Fiberboards Based on Sugarcane Bagasse Lignin and Fibers

Summary: Fiberboards were prepared using phenolic type resins (phenol‐formaldehyde) and sugarcane bagasse fibers. Lignin extracted through an organosolv process from sugarcane bagasse was used as substitute of phenol in phenolic resins from 40 (lignin‐phenol‐formaldehyde) to 100 wt.‐% (lignin‐formaldehyde) substitution. Some of the fibers were chemically modified by oxidation with chlorine dioxide and treatment with furfuryl alcohol (FA), leading to fibers coated with polyfurfuryl alcohol. Thermal analysis (DSC and TGA) of the prepolymers allowed setting up an efficient curing to prepare fiberboards. Impact strength and water absorption were measured showing the importance of the curing pressure to obtain good performance. When chemically modified fibers were used to prepare board samples, enhanced durability against white root fungi is observed, and to a less degree against brown root fungi. Sugarcane bagasse fiberboards were prepared from prepolymers where lignin substituted phenol up to 100%. This replaces these materials in advantageous position, relating to those prepared from phenol‐formaldehyde resins, due to their high content of renewable raw materials. The results obtained are promising for the utilization of sugarcane bagasse as raw materials for preparing fiberboards to be used in tropical areas.

Stabilization of sugarcane bagasse fiberboards made with unmodified and modified (ClO₂ + furfuryl alcohol) fibers and phenolic resin after 8 weeks exposure against fungi.     

Evaluation of the contribution of lignin stilbene phenol units in the photoyellowing of peroxide-bleached lignin-rich pulps

In order to assess and quantify the contribution of stilbene phenols in photoreversion of bleached high-yield pulps, a method to reduce the stilbene double bond and quantify the formed diphenylethane was developed on 4-benzyloxy-3,3′-dimethoxy-4′-hydroxystilbene, as lignin monomer model, and also on a more sophisticated lignin polymer model constituted by a polystyrene framework containing 4,4′-dihydroxy-3,3′-dimethoxystilbene elements as pendent groups. The method used RhCl(PPh₃)₃ as soluble catalyst to get an efficient hydrogenation and AlCl₃ in benzene to liberate the diphenylethane from the polymer framework. For the first time a semiquantitative evaluation of the content of the stilbene phenols formed from β-1 units was given for high-yield pulps. The value of 2 p-stilbene phenols for 1000 C₉ lignin units found indicates that they are present in very small quantities after the peroxide bleaching. UV irradiation of the polystyrene model adsorbed on solid cellulose matrix had revealed an efficient stabilization after the hydrogenation treatment. This was not the case for the peroxide bleached pulp showing that the p-stilbene phenols formed from β-1 units are not the main contributors of the rapid yellowing of bleached lignin-rich pulps. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2517–2531, 1998     

Attempt to protect wood using copper(II) complex with 1,7-diphenyl-1,6-heptadiene-3,5-dione,a non-phenolic curcuminoid

For the first time, curcuminoids known for their antioxidant and sunscreen properties were used for photoprotection of lignocellulosics. It was shown that complex between copper(II) and non-substituted curcumin 2, displaying remarkable photostability in ethyl acetate/ethanol solution, is able to photostabilize in some extend -carbonyl -O-4 lignin model and more efficiently spruce wood.

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Der Versuch, Holz mit einem Kupfer(II) Komplex mit 1.7-Diphenyl-1.6-Heptadien-3.5-Dion, einem nicht phenolischen Curcumin, zu schützen

Zusammenfassung Zum ersten Mal wurde Curcumin, das für seine antioxidante und sonnenschützende Wirkung bekannt ist, für den Lichtschutz von Lignin-Cellulosen eingesetzt. Es wurde gezeigt, dass der Kupfer(II)-Komplex mit einem unsubstituierten Curcumin 2, das in einer Lösung aus Ethylacetat/Ethanol über eine bemerkenswerte Photostabilität verfügt, die Fähigkeit besitzt, -Carbonyl -O-4 Lignin-Moleküle und noch effizienter Fichtenholz gegen Lichtabbau zu stabilisieren.

