The behavior of thermally modified wood after exposure in maritime/industrial and urban environments.

Natural and thermally modified Pine, Ash, and Acacia woods were exposed in two different environments: urban and maritime/industrial. The weathering effects were evaluated during 24 months regarding color, chemical, and structural changes. In all wood species, thermal modification induced color, chemical, and structural changes. All woods became darker (Pine ΔL*: -32.01; Ash ΔL*: -36.83; Acacia ΔL*: -27.50), total extractives content increased (Pine: 19 %; Ash: 32 % and Acacia: 18 %), and the samples presented deformation and damaged cells. Total lignin was not significantly changed, although there were detected changes in lignin, namely the reduction of G-units in Pine (≈2 %) and reduction of S/G ratio in Acacia (≈0.04 %). Ash remained almost the same. After weathering, modified woods suffered fewer color changes, indicating that the thermal modification could improve the resistance to color change. Acacia wood, when exposed to maritime/industrial conditions, revealed a higher color change (ΔE: 35.7 at 24 months) when compared with urban conditions (ΔE: 23.5 at 24 months). Delignification, possibly caused by photodegradation, occurred in all wood samples, and the loss of extractive happened, perhaps caused by rain. Modified woods were slightly less resistant to weathering in maritime/industrial environments. Some structural damage, namely cracked cells, the appearance of molds, blue staining, and particle deposition, was observed. The thermal modification enables color stabilization but does not seem to improve the weathering resistance in all studied wood species. Exposure to the different environments did not lead to significant differences in the morphology and chemical composition of the three natural and modified wood species.

Cork cellular and chemical features underlying bark environmental protection in the miombo species Parinari curatellifolia.

Parinari curatellifolia is an important evergreen tree from the Miombo woodland of south-central and eastern Africa. The bark is corky, suggesting an increased protection against the ecosystem high temperatures and drought conditions as well as against wild fires. The cork in the bark rhytidome of P. curatellifolia was analyzed here for the first time with a focus on chemical and cellular features. P. curatellifolia cork has the cellular characteristics of cork tissues, with typical honeycomb structure in the tangential section and a brick-wall layer in the transverse and radial sections, without intercellular voids. Chemically P. curatellifolia cork has 8.4 % extractives, 33.9 % suberin, 31.9 % lignin and 25.2 % polysaccharides of the cork. The hemicelluloses are mostly xylans, with a substantial proportion of arabinose and galactose. Suberin showed a proportion of long chain lipids to glycerol (LCLip:Gly, mass ratio) of 8.5, and the long chain monomeric composition included a similar proportion of α,ω-diacids and ω-hydroxy acids (35.4 % and 31.5 % of long chain monomers) with a substantial proportion of monoacids (19.4 % of long chain monomers). Lignin is a guaiacyl-syringyl lignin with S/G of 0.32 and H:G:S of 1:14.1:4.5. The rhytidome composition and the cellular and chemical features of its cork are in line with environment-targeted protective features namely as a transpiration and insulation barrier, and as an increased fire protection.

First Chemical Profile Analysis of Acacia Pods.

This study intended to evaluate the potential industrial applications of various Acacia species (Acacia melanoxylon, Acacia longifolia, Acacia cyclops, Acacia retinodes, Acacia pycnantha, Acacia mearnsii, and Acacia dealbata) by examining their chemical composition, antioxidant, and antimicrobial properties. Using high-resolution mass spectrometry, a comprehensive analysis successfully identified targeted compounds, including flavonoids (flavonols/flavones) and phenolic acids, such as 4-hydroxybenzoic acid, p-coumaric acid, and ellagic acid. Additionally, p-coumaric acid was specifically identified and quantified within the hydroxycinnamic aldehydes. This comprehensive characterization provides valuable insights into the chemical profiles of the studied species. Among the studied species, A. pycnantha exhibited a higher concentration of total phenolic compounds, including catechin, myricetin, quercetin, and coniferaldehyde. Furthermore, A. pycnantha displayed notable antibacterial activity against K. pneumoniae, E. coli, S. Typhimurium, and B. cereus. The identified compounds in Acacia pods and their shown antibacterial activities exhibit promising potential for future applications. Moreover, vibrational spectroscopy was a reliable method for distinguishing between species. These significant findings enhance our understanding of Acacia species and their potential for various industrial applications.

