Thomas Kuncinger

Laccase-catalyzed functionalization with 4-hydroxy-3-methoxybenzylurea significantly improves internal bond of particle boards

Abstract Enzymatic functionalization is an attractive tool to provide a reactive interface for further processing of lignocellulosic materials, such as wood particles and fibers. Here, spruce wood particles have been functionalized by fungal laccase combined with 4-hydroxy-3-methoxy-benzylamine (HMBA) or 4-hydroxy-3-methoxybenzylurea (HMBU). The expectation was crosslinking with resins in subsequent glueing processes, which should improve strength properties of particle boards. Essential process parameters, such as liquid to solid mass ratio and treatment time, were optimized on a laboratory scale resulting in HMBA and HMBU binding yields of 90% and above as determined by radiochemical mass balance analysis. We employed a multifactorial experimental design for board production from treated wood particles and urea/formaldehyde resin. Mechanical testing and multivariate data analysis revealed, for the first time, an increase of internal bond (IB) as a result of functionalization with HMBU. HMBA was not successful. Variance analysis of relevant parameters and their interactions demonstrated a highly significant difference (P>99.99%) between boards treated with laccase/HMBU versus untreated wood particles. Due to positive interactions, functionalization was most effective at high bulk density (750 kg m-3) and high resin content (10%) resulting in a calculated IB improvement of 0.12 N m-2 (21%).

Fungal pretreatment of pine wood to reduce the emission of volatile organic compounds

Abstract Sterilized pine wood strands were treated with the ascomycete Ophiostoma piliferum (Cartapip 97™) in an attempt to reduce aldehyde emissions through degradation of aldehyde-forming precursors. Wooden boards were then produced from the treated strands by means of a laboratory press. VOC emissions of these boards were characterized and the concentrations of seven major substances were followed for a period of 28 days in Markes μ-CTE micro-chambers employing Tenax-TDAS/GC/MS analytics. Boards made from treated strands showed a highly significant (P<0.001) reduction in aldehyde emissions by 70% compared to the control boards, while differences in the monoterpene emissions were not significant (P>0.05). Wood extractives from treated and untreated strands were also analyzed by GC/MS after milling and acetone/water extraction. A marked decrease of C18 unsaturated fatty acids was detected in agreement with the reduction of aldehyde emissions, and the monosaccharides as indicators of fungal growth were depleted and stilbenes and lignans were partially degraded.

Industrial waste water for biotechnological reduction of aldehyde emissions from wood products

Abstract Pine wood particles were treated with effluents from the wood-board manufacturing industry or from a communal clarification plant, and the effect of these treatments on aldehyde emissions of wood material was tested. Pine wood strands were treated in the same manner and strand boards were produced from the treated material on a laboratory scale. The 28-day volatile organic compound emissions of the boards were determined in a microchamber using Tenax-TDAS/GC-MS analytics. Boards made from treated strands exhibited significantly lower aldehyde emissions compared to control boards. Analyses of microflora and of wood extractives confirmed that microbial metabolism in industrial effluents consumed unsaturated fatty acids (UFAs) present in wood. As UFAs are the source of aldehyde emissions due to auto-oxidation, the aldehyde emission was consequently reduced. A routine treatment of wood raw material with properly chosen industrial effluents may therefore be regarded as a cost-reducing and efficient method for the utilisation of industrial waste waters.

Biodegradation of terpenes for emission-reduced oriented strand boards (OSB)

Abstract A bacterial mixture of Pseudomonas putida and Pseudomonas fluorescens has recently shown the potential to completely reduce monoterpenes within pine wood particles on a laboratory scale. This bacterial combination was then applied onto pine wood strands to obtain emission-reduced oriented strand boards (OSB) produced on a technical scale. Laboratory tests with bacterial inoculated strands were carried out to optimise parameters such as aeration and incubation time. Residual terpene emissions were measured by solid-phase microextraction/ gas chromatography-mass spectrometry (SPME/GC-MS) analysis. Daily aeration, specific pre-cultivation, and increased inoculum size eventually resulted in a reduction of the major softwood terpenes α-pinene, β-pinene, and Δ3-carene by 60, 70, and 40%, respectively, after only 2 days of incubation. Based on these results, OSB were manufactured from strands after bacterial pre-treatment for 2 or 4 days. As expected, terpene emissions from OSB decreased with increasing incubation time. However, even after only 2 days of incubation, α-pinene and β-pinene emissions were appreciably reduced by 40 and 70%, respectively. The method developed here thus appears to be feasible for industrial application although a further reduction of pre-treatment time would be advantageous. The inoculation step will also have to be adapted for technical implementation into the OSB production process.

Within-process and seasonal changes during industrial production of high-density fibreboard. Part 1: Influence of wood species composition on polyoses in the products

Abstract Industrially produced high-density fibreboard fibres are inhomogeneous in structure and chemical composition. Changes in polysaccharide chemistry during processing have an impact on strength loss, fibre separation and structural alterations. In the present study, carbohydrate composition of extracted wood chips and refiner fibres was monitored for a year at an industrial HDF plant. The polysaccharides were analysed via methanolysis and quantification of the monomeric sugars released. Significant reductions of arabinose, xylose, rhamnose and galacturonic acid were observed. The amount of glucose and extractable substances increased. The depletion of galacturonic acid and rhamnose indicates a degradation of pectin located in the compound middle lamella. The diminishing amounts of the other sugars and elevated extractive contents are a result of hemicellulose degradation. A pronounced seasonal variability of the data was observed depending on the processed wood species and degree of chemical degradation.