Effect of cryogenic process on Trametes versicolor and Fomitopsis palustris fungal destruction in ThermoWood® products of some wood specie

Aytin, A., Taşçıoğlu, C., Uygur, İlyas, & Ohmura , W. (2025). "Effect of cryogenic process on Trametes versicolor and Fomitopsis palustris fungal destruction in ThermoWood® products of some wood species," BioResources 20(2), 2827–2843.

Abstract

Aspen, ash, spruce, and fir trees naturally grown in Turkey were obtained directly from the forest and processed using ThermoWood®(TM) processing at two different temperatures (190 °C: TW1 and at 212 °C: TW2). Then, cryogenic treatment (Cr) was applied to the samples, and they were placed in a jar containing Trametes versicolor (COV) and Fomitopsis palustris (TYP) mushrooms. Their weight loss (WL) was measured after 12 weeks. Although WL results varied depending on the tree type and the applied processes, it has been understood that Cr application can be effective in reducing WL. According to the study, the lowest WL was determined to be in COV fungus with 1.2% in cryogenically treated fir tree TW2 samples. The highest WL was in TYP mushrooms with 56.1% in spruce TW1 samples that received heat treatment (HT). The results obtained from the study show that cryogenic treatment may be an alternative method for reducing WL in heat treated wood species.

Download PDF

Full Article

**Effect of Cryogenic Process on Trametes versicolor and Fomitopsis palustris Fungal Destruction in ThermoWood® Products of Some Wood Species**

Ayhan Aytin ,^a,* Cihat Tascioğlu ,^b İlyas Uygur ,^c and Wakako Ohmura ^d

DOI: 10.15376/biores.20.2.2827-2843

Keywords: Heat treatment; Cryogenic treatment; Weight loss; Trametes versicolor; Fomitopsis palustris

Contact information: a: Duzce University, Duzce Vocation School, Design Department, Düzce; b: Duzce University, Faculty of Forestry, Forest Industry Engineering Department, Düzce; c: Duzce University, Faculty of Engineering, Department of Mechanical Engineering, Düzce; d: Kyoto University, Research Institute of Sustainable Humanosphere, Kyoyo, Japan; *Corresponding author: ayhanaytin@duzce.edu.tr

INTRODUCTION

Trees, which have a wide range of uses as a natural and renewable raw material (Ramage et al. 2017), and the products (derivatives) obtained from them have been used by societies for thousands of years (Reinprecht 2016). Trees and their derivatives are under the influence of many external factors, mainly due to the climatic characteristics of the areas of use. Many of these factors cause some damage to the tree and its derivatives and shorten the lifespan of the materials. Dimensional changes occurring due to contraction and expansion in water exchange below the fiber saturation point, biological degradation resulting from fungal damage, and color change due to the distorting effects of light are considered as the most important disadvantages that arise in the use of wood material.

Biological degradation caused by fungi causes a significant decrease in the service life of wood materials. Wood materials, which are used extensively in all areas of life, such as construction, household products, and outdoor furniture products, are generally susceptible to fungal decay under suitable living conditions for fungi (such as 27% to 60% moisture content and 3 to 38 °C temperature). This not only reduces the service life of wooden materials but also causes huge economic losses (Bi et al. 2024). These decompositions caused by fungi in wooden materials are generally expressed as rot. The main fungal rots that cause significant value losses in wood materials are white (corrosion rot), brown (destruction rot), dry rot, and soft rot.

Although each type of rot has its own characteristics, the common feature of all of them is that they are more or less affected by the cell wall components cellulose, hemicellulose, and lignin. In white rot, all three main components of the cell wall are destroyed, but primarily because the lignin is destroyed, the tree acquires a whitish color, the appearance of the coloration is scattered, and the structure of the stained tree becomes spongy. Dark colored border lines are seen as the most striking characteristic feature of white rot. Brown rot fungi destroy cellulose and hemicellulose, which are cell wall components of the tree, and because lignin is not destroyed, the tree turns red or brown, which is the color of lignin. In this rot, there is a decrease in the volume of the tree, and in advanced stages, cracks in the transverse and longitudinal directions and loss of strength are observed, and the tree is divided into small cubes and prisms. In the soft rot type, the fungus shows its effect on the middle lamella of the wood cell walls (Bozkurt et al. 1993).

