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Article

Research on the Prevention and Control of Korean Pine Wood Decay by Bacillus amyloliquefaciens AW3

by
Jing Sun
1,
Yanan Wang
2,
Dongpeng Zhao
3,
Hao Li
4,
Yuanchao Li
5,*,
Jingkui Li
4 and
Dawei Qi
4,*
1
College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin 150040, China
2
Key Laboratory of Bio-Based Material Science and Technology of Ministry of Education, Material Science and Engineering College, Northeast Forestry University, Harbin 150040, China
3
School of Physics, Harbin Institute of Technology, Harbin 150001, China
4
College of Science, Northeast Forestry University, Harbin 150040, China
5
College of Food Science and Engineering, Lingnan Normal University, Zhanjiang 524048, China
*
Authors to whom correspondence should be addressed.
Forests 2025, 16(6), 1030; https://doi.org/10.3390/f16061030
Submission received: 12 May 2025 / Revised: 7 June 2025 / Accepted: 16 June 2025 / Published: 19 June 2025
(This article belongs to the Section Wood Science and Forest Products)
Browse Figures
Versions Notes

Abstract

As one of the decay-resistant woods, Korean pine is widely used in the construction industry. However, even the most corrosion-resistant wood is still susceptible to decay under the right humidity and temperature conditions. In this study, Bacillus amyloliquefaciens (B. amyloliquefaciens) bacterial liquid and filter bacterial solution were prepared for the anti-corrosion treatment of Korean pine wood, aiming to improve its decay-resistant property. Through the plate confrontation test, it was discovered that B. amyloliquefaciens AW3 could significantly inhibit the growth of Fomitopsis pinicola (F. Pinicola). The results of mass loss rate, mechanical properties test, XRD, FTIR and SEM analysis showed that the preserved Korean pine wood had significant improvement in various properties compared with the decayed wood, which was manifested in the significant reduction of mass loss, improvement of mechanical properties, and increased wood cellulose diffraction peak intensity. There is no mycelium infection of F. pinicola in Korean pine wood, and the antiseptic liquid can penetrate into the wood evenly, which plays an effective antiseptic role. The B. amyloliquefaciens bacterial liquid exhibited superior preservative performance compared to the B. amyloliquefaciens filter bacterial solution. In conclusion, B. amyloliquefaciens, as an efficient and environmentally friendly biological preservative, holds broad application prospects in improving the anti-corrosion performance of Korean pine wood.