Characterization of Mineral Composition and Nutritional Value of Acacia Green Pods.

The Acacia genus is considered one of the most invasive taxa in some habitats, namely coastal dunes, maritime calcareous soils, fresh lands in the valleys, mountainous areas, and the banks of watercourses and roadsides. In Portugal, the severity risk is very high, so this study aimed to evaluate the nutritional and mineral contents of the green pods as a potential source for livestock feeds and soil fertilizer because, as far as we know, there is no use for this species. The seven different species of Acacia (Acacia mearnsii Link, Acacia longifolia (Andrews) Willd, Acacia melanoxylon R. Br., Acacia pycnantha Bentham, Acacia dealbata Link., Acacia retinodes Schlecht, and Acacia cyclops A. Cunn. ex G. Don fil) were evaluated. The results showed that Acacia green pods have a high protein, fibre and minerals content, especially in potassium (K), calcium (Ca) and magnesium (Mg). All species present a different profile of the studied parameters, suggesting different potentials for their future use. Near-infrared spectroscopy was a potential tool to predict the earlier quality of the Acacia green pods to better select the raw material for the different applications.

Valorisation of Lignocellulosic Wastes, the Case Study of Eucalypt Stumps Lignin as Bioadsorbent for the Removal of Cr(VI).

The main objective of this work was to assess Eucalyptus globulus lignin as an adsorbent and compare the results with kraft lignin, which has previously been demonstrated to be an effective adsorbent. Eucalypt lignin was extracted (by the dioxane technique), characterised, and its adsorption properties for Cr(VI) ions were evaluated. The monomeric composition of both types of lignin indicated a high content of guaiacyl (G) and syringyl (S) units but low content of p-hydroxyphenyl (H), with an H:G:S ratio of 1:50:146 (eucalypt lignin) and 1:16:26 (kraft lignin), as determined by Py-GC/MS. According to elemental analysis, sulphur (2%) and sodium (1%) were found in kraft lignin, but not in eucalypt lignin. The adsorption capacity of the eucalypt lignin was notably higher than the kraft lignin during the first 8 h, but practically all the ions had been absorbed by both the eucalypt and kraft lignin after 24 h (93.4% and 95%, respectively). Cr(VI) adsorption onto both lignins fitted well using the Langmuir adsorption isotherm model, with capacities of 256.4 and 303.0 mg/g, respectively, for eucalypt and kraft. The study's overall results demonstrate the great potential of eucalypt lignin as a biosorbent for Cr(VI) removal from aqueous solutions.

Characterisation of the Phenolic Profile of Acacia retinodes and Acacia mearnsii Flowers' Extracts.

Acacia spp. is an invasive species that is widespread throughout the Portuguese territory. Thus, it is pertinent to better understand this species in order to find different applications that will value its use. To evaluate the phenolic profile in Acacia flowers, ethanolic extracts obtained through an energized guided dispersive extraction were analysed, focusing on two species, Acacia retinodes and Acacia mearnsii, at two flowering stages. The phytochemical profile of each extract was determined by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and high-performance liquid chromatography coupled with diode array detector. The FTIR-ATR technique was used to distinguish the different samples' compositions. The results showed the presence of high concentrations of phenolic compounds (>300 mg GAE/g extract), among which are flavonoids (>136 mg QE/g extract), for all combinations of species/flowering stages. The phytochemical profile showed a complex composition with 21 compounds identified and quantified (the predominant ones being epicatechin, rutin, vanillin, and catechol). Both species and flowering stages presented significant variations regarding the presence and quantity of phenols and flavonoids, so much so that a principal component analysis performed with FTIR-ATR spectra data of the extracts was able to discriminate between species and flowering stages.

Integrated bioprocess for structured lipids, emulsifiers and biodiesel production using crude acidic olive pomace oils.