Fungi that damage cell wall components result in weight loss (WL) in varying amounts during the degradation of wood and its derivatives. In addition to the fungal rots examined in areas of use, studies conducted with various fungi in open field and laboratory environments show that many factors, such as the type of fungus, tree species, and climatic conditions, affect the WL. For example, Mendonça et al. (2002) in their studies on Ceriporiopsis subvermispora mushroom and Pinus teada chips, reported that mushroom treatment caused weight loss from 2.3% to 13.8%. In the same study, it was understood that there was a loss of lignin from 9.6% to 22%, glucan from 0.9% to 2%, and extractive loss from 28% to 65%. Ferraz et al. (2000) reported 12% weight loss in Eucalyptus globulus chips treated with the same fungus for 90 days; Blanchette et al. (1988) stated that weight loss was 38% and lignin loss was 73% in Betula papyrifera chips treated with the white-rot fungus Phanerochaete chrysosporium BKM-F-1767 for 12 weeks.

Among the well known and applied methods, the most effective process to prevent fungal rots and therefore WL in wood and wood products is to impregnate the wood material with various chemicals and methods. The aim of impregnation is to penetrate various chemicals into the wood material in sufficient quantities and depth using different methods. Thus, the wood material, whose durability is increased by impregnation, is similarly protected from both insect damage and flammable effects (Bozkurt et al. 1993). With the impregnation process, the resistance of wood material against fungal rot can be increased as much as desired. However, substances, such as copper, creosote, and arsenic, in the composition of the chemicals used negatively affect living organisms and the environment. In addition, the impregnation processes pose a danger to non-target organisms, dimensional stability cannot be achieved, or dimensional changes may occur (Furniture decoration 2013). Because of their additional negative effects on the environment and human health, the use of impregnation classes with harmful properties has been limited worldwide since the recent past and today. With this potential, 117 harmful preservatives have been banned in Sweden since the 1990s to prevent harmful systems (Johansson 2005). At the same time, the development and use of more environmentally friendly production techniques, methods, and improvements that can be alternatives to harmful impregnation materials and methods in wood technology are encouraged (Korkut and Kocaefe 2009).

As an environmentally friendly production technology, heat treatment (HT) is one of the methods that improve wood material against biological degradation and to increase its resistance against biological threats such as fungi and insects (ThermoWood® Handbook 2003). Johansson (2005) defines HT as a physical process that results in permanent changes in the chemical composition of cell wall compounds. According to the general definition, the application temperature in HT ranges between 160 and 240 °C (TS CEN/TS 15679 2010). Yildiz et al. (2010) report that HT gives new properties to wood material, creates lower equilibrium moisture content, and improvement in dimensional stability, and reduces the amount of moisture exchange and equilibrium moisture. As a result, the amount of work required by HT is minimized and the performance of surface treatments increases by increasing biological resistance and permeability against destructive organisms. Belt et al. (2024) report that HT increases the resistance of wood material to decay, and the main reason for the increase in the decay resistance of wood is related to decreasing hygroscopicity. Biological durability tests performed using Coniophora puteana and Poria placenta fungi on thermally modified pine samples indicate that the resistance of HT wood materials to decay increases.

Heat treatment of wood materials is a production technique that dates back to the 10^th century, and similar studies were carried out and reported mostly in Germany and America from the 1930s to the 1970s. It is an important point that, together with the studies carried out in Finland, Germany, France, and the Netherlands since the 1990s, its potential in terms of both installed capacities and product diversity is quite valuable (ThermoWood®

Handbook 2003). As a result of these studies, many HT methods, such as ThremoWood®, Platowood, oil heat treatment, rectification, and Les Bois Perdure have been developed. Among these methods, TM is more common, has a higher production volume, and is also widely commercialized compared to the others. Today, TM is the name given both as a HT method and to the modified wood material obtained after HT (Aytin 2013).

The heat treatment and similar applications in wood materials provide improvements in many properties such as fungus resistance. However, as in HT, some properties, mostly mechanical properties, are negatively affected, especially by high temperature applications. It is important to eliminate these drawbacks, which are vital for use, with different but environmentally and human-friendly production techniques. In his study on cryogenic treatment, which he considers as a new modification method for wood materials, Pamukçu (2019) states that an application such as HT can initially improve the physical properties of wood materials, while the mechanical properties of wood materials treated with high temperatures are mostly negatively affected. Pamukçu also states that for this reason, efforts are being made to overcome the problem by combining the applied modification methods with different modification methods to eliminate the negative aspects, as in HT. In addition, he states that the search for new modification methods that do not include these negativities is among today’s current issues. A limited number of studies on cryogenic (Cr) processing reveal that the decreases seen in mechanical strength values in HT wood materials can be tolerated with Cr treatment (Aytin et al. 2016; Aytin 2019). Opening new areas of use for wood materials and improving the performance of wood materials in existing areas of use make it possible to consider the expectations regarding the increase in fungal resistance with Cr process, in addition to the recoveries obtained with Cr process. Considering the structural features, the changes in the chemical properties of the wood material with Cr treatment (Aytin et al. 2022) strengthen and support the idea that such an expectation can be realized. As the number of trees treated with HT increases and its use becomes more widespread, many studies have been conducted and continue to be conducted on the determination of resistance to fungal damage in terms of suitability for the intended use of HT-treated products. Such a study has not yet been found in the literature on both natural and HT wood derivatives that have been cryogenically treated.