1. Introduction

Wood is a necessity in human life and production, and it is widely used in the construction industry, paper industry, furniture making, and other industries [1]. Under natural conditions, wood is susceptible to damage from animals, forest fires, as well as microbial infections and damage caused by environmental factors such as frost and sun burns all of which are important factors limiting the service life of wood [2,3]. Among the various factors, wood decay caused by decay fungi stands out as the primary reason affecting the service life of wood [4]. Wood decay fungi can be divided into three categories according to distinct types of decay, namely brown-rot fungi, white-rot fungi, and soft-rot fungi [5].
Korean pine (Pinus koraiensis Siebold and Zucc.), a precious coniferous species native to northeast China, boasts high-quality wood characterized by its delicate texture and straight grain, rendering it an ideal material for construction, bridge building, and furniture manufacturing [6]. Fomitopsis pinicola (F. Pinicola) is a common wood-decaying fungus that causes brown rot of coniferous and broad-leaved trees in forests, and its decaying power is so strong that it often causes widespread decay of precious Korean pine [7]. Decay reduces the material and even makes it lose its use value, which has caused great economic losses to the protection and utilization of Korean pine resources. Therefore, in order to improve the anti-corrosion performance of Korean pine, conducting anticorrosive treatment on Korean pine wood, can effectively delay its decay and extend its service life.
At present, chemical preservatives are mainly used to preserve wood, but the environmental pollution caused by chemical preservatives has become a serious obstacle to the development of wood preservation [8]. Biological preservative methods introduce antagonistic microorganisms (such as Bacillus) to form a protective film on the surface of wood and produce chemically stable metabolites that inhibit harmful bacteria, preventing the invasion, reproduction, and growth of wood-decaying fungi and other harmful bacteria, and improving the corrosion resistance of wood [9,10]. This method is a green environmental technology, environmentally friendly and non-toxic, which reduces the use of chemical agents. Bacillus is an ideal biocontrol bacterium with advantages such as a wide antibacterial spectrum, fast growth, strong stress resistance, and ease of use [11]. Currently, it has emerged as a relatively ideal biocontrol bacterium. The main way for Bacillus to inhibit pathogens is through antagonistic effects. Bacillus produces a variety of antagonistic substances, such as enzymes, bacteria, and lipopeptides, through metabolism, which directly or indirectly act on pathogenic bacteria to achieve the purpose of inhibiting the growth of pathogenic bacteria [12,13]. The main biocontrol mechanism of Bacillus is the induction of plant resistance through microorganisms to induce plants to play a systemic resistance, the establishment of a defense system against pathogenic bacteria through the enhancement of the plant’s defense enzyme activity to enhance the plant’s resistance to pathogenic microorganisms so as to play the role of biological control [14,15]. Currently, the use of Bacillus in wood preservation is relatively new. Huang et al. have shown that Bacillus velezensis NHW-B72 has the ability to inhibit the growth of wood decay fungi, which is mainly attributed to the antibiotics and antibacterial substances it produces [16]. Strain NHW-B72 as a biocontrol agent was able to inhibit the decay of poplar wood. SEM results showed that wood-destroying decay fungi mycelia were not observed inside the wood after 3 months of treatment with the sterile fermentation solution of strain NHW-B72. Caldeira et al. obtained that Bacillus amyloliquefaciens CCMI 1051 has inhibitory activity against both surface wood discoloration fungi and plant pathogenic fungi, and its antifungal potential is based on the antifungal activity of the metabolites it produces [17]. Devkota et al. [18] conducted a plate confrontation test with 27 strains of Bacillus velezensis and different genera of plant pathogens and found that Bacillus velezensis was effective against wood rust and rhizosphere diseases of pine trees. The results indicate that several strains of bacteria have a protective effect on wood and that all of them have potential as biocontrol agents for wood protection [18].
At present, there are no reports of preservation studies on Korean pine using B. amyloliquefaciens (B. amyloliquefaciens). In this paper, B. amyloliquefaciens bacterial liquid and filter bacterial solution were prepared, and the inhibitory effect of B. amyloliquefaciens on F. pinicola was studied by the plate confrontation method. The vacuum impregnation method was used for the preparation of Bacillus preservative impregnated wood to improve the anti-corrosion performance of Korean pine. The purpose of this study is to provide new ideas for the biological control strategy for wood preservation and to reduce the reliance on traditional chemical preservatives for wood.

2. Materials

Korean pine (Pinus koraiensis Siebold and Zucc.) samples were taken from Korean pine forests in the southeast of Xiaoxing’an Mountains, Heilongjiang Province, China (47°12′57″ N–128°52′17″ E). Korean pine specimens were equally taken from a uniform distribution of each tree cross-section, with healthy sapwood without knots, cracks, mold infection or other obvious defects as the raw material to be tested. The wood samples were cut into blocks with dimensions of 10 mm (L) × 20 mm (T) × 20 mm (R) for mass loss rate measurement, XRD, and FTIR analysis, and strips with dimensions of 80 mm (L) × 7 mm (T) × 7 mm (R) for mechanical property tests.
F. pinicola strain was identified from the fruiting bodies substrate of decayed Korean pine stumps cut in Xiaoxing’an Mountains and named NE1. B. amyloliquefaciens, named AW3, was isolated from the root of turnip (Brassica rapa L.), and the strain was deposited in the China General Microbial Strain Collection Center under the accession number CGMCC 1.16683. PDA medium and PD liquid medium were used.