Olive pomace oil (OPO), a by-product of olive oil industry, is directly consumed after refining. The novelty of this study consists of the direct use of crude high acidic OPO (3.4-20% acidity) to produce added-value compounds, using sn-1,3-regioselective lipases: (i) low-calorie dietetic structured lipids (SL) containing caprylic (C8:0) or capric (C10:0) acids by acidolysis or interesterification with their ethyl esters, (ii) fatty acid methyl esters (FAME) for biodiesel, and (iii) sn-2 monoacylglycerols (emulsifiers), as by-product of FAME production by methanolysis. Immobilized Rhizomucor miehei lipase showed similar activity in acidolysis and interesterification for SL production (yields: 47.8-53.4%, 7 h, 50℃) and was not affected by OPO acidity. Batch operational stability decreased with OPO acidity, but it was at least three-fold in interesterification that in acidolysis. Complete conversion of OPO into FAME and sn-2 monoacylglycerols was observed after 3 h-transesterification (glycerol stepwise addition) and lipase deactivation was negligeable after 11 cycles.

The Identification of New Triterpenoids in Eucalyptus globulus Wood.

Eight polyhydroxy triterpenoid acids, hederagenin, (4α)-23-hydroxybetulinic acid, maslinic acid, corosolic acid, arjunolic acid, asiatic acid, caulophyllogenin, and madecassic acid, with 2, 3, and 4 hydroxyl substituents, were identified and quantified in the dichloromethane extract of Eucalyptus globulus wood by comparing their GC-retention time and mass spectra with standards. Two other triterpenoid acids were tentatively identified by analyzing their mass spectra, as (2α)-2-hydroxybetulinic acid and (2α,4α)-2,23-dihydroxybetulinic acid, with 2 and 3 hydroxyl substituents. Two MS detectors were used, a quadrupole ion trap (QIT) and a quadrupole mass filter (QMF). The EI fragmentation pattern of the trimethylsilylated polyhydroxy structures of these triterpenoid acids is characterized by the sequential loss of the trimethylsilylated hydroxyl groups, most of them by the retro-Diels-Alder (rDA) opening of the C ring with a π-bond at C12-C13. The rDA C-ring opening produces ions at m/z 320 (or 318) and m/z 278 (or 277, 276, 366). Sequential losses of the hydroxyl groups produce ions with m/z from [M - 90] to [M - 90*y], where y is the number of hydroxyl substituents present (from 2 to 4). Moreover, specific cleavage in ring E was observed, passing from m/z 203 to m/z 133 and conducting other major fragments such as m/z 189.

Energetic characterization and radiographic analysis of torrefied coated MDF residues.

The use of wood panel residues as biomass for energy production is feasible. Heat treatments can improve energy properties while minimizing the emission of toxic gases due to thermoset polymers used in Medium Density Fiberboard (MDF) panels. Torrefaction or pre-carbonization, a heat treatment between 200 and 300 °C with low oxygen availability accumulates carbon and lignin, decreases hygroscopicity, and increases energy efficiency. The objective of this work was to evaluate the energy parameters (immediate, structural, and elementary chemical composition, moisture content, and yield) and density in torrefied MDF panels. The torrefaction improved the energetic features of coated MDF, decreasing the moisture content, volatile matter, and consequently, concentrating the carbon with better results in the samples torrefied for 40 min. The densitometric profiles of the torrefied MDF, obtained by X-ray densitometry, showed a decrease in the apparent density as torrefaction time increased. The digital X-ray images in gray and rainbow scale enabled the most detailed study of the density variation of MDF residues.

Quality of Pinus sp. pellets with kraft lignin and starch addition.