Cryogenic treatment is a secondary specialized process that involves rapid cooling materials to extremely low temperatures, typically below -80 °C to -195 °C, to enhance their mechanical properties and performance. This treatment has gained significant attention in various fields, particularly in materials science and mechanical engineering, due to its ability to improve wear resistance, hardness, and overall durability of metals and alloys. One of the primary benefits of cryogenic treatment is the transformation of retained austenite into martensite, which significantly enhances the wear resistance of materials. For instance, Uygur et al. (2015) demonstrated that Cr treatment leads to less retained austenite and more uniform distribution of carbides and the precipitation of fine carbides, which collectively contribute to improved wear resistance in AISI D3 tool steel punches. Similarly, Kara et al. (2021) reported that deep Cr treatment enhances the hardness and homogeniziting microstructure of Sleipner cold work tool steels by facilitating carbide precipitation and reducing residual stresses and reducing retained austenite. Moreover, the optimization of Cr treatment parameters, such as soaking time and temperature, plays a vital role in achieving desired material properties. The effectiveness of Cr treatment can vary significantly based on these parameters, which must be tailored to the specific material (Çicek et al. 2012; Kara et al. 2021, 2023). This adaptability allows for targeted improvements in performance, making Cr treatment a valuable tool in material engineering. Furthermore, Savas et al. (2023) indicated that Cr treatment can cause 30% energy saving the machining of GGG-42 cast iron material by uniform microstructure and increased hardness. The application of Cr treatment is not limited to ferrous materials; it has also been effectively utilized in nonferrous alloys. For instance, Ates et al. (2017) highlighted that deep cryogenic treatment serves as a supplementary process to conventional heat treatment, enhancing the mechanical properties of AA5xxx series Al-alloys, which were joined by MIG welding technique. This versatility underscores the importance of Cr treatment across different material types and applications. The ongoing research and development in this field continue to reveal new benefits and applications, solidifying the importance of cryogenic treatment in advancing material performance.

Cryogenic applications of wood materials are almost non-existent. In this respect, it is still unclear what kind of changes the Cr process causes in the microstructural, physical, mechanical, and chemical properties of wood materials. In the literature, only limited studies can be seen. Aytin et al. (2016) subjected TM Populus tremula samples to deep Cr treatment at -145 °C for 24 h and then measured the compressive strength parallel to the fibers, and determined that the resistance values of the Cr-treated TM samples increased 24% to 54% compared to the control samples. Aytin (2019) in another study shallow Cr was applied to TM Sorbus torminalis samples at -80 °C for three different periods (6, 18, and 54 hours) and an increase of up to 43% in compressive strength was observed compared to the control samples. Moreover, the findings revealed that the improvement in shrinkage and swelling continued with the heat treatment (dimensional stability increased), with an average increase of 18% and 14.5% in the pressures parallel to the fibers compared to the samples observed in the control and heat treatment, respectively. The FT-IR analysis showed that the wood compound structure was mostly cellulosic. The difference between the carbon-oxygen ratio in the cryogenically-treated wood decreased compared to the percentage change in the three basic elements, and the amount of hydrogen increased proportionally (Aytin et al. 2022).

Therefore, because there is no research on fungal damage testing on Cr-applied wood materials in the literature, this study is novel in terms of testing natural state, HT, and Cr-treated samples for fungus damage in wood materials. Within the scope of the study, aspen (Populus tremula L.), narrow-leaved ash (Fraxinus angustifolia Vahl), spruce (Picea orientalis (L.) Link.), and fir (Abies bornmuelleriana Mattf.) that grow naturally in Turkey and have commercial potential were used. Tree research is of particular importance as it has the potential to contribute to the most efficient use of wood raw material resources.

EXPERIMENTAL

Materials

Within the scope of the study, aspen (Populus tremula L.), ash (Fraxinus angustifolia Vahl), spruce (Picea orientalis (L.) Link.), and fir (Abies bornmuelleriana Mattf.), trees that grow naturally in Turkey, were evaluated. Trees were taken from the stand according to TS 4176 (1984) standard and then sawn into 60-mm-thick planks with the sharp cutting method according to TS 2470 (1976). Then, after drying to an average of 12% moisture, the planks were made ready for HT with dimensions of 20 × 100 × 500 (mm × mm × mm) and subjected to heat treatment with the TM method.

