Lipase-Mediated Selective TEMPO Oxidation of Hydroxyethylcellulose

2002 ◽  
pp. 253-264 ◽  
Author(s):  
Shanghui Hu ◽  
Wei Gao ◽  
Rajesh Kumar ◽  
Richard A. Gross ◽  
Qu-Ming Gu ◽  
...  
Keyword(s):  
Tempo Oxidation

scholarly journals A molecular scale analysis of TEMPO-oxidation of native cellulose molecules

Heliyon ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. e05776
Author(s):  
Milad Asgarpour Khansary ◽  
Peyman Pouresmaeel-Selakjani ◽  
Mohammad Ali Aroon ◽  
Ahmad Hallajisani ◽  
Jennifer Cookman ◽  
...  
Keyword(s):  
Scale Analysis ◽  
Tempo Oxidation ◽  
Native Cellulose ◽  
Molecular Scale

scholarly journals Applicability of Recombinant Laccases From the White-Rot Fungus Obba rivulosa for Mediator-Promoted Oxidation of Biorefinery Lignin at Low pH

2020 ◽  
Vol 8 ◽  
Author(s):  
Jussi Kontro ◽  
Riku Maltari ◽  
Joona Mikkilä ◽  
Mika Kähkönen ◽  
Miia R. Mäkelä ◽  
...  
Keyword(s):  
White Rot ◽  
White Rot Fungus ◽  
Lignin Biodegradation ◽  
Reaction Conditions ◽  
Tempo Oxidation ◽  
Chemical Treatments ◽  
Mediator Systems ◽  
Phenolic Components ◽  
Lignin Model ◽  
Rich Side

Utilization of lignin-rich side streams has been a focus of intensive studies recently. Combining biocatalytic methods with chemical treatments is a promising approach for sustainable modification of lignocellulosic waste streams. Laccases are catalysts in lignin biodegradation with proven applicability in industrial scale. Laccases directly oxidize lignin phenolic components, and their functional range can be expanded using low-molecular-weight compounds as mediators to include non-phenolic lignin structures. In this work, we studied in detail recombinant laccases from the selectively lignin-degrading white-rot fungus Obba rivulosa for their properties and evaluated their potential as industrial biocatalysts for the modification of wood lignin and lignin-like compounds. We screened and optimized various laccase mediator systems (LMSs) using lignin model compounds and applied the optimized reaction conditions to biorefinery-sourced technical lignin. In the presence of both N–OH-type and phenolic mediators, the O. rivulosa laccases were shown to selectively oxidize lignin in acidic reaction conditions, where a cosolvent is needed to enhance lignin solubility. In comparison to catalytic iron(III)–(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation systems, the syringyl-type lignin units were preferred in mediated biocatalytic oxidation systems.

scholarly journals Water Dynamics in Hydrated Carboxylated Cellulose Nanofibril Membranes

2019 ◽  
Author(s):  
Shun Yu ◽  
Valentina Guccini ◽  
Franz Demmel ◽  
Germán Salazar-Alvarez
Keyword(s):  
Surface Charge ◽  
Network Formation ◽  
Water Movement ◽  
Polymer Electrolyte Membrane ◽  
Cellulose Nanofibrils ◽  
Bulk Water ◽  
Water Dynamics ◽  
Surface Charges ◽  
Tempo Oxidation ◽  
Elastic Neutron

Cellulose nanofibrils (CNF) are a class of materials with good mechanical properties, surface functionality and bio-/environmental friendliness. They have been used in many applications as loading material or function materials, where water-cellulose interaction determines the materials performance. Especially, CNF with carboxylated groups can be used as the separation membrane in polymer electrolyte membrane fuel cell. The water dynamics is closely related to the proton conductivity. The Non-destructive quasi-elastic neutron scattering (QENS) is used to characterized water movement in hydrated membrane made of CNF prepared by TEMPO-oxidation with different surface charges. However, neither surface charge nor the nanoconfinement due to membrane swelling has large impact on water dynamics mechanism. A slow diffusive motion is found with the diffusion coefficient close to bulk water and that in hydrated Nafion membrane regardless the surface charge, while a fast motion is rather localized with a correlation time increasing as temperature increase, which might related to the hydrogen bond network formation between water and CNF.

scholarly journals Nanofibrillated Cellulose from Appalachian Hardwoods Logging Residues as Template for Antimicrobial Copper

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Masoumeh Hassanzadeh ◽  
Ronald Sabo ◽  
Alan Rudie ◽  
Richard Reiner ◽  
Roland Gleisner ◽  
...  
Keyword(s):  
Oxidation Process ◽  
Metallic Copper ◽  
Nanofibrillated Cellulose ◽  
Strength Properties ◽  
Red Oak ◽  
Northern Red Oak ◽  
Yellow Poplar ◽  
Tempo Oxidation ◽  
Mechanical Fibrillation ◽  
Appalachian Hardwoods