Pellets are widely used for power generation because they use renewable raw material with easy storage, transport and high energy density. However, the structural fragility, disintegrating during handling, transport and storage, is one of the main problems of pellets, but the addition of binders/additives can minimize this fragility. The objective of this study was to evaluate the properties of wood pellets with the addition of starch (corn and wheat) and kraft lignin in different proportions. Pellets were produced with the addition of starch (wheat and corn) and kraft lignin in the proportions of 1, 2, 3, 4 and 5% in relation to the mass of wood particles of Pinus sp., with 12% moisture (dry basis), classified in 3 and 1 mm sieves and compacted in a pelleting press in the laboratory, according to European standard EN 14961-2. Physical and mechanical properties of the pellets were evaluated and their densitometric profiles obtained from the Faxitron LX-60 X-ray equipment. Corn starch and kraft lignin additives at 4% improved pellet properties (density, fines and hardness), reducing their losses during handling, storage and transport.

Cellulose Structural Changes during Mild Torrefaction of Eucalyptus Wood.

The changes in the cellulose structure of eight Eucalyptus species (E. botryoides, E. globulus, E. grandis, E. maculata, E. propinqua, E. rudis, E. saligna and E. viminalis) in a mild torrefaction (from 160 °C to 230 °C, 3 h) were studied in situ and after cellulose isolation from the wood by solid-state carbon nuclear magnetic resonance (13C NMR), wide angle X-ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR) and by analytic pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS). Changes in molecular weight were assessed by viscosimetry. A small decrease in cellulose crystallinity (ca. 2%-3%) was attributed to its amorphization on crystallite surfaces as a result of acid hydrolysis and free radical reactions resulting in the homolytic splitting of glycosidic bonds. The degree of the cellulose polymerization (DPv) decreased more than twice during the heat treatment of wood. It has been proposed that changes in the supramolecular structure of cellulose and in molecular weight during a heat treatment can be affected by the amount of lignin present in the wood. The limitations of FTIR and Py-GC/MS techniques to distinguish the minor changes in cellulose crystallinity were discussed.

An extensive study on the chemical diversity of lipophilic extractives from Eucalyptus globulus wood.

Three mature Eucalyptus globulus trees with 40 years of age were studied at three height levels (0%, 35%, and 60% of total tree height) and at three radial regions (sapwood, inner and outer heartwood). The composition of lipophilic extracts was evaluated and an extensive list of 202 compounds was reported for the first time. The fatty acids were the major chemical family, representing 40.8% of the total compounds, followed by phytosterols (19.0%), aromatics (10.5%) and triterpenes (10.4%). Saturated fatty acids accounted for 74.2% of total compounds (C16:0, C24:0 and C26:0 were predominant), ß-Sitosterol and stigmastanol were the main sterols (80 and 7% respectively), while aromatics were mainly represented by syringic acid, 4-hydroxy-3,5-dimethoxybenzaldehyde, vanillic acid, and vanillin. The main triterpenes were asiatic and arjunolic acids.

Lignin from Tree Barks: Chemical Structure and Valorization.

Lignins from different tree barks, including Norway spruce (Picea abies), eucalyptus (Eucalyptus globulus), mimosa (Acacia dealbata) and blackwood acacia (A. melanoxylon), are thoroughly characterized. The lignin from E. globulus bark is found to be enriched in syringyl (S) units, with lower amounts of guaiacyl (G) and p-hydroxyphenyl (H) units (H/G/S ratio of 1:26:73), which produces a lignin that is highly enriched in ß-ether linkages (83 %), whereas those from the two Acacia barks have similar compositions (H/G/S ratio of ≈5:50:45), with a predominance of ß-ethers (73-75 %) and lower amounts of condensed carbon-carbon linkages; the lignin from A. dealbata bark also includes some resorcinol-related compounds, that appear to be incorporated or intimately associated to the polymer. The lignin from P. abies bark is enriched in G units, with lower amounts of H units (H/G ratio of 14:86); this lignin is thus depleted in ß-O-4' alkyl-aryl ether linkages (44 %) and enriched in condensed linkages. Interestingly, this lignin contains large amounts of hydroxystilbene glucosides that seem to be integrally incorporated into the lignin structure. This study indicates that lignins from tree barks can be seen as an interesting source of valuable phenolic compounds. Moreover, this study is useful for tailoring conversion technologies for bark deconstruction and valorization.