Heat Treatment

Wood samples prepared from working trees were subjected to HT together with air-dried wood materials in the factory of Nova Forest Products Inc. in Gerede / Bolu and TM products were produced.

Shallow Cryogenic Treatment

Afterwards, samples with nominal dimensions of 20 × 20 × 300 (mm × mm × mm) were prepared from TM templates and Cr was applied together with the control sample (CON). Shallow cryogenics was applied to the samples in a specially manufactured deep freezer.

A Core DF 490 type deep freezer with 611 L capacity and 1 °C temperature sensitivity without icing was used in the shallow cryogenic process. An N-SmArt™ control system that can store temperature data numerically and graphically for ten years with 1-h recording intervals, was used in the Core DF 490 type deep freezer and the device could be cooled down to -86 ℃. After all the samples were placed in separate compartments, a 12 h pre-waiting was performed to allow the ambient temperature to reach -80 °C, and then Cr was started. At this stage, the samples were kept at -80 °C for 72 h.

Fungus Test and the Development of the Working Pattern

Test samples of 10 mm size were subjected to 12 weeks of decay test. The decay test was performed according to Japanese Industrial Standards (JIS) K 1571 (2010). Sugi (Cryptomeria japonica (L.f.) D. Don) sapwood specimens were also prepared in the same size and utilized as controls. All specifications were oven-dried at 60 °C before their pre-decay test weights were recorded. The sterilization was carried out under vacuum conditions with ethyhlene oxide gas for 18 h. Five species were exposed to a monoculture of either the white-rot fungus Trametes versicolor (L:Fr.) Pilat (Source or Fungi : Forestry and Forest Products Research Institute of Japan, FFPRI 1030) the brown-rot fungus Fomitopsis palustris (Berk et Curt.) Gilb & Ryv. (Source of fungi FFRPI 0507).

The nutritional media was prepared from glucose (2%), peptone (0.15%), malt extract (0.75%), and distilled water (97.1%) and immersed into white quartz sand at the bottom of glass decay containers. Three decay containers were used for 9 replicates from each wood species and treatment conditions and for each test fungus. The total number of specimens were 288, representing all four wood species and all CON, HT, and Cr groups. Furthermore, 18 sugi specimens were also tested as controls for each fungus type (Table 1).

Table 1. Classification of Working Samples and Abbreviations

One group of control and HT variants were used for control purposes without undergoing shallow Cr treatment and were expressed as control samples (CON) within the study. Samples subjected to shallow Cr were named as working samples and expressed with the abbreviation Cr.

Determining Weight Loss

At the end of the decay tests, immediately after removal of the surface mycelium, the specimens were oven-dried at 60 ± 2 ℃ for 48 h and weighed to determine their weight loss in terms of percent (%):

(1)

In the formula, WL is Weight loss, M_i is Initial weight, and M_e is End weight.

Statistical Evaluation

The SPSS package program (IBM, SPSS 15.0 for Windows, Armonk, NY, USA) was used for the statistical evaluation of the data. Analysis of variance was used to determine whether the factors influenced the results obtained, and Duncan’s test was performed to determine the size of the difference on the factors that were found to be significant.

RESULTS AND DISCUSSION

The results of multiple variance analysis (MVA) regarding the WL values found after the weight loss test of Trametes versicolor and Fomitopsis palustris mushrooms in TM products are given in Table 2.

Table 2. Multiple Analysis of Variance Results of WL Values Found after the Weight Loss Test of T. versicolor and F. palustris Fungi in TM Products

Based on the PEA values in Table 2, it was understood that each of the WT, VAR, and FUN factors was effective on WL. Starting from the control samples (CON), the PEA value of the groups treated with HT and Cr and classified as subgroups was determined to be 0.522 at the highest VAR factor. To see these differences more clearly, the arithmetic mean values and Duncan test results, where all sub-variations for each tree are analyzed as a whole, are given in Table 3.

Table 3. Average Values of WT in the Weight Loss Study and Results of the Duncan Test

The degradation of wood material by fungi occurs at different rates in broad-leaved and coniferous trees due to the different structural properties of the trees (Bozkurt et al. 1993). As shown in Table 3, the WL due to Trametes versicolor and Fomitopsis palustris mushrooms varied according to tree species. Some analysis results of both mushroom species and all tree species indicate that WL occurred the least in fir and the most in poplar. However, to better understand the effect of both Cr and HT on WL, it would be useful to see the average WL values and Duncan test results of the sub-main groups for both mushrooms. For this purpose, WL values and Duncan test results of the sub-main groups are given in Table 4.

