Abstract:
Wood color has an important economical impact on wood products. The hardwood lumber industry has shown a particular increase in demand by their customers for wood with an attractive, consistent and specified color. Fungi are a specific group of micro-organisms that can affect wood color. Some fungi produce various colourful pigments during their growth and can produce a preferable uniform color on wood products. The present invention includes methods to use selected fungi for producing various commercially desirable colors on wood and wood products. The methods include manners of fungal selection, culturing conditions, wood treating procedure, incubation timeframe, and drying process. The present invention also describes the wood produced by the method.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to producing a desirable wood color with particular fungal species and the lumber treating process with the fungi. 
       BACKGROUND 
       [0002]    Wood color is produced by progressive accumulation of wood cells with a complex of diverse substances called extractives during tree growing. Pigmented extractives determine most of the visual appearance quality of the hardwood species; therefore, they affect wood usefulness and value of the wood products. Many recognizable and commercially desirable qualities of the heartwood such as cherry, walnut and rosewood etc are a result of the presence of pigmented extractives. The presence of the pigmented extractives is mostly distributed in the heartwood of trees. In some species such as maple or spruce the extractives are light color, and the heartwood of these species remains light color similar to the sapwood; these wood species are called light heartwood trees. In some other species such as oak or cedar the extractives presented in heartwood are a dark-color; therefore, the heartwood has various color intensities and can be visually recognized from sapwood. These trees are described as regular heartwood trees. 
         [0003]    Fungal infection of wood can cause wood color change (lighter or darker). The well-known fungal discoloration of wood is called blue stain. Blue stain is caused by a particular group of fungi that commonly attack only the sapwood of trees to bluish or greyish discoloration of the wood; therefore, it is also called sapstain. This type of fungi utilizes simple sugars and starches presented in the sapwood as nutrients and produce dark pigment called melanin during their growth. The wood discoloration caused by fungal melanin may cover the whole sapwood or may appear as streaks or patches of bluish to black intensities. However, the bluish black wood color resulted from these fungi is not desirable for wood end users. Most studies on wood blue stain are focused on preventing or controlling color development on wood products. One of such approaches is inoculating wood with a colorless mutant of a sapstain fungus such as  Ophiostoma piliferum , and the preoccupation of wood surfaces by the colorless fungus can prevent later invasion of wood by staining fungi and thereafter wood color change. No study has been conducted to artificially inoculate blue stain fungi to produce bluish black wood color far high wood value use. 
         [0004]    Another wood color change caused by fungal infection is a green color caused by  Chlorociboria  species. The wood discoloration is caused by the production of a fungal pigment xylindein, which is classified as a napthaquinone. The naturally green-stained wood had been used as woodcrafts in European countries since 14 th -15 th  century. 
         [0005]    Wood decay can also change wood color. A well known example is called spalted wood that is in high demand in the decorative wood market. Spalted wood is caused by certain decay fungi growing in wood (white-rot). The decay fungal attack can cause random patches of contrasting colors to appear on the surface of some hardwoods such as maple and birch. In addition, when two or more competing fungi are meeting together in wood, it may create brown to black zone lines on wood in the border of each fungal territories. In this way, spalted wood forms map-like figures of different shapes and color contrasts. It may also produce unusual multicoloured streaks on wood caused by reaction between the wood and decay fungi. However, the pattern and color changes produced on spalted wood by these decay fungi are not predictable and repeatable. 
         [0006]    Most common methods for coloring wood products are using pigments or dye materials which are carried either in a liquid solution or as a dispersion. 
       SUMMARY 
       [0007]    In accordance with one aspect of the present invention, there is provided a method of coloring and treating wood with a pigmented fungal species, the method comprising: providing the fungal species in an active form; providing the wood to be treated; applying the active form of the fungal species to the wood to produce a treated wood; incubating the treated wood for a period of time; drying the treated wood. 
         [0008]    In accordance with another aspect of the method described herein, the fungal species provided is selected from the group consisting of  Penicillium variabile; Fusarium culmorum; Coryne microspora; Diatrypella placenta; Arthrographis cuboidea; Poria aurea; Corticium polosum; Lentinus cyathiformis; Lecythophora hoffmannii; Tyromyces balsameus; Trogia crispa; Polyporus dryophilus; Polyporus dryophilus  var.  vulpinus; Peniophora piceae; Sporotrichum dimorphosporum; Gliocladium verticilloides; Nectria ochroleuca; Trichoderma atroviride; Trichoderma  sp;  Verticillium  sp;  Chlorosplenium aeruginascens; Scytalidium lignicola; Ophiostoma piceae; Aureobasidium pullulans; Phialophora alba; Penicillium expansum; Penicillium implicatum; Fusarium verticillioides; Dactylium dendroides; Phialemonium dimorphosporum, Fusarium oxysporum, Ascocoryne cylichnium; Cephalotheca purpurea  and combinations thereof. 