Production of low-calorie structured lipids from spent coffee grounds or olive pomace crude oils catalyzed by immobilized lipase in magnetic nanoparticles.

In this study, crude oils extracted from spent coffee grounds (SCG) and olive pomace (OP) were used as raw-material to synthesize low-calorie triacylglycerols, either by acidolysis with capric acid, or by interesterification with ethyl caprate, in solvent-free media, catalyzed by sn-1,3 regioselective lipases. The Rhizopus oryzae lipase (ROL) was immobilized in magnetite nanoparticles (MNP-ROL) and tested as novel biocatalyst. MNP-ROL performance was compared with that of the commercial immobilized Thermomyces lanuginosus lipase (Lipozyme TL IM). For both oils, Lipozyme TL IM preferred interesterification over acidolysis. MNP-ROL catalyzed reactions were faster and acidolysis was preferred with yields of c.a. 50% new triacylglycerols after 3 h acidolysis of OP or SCG oils. MNP-ROL was very stable following the Sadana deactivation model with half-lives of 163 h and 220 h when reused in batch acidolysis and interesterification of OP oil, respectively.

Hydroxystilbene Glucosides Are Incorporated into Norway Spruce Bark Lignin.

Recent investigations have revealed that, in addition to monolignols, some phenolic compounds derived from the flavonoid and hydroxystilbene biosynthetic pathways can also function as true lignin monomers in some plants. In this study, we found that the hydroxystilbene glucosides isorhapontin (isorhapontigenin-O-glucoside) and, at lower levels, astringin (piceatannol-O-glucoside) and piceid (resveratrol-O-glucoside) are incorporated into the lignin polymer in Norway spruce (Picea abies) bark. The corresponding aglycones isorhapontigenin, piceatannol, and resveratrol, along with glucose, were released by derivatization followed by reductive cleavage, a chemical degradative method that cleaves ß-ether bonds in lignin, indicating that the hydroxystilbene glucosides are (partially) incorporated into the lignin structure through ß-ether bonds. Two-dimensional NMR analysis confirmed the occurrence of hydroxystilbene glucosides in this lignin, and provided additional information regarding their modes of incorporation into the polymer. The hydroxystilbene glucosides, particularly isorhapontin and astringin, can therefore be considered genuine lignin monomers that participate in coupling and cross-coupling reactions during lignification in Norway spruce bark.

An integrated characterization of Picea abies industrial bark regarding chemical composition, thermal properties and polar extracts activity.

The present work determines the chemical and thermal characteristics as well as the phytochemical and antioxidant potential of the polar extractives of the Picea abies bark from an industrial mill, their wood and bark components and also different bark fractions obtained by mechanical fractionation (fine B1, Φ<0.180 mm, medium B3, 0.450 < Φ<0.850 mm and coarse B6, 2 < Φ<10 mm). The aim is to increase the knowledge on the Picea abies bark to better determine possible uses other than burning for energy production and to test an initial size reduction process to achieve fractions with different characteristics. Compared to wood, bark presented similar lignin (27%), higher mineral (3.9% vs 0.4%) and extractives (20.3% vs 3.8%) and lower polysaccharides (48% vs 71%) contents. Regarding bark fractions the fines showed higher ash (6.3%), extractives (25%) and lignin (29%) than the coarse fraction (3.9%, 19% and 25% respectively). Polysaccharide contents increased with particle size of the bark fractions (38% vs 52% for B1 and B6) but showed the same relative composition. The phytochemical profile of ethanol and water extracts presented higher contents for bark than wood of total phenols (2x higher), flavonoids (3x higher) and tannins (4-10x higher) with an increasing tendency with particle size. Bark antioxidant activity was higher than that of wood for ferric-reducing antioxidant power (FRAP, 10 vs 6 mmolFe2+/gExt for the ethanol extract) and free radical scavenging activity (DPPH, 6 vs 18 mg/L IC50 for the ethanol extract) methods. The different bark fractions antioxidant activity was very similar. Bark thermal properties showed a much lower volatiles to fixed carbon ratio (V/FC) than wood (3.1 vs 5.2) although the same higher heating value (20.3 MJ/kg). The fractions were quite similar. Bark presented chemical features that point to their possible upgrade, whether by taking advantage of the high extractives with bioactive compounds or the production potential for hemicellulose-derived oligomers with possible use in nutraceutical and pharmaceutical industries.