Table 4. Arithmetic Mean Values and Duncan Test Results after Weight Loss Test in Subgroups

According to Table 4, the lowest weight loss was in TW₂Cr with 14.9, and the highest WL is in the CON and CONCr subgroups. According to these results, as the HT temperature increased, the decrease in WL also increased. The results also indicate that Cr further reduced WL in HT-treated samples.

To date, no fungal testing of Cr-treated wood samples appears in the known literature. In this regard, the results obtained from Cr applied samples are of particular importance in this regard. However, the fungal resistance acquired by HT against both rot fungi of the same tree species is of great importance in terms of both HT and general comparison. For this reason, the rot test results were analyzed separately for each tree with all its variations, and the results were discussed in detail for both HT and Cr. In Table 5, simple variance analysis results (BVA), averages (WL), standard deviation values of the averages (SD), and homogeneity test (HG) results for the ash tree values are given together.

Table 5. BVA, WL, SD, and HG Values of Ash Tree

According to the BVA results given for the ash samples in Table 5, it is understood that there are differences between the WL values. The Duncan test for differences found the highest and lowest WL, respectively, to be 48.6% and 5.6% in CONCOV and TW₂CrTYP variations. In the rot test performed on ash tree samples with the white-rot fungus Trametes versicolor, Cr treatment reduced the WL compared to both CON and HT, and the difference between the WL of Cr-treated samples and HT-treated samples was 68% in TW₁ samples and 64.8% in TW₂ samples. According to the results of the brown-rot fungus Fomitopsis palustris, WL, TW₁ samples it was 17.2% and 43% less in TW₂ samples. In the case of ash wood, WL results indicate that fungal resistance increases with Cr treatment in both fungal species. In contrast, it was determined that WL decreased with HT, and in both fungal species, the WL of TW₁ samples had lower values than the WL of CON samples.

Cross-sectional images of ash samples (UF) that were not subjected to the fungus test and ash samples after the fungus test are given in Fig. 2. In the images, mycelia belonging to fungi can be seen on the samples subjected to fungal resistance testing.

Fig. 2. Cross-sectional view of ash tree samples after the weight loss experiment (*) UF: Comparison samples that did not undergo the fungus test, (**): Fungal mycelia

According to the cross-sectional views given in Fig. 2, fungal degradation on the surface was very clearly apparent in all CON and other TW₁ variations except TW₁CrCOV. The results were compatible with the visuals of the variations and the WL ratios given in Table 5.

In Table 6, simple variance analysis, averages, standard deviation values of the averages and homogeneity test results for aspen tree values are given together.

According to the BVA results given for Aspen samples in Table 6, it is understood that there were differences between the WL values. According to the results of the Duncan test for differences, the highest and lowest WL in % were found to be 55.14 and 7.26 in CONCrCOV and TW₂CrTYP variations, respectively. In the rot test performed with Trametes versicolor on Aspen wood, WL occurred in 47.4% and 45.4% in TW₁ samples and TW₁Cr samples, and 24.6% and 29.6% in TW₂ and TW₂Cr samples, respectively. According to these results, there was a 4% decrease in TW₁ samples and a 20.3% increase in WL in TW₂ samples. In Aspen, WL occurred at percentages of 35.2% and 38.3% in Fomitopsis palustris TW₁ samples and TW₁Cr samples, respectively, and 7.3% and 11.2% in TW₂ and TW₂Cr samples, respectively. Tests performed with the Fomitopsis palustris mushroom show that there was an 8.7% increase in WL in TW₁ samples and a 35.1% decrease in TW₂ samples. Figure 3 shows cross-sectional images of Aspen samples that were not subjected to the fungus test and aspen samples after the fungus.

Table 6. BVA, WL, SD, and HG Values of Aspen Tree

Fig. 3. Cross-sectional view of Aspen samples after the weight loss experiment

When Fig. 3 and Table 6 are examined, it is seen that both data were compatible with each other.

In Table 7, the simple variance analysis results, averages, standard deviation values of the averages and homogeneity test results regarding the fir tree values are given together.

According to the BVA results given for the fir samples in Table 7, it is understood that there were differences between the WL values. According to the results of the Duncan test for differences, it was understood that the highest and lowest WL were 38.6 and 1.20 in CONTYP and TW₂CrCOV variations, respectively. In the rot test performed on fir tree samples with the white-rot fungus Trametes versicolor, it was determined that the WL of the samples treated with Cr was lower, and there was a difference of 16.4% in the TW₁ samples and 66% in the TW₂samples between the WL of the Cr-applied HT samples and the heat-treated samples only. According to the results of the brown-rot fungus Fomitopsis palustris, it was understood that WL did not change in TW₁ samples, but increased 28.6% in TW₂ samples. In the case of fir tree, WL results show that fungal resistance produces different results between the two fungi. Cross-sectional images of fir samples that were not subjected to the fungus test and fir samples after the fungus test are given in Fig. 4.