         [0009]    In accordance with yet another aspect of the method described herein, the step of providing the fungal species in an active form comprises incubating the fungal species to produce a fungal culture, homogenizing the culture to produce a suspension. 
         [0010]    In accordance with still another aspect of the method described herein, the suspension produced comprises a concentration of spores/mycelia fragments per ml of suspension of at least about 1×10 5 . 
         [0011]    In accordance with yet still another aspect of the method described herein, the suspension produced comprises a concentration of spores/mycelia fragments per ml of suspension of about but not limits from 1×10 6  to 1×10 8 . 
         [0012]    In accordance with a further aspect of the method described herein, the wood provided to be treated is sapwood and heartwood of sugar maple, white birch and yellow birch but may extend to all other hardwood and softwood species. 
         [0013]    In accordance with yet a further aspect of the method described herein, the step of applying the active form of the fungal species to the wood is by dipping, by spraying or by brushing. 
         [0014]    In accordance with stiff a further aspect of the method described herein, the step of applying the active form of the fungal species to the wood is by dipping. 
         [0015]    In accordance with yet still a further aspect of the method described herein, the step of incubating the treated wood for a period of time is for more than 1 week at a temperature from 5° C. to 35° C. and a relative humidity at least 75% or higher. 
         [0016]    In accordance with one embodiment of the method described herein, the treated wood is incubated at 25° C. and 75% RH for 1 to 4 weeks. 
         [0017]    In accordance with another embodiment of the method described herein, the treated wood is dried at a temperature from 50° C. to 105° C. 
         [0018]    In accordance with yet another embodiment of the method described herein, the wood color change is evaluated visually or with a colorimeter. 
         [0019]    In accordance with still another aspect of the present invention, there is provided a fungal species treated wood product produced by a method comprising: providing the fungal species in an active form; providing the wood to be treated; applying the active form of the fungal species to the wood to produce a treated wood; incubating the treated wood for a period of time; drying the treated wood. 
         [0020]    In accordance with another aspect of the product described herein, the fungal species provided is selected from the group consisting of  Penicillium variabile; Fusarium culmorum; Coryne microspora; Diatrypella placenta; Arthrographis cuboidea; Poria aurea; Corticium polosum; Lentinus cyathiformis; Lecythophora hoffmannii; Tyromyces balsameus; Trogia crispa; Polyporus dryophilus; Polyporus dryophilus  var.  vulpinus; Peniophora piceae; Sporotrichum dimorphosporum; Gliocladium verticilloides; Nectria ochroleuca; Trichoderma atroviride; Trichoderma  sp;  Verticillium  sp;  Chlorosplenium aeruginascens; Scytalidium lignicola; Ophiostoma piceae; Aureobasidium pullulans; Phialophora alba; Penicillium expansum; Penicillium implicatum; Fusarium verticillioides; Dactylium dendroides; Phialemonium dimorphosporum, Fusarium oxysporum, Ascocoryne cylichnium; Cephalotheca purpurea  and combinations thereof. 
         [0021]    This invention provides methods and manufacturing processes to produce various desirable wood colors with different particular fungal species for high wood value use by 1) using selected fungal species to produce a particular desirable wood color, and 2) producing wood color changes predictable, uniform, stable and repeatable. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a histogram illustrating a brown wood color variation between sapwood and heartwood produced by  Trogia crispa  (FTK 473C) according to one embodiment of the present invention; 
           [0023]      FIG. 2  is a histogram illustrating a grey wood color variation between sapwood and heartwood caused by  Penicillium expansum  (FTK 828A) according to one embodiment of the present invention; 
           [0024]      FIG. 3  is a histogram illustrating a black wood color variation between sapwood and heartwood caused by  Aureobasidium pullulans  (FTK 1321) according to one embodiment of the present invention; 
           [0025]      FIG. 4  is a histogram illustrating a purple wood color variation between sapwood and heartwood caused by  Dactylium dendroides  (FTK 597A) according to one embodiment of the present invention; 
           [0026]      FIG. 5  is a histogram illustrating a red wood color variation between sapwood and heartwood  Arthrographis cuboidea  (FTK 706B) according to one embodiment of the present invention; 
           [0027]      FIG. 6  is a histogram illustrating a green wood color variation between sapwood and heartwood  Chlorosplenium aeruginascens  (FTK 401A) according to one embodiment of the present invention; 
           [0028]      FIG. 7  is a photograph of black coloration of sugar maple sapwood (left) and heartwood caused by  Aureobasidium pullulans  according to one embodiment of the present invention; 
           [0029]      FIG. 8  is a photograph of purple coloration of yellow birch sapwood (left) and heartwood caused by  Dactylium dendroides  according to one embodiment of the present invention; 
           [0030]      FIG. 9  is a photograph of red coloration of white birch sapwood (left) and heartwood caused by  Arthrographis cuboidea  according to one embodiment of the present invention; 
           [0031]      FIG. 10  is a photograph of green coloration of sugar maple sapwood (left) and heartwood caused by  Chlorosplenium aeruginascens  according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     Example 1 
     Selection of Fungal Species for Coloring 
