Volume 73, Issue 5

Lignans are major bioactive secondary metabolites, which are also formed in the heartwood (hW) of Taiwania ( Taiwania cryptomerioides ). Their biosynthesis pathways are complex and involve many enzymes and intermediates. To evaluate the extent of the genetic components leading to the variety of lignans in Taiwania hW, 35 Taiwania genotypes of four provenances were surveyed using the proton nuclear magnetic resonance ( 1 H-NMR) and liquid chromatography-mass spectrometry (LC-MS) analyses. The metabolite profiles were statistically evaluated by principal component analysis (PCA) and the general linear model (GLM). The broad-sense heritability ( H 2 ) was further evaluated by linear mixed model (LMM) analysis. It was demonstrated that the genetic factor is the major contributor to the abundance of lignans, though the environmental factor also has some effect on it. Among the metabolites detected by 1 H-NMR, lignans were the major compounds that exhibited high a H 2 (0.52–0.82), which was further verified by LC-MS. The conclusion is that 1 H-NMR spectroscopy is suitable for quick screenings, predictions and semi-quantitation of lignans. The high H 2 is also indicative of the lignan abundances as traits that can be genetically modified to achieve a significant wood quality improvement.

Aquilaria is an endangered agarwood-producing genus that is currently protected by international laws. The agarwood trade is strictly monitored to prevent illegal harvesting, which has caused high demand for this natural product. Other plant sources of similar appearance or fragrance as agarwood are used as adulterant species in counterfeit products. To promote species identification via the DNA barcoding technique, the existing DNA barcoding database in our laboratory was enriched with seven plant barcoding sequences from a commercially important Aquilaria species ( Aquilaria beccariana ) and seven adulterant species ( Cocos nucifera , Dalbergia latifolia , Pinus contorta var. latifolia , Santalum album , Strychnos ignatii , Thuja sp. and Terminalia catappa ). DNA barcoding with high-resolution melting analysis (Bar-HRM) showed that the mini-barcode internal transcribed spacer 1 (ITS1) was an effective gene locus that allows for a rapid and species-specific detection of Aquilaria and their adulterants, while four other mini-barcodes ( rbc L, trn L intron, ITS2 and 5.8s) functioned as a support and a crosscheck for the barcoding results. The accuracy of the Bar-HRM technique in species origin identification was further assessed with seven agarwood blind specimens. The Bar-HRM technique is a potential tool for validating agarwood-species origin and detecting products with adulterant species.

As wet wood is prone to degradation by wood-destroying fungi, the monitoring of the moisture content (MC) of wood can be used to quantify the risk of fungal infestation. Fungal decay alters the sorption and electrical conductivity of wood, and thus the goal of the present study was to measure the electrical resistance (R) of wood after fungal decay as a function of MC. Scots pine sapwood ( Pinus sylvestris L.) and European beech wood ( Fagus sylvatica L.) were submitted to decay by Coniophora puteana (a brown rot fungus, BR) and Trametes versicolor (a white rot fungus, WR) and the mass loss (ML) due to the fungal metabolism was measured. The sorption isotherms were determined by dynamic vapor sorption (DVS), and comparative gravimetric- and R-based MC measurements were conducted. BR and WR reduced the sorption of wood and lowered its R in the hygroscopic range, where the decay led to an overestimation of wood MC, while wood MC was dramatically underestimated above fiber saturation (FS). Specimens showed an MC well above FS if measured directly after harvesting and an increased R compared to undecayed wood at a given MC. BR-decayed specimens were dried and rewetted, and such specimens showed an elevated R beyond FS. In the case of WR-decayed wood, the R was reduced at a given MC.

Amongst polyphenols, tannins belong to the most effective chemical protection systems against biological attack on trees. Tannins are water-soluble and are thus leached out easily when used for wood protection. In situ polymerized tannin-hexamine wood preservatives have better leaching resistance (LR), but they do not resist weathering. In this study, tannin copolymer formulations were prepared with hexamine, formaldehyde, furfural, glyoxal, furfuryl alcohol and maleic anhydride, impregnated in wood, and cured at higher temperatures. The wood samples treated with these formulations were tested for their anti-swelling efficiency (ASE), leaching behavior, mechanical properties, and their resistance against fire, weathering and biological attack. Several tannin-treated specimens showed improved hardness and enhanced leaching and fire resistance. Some formulations also responded well to artificial weathering cycles, but natural weathering cycles deteriorated their performance. Samples treated with maleic anhydride showed improved leachability and high biological resistances, even without the addition of inorganic biocides. These organic and bio-friendly products can be considered as promising alternatives to heavy metal-based wood preservatives.