Table 7. BVA, WL, SD, and HG Values of Fir Tree

Fig. 4. Cross-sectional view of fir samples after weight loss experiment

When Fig. 4 and Table 7 were examined, it was seen that both data were compatible with each other.

In Table 8, the simple variance analysis results, averages, standard deviation values of the averages, and homogeneity test results for the spruce tree values are given together. In Table 8, it is understood that there were differences between the WL values according to the BVA given for the spruce samples. According to the Duncan test for the differences made, the highest and lowest WL values were determined as 56.2% and 7.0%, respectively, TW₁TYP and TW₂COV. In the rot test performed on spruce tree samples with Trametes versicolor, WL is 6.4% lower in TW₁ rates and 48.9% higher in TW₂ variations in Cr applied samples compared to HT samples alone. It is seen that the WL values in all samples (TW₂) where Cr was applied at high HT in the same mushroom are lower than CON samples. According to the Fomitopsis palustris test, WL was determined to be 42.9% less in Cr-treated TW₁ samples and 30.19% less in TW₂ samples. Cross-sectional images of spruce samples that were not subjected to fungus testing and spruce samples after fungus testing are given in Fig. 5.

Table 8. BVA, WL, SD, and HG Values of the Spruce Tree

Fig. 5. Cross-sectional view of spruce samples after weight loss experiment

When Fig. 5 and Table 8 were examined, it is seen that both data were compatible with each other.

Research and review studies in the literature on the effect of HT on fungal degradation show that HT increases the resistance of wood material against fungal decay. In one of these repairs (Suri et al. 2023) HT-treated Paulownia tomentosa wood was exposed to the brown-rot fungus (Fomitopsis palustris) in diseases where they were exposed to the brown-rot fungus (Fomitopsis palustris) with cycles of WL and CON at 180 and 220 °C were determined as 13.4%, 14.7%, and 1.2%. Accordingly, although the low temperature has increased slightly in amount, the WL value, which remained almost the same, decreased quite sharply in parallel with the increase in temperature and supports 91.0%. The same researchers found WL in Pinus koraiensis wood as 21.8%, 32.4%, and 8.8% in terms of its sequence, and reported that WL, which increases in low HT, decreases with increasing temperature (72.8%). Belt et al. (2024) reported that heat treatment increases the decay resistance of wood by reducing its hygroscopicity. Candelier et al. (2016) in their review study on the control of wood heat treatment and its effects on decay resistance, showed that HT makes wood species with low natural durability resistant to decay. They also report that HT temperature has more effect than time on decay resistance. However, the same studies indicate that fungi also increase the hygroscopicity of wood material over time. They state that this situation will gradually deteriorate the quality of use due to fungal degradation as the period of use increases.

Determining the changes in the chemical structure of the study samples through decay tests is planned as the next step in the study to better understand the differences between the results and to serve as a source for future research studies on the subject.

Classifications are made for the tested trees according to the results obtained after rot tests carried out in various national and international standards. The WL values obtained as a result of this study were classified according to the Standard Test Method of Accelerated Laboratory Test of Natural Decay Resistance of Woods (ASTM D2017-5 2017), and are given in Table 9.

Table 9. Classification of Weight Loss Values according to ASTM D2017-5 (2017)

Although HT generally increases fungal resistance, it has been determined that some variations also have opposite results. In all tree species, HT causes an increase in resistance, especially against the white-rot fungus Trametes versicolor, except for the TW1COV variation, while in the brown-rot fungus Fomitopsis palustris, resistance increases with HT in ash and Aspen, and variable resistance in fir and spruce samples. A fungal resistance is noteworthy. In contrast, because no fungus test has been performed on Cr-treated wood samples in the literature yet adds a special meaning to the results. In Fig. 6, all sub-variations and WL values of the Sugi tree are presented graphically.

Fig. 6. WL values of working test samples and Sugi control tree

According to Fig. 6, the WL of the TW₂ test samples in both HT only and HT+Cr, except for the test with spruce TW₂ Fomitopsis palustris, was less than the weight losses in Sugi.

Since this study is the first in a series, the next step will be to conduct more detailed studies to better understand the decrease in weight loss in samples treated with HT through cryogenic treatment. In this context, it is planned to examine the changes in the chemical structure.