       [0032]    Selection of fungal species for coloring wood was performed in Petri plates (85 mm in diameter) holding 20 ml of a 2% (w/v) malt extract agar medium in each plate. One mycelia plug (5 mm in diameter) was cut from each fungal colony and transferred to the middle of each plate. The plates were sealed with a Parafilm and incubated at 25° C. and 75% RH for 14 days. The colors produced by these fungi on agar were visually evaluated. Based on the principal colors produced by these fungi, 33 fungal species were selected for testing on wood. The principal colors are pink, red, brown, orange, yellow, green, black, blue and purple. 1 to 5 fungal species per color were selected for the test on wood. The selected fungal species and associated colors in agar plates are shown in Table 1. 
         [0033]    All these fungal species came from the Culture Collection of Wood-inhabiting Fungi (FTK) holding by FPInnovations, Quebec, Canada. All fungal cultures were maintained in a liquid nitrogen reservoir for cryopreservation at −198° C. before use. 
       Example 2 
     Preparation of Fungal Solutions and Wood Specimens for Coloring 
       [0034]    The selected fungal species were retrieved from the liquid nitrogen reservoir and grown on a 2% (w/v) malt extract agar medium in Petri plates at 25° C. for one week. Mycelia plugs (5 mm in diameter) were cut from each fungal colony and transferred 3 plugs to each 125 ml flask containing 50 ml of a sterile 2% (w/v) Difco malt extract broth (Becton, Dickinson and Company, Sparks, Md., USA) in distilled water. After incubation, the fungal cultures were homogenized 3 times (30 seconds per time) with a homogenizer into a fine mycelia fragments and spore suspension. One drop of the suspension was loaded on a hemacytometer and spores and mycelia fragments in the solution were counted under a microscope. Fungal suspensions having at least 1×10 5  spores/mycelia fragments per ml of suspension have been found to be effective. However, concentrations of the present fungal suspensions were determined to be 1×10 6  to 1×10 8  spores/mycelia fragments per ml of the solution. These fungal suspensions were used immediately to treat wood specimens. 
         [0035]    Fresh log sections of sugar maple ( Acer saccharum  Marshall), white birch ( Betula papyrifera  Marshall) and yellow birch ( Betula alleghaniensis  Britton) were provided by a local Quebec company. The sapwood and heartwood of log sections were identified and cut separately into wood specimens at the size of 60 mm×20 mm×5 mm. A total of 792 wood samples were prepared from these 3 wood species for testing selected 33 fungal species. 
       Example 3 
     Treatment of Wood Specimens and Evaluation 
       [0036]    Wood specimens were placed in containers based on wood species and autoclaved at 121° C. for 10 minutes. After cooling, wood specimens were dipped for 30 seconds in a fungal solution. 4 specimens per treatment. Following the treatment, two pieces of specimens were placed on a W-shaped glass support sitting over 2 layers of wet filter paper in a Petri plate. These plates were incubated in a growth chamber set at 25° C. and 75% RH. Wood specimens were visually inspected for wood color change each week up to 4 weeks. At the end of the test, half amount of the wood specimens was dried at 50° C. and another half was dried at 105° C. The final wood colors after drying were measured with a colorimeter. 
         [0037]    The wood coloring with selected fungal species is shown in Table 1. In most cases, one fungal species colored all three wood species tested into a similar color. In addition to wood species, most of the fungal species colored sapwood and heartwood of a wood species at a similar intensive level. Therefore, wood colors shown in Table 1 represented the major color observed from all wood specimens treated with each fungal species. 
         [0038]    Because of the interference of wood cells, the colors shown on agar may or may not be the same as the one shown on wood. For example, agar and wood were both colored into green by  Verticillium  sp. (FTK 164C) and  Chlorosplenium aeruginascens  (FTK 401A); colored into purple by  Dactylium dendroides  (FTK 597A) and  Phialemonium dimorphosporum  (FTK 669A); colored into brown by  Trogia crispa  (FTK 473C) and  Polyporus dryophilus  var.  vulpinus  (FTK 483A); and colored into black by  Aureobasidium pullulans  (FTK 1321). Some fungal species produced different colors on agar and on wood. For example,  Fusarium culmorum  (FTK 750A) produced red color on agar, but purple on wood; and  Fusarium oxysporum  (FTK 31A) produced dark purple color on agar, but brown on wood. Other fungal species produced a similar color on agar, but different colors on wood. For examples, both  Phialophora alba  (FTK 772A) and  Penicillium expansum  (FTK 828A) produced pink pigments on agar, but on wood the former caused light brown and the later caused grayish color. Still some fungal species produced different colors on agar, but a similar color on wood. For example,  Arthrographis cuboidea  (FTK 706B) produced light brown and  Poria aurea  (FTK 110A) produced brown color on agar, but both species produced red color on wood. There were several fungal species that produced pigments on agar but not on wood such as, in agar plate cultures,  Penicillium variabile  (FTK 659B) produced red pigment,  Coryne microspora  (FTK 239A) produced light brown pigment, and  Sporotrichum dimorphosporum  (FTK 306D) produced yellow pigment, while none of them produced any color on wood. 
         [0039]    Wood specimens dried at different temperatures, in general, did not significantly change principal wood colors but significantly changed color lightness. Those wood specimens dried at 105° C. were significantly darker than those dried at 50° C. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Fungal coloring from agar plate test and on wood specimens 
               
