Lignin–carbohydrate complexes (LCC) were isolated from the fibers of sisal (Agave sisalana) and abaca (Musa textilis) according to a plant biomass fractionation procedure recently developed and which ...was termed as “universally” applicable to any type of lignocellulosic material. Two LCC fractions, namely glucan–lignin (GL) and xylan–lignin (XL), were isolated and differed in the content and composition of carbohydrates and lignin. In both cases, GL fractions were enriched in glucans and comparatively depleted in lignin, whereas XL fractions were depleted in glucans, but enriched in xylans and lignin. Analysis by two-dimensional Nuclear Magnetic Resonance (2D-NMR) and Derivatization Followed by Reductive Cleavage (DFRC) indicated that the XL fractions were enriched in syringyl (S)-lignin units and β-O-4' alkyl-aryl ether linkages, whereas GL fractions have more guaiacyl (G)-lignin units and less β-O-4' alkyl-aryl ether linkages per lignin unit. The data suggest that the structural characteristics of the lignin polymers are not homogeneously distributed within the same plant and that two different lignin polymers with different composition and structure might be present. The analyses also suggested that acetates from hemicelluloses and the acyl groups (acetates and p-coumarates) attached to the γ-OH of the lignin side chains were extensively hydrolyzed and removed during the LCC fractionation process. Therefore, caution must be paid when using this fractionation approach for the structural characterization of plants with acylated hemicelluloses and lignins. Finally, several chemical linkages (phenylglycosides and benzyl ethers) could be observed to occur between lignin and xylans in these plants.
▸ A laccase-mediator treatment removed lignin from whole woody and nonwoody feedstocks. ▸ A high-redox potential laccase and 1-hydroxybenzotriazole (as mediator) were used. ▸ This laccase-mediator ...treatment was combined with an alkaline peroxide extraction. ▸ 2D NMR analyses revealed oxidative removal of lignin aromatic units and side-chains. ▸ The enzymatic pretreatment increased the sugar and ethanol yields.
The ability of Trametes villosa laccase, in conjuction with 1-hydroxybenzotriazole (HBT) as mediator and alkaline extraction, to remove lignin was demonstrated during treatment of wood (Eucalyptus globulus) and non-wood (Pennisetum purpureum) feedstocks. At 50Ug−1 laccase and 2.5% HBT concentration, 48% and 32% of the Eucalyptus and Pennisetum lignin were removed, respectively. Two-dimensional nuclear magnetic resonance of the feedstocks, swollen in dimethylsulfoxide-d6, revealed the removal of p-hydroxyphenyl, guaiacyl and syringyl lignin units and aliphatic (mainly β-O-4′-linked) side-chains of lignin, and a moderate removal of p-coumaric acid (present in Pennisetum) without a substantial change in polysaccharide cross-signals. The enzymatic pretreatment (at 25Ug−1) of Eucalyptus and Pennisetum feedstocks increased the glucose (by 61% and 12% in 72h) and ethanol (by 4 and 2gL−1 in 17h) yields from both lignocellulosic materials, respectively, as compared to those without enzyme treatment.
Pineapple leaf fibers (PALF) were modified by the mercerization process to improve their mechanical properties for applications in composites. The changes in the morphology and mechanical properties ...of fibers were evaluated after using different conditions (temperature and sodium hydroxide concentration) for the mercerization process. The study was done using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Mercerization treatments caused a reduction in the diameter of fibers, either due removal of surface impurities, disintegration of middle lamella and/or interfibrillar swelling. Mechanical properties of mercerized fibers were modified. The highest tensile strength was observed when mercerization was done at a temperature of 60 °C and alkali concentration of 3 % wt.
Biofuels production from organic waste requires an efficient hydrolysis to produce fermentable sugars. Physicochemical and biological pretreatment corresponds to good alternative to improve biofuel ...yield. Nonetheless, physical treatments can result in a negative energy balance and chemical treatments can generate inhibitors for a fermentative process, as well as difficulties in the recycling of organic matter. Thus, enzymatic pretreatments lead to fast and ecofriendly processes for conversion of waste biomass into monomeric units. In this work, fruit and vegetable wastes were hydrolyzed applying three types of enzymatic complexes: Viscozyme® L and a mixture of Multifect® B and Naturalzyme 40 XLTM. Production of reducing sugars as a temperature function and enzyme concentration was optimized by response surface analysis. Enzymatic complexes revealed high hydrolysis yield. Viscozyme® L application is highlighted; obtaining a hydrolysis higher than with the mixture of Multifect® B and Naturalzyme 40 XLTM (80% and 60% respectively) and being a promising treatment for the development of an efficient saccharification process of fruit and vegetable wastes. The optimum application conditions for Viscozyme® L were of 0.24 ppm and 40 °C and were validated with an error rate of 5%. For the mixture of Multifect® B and Naturalzyme 40 XLTM with Pectinase/Polygalacturonase activity, an optimum 0.93 ppm and 41 °C was found; these were validated with an error of 6%. Therefore, cellulases, xylanases and hemicellulases (Viscozyme® L) assured the hydrolysis of food wastes obtaining better available sugars for successive fermentative processes.