TEMPO nanofibrillated cellulose (TNFC) from two underutilized Appalachian hardwoods, Northern red oak (Quercus rubra) and yellow poplar (Liriodendron tulipifera), was prepared to determine its feasibility to be used as template for antimicrobial metallic copper particles. In addition, a comparison of the TNFC from the two species in terms of their morphological, chemical, thermal, and mechanical properties was also performed. The woody biomass was provided in the form of logging residue from Preston County, West Virginia. A traditional kraft process was used to produce the pulp followed by a five-stage bleaching. Bleached pulps were then subjected to a TEMPO oxidation process using the TEMPO/NaBr/NaClO system to facilitate the final mechanical fibrillation process and surface incorporation of metallic copper. The final TNFC diameters for red oak and yellow poplar presented similar dimensions, 3.8±0.74 nm and 3.6±0.85 nm, respectively. The TNFC films fabricated from both species exhibited no statistical differences in both Young’s modulus and the final strength properties. Likely, after the TEMPO oxidation process both species exhibited similar carboxyl group content, of approximately 0.8 mmol/g, and both species demonstrated excellent capability to incorporate antimicrobial copper on their surfaces.

TEMPO oxidation

2009 ◽  
pp. 544-545
Author(s):  
Jie Jack Li
Keyword(s):  
Tempo Oxidation

Isolation of Cellulose Nanofibers (CNFs) based on Ball-milling Technique Combined with Supercritical Carbon dioxide/ethanol Pretreatment

2021 ◽  
Author(s):  
Zhijun Hu ◽  
Xinyu Cao ◽  
Guanhong Huang ◽  
Daliang Guo
Keyword(s):  
Thermal Stability ◽  
Reaction Time ◽  
Ball Milling ◽  
High Efficiency ◽  
Cellulose Nanofibers ◽  
Sem Images ◽  
Tempo Oxidation ◽  
Good Thermal Stability ◽  
Ethanol Pretreatment ◽  
Ball Milling Technique

Abstract Here, a new pretreatment method has been developed to produce CNFs from micro-fibrillated cellulose (MFC) by supercritical CO 2 pretreatment followed with ball-milling (SCB). MFC was obtained from cotton stalk by chemical purification.Experimental factors were controlled to enhance the properties of SCB-CNF, meanwhile a comparative study was conducted with the method of TEMPO oxidation and microfluid homogenization (TMH). Compared to TMH-CNF, the SCB-CNF has such advantages as Energy saving, high efficiency and environmental protection, indicating a wide application in heat-resistant materials, load materials and other fields. The solid yields of P-MFC after supercritical CO 2 pretreatment gradually decreased together with the temperature and the reaction time. Scanning electron microscope (SEM) images of the SCB-CNF and TMH-CNF show that the morphology of the SCB-CNF was basically acicular but that of the TMH-CNF was mainly soft fibrous. The SCB-CNF is smaller in width and shorter in length, and its size is between CNC and CNF. Thermal gravimetric results suggest that the thermal stability of the SCB-CNF was substantially higher than those of the TMH-CNF. XRD results indicate that the crystallinity showed an initial increasing trend and then declined with increasing temperature and reaction time, and the crystallinity value of SCB-CNF was larger than that of CNFs. The smaller SCB-CNF became rougher and had a larger surface area. High crystallinity make good thermal stability, short and coarse fiber, easier to disperse than CNF, less energy consumption for dispersion, better than 3D mesh. It can be widely used in polymer composites, reinforcing agents, membrane materials and other fields.

scholarly journals Characterisation of Cellulose Nanofibres Derived from Chemical and Mechanical Treatments

2019 ◽  
Vol 253 ◽  
pp. 01002 ◽  
Author(s):  
Martini Muhamad ◽  
Peter Hornsby ◽  
Eugene Carmichael ◽  
Muhammad Zakaria ◽  
Yew Been Seok ◽  
...  
Keyword(s):  
High Pressure ◽  
Aspect Ratio ◽  
Mechanical Treatment ◽  
Cellulose Microfibrils ◽  
Tempo Oxidation ◽  
Particle Size Distribution Measurement ◽  
Cellulose Nanofibres ◽  
Nano Cellulose ◽  
Measurement Laser ◽  
Zeta Potential Analysis

Optimised routes have been established to obtain high aspect ratio cellulose microfibrils derived from plant feedstocks, involving a combination of a chemical and mechanical treatment using a high pressure microfluidizer. By this means, nano-cellulose was produced using different pretreatment protocols. The nanofibres produced were characterised for its particle size distribution measurement (laser diffraction and zeta potential analysis) and fourier transform infrared for its structural analysis. Results obtained and subsequent trends observed in chemical, mechanical and chemo-mechanical treated nanofibres were compared and contrasted. The chemomechanical treatment (TEMPO-oxidation and high pressure microfluidisation) yielded higher aspect ratio nanofibrils than nanofibrils made by solely chemical or mechanical treatment.

Preparation of cellulose nanofibers by TEMPO-oxidation of bleached chemi-thermomechanical pulp for cement applications

2019 ◽  
Vol 203 ◽  
pp. 238-245 ◽  
Author(s):  
Mounir El Bakkari ◽  
Vivek Bindiganavile ◽  
Jose Goncalves ◽  
Yaman Boluk
Keyword(s):  
Cellulose Nanofibers ◽  
Thermomechanical Pulp ◽  
Tempo Oxidation
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