentration is about 6 mM. Shake the solution overnight at 4°C. Finally, separate the unreacted dextran through size exclusion chromatography using a Sephadex (G25) column or by overnight dialysis (using a 12–14 kDa molecular weight cutoff membrane and against deionized water) for dextran 1 K and dextran 6 K.
An integrated approach to the sustainable production of xylanolytic enzymes from Aspergillus niger using agro-industrial by-products
Published in Preparative Biochemistry & Biotechnology, 2020
Antonela Taddia, Gerónimo Nicolás Brandaleze, María Julia Boggione, Santiago Andrés Bortolato, Gisela Tubio
An optimized enzymatic extract rich in xylanolytic enzymes from A. niger was produced and characterized in the present study. The submerged fermentation process was optimized for maximum production of xylanolytic enzymes with no additional nutrient supplements by the utilization of low-cost raw materials, such as WF. Besides, the solid residue obtained from the submerged fermentation can be used in the framework of a circular economy as an animal feed supplement, or in the production of biosurfactants. The xylanolytic enzymes of the enzymatic extract presented significant stability at 40 °C and over a broad range of pHs. The inhibitory effect of ions was similar to most xylanase reported. The polyvinylpyrrolidone and dextran (1% w/v) showed a stabilizing effect of xylanolytic enzymes. In addition, a large-scale of the optimized fermentation process was also successful. Therefore, the use of WF, the increase in yield and productivity and the simultaneous cost reduction, makes xylanolytic enzyme production by A. niger likely to be considered as an economically attractive and environmentally friendly alternative to the industry.