     

Water‐soluble cellulose oligomer production by chemical and enzymatic synthesis: a mini‐review

This mini‐review focuses on the production of water‐soluble cellulose oligomers. They are easier to handle than cellulose while still having some very interesting cellulose features. Their production is not trivial and they are thus seldom commercially available or are available at high prices and only in small quantities (100 mg or less). The goal of this mini‐review is to describe various routes to obtain these cellulose oligomers. Several examples of chemical or enzymatic synthesis and enzymatic or acidic depolymerization are presented. All the pathways considered are then compared according to several criteria: polymerization degree, yield, availability and cost of reagents, reaction time, etc. As most of the pathways produce a mixture of cellulose oligomers, techniques to separate them according to their length are also discussed. © 2017 Society of Chemical Industry     

The spectrophotometric determination of uroporphyrinogen I synthetase activity

The duration of the movement aftereffect was measured in twenty-four normally binocular subjects and in eighteen subjects who lacked steropsis as a consequence of childhood strabismus. Aftereffects were generated monocularly and binocularly, and compared to those which occurred after adaption of one eye and testing with the other. Normal subjects were categorized on two indices of eye dominance, which involved sighting and rivalry tests. The monocular-aftereffect durations were slightly longer when the dominant eye was use, and interocular transfer from the dominant eye to the nondominant eye was greater than the transfer in the reverse direction; however, these differences were not statistically significant. The results from the strabismic subjects suggested that they fell into two distinct groups: one group (seven of the eighteen subjects) experienced no interocular transfer in either direction; the group did yield some interocular transfer, and it was generally greater after adaptation of the dominant eye and testing the nondominant eye than in the reverse direction. Six of the seven subjects who failed to show any transfer still had misalignment of the visual axes, but this was not the case in any of the subjects exhibiting transfer.     

Impact of Fatty Acid Structure on CALB‐Catalyzed Esterification of Glucose

Enzymatic synthesis of fatty acid glucose esters from different fatty acyl donors are performed via enzymatic catalysis in the presence of Candida antarctica lipase B (CALB), using acetonitrile as the solvent. The acyl donor nature (fatty acid or fatty acid vinyl ester) and structure are varied. Lower reaction rates and lower conversions are obtained with fatty acids in comparison to their corresponding vinyl esters. Moreover, the acyl donor with the longest chain length gives the highest conversions. The presence of unsaturation on the acyl donor chain is also shown to be detrimental to the conversion. Practical Applications: The practical applications of the present work are related to the production of gluco‐esters that could be used as nonionic surfactants as detergents, cosmetics and food emulsifiers, emollients or conservatives, respectively. In this study, it is shown that in order to get high production yields, each reaction parameter has to be tuned properly.     

Chitosan Polymer as Bioactive Coating and Film against Aspergillus niger Contamination

ABSTRACT: The inhibitory activity of chitosan-based edible coatings and films was assessed against the Aspergillus niger food pathogen and deterioration microorganism. Spore-counting assays showed an almost total inhibition of A. niger growth when either film-forming solution or film were used at a low concentration of chitosan (0.1% w/v). Epifluorescence microscopic results showed the action of chitosan on the relative proportion of RNA compared with DNA. The water vapor permeability (WVP) of chitosan film was relatively low compared with the poor moisture barrier of some polysaccharide films. Moreover, a coating with chitosan film on an agar gel, used as a food model, induced a 30% reduction in water loss. These results showed potential applications of chitosan-based films as bioactive packaging with properties to limit the food dehydration phenomenon.     

DAMPs and RAGE Pathophysiology at the Acute Phase of Brain Injury: An Overview

Early or primary injury due to brain aggression, such as mechanical trauma, hemorrhage or is-chemia, triggers the release of damage-associated molecular patterns (DAMPs) in the extracellular space. Some DAMPs, such as S100B, participate in the regulation of cell growth and survival but may also trigger cellular damage as their concentration increases in the extracellular space. When DAMPs bind to pattern-recognition receptors, such as the receptor of advanced glycation end-products (RAGE), they lead to non-infectious inflammation that will contribute to necrotic cell clearance but may also worsen brain injury. In this narrative review, we describe the role and ki-netics of DAMPs and RAGE at the acute phase of brain injury. We searched the MEDLINE database for “DAMPs” or “RAGE” or “S100B” and “traumatic brain injury” or “subarachnoid hemorrhage” or “stroke”. We selected original articles reporting data on acute brain injury pathophysiology, from which we describe DAMPs release and clearance upon acute brain injury, and the implication of RAGE in the development of brain injury. We will also discuss the clinical strategies that emerge from this overview in terms of biomarkers and therapeutic perspectives     

Growth inhibition of wood-decay fungi by lignin-related aromatic compounds

European Journal of Wood and Wood Products - The relation between lignin-related structure and antifungal activities was assessed against the white-rot fungus Trametes versicolor and two brown-rot...