Novel magnetic cellulose-chitosan composite microspheres were prepared by sol-gel transition method using ionic liquids as solvent for dissolution and regeneration. Subsequently, the composite microspheres activated by glutaradehyde to immobilize enzyme. Which of their structure, properties and morphology were studied by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating-sample magnetometer showed Fe3O4 nanoparticles with mean size of -10 nm were successfully embedded in the composite microspheres. The microshpheres were examined to be with the mean size of 20 μm and good magnetic property with saturation magnetization of 30.1 emu g(-1). The effect of pH and temperature on the immobilization of laccase was also investigated. Compared with free laccase, the pH, thermal and operational stabilities of the immobilized laccase were improved and the activity recovery of immobilized laccase reached 80.6%. Immobilized laccase retained 88.9% activity after 12 reaction cycles. Therefore, the cellulose-chitosan composite microspheres were expected to be a novel support for enzyme immobilization.
A method for production of high-value-added phenolics by combining organosolv lignin extraction with lignin hydrothermal depolymerization without catalysts under mild conditions was successfully developed. During lignin extraction, the optimal ethanol concentration in mixed solvent is 65 vol %, with which 78% purity (based on Klason lignin) of crude lignin was obtained. High yield of liquid products up to 65.5% was recovered from lignin depolymerization under conditions of 523 K, 90 min, 65 vol % ethanol, and 3% lignin; meanwhile, only 17% solid residue was obtained. The gas chromatography–mass spectrometry (GC–MS) analyses of the obtained liquid products confirmed the presence of value-added phenolics, among which the yields of 4-ethylphenol, 4-vinylphenol, guaiacol, 4-ethylguaiacol, and 4-vinylguaiacol were very high (∼30% of the identified compounds). Gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy of these liquid products indicated that lignin was really depolymerized to low molecular weight compounds and that the cleavage of ether bonds and decarbonylation were the major reactions during lignin depolymerization.
In this study, lignin was characterized through elemental analysis, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) in order to understand the potential use for future value added applications, with a major focus on composite materials. Lignins exhibited a little high sulphur. Thermogravimetric curves of the lignin demonstrated good thermal stability. Ligin/PVC composites were prepared and the effect of lignin incorporation was investigated by means of mechanical properties. Lignin added to the composite was obtained by the dual-roll milling process. The composites were prepared by molding and assessed by means of tensile testing. The results showed that no more than 15w% of lignin did not reduce tensile strength and in its presence hardness property was improved.
Biomass energy is an ideal renewable energy source. More and more countries pay attention on it because its CO_(2) discharge colse zero, it can effectively reduce greenhouse effect. This article briefly introduces the conception and transform mode of biomass energy; emphasis introduces the technology at home and abroad and its state of the art. Through the contrast between technical performance of fixed bed gasification furnace and fluidized bed gasification furnace, puts forward the economic feasible and high efficiency biomass power system, this is the developing direction of biomass energy effectively utilization in our country.
Glutaraldehyde was used as a cross-linking agent for immobilization of purified ${\alpha}$-amylase from Exiguobacterium sp. DAU5. Befitting concentration of glutaradehyde and cross-linking time is the key to preparation of cross-linking chitosan beads. Based on optimized immobilization condition for ${\alpha}$-amylase, an overall yield of 56% with specific activity of 2,240 U/g on chitosan beads and 58% with specific activity of 2,320 U/g on chitosan-carbon beads was obtained. The optimal temperature and pH of each immobilized enzyme activity were $50^{\circ}C$ and 50 mM glycine-NaOH buffer pH 8.5, respectively. Those retained more than 75 and 90% of its maximal enzyme activity at pH 7.0-9.5 and after incubation at $50^{\circ}C$ for 1 h, respectively. In addition, the immobilization product showed higher organic-solvent tolerance than free enzymes. The mode of hydrolyzing soluble starch revealed that the ${\alpha}$-amylase possessed high hydrolyzing activity. These results indicate that chitosan is good support and has broad application prospects of enzyme immobilization.
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