             
          
           
               
                 Num- 
                 Fungal 
                   
                 Color on 
                 Color on 
               
               
                 ber 
                 code 
                 Fungal species 
                 agar 
                 wood 
               
               
                   
               
             
          
           
               
                 1 
                 FTK 
                 
                   Penicillium variabile 
                 
                 Red 
                 No 
               
               
                   
                 659B 
                 Sopp 
                   
                 coloring 
               
               
                 2 
                 FTK 
                 
                   Fusarium culmorum 
                 
                 Red 
                 Purple 
               
               
                   
                 750A 
                 (W. G. Sm.) Sacc. 
               
               
                 3 
                 FTK 
                 
                   Coryne microspora 
                 
                 Light 
                 No 
               
               
                   
                 239A 
                 Ellis &amp; Everh. 
                 brown 
                 coloring 
               
               
                 4 
                 FTK 
                 
                   Diatrypella placenta 
                 
                 Light 
                 No 
               
               
                   
                 430A 
                 Rehm 
                 brown 
                 coloring 
               
               
                 5 
                 FTK 
                 
                   Arthrographis cuboidea 
                 
                 Light 
                 Red 
               
               
                   
                 706B 
                 (Sacc. et Ellis) Sigler 
                 brown 
               
               
                 6 
                 FTK 
                 
                   Poria aurea 
                 
                 Brown 
                 Red 
               
               
                   
                 110A 
                 Peck 
               
               
                 7 
                 FTK 
                 
                   Corticium polosum 
                 
                 Brown 
                 Brown 
               
               
                   
                 534A 
                 Burt 
               
               
                 8 
                 FTK 
                 
                   Lentinus cyathiformis 
                 
                 Brown 
                 Brown 
               
               
                   
                 795A 
                 Bres. 
               