Lignin Composition and Structure Differs between Xylem, Phloem and Phellem in Quercus suber L.

The composition and structure of lignin in different tissues-phellem (cork), phloem and xylem (wood)-of Quercus suber was studied. Whole cell walls and their respective isolated milled lignins were analyzed by pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) and derivatization followed by reductive cleavage (DFRC). Different tissues presented varied p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) lignin compositions. Whereas lignin from cork has a G-rich lignin (H:G:S molar ratio 2:85:13), lignin from phloem presents more S-units (H:G:S molar ratio of 1:58:41) and lignin from xylem is slightly enriched in S-lignin (H:G:S molar ratio 1:45:55). These differences were reflected in the relative abundances of the different interunit linkages. Alkyl-aryl ethers (ß-O-4') were predominant, increasing from 68% in cork, to 71% in phloem and 77% in xylem, as consequence of the enrichment in S-lignin units. Cork lignin was enriched in condensed structures such as phenylcoumarans (ß-5', 20%), dibenzodioxocins (5-5', 5%), as corresponds to a lignin enriched in G-units. In comparison, lignin from phloem and xylem presented lower levels of condensed linkages. The lignin from cork was highly acetylated at the γ-OH of the side-chain (48% lignin acetylation), predominantly over G-units; while the lignins from phloem and xylem were barely acetylated and this occurred mainly over S-units. These results are a first time overview of the lignin structure in xylem, phloem (generated by cambium), and in cork (generated by phellogen), in agreement with literature that reports that lignin biosynthesis is flexible and cell specific.

Stumps of Eucalyptus globulus as a source of antioxidant and antimicrobial polyphenols.

These past years have seen an enormous development of the area of natural antioxidants and antimicrobials. Eucalyptus globulus is widely cultivated in subtropical and Mediterranean regions in intensive short rotation coppice plantations. In the Portuguese context, E. globulus is the third species in terms of forest area. The stump is the basal part of the tree, including the near-the-ground stem portion and the woody roots that remain after stem felling. The purpose of this work was to study the phytochemical profile and to evaluate the antioxidant and antimicrobial properties of several crude stump wood and stump bark extracts of E. globulus, comparing it with similar extracts of E. globulus wood (industrial chips). The results showed the presence of high concentrations of total phenolic compounds (>200 mg GAE/g extract) and flavonoids (>10 mg QE/g extract) in E. globulus stump extracts. Generally the stump wood extracts stands out from the other ones, presenting the highest percentages of inhibition of linoleic acid oxidation. It was also possible to conclude that the extracts were more active against Gram-positive bacteria, presenting low MIC values. This study thus provides information supporting the economic valorization of E. globulus stump wood.

Reactivity of syringyl and guaiacyl lignin units and delignification kinetics in the kraft pulping of Eucalyptus globulus wood using Py-GC-MS/FID.

Eucalyptus globulus sapwood and heartwood showed no differences in lignin content (23.0% vs. 23.7%) and composition: syringyl-lignin (17.9% vs. 18.0%) and guaiacyl-lignin (4.8% vs. 5.2%). Delignification kinetics of S- and G-units in heartwood and sapwood was investigated by Py-GC-MS/FID at 130, 150 and 170°C and modeled as double first-order reactions. Reactivity differences between S and G-units were small during the main pulping phase and the higher reactivity of S over G units was better expressed in the later pulping stage. The residual lignin composition in pulps was different from wood or from samples in the initial delignification stages, with more G and H-units. S/G ratio ranged from 3 to 4.5 when pulp residual lignin was higher than 10%, decreasing rapidly to less than 1. The S/H was initially around 20 (until 15% residual lignin), decreasing to 4 when residual lignin was about 3%.