Clones of Eucalyptus globulus Labill. (5- to 7-year-old), from a common geographic area, were evaluated for chemical pulping easiness. Significant variations were observed in the pulp yield and specific wood consumption to produce pulps with similar kappa numbers, as well as in the strength properties of the resulting kraft pulps. Comprehensive lignin analyses were undertaken in an attempt to rationalize the observed differences in these clones’ pulping performance. While lignin content did not correlate with pulp yield, the data reported here provides evidence of the influence of lignin features on the pulping response of different eucalyptus clones. Significant correlations were observed between pulp yield and specific wood consumption and the content of syringyl-type arylglycerol-β-aryl structures (β-O-4 linkages). Furthermore, eucalyptus woods with a greater content of uncondensed β-O-4 linkages were found to require more PFI revolutions to obtain pulps with a given drainability. In contrast, no relationship between pulping efficiency and the other lignin structural features evaluated was apparent, including syringyl/guaiacyl ratio (S/G), total aliphatic and phenolic hydroxyl groups, syringyl and guaiacyl units bearing free phenolic hydroxyls, and the erythro-to-threo ratio of β-O-4 structures. These findings support the use of the content of syringyl-type arylglycerol-β-aryl structures as a selection parameter in clonal breeding programs for pulpwood production.
Enzymatic mild acidolysis lignins (EMAL) isolated from different species of softwood and Eucalyptus globulus were submitted to comparative analysis that included thioacidolysis, derivatization followed by reductive cleavage (DFRC), and DFRC followed by quantitative 31 P NMR (DFRC/ 31 P NMR). While gas chromatography (GC) was used to determine the monomer yields from both thioacidolysis and DFRC, 31 P NMR studies quantified the various phenolic hydroxy groups released by DFRC. The monomer yields from thioacidolysis and DFRC were substantially different, with thioacidolysis resulting in higher yields. In contrast, an excellent agreement was obtained in the total number of -aryl ether structures determined by thioacidolysis and DFRC/ 31 P NMR, indicating that the combination of DFRC with quantitative 31 P NMR overcomes, at least in part, the limitations presented by the DFRC method. Both thioacidolysis and DFRC/ 31 P NMR were further used to better understand the lignin isolation process from wood. The results show that mild rotary ball milling minimizes, but does not prevent, the degradation of -O-4 structures during the early stages of wood pulverization. The extent of such degradation was found to be higher for E. globulus than for a variety of softwoods examined. Furthermore, the structures of the EMALs isolated at yields ranging from 20% to 62% were very similar, indicating structural homogeneity in the lignin biopolymer within the secondary wall.Lignin is a complex and irregular natural polymer built up of different interunit linkages. 1 While the bulk of lignin in wood consists of nonphenolic -aryl ether units, other units, such as phenylcoumaran ( -5), resinol ( -), and dibenzodioxocins (5-5/ -O-4, R-O-4), are also present in lower amounts within the lignin macromolecule. 1,2 According to the current understanding, almost all lignin macromolecules in softwood and softwood pulps are covalently linked to polysaccharides, mainly hemicelluloses. 3,4 A primary problem in elucidating lignin structure has been the isolation of total lignin from wood in a chemically unaltered form. 5-9 Overall, two approaches have been used to isolate lignin from lignocellulosics: acidolysis methods 10,11 and extraction of lignin after ball milling. 5,6,12 Despite resulting in lignin preparations with high yields and purities, severe acid concentrations (usually 0.2 M) trigger some changes in lignin structure. 10,11 On the other hand, traditional ball-milling-based methods, such as the milled wood lignin (MWL) and cellulolytic enzyme lignin (CEL) protocols, offer less modified lignin than those obtained by severe acid treatments. However, the yields of such lignins are dependent on milling intensity. [7][8][9]13 Intensive milling protocols offered by vibratory-and orbital-milling devices provide higher lignin yields within relatively short milling intervals, although at the expense of the integrity of the lignin macromolecule and associated condensation and oxidation reactions. 8,9,13,14 Low-intensity milling minimizes structural c...
An Ultic Haploxeralf soil collected from ridges built into the slopes of the Coastal Mountain Range of Central Chile was used in applications of humic and fulvic acids (HFA) extracted from sludge from sewage treatment plants, in combination with gypsum (CaSO 4 ). A total of 12 treatments were applied by combining four doses of HFA (0, 20, 30 and 40 t ha -1 ) with three doses of gypsum (0, 1.2 and 6.0 t ha -1 ). The effect of these treatments was assessed using three indicators of the degree of soil aggregation: macroporosity (MA), bulk density (Da) and microinfiltration (MI). The experiment was set up in a laboratory using a completely randomised design (CRD). Factorial variance analysis was also performed using two factors: gypsum in three doses and HFA in four doses. For all three indicators, MA, Db and MI, it can be seen that there is interaction between the HFA treatments and the gypsum treatments in the studied soil. The macroporosity increased with HFA treatments with 20 or 30 t ha -1 (9%) and with gypsum of 1.2 t ha -1 plus 20 t ha -1 HFA (11%). It can also be seen that the gypsum treatments have no effect on Db when HFA is not applied. Microinfiltration is the variable that shows the greatest effects from the treatments applied. The results also clearly show that high amounts of HFA (40 t ha -1 ) and of gypsum (6.0 t ha -1 ) cancel out the differential effects and cause negative effects on the three indicators for the studied soils. The use of liquid humus and its combination with calcium sulphate (20/1.2 t ha -1 ) improves soil aggregation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.