CONCLUSIONS

According to the general trend of the study results of the effect of cryogenic process on fungal destruction of Trametes versicolor and Fomitopsis palustris in Thermowood® products of some wood species, it has been understood that cryogenic process reduces weight loss (WL) in fungal damage. However, there are some differences between the variations, and these differences naturally arise from the tree type, mushroom type, and the modification processes applied.
In this study, the fungal degradation was determined in samples that were only heat-treated along with cryogenic treatment, and showed that heat treatment temperature contributed significantly to fungal resistance and that resistance increased as the temperature increased. Thus, the effect of heat treatment (HT) on the reduction of weight loss (WL) in fungal destruction is important, and as the temperature increases, weight loss also decreases. Accordingly, considering the suitability of the values in other wood properties required for the usage areas, it is recommended to apply the highest possible HT temperature.
According to tree species, the highest resistance in the effect of Cr treatment on fungal resistance was obtained in ash, aspen, and fir at 212 °C treatment, and in terms of heat treatment (HT) only, the same variations were obtained in ash, fir, and spruce trees. It appears that the nonheat-treated samples, which are the main control samples of the trial trees, had little or no resistance to decay.
All wood species that had undergone both cryogenic and heat treatment exhibited higher resistance values in almost all variations compared to the control samples. This makes it clear that it is important to highlight the fungal resistance of both processes as environmentally friendly production technologies and to consider their further improvement.

REFERENCES CITED

ASTM D2017-5 (2017). “Standard test method of accelerated laboratory test of natural decay resistance of woods,” ASTM International, West Conshohocken, PA, USA.

Ateş, H., Özdemir, A. T., Uzun, M., and Uygur, I. (2017). “Effect of deep sub-zero treatment on mechanical properties of AA5XXX aluminum plates adjoined by MIG welding technique,” Scientia Iranica 24(4), 1950-1957.

Aytin, A. (2013). Effect of High Temperature Treatment on Physical, Mechanic and Technological Properties of Wild Cherry (Cerasus avium (L.) Monench) Wood, Doctoral Thesis, Department of Forest Industry Engineering, Düzce University, Düzce, Turkey.

Aytin, A., Korkut, S., Çakıcıer, N., and Arslan, Y. (2016). “The effect of cryogenic processing on fiber parallel pressure resistance in ThermoWood Populus tremula wood,” in: 27^thInternational Conference on Wood Science and Technology-Ambienta, Implementatıon of Wood Scıence In Woodworkıng Sector, Zagreb, Croatia, pp. 1-6.

Aytin, A. (2019). “The effect of cryogenic application on parallel fiber pressure resistance of Thermowood-treated Sorbus torminalis,” Journal of Anatolian Environmental and Animal Sciences 4(4), 684-687. DOI: 10.35229/jaes.643486

Aytin, A., Uygur, I., Demirci, T., and Akgül, İ. (2022). “The effect of cryogenic treatment on some chemical, physical, and mechanical properties of ThermoWood Oriental spruce,” BioResources 17(4), 6983-6996. DOI: 10.15376/biores.17.4.6983-6996

Belt, T., Altgen, M., Awais, M., Nopens, M., and Rautkari, L. (2024). “Degradation by brown rot fungi increases the hygroscopicity of heat-treated wood,” International Biodeterioration & Biodegradation 186(9), article ID 105690. DOI: 10.1016/j.ibiod.2023.105690

Bi, Z., Gao, X., Zhang, J., Lei, Y., and Yan, L. (2024). “Antifungal activity of heat-treated wood extract against wood decay fungi,” International Biodeterioration and Biodegradation 193, article ID 105843. DOI: 10.1016/j.ibiod.2024.105843

Blanchette, R. A., Burnes, T. A., Leatham, G. F., and Effland, M. J. (1988). “Selection of white rot fungi for biopulping,” Biomass 15(2), 93-101. DOI: 10.1016/0144-4565(88)90099-6

Bozkurt, Y. A., Göker, Y., and Erdin, N. (1993). “Impregnation technique,” Istanbul University Faculty of Forestry Publications, Faculty of Forestry Publication No: 425. Istanbul University Publication No: 3779, Istanbul, Turkey.

Candelier, K., Thevenon, M. F., and Petrissans, A. (2016). “Control of wood heat treatment and its effects on decay resistance: A review,” Annals of Forest Science 73, 571-583. DOI: 10.1007/s13595-016-0541-x

Çicek, A., Ekici, E., Uygur, I., Akıncıoğlu, S., and Kıvak, T. (2012). “Investigation of the effects of deep cryogenic treatment on tool life in drilling aısı D2 cold work tool steel,” International Journal of Technological Sciences 4(1), 1-9.