               
                 9 
                 FTK 
                   Lecythophora hoffmannii  (van 
                 Brown 
                 8rown 
               
               
                   
                 893A 
                 Beyma) W. Gams &amp; McGinnis 
               
               
                 10 
                 FTK 
                 
                   Tyromyces balsameus 
                 
                 Dark 
                 Brown 
               
               
                   
                 79A 
                 (Peck) Murrill 
                 brown 
               
               
                 11 
                 FTK 
                 
                   Trogia crispa 
                 
                 Dark 
                 Brown 
               
               
                   
                 473C 
                 Fr. 
                 brown 
               
               
                 12 
                 FTK 
                 
                   Polyporus dryophilus 
                 
                 Dark 
                 Brown 
               
               
                   
                 482B 
                 Berk. 
                 brown 
               
               
                 13 
                 FTK 
                   Polyporus dryophilus  var. 
                 Dark 
                 Brown 
               
               
                   
                 483A 
                   vulpinus  (Fr.) Overh. 
                 brown 
               
               
                 14 
                 FTK 
                 
                   Peniophora piceae 
                 
                 Dark 
                 Brown 
               
               
                   
                 840A 
                 (Pers.) J. Erikss. 
                 brown 
               
               
                 15 
                 FTK 
                 
                   Sporotrichum dimorphosporum 
                 
                 Yellow 
                 No 
               
               
                   
                 306D 
                 v. Arx. 
                   
                 coloring 
               
               
                 16 
                 FTK 
                 
                   Gliocladium verticilloides 
                 
                 Yellow 
                 Grayish 
               
               
                   
                 790A 
                 Pidoplichko 
                   
                 yellow 
               
               
                 17 
                 FTK 
                 
                   Nectria ochroleuca 
                 
                 Yellow 
                 Grayish 
               
               
                   
                 843C 
                 (Schweinitz) Berkeley 
                   
                 yellow 
               
               
                 18 
                 FTK 
                 
                   Trichoderma alroviride 
                 
                 Yellowish 
                 Grayish 
               
               
                   
                 585E 
                 P. Karst. 
                 orange 
                 brown 
               
               
                 19 
                 FTK 
                   Trichoderma  sp. 
                 Yellowish 
                 Yellowish 
               
               
                   
                 872B 
                   
                 orange 
                 brown 
               
               
                 20 
                 FTK 
                   Verticillium  sp. 
                 Green 
                 Green 
               
               
                   
                 164C 
               
               
                 21 
                 FTK 
                 
                   Chlorosplenium aeruginascens 
                 
                 Green 
                 Green 
               
               
                   
                 401A 
                 (Nyl.) Karst 
               
               
                 22 
                 FTK 
                 
                   Scytalidium lignicola 
                 
                 Dark 
                 Grayish 
               
               
                   
                 197P 
                 Pesante 
                 blue 
                 blue 
               
               
                 23 
                 FTK 
                   Ophiostoma piceae  (Münch) 
                 Dark 
                 Grayish 
               
               
                   
                 387AN 
                 Syd., H. &amp; P. Syd. 
                 blue 
                 brown 
               
               
                 24 
                 FTK 
                 
                   Aureobasidium pullulans 
                 
                 Black 
                 Black 
               
               
                   
                 132I 
                 (deBary) Arnaud 
               
               
                 25 
                 FTK 
                 
                   Phialophora alba 
                 
                 Pink 
                 Light 
               
               
                   
                 772A 
                 von Beyma 
                   
                 Brown 
               
               
                 26 
                 FTK 
                 
                   Penicillium expansum 
                 
                 Pink 
                 Gray 
               
               
                   
                 828A 
                 Link 
               
               
                 27 
                 FTK 
                 
                   Penicillium implicatum 
                 
                 Pink 
                 Green 
               
               
                   
                 837A 
                 Biourge 
               
               
                 28 
                 FTK 
                 
                   Fusarium verticillioides 
                 
                 Light 
                 Light 
               
               
                   
                 754A 
                 (Sacc.) Nirenberg 
                 purple 
                 Brown 
               
               
                 29 
                 FTK 
                 
                   Dactylium dendroides 
                 
                 Purple 
                 Purple 
               
               
                   
                 597A 
                 (Bulliard) Fr. 
               
               
                 30 
                 FTK 
                 
                   Phialemonium dimorphosporum 
                 
                 Purple 
                 Purple 
               
               
                   
                 669A 
                 W. Gams &amp; W. B. Cooke 
               
               
                 31 
                 FTK 
                 
                   Fusarium oxysporum 
                 
                 Dark 
                 Brown 
               
               
                   
                 31A 
                 Schlechtend.: Fr. 
                 purple 
               
               
                 32 
                 FTK 
                 
                   Ascocoryne cylichnium 
                 
                 Dark 
                 Brownish 
               
               
                   
                 392A 
                 (Tul.) Korf 
                 purple 
                 purple 
               
               
                 33 
                 FTK 
                 
                   Cephalotheca purpurea 
                 
                 Dark 
                 Light 
               
               
                   
