Scots pine (Pinus sylvestris) bark composition and degradation by fungi: potential substrate for bioremediation

The composition of Scots pine bark, its degradation, and the production of hydrolytic and ligninolytic enzymes were evaluated during 90 days of incubation with Phanerochaete velutina and Stropharia rugosoannulata. The aim was to evaluate if pine bark can be a suitable fungal substrate for bioremediation applications. The original pine bark contained 45% lignin, 25% cellulose, and 15% hemicellulose. Resin acids were the most predominant lipophilic extractives, followed by sitosterol and unsaturated fatty acids, such as linoleic and oleic acids. Both fungi degraded all main components of bark, specially cellulose (79% loss by P. velutina). During cultivation on pine bark, fungi also degraded sitosterol, produced malic acid, and oxidated unsaturated fatty acids. The most predominant enzymes produced by both fungi were cellulase and manganese peroxidase. The results indicate that Scots pine bark supports enzyme production and provides nutrients to fungi, thus pine bark may be suitable fungal substrate for bioremediation.

Comparison of microencapsulation properties of spruce galactoglucomannans and arabic gum using a model hydrophobic core compound

In the present study, microencapsulation and the physical properties of spruce ( Picea abies ) Omicron-acetyl-galactoglucomannans (GGM) were investigated and compared to those of arabic gum (AG). Microcapsules were obtained by freeze-drying oil-in-water emulsions containing 10 wt % capsule materials (AG, GGM, or a 1:1 mixture of GGM-AG) and 2 wt % alpha-tocopherol (a model hydrophobic core compound that oxidizes easily). Microcapsules were stored at relative humidity (RH) of 0, 33, and 66% at 25 degrees C for different time periods, and their alpha-tocopherol content was determined by HPLC. X-ray microtomography analyses showed that the freeze-dried emulsions of GGM had the highest and those of AG the lowest degree of porosity. According to X-ray diffraction patterns, both freeze-dried AG and GGM showed an amorphous nature. The storage test showed that anhydrous AG microcapsules had higher alpha-tocopherol content than GGM-containing capsules, whereas under 33 and 66% RH conditions GGM was superior in relation to the retention of alpha-tocopherol. The good protection ability of GGM was related to its ability to form thicker walls to microcapsules and better physical stability compared to AG. The glass transition temperature of AG was close to the storage temperature (25 degrees C) at RH of 66%, which explains the remarkable losses of alpha-tocopherol in the microcapsules under those conditions.

Oxidation of polysaccharides by galactose oxidase

Galactose oxidase was used as a catalyst to oxidize selectively the C-6 hydroxyls of terminal galactose to carbonyl groups. The polysaccharides studied included spruce galactoglucomannan, guar galactomannan, larch arabinogalactan, corn fiber arabinoxylan, and tamarind seed xyloglucan, with terminal galactose contents varying from 6% to 40%. A multienzyme system was used, with catalase and horseradish peroxidase to enhance the action of galactose oxidase. An analysis technique was developed for the quantification of the reactive aldehydes with GC-MS, utilizing NaBD4 reduction and acidic methanolysis. The best oxidation degrees of terminal galactosyls were obtained with xyloglucan (85% of galactose) and spruce galactoglucomannan (65% of galactose). The highest oxidation degree based on total carbohydrates was achieved with guar gum (28%), which had the highest galactose content. The oxidation resulted in changes in the physicochemical properties of the polysaccharide solutions, and the changes observed varied between the polysaccharides. The clearest change was in tamarind xyloglucan, which formed a gel after the oxidation. After the oxidation, larger particles were present in the solution of spruce galactoglucomannan, but changes in its rheological properties were not observed.

Structural investigation of biologically active phenolic compounds isolated from European tree species

X-ray structures of two compounds isolated from wood knots of coniferous trees, namely dihydrokaempferol (3,5,8,13-tetrahydroxyflavanon) and lariciresinol (3,14-dimetoxy-7,10-epoxylignan-4,15,19-triol), are presented here. Diffraction data for the dihydrokaempferol crystals were collected on a CAD4 diffractometer and on a synchrotron for the lariciresinol crystal. The investigated compounds inhibit lipid peroxidation and lariciresinol is additionally a good scavenger of superoxide radicals. The structural data presented in this work provide a useful basis for designing more active compounds with potential use as antioxidants.

Kinetics of acid hydrolysis of water-soluble spruce O-acetyl galactoglucomannans

Water-soluble O-acetyl galactoglucomannan (GGM) is a softwood-derived polysaccharide, which can be extracted on an industrial scale from wood or mechanical pulping waters and now is available in kilogram scale for research and development of value-added products. To develop applications of GGM, information is needed on its stability in acidic conditions. The kinetics of acid hydrolysis of GGM was studied at temperatures up to 90 degrees C in the pH range of 1-3. Molar mass and molar mass distribution were determined using size exclusion chromatography with multiangle laser light scattering and refractive index detection. The molar mass of GGM decreased considerably with treatment time at temperatures above 70 degrees C and pH below 2. The molar mass distribution broadened with hydrolysis time. A first-order kinetic model was found to match the acid hydrolysis. The reaction rate constants at various pH values and temperatures were calculated on the basis of the first-order kinetic model. Furthermore, the activation energy, E, was obtained from the Arrhenius plot. The activation energy E was 150 kJ mol (-1) for acid hydrolysis of spruce GGM. The apparent rate constant during acid hydrolysis increased by a factor of 10 with a decrease in pH by 1 unit, regardless of temperature. In addition, gas chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were applied to study the released GGM monomers and oligomers.