Ferraz, A., Rodriguez, J., Freer, J., and Baeza, J. (2000). “Estimating chemical composition of biodegraded pine and eucalyptus by DRIFT spectroscopy and multivariate analysis,” Bioresource Technology 74, 201-212. DOI: 10.1016/S0960-8524(00)00024-9

Furniture Decoration (2013). “Furniture decoration,” (https://www.mobilyadergisi.com.tr/haber/ahsap-malzemenin-korunmasi-emprenye-ile-ilgili-sikca-sorulan-sorular), Accessed 03 Jan 2025. (In Turkish)

JIS K1571 (2010). “Wood preservatives — Performance requirements and their test methods for determining effectiveness standard by Japanese Industrial Standard,” Japanese Standards Association, Tokyo, Japan.

Johansson, D. (2005). Strength and Color Response of Solid Wood to Heat Treatment, Licentiate Thesis, Luleå University of Technology, Department of Skellefteå Campus, Sweden.

Kara, F., Ozbek, O., Ozbek, N. A., and Uygur, I. (2021). “Investigation of the effect of deep cryogenic process on residual stress and residual austenite,” Gazi Journal of Engineering Sciences 7(2), 143-151. DOI: 10.30855/gmbd.2021.02.07

Kara, F., Kücük, Y., Özbek, O., Ozbek, N. A., Gok, M. S., Altas, E., and Uygur, I. (2023). “Effect of cryogenic treatment on wear behavior of sleipner cold work tool steel,” Tribology International 180, article ID 108301.

Korkut, S., and Kocaefe, D. (2009). “Effect of heat treatment on wood properties,” Düzce Üniversitesi Ormancılık Dergisi 5(2), 11-34.

Mendonça, R., Guerra, A., and Ferraz, A. (2002). “Delignification of Pinus teada wood chips treated with Ceriporiopsis subvermispora for preparing high-yield kraft pulps,” Journal of Chemical Technology and Biotechnology 77, 411-418. DOI: 10.1002/jctb.569

Pamukçu, E. (2019). The Effect of Cryogenic Process on the Mechanical Properties of Scots Pine Wood, Master’s Thesis, Woodworking Industrial Engineering Department, Düzce University, Düzce, Turkey.

Ramage, M., Burridge, H., Busse-Wicher, M., Fereday, G., Reunolds, T., Shah, U. D., Wu, G., Yu, I., Fleming, P., Densley-Tingley, D., et al. (2017). “The wood from the trees: The use of timber in construction,” Renewable and Sustainable Energy Reviews 68(Part 1), 333-359. DOI: 10.1016/j.rser.2016.09.107

Reinprecht, L. (2016). Wood Deterioration, Protection and Maintenance, John Wiley & Sons, Ltd., Hoboken, NJ, USA, pp. 62-125. DOI: 10.1002/9781119106500.ch3

Savaş, A. F., Öktem, H., Öztürk, B., Uygur, İ., and Küçük, Ö. (2023). “Energy consumption. mechanical and metallographic properties of cryogenically treated tool steels,” Open Chemistry 21(1), article ID 20220322.

Suri, I. F., Purusatama, B. D., Kim, J. H., Hidaya, T. W., Hwang, W. J., Iswanto, A. H., Park, S. Y., Lee, S. H., and Kim N. H. (2023). “Durability of heat-treated Paulownia tomentosa and Pinus koraiensis woods in palm oil and air against brown- and white-rot fungi,” Scientific Reports 13, article ID 21929. DOI: 10.1038/s41598-023-48971-z

ThermoWood® Handbook (2003). ThermoWood® Handbook, (http://www.thermowood.fi), Accessed 28 Oct 2024.

TS 4176 (1984). “Taking sample trees and laboratory samples from homogeneous stands to determine the physical and mechanical properties of wood,” Turkish Standards Institute, Ankara, Turkey.

TS 2470 (1976). “Sampling methods and general properties for physical and mechanical tests on wood,” Turkish Standards Institute, Ankara, Turkey.

TS CEN/TS 15679 (2010). “Timber shaped by heat treatment – Terms and characteristics,” Turkish Standards Institute, Ankara, Turkey.

Uygur, I., Gerengi, H., Arslan, Y., and Kurtay, M. (2015). “The effects of cryogenic treatment on the corrosion of AISI D3 steel,” Materials Research 18(3), 569-574. DOI: 10.1590/1516-1439.349914

Yıldız, S., Yıldız, Ü. C., and Tomak, E. D. (2011). “The effects of natural weathering on the properties of heat treated alder wood,” in: International Research Group on Wood Preservation 41. IRG Annual Conference, Biarritz, France, pp. 48-53.

Article submitted: December 2, 2024; Peer review completed: February 1, 2025; Revised version received and accepted: February 4, 2025; Published: February 20, 2025.

DOI: 10.15376/biores.20.2.2827-2843