Physisporinus Vitreus: a Versatile White Rot Fungus for Engineering Value-Added Wood Products
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CORE Metadata, citation and similar papers at core.ac.uk Provided by RERO DOC Digital Library Appl Microbiol Biotechnol (2011) 92:431–440 DOI 10.1007/s00253-011-3539-1 MINI-REVIEW Physisporinus vitreus: a versatile white rot fungus for engineering value-added wood products Francis W. M. R. Schwarze & Mark Schubert Received: 3 June 2011 /Revised: 28 July 2011 /Accepted: 5 August 2011 /Published online: 8 September 2011 # Springer-Verlag 2011 Abstract The credo of every scientist working in the field Introduction of applied science is to transfer knowledge “from science to market,” a process that combines (1) science (fundamental Using wood decay fungi for biotechnological applications discoveries and basic research) with (2) technology devel- in the forest products industry has been studied for several opment (performance assessment and optimization) and (3) decades because the specificity of their enzymes and the technology transfer (industrial application). Over the past mild conditions under which degradation proceeds make 7 years, we have intensively investigated the potential of them potentially suitable agents for wood modification the white rot fungus, Physisporinus vitreus, for engineering (Majcherczyk and Hüttermann 1988; Messner et al. 2002; value-added wood products. Because of its exceptional Schwarze 2008). For example, fungi are successfully used wood degradation pattern, i.e., selective lignification with- in the biopulping or biobleaching of kraft pulp (Mai et al. out significant wood strength losses and a preferential 2004) or in bioremediation and detoxification of degradation of bordered pit membranes, it is possible to use preservative-treated waste wood because of their tolerance this fungus under controlled conditions to improve the and ability to degrade creosote, toxic polyaromatic hydro- acoustic properties of tonewood (i.e., “mycowood”) as well carbon compounds, and pentachlorophenol (Shuen and as to enhance the uptake of preservatives and wood Buswell 1992; Cerniglia 1997; Samson et al. 1998; Richter modification substances in refractory wood species (e.g., et al. 2003; Mai et al. 2004). The alterations in the woody Norway spruce), a process known as “bioincising.” This cell wall structure reflect the plasticity of the degradation minireview summarizes the research that we have per- modes of wood decay fungi and can be used for the formed with P. vitreus and critically discusses the challenges purpose of wood engineering (Deflorio et al. 2005; encountered during the development of two distinct Schwarze 2007, 2008). During the early 1960s, industrially processes for engineering value-added wood products. cultivated white rot fungus (Trametes versicolor L.) was Finally, we peep into the future potential of the bioincising used in the German Democratic Republic, mainly on beech and mycowood processes for additional applications in the wood for pencil or ruler production (i.e., “mykowood,” forest and wood industry. Unbehaun et al. 2000; Mai et al. 2004). More recently, we have investigated the potential of a Keywords Physisporinus vitreus . Bioincising . range of wood decay fungi for biotechnological applica- Mycowood . Wood permeability . Acoustic properties . tions in the forest product industry. In Switzerland, 65% of Tonewood . Value-added wood products the forest stand consists of Norway spruce [Picea abies (L.) Karst.] and European silver fir (Abies alba Mill.). The F. W. M. R. Schwarze (*) : M. Schubert wood of either of these species to be used outdoors requires Wood Protection & Biotechnology Wood Department, preservative treatment, which involves impregnating the Empa Swiss Federal Laboratories for Materials wood cells with chemical preservatives or wood modifica- Testing and Research, tion substances to suppress colonization by wood decay Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland fungi. In most cases, the substance is infused into the wood e-mail: [email protected] cells using vacuum pressure impregnation, but the wood of 432 Appl Microbiol Biotechnol (2011) 92:431–440 difficult-to-treat (refractory) species such as P. abies and A. The objective of this minireview is to summarize the alba must be incised to enhance the uptake and distribution work that has been conducted to implement the ambitious of the chemicals in the wood. Incising is a pretreatment goal of transferring a standardized biotechnology process process in which small incisions, or slits, are made in the using P. vitreus from “science to market” (Fig. 1). The wood surface to increase the exposed end and side grain fundamental discoveries and basic research conducted on P. surface area (Hernandez and Winandy 2005). “Bioincising” vitreus