                 433A 
                 (Shear) Chesters 
                 purple 
                 Brown 
               
               
                   
               
             
          
         
       
     
       Example 4  
     Matching Color on Sapwood and Heartwood 
       [0040]    Color evaluation of sapwood and heartwood wood blocks after fungal treatment and drying were performed with a colorimeter Color-guide 45/0 de SYK-Gardner USA. 
         [0041]    Colors are perceived as combinations of green and yellow, red and blue, and red and yellow. Based upon the equation of the CIE 1976 from Haegen et al.: 
         [0042]    L*a*b* color space system, colors are assigned to a rectangular coordinate system. The color coordinates are L* the lightness coordinate, a* the red/green coordinate (+a* indicating red and −a* indicating green), and b* the yellow*/blue coordinate (+b* indicating yellow and −b* indicating blue). Because the CIE L*a*b* colors space system is three-dimensional, it can often be difficult to relate actual differences in color values to visually perceived differences. One method developed for examining color differences uses the color metric difference (ΔE* ab ) where: 
         [0000]      Δ E*   ab =√{square root over ((( L*   1   −L*   2 ) 2 +( a*   1   −a   2 ) 2 +( b*   1   −b*   2 ) 2 ))}{square root over ((( L*   1   −L*   2 ) 2 +( a*   1   −a   2 ) 2 +( b*   1   −b*   2 ) 2 ))}{square root over ((( L*   1   −L*   2 ) 2 +( a*   1   −a   2 ) 2 +( b*   1   −b*   2 ) 2 ))}
 
         [0043]    Mathematically, the color metric difference (ΔE* ab ) is the Euclidean distance between two colors, L* 1 a* 1 b* 1  and L* 2 a* 2 b* 2 . It is relatively proportional to color differences perceived by human observers (Billmeyer and Saltzman 1981). Haeghen et al. (2000) determine that ΔE* ab  color difference values less than 3 are considered unnoticeable to the human eye. 
         [0044]    In a study on white beech looking at color problems with the drying process (Rodolfo et al. 2007), the magnitude of ΔE* ab  was classified according to the grading rules as follows: 
         [0045]    0.2&lt;ΔE* ab =Not visible difference; 
         [0046]    0.2&lt;ΔE* ab &lt;2=Small difference: 
         [0047]    2&lt;ΔE* ab &lt;3=Colour difference visible with high quality screen; 
         [0048]    3&lt;ΔE* ab &lt;6=Colour difference visible with medium quality screen; 
         [0049]    6&lt;ΔE* ab &lt;12=High colour difference; and 
         [0050]    ΔE* ab &gt;12=Different colours. 
         [0051]    With this classification, ΔE* ab &gt;6 correspond to a high color difference and if&gt;12 as different colours. 
         [0052]    Color variations (ΔE* ab ) of all fungal treated wood samples compared with the untreated controls are presented in Table 2. All of the fungal treatments lead to a significant color change of the tree hardwood species, both on sapwood and heartwood, with ΔE* ab  value going from 25.2 and up to 73.6. 
         [0053]    We also looked at the wood color variation between sapwood section and heartwood section of a same wood species ( FIGS. 1 to 6 ). Most of the fungal treated samples had a ΔE* ab  value below 10 with a least one representative of each wood color below 3, the critical level of what could be seen by the human eye. Pictures of different wood colors obtained by fungal coloration are presented in  FIG. 7 to 10 . 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Wood color change (ΔE* ab ) after fungal treatment 
               
             
          
           
               
                   
                 Sugar 
                 White 
                 Yellow 
               
               
                   
                 maple 
                 birch 
                 birch 
               
             
          
           
               
                   
                 Fungal 
                   
                 heart- 
                 sap- 
                 heart- 
                 sap- 
                 heart- 
                 sap- 
               
               
                 Number 
                 code 
                 Fungal name 
                 wood 
                 wood 
                 wood 
                 wood 
                 wood 
                 wood 
               
               
                   
               
             
          
           
               
                 6 
                 FTK 110A 
                 
                   Poria aurea 
                 
                 57.1 
                 52.5 
                 56.5 
                 55.1 
                 60.3 
                 46.4 
               
               
                 24 
                 FTK 132I 
                 
                   Aureobsidium 
                 
                 35 
                 33.5 
                 46.1 
                 44.5 
                 47.6 
                 43 
               
               
                   
                   
                 
                   pullulans 
                 
               
               