Norway spruce galactoglucomannans exhibiting immunomodulating and radical-scavenging activities

Wood-derived naturally acetylated galactoglucomannans (AcGGM) can be recovered even in ton-scale at mechanical pulp mills using spruce as raw material. These cell wall polysaccharides have a great potential as hydrocolloids and bioactive polymers in food and pharmaceutical applications, or as starting material for production of functional polymers. The immunostimulatory activity of both AcGGM and its deacetylated form (GGM) was now in vitro tested. The biological response of both AcGGM and GGM in the lymphocyte transformation test was dose-dependent. The direct mitogenic as well as comitogenic activities of the AcGGM were comparable to those of the immunogenic corn cob xylan used as control, and GGM showed significantly higher biological responses also at lower doses. In contrast to GGM, AcGGM possessed also DPPH radical-scavenging activity. The results suggested that the spruce AcGGM and GGM are potentially important as additives with immuno-potentiating and antioxidant properties in food products and pharmaceutical formulations.

Antimicrobial and cytotoxic knotwood extracts and related pure compounds and their effects on food-associated microorganisms

Knotwood or bark extracts prepared from 30 species of hard and soft wood trees as well as selected pure compounds (lignans, stilbenes and flavonoids) were assayed for their antimicrobial activity against a battery of both gram positive and negative bacteria, yeasts, and filamentous fungi (Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Lactobacillus plantarum, Escherichia coli, Salmonella infantis, Pseudomonas fluorescens, Candida albicans, Saccharomyces cerevisiae, Aspergillus fumigatus and Penicillium brevicompactum). By far the most consistent antibacterial and antifungal properties were associated with extracts of Pinus species. These extracts showed also cytotoxicity against a mouse hepatoma cell line. Both antimicrobial and cytotoxic properties correlated with the stilbene content of the extracts. Purified stilbenes showed the most consistent antimicrobial and cytotoxic activities, while purified lignans had marginal effects, only. The results suggest that stilbenes account both for the antimicrobial and cytotoxic properties of Pinus knotwood extracts.

A novel antioxidant phenyl disaccharide from Populus tremula knotwood

The complete characterization of two compounds obtained from the acetone extract of Populus tremula knotwood has been was achieved using LC-DAD-MS, MS/MS, IR and NMR. The new compounds were unequivocally identified as a mixture of the ester isomers of the (E) and (Z) p-coumarate of 1-O-rutinose. The isomers showed the capacity to inhibit lipid peroxidation induced by tert-butylhydroperoxide and to trap peroxyl radicals, as determined by a chemiluminescence method. These new phenyl disaccharides also showed a significant ORAC (oxygen radical absorbance capacity) value, i.e. 11.7 microM TE (Trolox Equivalents).

Characterisation of volatile organic compounds in stemwood using solid-phase microextraction

Solid-phase microextraction (SPME), hydrodistillation and dynamic headspace combined with GC and GC-MS were applied and compared for the analysis of volatile organic compounds (VOCs) from coniferous wood. The SPME conditions (type of fibre, size of wood sample, temperature and exposure time) were optimised, and more than 100 VOCs and semi-volatile compounds extracted and identified from the sapwood and heartwood of Norway spruce (Picea abies). The total number of mono- and sesquiterpenes eluted and identified was similar for the SPME and hydrodistillation methods, but more semi-volatile compounds were released by hydrodistillation. By applying dynamic headspace at room temperature, it was possible to analyse only the most volatile compounds. The qualitative composition of VOCs was similar in spruce sapwood and heartwood, although Z-beta-ocimene occurred only in sapwood while fenchol was present only in heartwood. SPME sampling coupled with GC, applied here to the analysis of VOCs released from stemwood of firs for the first time, is a convenient, sensitive, fast, solvent-free and simple method for the determination of wood volatiles. The technique requires much smaller sample amounts compared with hydrodistillation, and the total amount of VOCs extracted and identified is higher than that obtained by hydrodistillation or dynamic headspace. The relative ratios of the main mono- and sesquiterpenes and -terpenoids were similar using the SPME-GC and hydrodistillation methods.

A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds in Scots pine (Pinus sylvestris) wood. Part II. Hydrophilic compounds

Hydrophilic extracts of Scots pine (Pinus sylvestris) heartwood and sapwood and a solid Scots pine knotwood sample were studied by UV resonance Raman spectroscopy (UVRRS). In addition, UVRR spectra of two hydrophilic model compounds (pinosylvin and chrysin) were analysed. UV Raman spectra were collected using 244 and 257 nm excitation wavelengths. The chemical composition of the acetone:water (95:5 v/v) extracts were also determined by gas chromatography. The aromatic and oleophilic structures of pinosylvin and chrysin showed three intense resonance enhanced bands in the spectral region of 1649-1548 cm(-1). Pinosylvin showed also a relatively intense band in the aromatic substitution region at 996 cm(-1). The spectra of the heartwood acetone:water extract showed many bands typical of pinosylvin. In addition, the extract included bands distinctive for resin and fatty acids. The sapwood acetone:water extract showed bands due to oleophilic structures at 1655-1650 cm(-1). The extract probably also contained oligomeric lignans because the UVRR spectra were in parts similar to that of guaiacyl lignin. The characteristic band of pinosylvin (996 cm(-1)) was detected in the UVRR spectrum of the resin rich knotwood. In addition, several other bands typical for wood resin were observed, which indicated that the wood resin in the knotwood was resonance enhanced even more than lignin.

A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine (Pinus sylvestris) wood. Part I: lipophilic compounds

The wood resin in Scots pine (Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm(-1). Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at approximately 1650 cm(-1) due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.