are the science; characterization of fungal activity, is a biotechnological process that has been developed to the performance assessment of fungally modified wood, and improve the permeability of refractory wood species by optimization of the process comprise the development of the incubation under controlled conditions for short periods technology; and the benefits of applying the bioincising and with a white rot fungus, Physisporinus vitreus. Our studies mycowood processes for the forest and wood industry (i.e., show that isolates of P. vitreus have an extraordinary technology transfer) are all discussed in detail. capacity to induce substantial permeability changes in the heartwood of P. abies without causing significant loss of impact bending strength (Schwarze and Landmesser 2000; Science Schwarze et al. 2006, 2007; Lehringer et al. 2009). In fact, wood durability of P. abies and A. alba is enhanced by the Bioincising: improving the permeability of refractory wood bioincising process, which is a promising technology for species dollars efficiently distributing wood modification substances, pro- moting desired improvements in wood properties, as well P. vitreus is a basidomycete (Polyporales, Meripilaceae) that as leaving the wood surface aesthetically pleasing and the belongs to the large and puzzling Polyporus lignosus mechanical wood properties unaltered (Lehringer et al. complex. It can be very easily confused with Poria 2011). Another application of the controlled use of the nigrescens and Physisporinus sanguinolenta, but is most degradation pattern of P. vitreus is the production of easily distinguished by its characteristic decay, a conspic- mycowood with improved acoustic properties to overcome uous white pocket rot. When fresh, the basidiocarp appears the shortages of natural wood with the superior tonal much like P. sanguinolenta, which differs in usually turning qualities desired by traditional musical instrument makers. reddish where bruised and on drying and in having Fig. 1 Steps required for implementation of the “bioincising” and “mycowood” process and steps involved in technology transfer Appl Microbiol Biotechnol (2011) 92:431–440 433 somewhat larger pores. P. sanguinolenta var. expallescens, Complete or partial hydrolysis of bordered pits and cross- however, is so similar that in the absence of decayed wood, field pits in regions of the wood that were stained with a clear distinction is difficult. P. vitreus occurs on Neolan Glaucin E-A was apparent, whereas in unstained angiosperms and more rarely on gymnosperms, in the regions, the pit membranes were intact (Fig. 2,Schwarzeet USA apparently more abundant southward, but known al. 2006). The hyphae entered the pit chamber via the from Ontario southward in eastern North America to apertures, and the membranes were subsequently degraded Missouri, in Alaska, Idaho, British Columbia, Washington, (Fig. 2). Degradation commenced from the thickened, Puerto Rico, Europe, and New Zealand. central part of the membrane (the torus). Calcium Interestingly, P. vitreus decomposes water-saturated tim- oxalate crystals were regularly observed on the hyphae ber in cooling towers by a fibrous, white pocket rot (Van (Fig. 2), and in the wood of A. alba,theyoften Acker et al. 1995; Schmidt et al. 1996, 1997; Schmidt accumulated within bordered pits in close proximity to 2007). In the laboratory, the fungus reveals a remarkable the hyphae (Fig. 2). We will discuss how we optimized the pattern of colonization. In crosswise piled water-saturated uniformity of wood colonization and the duration of pine wood, the fungus decomposes only those parts of the incubation, in order to improve the permeability of substrate not surrounded by air (Schmidt et al. 1996, 1997). water-borne wood preservatives or wood modification Some isolates of this fungus have an extraordinary capacity agents applied by brushing, dipping, and impregnation, to induce significant permeability changes in the heartwood under the “Technology development” section below. of Norway spruce and silver fir after hydrolysis of bordered The P. vitreus strain (Empa No. 642) used in all of our pit membranes without causing significant loss of wood studies was assigned by PCR amplification and sequencing strength (Schwarze et al. 2006). The effects of treating of the ITS1-5.8S-ITS2 region of the rDNA followed by conifer wood with commercial pectinases or bacteria to alignment with published sequences using nucleotide improve penetration of preservatives have been studied in BLAST (Begerow et al. 2010). The ITS1-5.8S-ITS2 detail (Nicholas and Thomas 1968; Bauch et al. 1970; sequence of the P. vitreus (Empa strain No. 642) was Johnson 1979; Sharma and Kumar 1979; Mai et al. 2004). submitted to the EMBL databank under the following Commercial pectinase treatment improves