                 20 
                 FTK 164C 
                   Verticillium  sp. 
                 59.4 
                 55.8 
                 56.1 
                 59.5 
                 57.4 
                 57.7 
               
               
                 22 
                 FTK 197P 
                 
                   Scytalidium 
                 
                 46.1 
                 52.1 
                 45.8 
                 39.4 
                 51.5 
                 41.9 
               
               
                   
                   
                 
                   lignicola 
                 
               
               
                 3 
                 FTK 239A 
                 
                   Coryne microspora 
                 
                 64.7 
                 65.9 
                 67.3 
                 66.7 
                 63.9 
                 68.1 
               
               
                 15 
                 FTK 306D 
                 
                   Sporatrichum 
                 
                 62.7 
                 66.5 
                 63.2 
                 68.8 
                 58.7 
                 68 
               
               
                   
                   
                 
                   dimorphosporum 
                 
               
               
                 31 
                 FTK 31A 
                 
                   Fusarium 
                 
                 55.2 
                 61.5 
                 61.9 
                 59.5 
                 58.7 
                 60.5 
               
               
                   
                   
                 
                   oxysporum 
                 
               
               
                 23 
                 FTK 
                 
                   Ophiostoma piceae 
                 
                 59.7 
                 60.5 
                 61.1 
                 53.6 
                 54.6 
                 54.1 
               
               
                   
                 387AN 
               
               
                 32 
                 FTK 392A 
                 
                   Ascocorune 
                 
                 40.2 
                 25.2 
                 55.7 
                 54.5 
                 54.6 
                 49.3 
               
               
                   
                   
                 
                   cylichnium 
                 
               
               
                 21 
                 FTK 401A 
                 
                   Chlorosplenium 
                 
                 57.3 
                 62.8 
                 59 
                 61.5 
                 59.1 
                 57.2 
               
               
                   
                   
                 
                   aeruginascens 
                 
               
               
                 4 
                 FTK 430A 
                 
                   Diatrypella placenta 
                 
                 64.8 
                 70.9 
                 69.6 
                 70.1 
                 61.9 
                 70.4 
               
               
                 33 
                 FTK 433A 
                 
                   Cephalotheca 
                 
                 60.3 
                 63.8 
                 60.9 
                 58.8 
                 56.6 
                 62.7 
               
               
                   
                   
                 
                   purpurea 
                 
               
               
                 11 
                 FTK 473C 
                 
                   Trogia crispa 
                 
                 56.2 
                 60.8 
                 59.2 
                 58.3 
                 57.1 
                 56.6 
               
               
                 12 
                 FTK 482B 
                 
                   Polyporus 
                 
                 64.6 
                 67.5 
                 66.7 
                 61.8 
                 64.8 
                 66.7 
               
               
                   
                   
                 
                   dryophilus 
                 
               
               
                 13 
                 FTK 483A 
                 
                   Polyporus 
                 
                 41.3 
                 65.8 
                 42.6 
                 44.1 
                 47.9 
                 58.2 
               
               
                   
                   
                   dryophilus  var. 
               
               
                   
                   
                 
                   vulpinus 
                 
               
               
                 7 
                 FTK 534A 
                 
                   Corticium polosum 
                 
                 65.6 
                 61.3 
                 65.1 
                 66 
                 54.1 
                 60.3 
               
               
                 18 
                 FTK 585E 
                 
                   Trichoderma 
                 
                 62.7 
                 68.6 
                 57.3 
                 63.8 
                 55.6 
                 64.6 
               
               
                   
                   
                 
                   atroviride 
                 
               
               
                 29 
                 FTK 597A 
                 
                   Dactylium 
                 
                 64.2 
                 65.6 
                 55.9 
                 52.3 
                 54.6 
                 51.1 
               
               
                   
                   
                 
                   dendroides 
                 
               
               
                 1 
                 FTK 659B 
                   Penicillium  variabile 
                 65.2 
                 69.3 
                 61 
                 66.1 
                 64.4 
                 63.6 
               
               
                 30 
                 FTK 669A 
                 
                   Phialemonium 
                 
                 49.7 
                 44.9 
                 48.4 
                 65 
                 51 
                 59.3 
               
               
                   
                   
                 
                   dimorphosporum 
                 
               
               
                 5 
                 FTK 706B 
                 
                   Arthrographis 
                 
                 42 
                 48 
                 37.1 
                 39.9 
                 42.2 
                 40.4 
               
               
                   
                   
                 
                   cuboidea 
                 
               
               
