Bioinformatic Analysis Reveals High Diversity of Bacterial Genes for Laccase-Like Enzymes

Fungal laccases have been used in various fields ranging from processes in wood and paper industries to environmental applications. Although a few bacterial laccases have been characterized in recent years, prokaryotes have largely been neglected as a source of novel enzymes, in part due to the lack of knowledge about the diversity and distribution of laccases within Bacteria. In this work genes for laccase-like enzymes were searched for in over 2,200 complete and draft bacterial genomes and four metagenomic datasets, using the custom profile Hidden Markov Models for two- and three- domain laccases. More than 1,200 putative genes for laccase-like enzymes were retrieved from chromosomes and plasmids of diverse bacteria. In 76% of the genes, signal peptides were predicted, indicating that these bacterial laccases may be exported from the cytoplasm, which contrasts with the current belief. Moreover, several examples of putatively horizontally transferred bacterial laccase genes were described. Many metagenomic sequences encoding fragments of laccase-like enzymes could not be phylogenetically assigned, indicating considerable novelty. Laccase-like genes were also found in anaerobic bacteria, autotrophs and alkaliphiles, thus opening new hypotheses regarding their ecological functions. Bacteria identified as carrying laccase genes represent potential sources for future biotechnological applications

Industrial scale evaluation of cationic tannin as a binder for hardboard

Hardboards (HBs) (wet-process high-density fibreboards) were made in an industrial trial using a binder system consisting of cationic mimosa tannin and laccase or just cationic tannin without any thermosetting adhesive. The boards displayed superior mechanical strength compared to reference boards made with phenol–formaldehyde, easily exceeding the European standards for general-purpose HBs. The thickness swell of most of the boards was slightly greater than the standards would allow, so some optimisation is required in this area. The improved board properties appear to be mainly associated with ionic interactions involving quaternary amino groups in cationic tannin and negatively charged wood fibres rather than to cross-linking of fibres via laccase-assisted formation and coupling of radicals in tannin and fibre lignin

Environmental performance assessment of hardboard manufacture

11 páginas, 5 figuras, 4 tablas -- PAGS nros. 456-466Background, aim and scope The forest-based and related industries comprise one of the most important industry sectors in the European Union, representing some 10% of the EU's manufacturing industries. Their activities are based on renewable raw material resources and efficient recycling. The forest-based industries can be broken down into the following sectors: forestry, woodworking, pulp and paper manufacturing, paper and board converting and printing and furniture. The woodworking sector includes many sub-sectors; one of the most important is that of wood panels accounting for 9% of total industry production. Wood panels are used as intermediate products in a wide variety of applications in the furniture and building industries. There are different kinds of panels: particleboard, fibreboard, veneer, plywood and blockboard. The main goal of this study was to assess the environmental impacts during the life cycle of wet-process fibreboard (hardboard) manufacturing to identify the processes with the largest environmental impacts. Methods The study covers the life cycle of hardboard production from a cradle-to-gate perspective. A hardboard plant was analysed in detail, dividing the process chain into three subsystems: wood preparation, board forming and board finishing. Ancillary activities such as chemicals, wood chips, thermal energy and electricity production and transport were included within the system boundaries. Inventory data came from interviews and surveys (on-site measurements). When ecessary, the data were complemented with bibliographic resources. The life cycle assessment procedure followed the ISO14040 series. The life cycle inventory (LCI) and impact assessment database for this study were constructed using SimaPro Version 7.0 software. Results Abiotic depletion (AD), global arming (GW), ozone layer depletion (OLD), human toxicity (HT), ecotoxicity, photochemical oxidant formation (PO), cidification (AC) and eutrophication (EP) were the impact categories analysed in this study. The wood preparation subsystem contributed more than 50% to all impact categories, followed by board forming and board finishing, which is mainly due to chemicals consumption in the wood preparation subsystem. In addition, thermal energy requirements (for all subsystems) were fulfilled by on-site wood waste burning and, accordingly, biomass energy converters were considered. Several processes were identified as hot spots in this study: phenol-formaldehyde resin production (with large contribution to HT, fresh water aquatic ecotoxicity and PO), electricity production (main contributor to marine aquatic cotoxicity), wood chips production (AD and OLD) and finally, biomass burning for heat production (identified as the largest contributor to AC and EP due to NOX emissions). In addition, uncontrolled formaldehyde emissions from manufacturing processes at the plant such as fibre drying should be controlled due to relevant contributions to terrestrial ecotoxicity and PO. A sensitivity analysis of electricity profile generation (strong geographic dependence) was carried out and several European profiles were analysed.Peer reviewe

Enzymatic surface functionalisation of lignocellulosic materials with tannins for enhancing antibacterial properties

10 páginas, 11 figuras, 2 tablas -- PAGS nros. 1072-1081Grafting natural antibacterial phenols onto lignocellulosic materials is an environmentally friendly way of imparting antibacterial properties to the substrates. In the present investigation, wood veneer and pulp were treated with tannins in the presence or absence of laccase. Treatments with hydrolysable tannins significantly improved the antibacterial resistance of veneers and paper made from tannin-treated pulp against a Gram-positive bacterium (Staphylococcus aureus) while a more modest protective effect was observed against a Gram-negative bacterium (Escherichia coli). Condensed tannin improved the antibacterial resistance against S. aureus, albeit less than hydrolysable tannin, but had little effect on E. coli. A cationic condensed tannin derivative bearing a quaternary amino group provided far better resistance to pulp against S. aureus and E. coli than the corresponding unmodified condensed tannin. These findings agree with the minimal inhibitory concentrations (MICs) of the tannins and their reactivities toward laccase as determined by O2 consumption measurements. Due to a better retention of tannins via covalent bonding, treatments with laccase usually resulted in greater antibacterial effects than those without laccase. LC–MS investigations with monomeric tannin and lignin model compounds showed that covalent bonding of tannin to lignin via radical coupling occurred in the presence of laccase.European Union Biorenew Project (6th Framework Program, FP6-2004-NMP-NI-4). Austrian Academic Exchange Service (OEAD) for financial supportPeer reviewe