Poplar wood samples (2×2×2 cm 3 ) were vacuum/pressure impregnated in alcoholic solution with 2-hydroxyethyl methacrylate (HEMA) and 3-(methacryloxy)propyltrimethoxysilane (MAPTES) in a mass ratio of 3/1 in the presence of catalytic amounts of azobisisobutyronitrile (AIBN). Because of their good solubility and permeability, the HEMA/MAPTES precursors evenly penetrate the poplar cell wall. The impregnated samples were heated at 75°C for 8 h, followed by a heating period at 103±2°C for 8 h, in the course of which an in situ polymerization occurred in the cell wall. The modified wood was characterized by Fourier transform infrared (FTIR) and Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, the dimensional stability of the modified wood was measured and found to be considerably improved.

The aim of the study was to find appropriate non-chlorinated solvent systems for the extraction and separation of pure pinosylvin (PS) and pinosylvin monomethylether (PSMME) from Scots pine/Norway spruce wood residues. The extraction was performed in a pressurized solvent extractor and the purification and isolation of pure substances was done by flash chromatography. More precisely, pure PS was isolated via sequential flash chromatography in two repetitions in the gradient mode of the mobile phase, with cylcohexane (CX) and ethylacetate (EtOAc), beginning with 100% CX and ending up with 100% EtOAc. The extractives were qualitatively and quantitatively analyzed in terms of PS and PSMME contents by gas chromatography-flame ionization detector (GC-FID), gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy.

Organosolv lignin (OL) extracted from pine wood was self-assembled into uniform nanocolloidal spheres (OLCS) in acetone/water and blended with varnish for better UV-blocking and antioxidant performance. The UV transmittance of the varnish with 1% OL was lower than that of a commercial varnish containing synthetic UVA and UVB blocker. Samples coated with OL-based varnish and UV irradiated for 100 h showed 84 and 69% less color change, respectively, compared to that of pure and commercial varnishes. Due to the higher surface area and better compatibility, the varnish blended with 1% OLCS showed better UV-blocking and photostability than those based on 1% OL additive. The color change of varnish was not perceptible. The lignin-based additives significantly enhanced the hardness and adhesion performance of the varnish and had little influence on the esthetic appearance of the samples. The hardness and modulus of elasticity of varnish increased by 61 and 36%, respectively, in the presence of 1% OLCS. The possible enhancement mechanism was explained by molecular interaction forces.

For ground pulp (GP) utilization in wood fiber composites as reinforced material, its thermal behavior is relevant. The contribution of lignin to thermal performance of GP from Pinus densiflora was the focus of the present study. Dimeric lignin model compounds and isolated milled wood lignins (MWLs) from three sources were submitted for thermogravimetric analysis (TGA). The temperatures leading to 1% weight loss (T per 1% WL) for the material were determined. The thermal stability of β-O-4 models was the lowest. Among the MWLs, the abaca MWL with its high β-O-4 content was the least thermostable. An acetylated nonphenolic β-O-4 lignin model compound showed that acetylation improves the thermal stability of this type of dimeric models. The acetylation of benzylic OH groups in β-O-4 linkages is especially relevant for the thermal resistance, which was also shown based on pre-acetylated benzylic OH groups in the GP before the total acetylation.

Sulfonated cellulose (SC) with varying degrees of substitution (DS) were prepared with the pyridine sulfur trioxide complex (Py-SO 3 ) as a sulfonation reagent (as a source of sulfur trioxide) in dimethyl formamide (DMF) as a solvent, where the DS was primarily affected by the molar ratio between Py-SO 3 and the anhydroglucose (AHG) unit. Sulfonation temperature and residence time have less effect on DS. The ratio of the crystalline domain of SC decreased gradually with incremental DS, and the crystalline cellulose I of SC at DS 0.81 nearly disappeared, and the moiety of the paracrystalline SC with high hydrophilicity increased. The thermostability decreased with increasing DS as a consequence of crystalline domain decrement. The adsorption performance of SC to metal ions was enhanced with increasing DS. However, above DS 0.62, the adsorption capacity enhancement is negligible. For an economic adsorption of heavy meatal ions in effluents, the DS of SC must be optimized.

Lignin, a substance considered as a residue in biomass and ethanol production, has been identified as a renewable resource suitable for making inexpensive carbon fibers (CFs), which would widen the range of possible applications for light-weight CFs reinforced composites. Wet spinning of lignin-cellulose ionic liquid solutions is a promising method for producing lignin-based CFs precursors. However, wet-spinning solutions containing lignin pose technical challenges that have to be solved to enable industrialization. One of these issues is that a part of the lignin leaches into the coagulation liquid, which reduces yield and might complicate solvent recovery. In this work, the mass transport during coagulation is studied in depth using a model system and trends are confirmed with spinning trials. It was discovered that during coagulation, efflux of ionic liquid is not hindered by lignin concentration in solution and the formed cellulose network will enclose soluble lignin. Consequently, a high total concentration of lignin and cellulose in solution is advantageous to maximize yield. This work provides a fundamental understanding on mass transport during coagulation of lignin-cellulose solutions, crucial information when designing new solution-based fiber forming processes.