Graphic Abstract
Brightness in totally chlorine-free (TCF) pulp is more unstable than it is in elemental chlorine-free (ECF) pulp, seemingly by effect of the former containing greater amounts of oxidizable structures ...such as hexenuronic acids (HexA). Accelerated ageing tests involving the application of moist heat to pulp revealed that brightness reversion can be alleviated by using an effective biotechnological method involving an enzyme–mediator treatment. Thus, the joint use of laccase from
Trametes villosa and the mediator hydroxybenzotrialoze (HBT) in TCF pulp removes hexenuronic acids by 23% and reduces brightness reversion by 8.4%. Additional tests conducted to assess the effect of HexA on pulp refining revealed that these oxidizable structures introduce hydrophilicity in the pulp. Removing hexenuronic acids from TCF pulp alters its refining outcome as regards drainability (°SR) and water retention capacity (%WRV); also, it leads to paper with comparable strength-related properties which requires no additional refining energy.
Agricultural crops from plantain produce a significant amount of wastes and they are currently considered worthless. Accordingly, in this study, non-wood fibers from pseudostem of plantain plants ...were extracted through mechanical processing to be used as reinforcing material in polyester composites. Bio-based composites were obtained using a 4% wt. of lignocellulosic reinforcement and were prepared after the fibers underwent alkaline and acetylation treatments in order to enhance the compatibility of organic loads with the polyester matrix. The higher cellulose content of plantain fibers indicates that they can be used to reinforce composites with a polymeric matrix. The plantain fibers have bast fiber bundle of around 120 µm; single fibers of around 5 µm; and mesofibers with a diameter between 0.5 and 1 µm. The results showed that plantain fibers can be used as a filler material to obtain an alternative polymer composite. The flexural strength of composites (polyester with acetylated plantain fibers) was improved 28% when the properties are compared to control composite.
► Different enzyme combinations were applied to biobleach eucalypt cellulose fibres. ► A diverse mode of action on lignin and hexenuronic acids was found between enzymes. ► Biobleached eucalypt ...cellulose fibres with added value were obtained.
Various combinations of laccases, xylanase and cellulase were used to biobleach cellulose fibres from eucalyptus. The Trametes villosa and Myceliophthora thermophila laccases were used in combination with violuric acid (VATvL system) and methyl syringate (MeSMtL system), respectively, as mediator. A dissimilar mode of action of the two systems was found: the VATvL treatment released both hexenuronic acids and lignin, whereas the MeSMtL released lignin alone. Pulp properties were further improved by applying the mediator before the enzyme during treatment. Pulp properties comparable to those provided by industrial TCF sequences were obtained by inserting a xylanase pretreatment before VATvL, but no significant effect was observed after the cellulase pretreatment. As an added value, the resulting enzymatically bleached fibres possess a reduced hexenuronic acid content. The chemical oxygen demand of the effluents from each stage was also assessed.
Application of a laccase mediator system (an L stage) to TCF and ECF bleached pulp from
Eucalyptus globulus with low residual lignin content (KN
lig
⩽
1.0) provides useful information about its ...effects on hexenuronic acids, functional groups (carboxyl and carbonyl) and electrokinetic properties such as
ζ potential and surface charge. The use of laccase from
Trametes villosa in combination with the mediator 1-hydroxybenzotriazole (HBT) was found to oxidize cellulose to carbonyl groups and reduce the amount of carboxyl groups present in TCF pulp by effect of its partially removing hexenuronic acids from it. This result may open up new prospects for improving brightness stability in pulp. In addition, the laccase mediator system modifies the surface charge and
ζ potential in the fibre suspension for the removal of ionizables groups in TCF pulp. This result has no adverse effect on the pulp refining efficiency. L treatment requires less mechanical energy than conventionally refined pulp to obtain an optimal tensile and tear index in handsheets. This behavior may be attributable to the modification of the electrokinetic properties.
Flax soda/AQ pulps were treated with different fungal laccase–mediator combinations followed by physical and chemical characterization of the pulps to obtain a thorough understanding of the ...laccase/mediator effects on hexenuronic acid (HexA) removal and the coupling of mediator onto pulps for fiber functionalization. Large differences were found and the presence of lauryl gallate (LG) during Trametes villosa laccase (TvL) treatment (TvL+LG) resulted in a much larger reduction of pulp-linked HexA than the combination of p-coumaric acid (PCA) and Pycnoporus cinnabarinus laccase (PcL). A major portion of LG became attached to the pulp as revealed by an increase in the kappa number and further confirmed by thioacidolysis and 1H NMR analysis of solubilized pulp fractions. Additional experiments with other chemical pulps and isolated pulp xylan and lignin revealed that HexA seems to be the sole pulp component attacked by TvL+LG. As a substrate for TvL, the reaction preference order is PCA>HexA>LG.
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