                 2 
                 FTK 750A 
                 
                   Fusarium culmorum 
                 
                 61.4 
                 52.1 
                 61.4 
                 62 
                 59.3 
                 58.9 
               
               
                 28 
                 FTK 754A 
                 
                   Fusarium 
                 
                 54.8 
                 60.6 
                 65.3 
                 63.3 
                 57.2 
                 60.6 
               
               
                   
                   
                 
                   verticillioides 
                 
               
               
                 25 
                 FTK 772A 
                 
                   Phialophora alba 
                 
                 68 
                 73.6 
                 65.9 
                 67.3 
                 60.8 
                 69.6 
               
               
                 16 
                 FTK 790A 
                 
                   Gliocladium 
                 
                 66 
                 68 
                 65.1 
                 71.8 
                 67.4 
                 69.3 
               
               
                   
                   
                 
                   verticilloides 
                 
               
               
                 8 
                 FTK 795A 
                 
                   Lentinus 
                 
                 61.4 
                 59.3 
                 57.4 
                 63.1 
                 54.4 
                 57.2 
               
               
                   
                   
                 
                   cyathiformis 
                 
               
               
                 10 
                 FTK 79A 
                 
                   Tyromoces 
                 
                 64.6 
                 66 
                 71 
                 70 
                 64.3 
                 66.3 
               
               
                   
                   
                 
                   balsameus 
                 
               
               
                 26 
                 FTK 828A 
                 
                   Penicillium 
                 
                 60.5 
                 59.3 
                 63.8 
                 61 
                 65.5 
                 62.1 
               
               
                   
                   
                 
                   expansum 
                 
               
               
                 27 
                 FTK 837A 
                 
                   Penicillium 
                 
                 52.3 
                 52.1 
                 53.2 
                 51.3 
                 48.1 
                 58.9 
               
               
                   
                   
                 
                   implicatum 
                 
               
               
                 14 
                 FTK 840A 
                 
                   Peniophora piceae 
                 
                 54.4 
                 60.3 
                 59.4 
                 62.9 
                 56.2 
                 68.7 
               
               
                 17 
                 FTK 843C 
                 
                   Nectria ochroleuca 
                 
                 63.2 
                 71.9 
                 61.7 
                 72.4 
                 64.6 
                 68.6 
               
               
                 19 
                 FTK 872B 
                   Trichoderna  sp. 
                 58.5 
                 71.3 
                 61.7 
                 65.7 
                 57.7 
                 66.2 
               
               
                 9 
                 FTK 893A 
                 
                   Lecythophora 
                 
                 65.3 
                 69.5 
                 64.6 
                 69.7 
                 65.2 
                 66.4 
               
               
                   
                   
                 
                   hoffmannii 
                 
               
               
                   
               
             
          
         
       
     
         [0054]    Using biological method for coloring wood with fungi is a new innovative approach and has a potential to produce preferable wood colors and patterns. The resultant product could be sold as a water based stain substitute in the form of fungal spore suspension. One litre of such suspension is relatively inexpensive, and can be further diluted into 100 L with water as application solution. In an industrial factory application situation, the product can be applied to lumber either by a spraying line or by a dipping tank, which will consume 20 L or 50 L of application solution per thousand board feet measure (Mfbm) of lumber, respectively. Applying the product to lumber at an industrial scale will lead to a cost effective product. After application of the fungal suspension onto lumber, the lumber must be stored in a yard for more than 1 week to allow fungus changing wood color. Of course, this process will take longer time than standard water-based staining methods; however, the process allows color change in depth of wood, whereas the standard staining method can not. Such technology will increase wood market value and enhance the utilization of wood products in competitive marketing of lumber and furniture manufacturing. 
       References 
       [0000]    
       
         Billmeyer, F. W. and M. Saltzmann, 1981, Principles of color Technology, 2 nd  Ed. John Wiley end Sons Inc., NY, 240 pp. 
         Haeghen, Y. V., J. M. Naeyaert, I. Lemahieu and W. Phillips, 2000, An imaging system with calibrated color image acquisition for use in dermatology, IEEE Transactions on Medical Imaging, 19(7):722-30. 
         Rodolfo, C. T. Livio, A. Ottaviano, 2007, White beech: a tricky problem in the drying process, ISCHP&#39;07, p. 135-140. 
         H. Sugawara et al. (Editor), Bacteria, Fungi and Yeasts, 4th Edition, 1993. World Discovery of Collection of Cultures of Microorganism, WFCC World Data Center on Microorganisms.