3. Methods

3.1. Preparation of Bacillus Bacterial Liquid and Filter Bacterial Solution

The purified Bacillus was inoculated into LB medium at a 1% inoculation rate and incubated at 37 °C, with shaking at 220 r/min for 24 h. The bacterial solution was diluted to a concentration of about 1.2 × 108 CFU/mL, with the OD value ranging between 0.2 and 0.8. The fermentation broth was collected and transferred into a centrifuge, where it was centrifuged at 4 °C and 10,000 r/min for 10 min for the following use. The samples were placed in a vacuum impregnation tank for 1 h under the pressure of −0.09 MPa before the inhalation of Bacillus liquid. The introduction of the preservative was halted once the solution fully submerged the samples, which were then left to soak continuously for 24 h until they became saturated and sank. The impregnated specimens were subsequently removed to yield the impregnated wood.

3.2. Test Results of Plate Confrontation

After the colonies had grown all over the plate, the newborn area at the edge of the colony was taken with a hole punch to obtain a 5 mm diameter plug of F. pinicola, which was inverted and placed in the center of a new PDA medium, respectively. A cross was drawn with the F. pinicola in the center, and the antagonist strain B. amyloliquefaciens AW3 was inoculated at the four ends of the cross lines, 3.5 cm from the center. PDA medium without inoculation of Bacillus was used as a control until the F. pinicola in the center of the medium grew to the edge of the medium, and the radius of the circle of inhibition was counted and photographed. The antagonistic ability of B. amyloliquefaciens AW3 against F. pinicola NE1 was judged by the radius of the inhibition circle.

3.3. Wood Decay Test and Determination of Mass Loss Rate

Under sterile conditions, F. pinicola was inoculated on PDA medium (diameter 9 cm) and grown in a constant temperature incubator at 28 °C with 75% RH for 9 days until the medium was fully covered with F. pinicola mycelium [18]. A 9 mm diameter cake of F. pinicola was taken with a sterile hole punch and inoculated into the center of the PDA medium [19].
The experiment carried out a decay experiment in accordance with the Chinese National Standard GB/T 13942.1-2009 [20] and evaluated the natural decay resistance grade (Table 1). The Korean pine blocks decayed by F. pinicola for 30 days, 60 days, and 90 days were taken out from the PDA. The mycelium of F. pinicola and impurities growing on the surface of the blocks were scraped off. Then, the blocks were dried to a constant weight in an oven at 60 °C, weighed (accurate to 0.01 g), and the sample numbers and masses were recorded for subsequent use [21]. The mass loss rate of the specimens was calculated by Formula (1).
      W = m 1 − m 2 m 1 × 100 %  
where W stands for the mass loss rate, %; m1 is the constant weight mass of the sample before decay, g; and m2 is the constant weight mass of the decayed sample, g.

3.4. Material Characterization and Performance Testing

3.4.1. X-Ray Diffractometry (XRD)

The samples of decayed and anti-corrosion treatments were characterized by X-ray diffraction (XRD) on an XRD-6100 instrument (SHIMADZU Co., Ltd., Tokyo, Japan). The test was carried out under the conditions of radiation tube voltage of 40 kV, tube current of 30 mA, scanning range of 5° to 60°, sample holder inclination angle of 4°, step size of 0.02, and scanning speed of 4°/min [22].

3.4.2. FTIR Spectroscopy

Using the attenuated total reflection (ATR) method, the functional group changes in preservative-treated Korean pine wood were determined using a Nicolet iS10 Fourier-transform infrared (FTIR) spectrometer (Thermo Fisher Scientific Co., Ltd., Waltham, MA, USA). The spectral acquisition range was set to 500–4000 cm⁻1, with a resolution of 4 cm⁻¹ and 32 scans per measurement. Each treatment group was subjected to three repeated scans, with each sample being scanned at three different locations.

3.4.3. Mechanical Properties Testing

The mechanical properties of decayed and preservative-treated samples were evaluated using a CMT-6305 universal testing machine (SASCK Co., Ltd., Zhuhai, China). The parameters measured included compressive strength parallel to the grain, modulus of rupture (MOR), and modulus of elasticity (MOE). According to the Chinese Standard GB/T 1935-2009 [23], the mechanical properties of each group were averaged from five samples [24]. Prior to testing, wood block samples of dimensions 10 mm (L) × 20 mm (T) × 20 mm (R) were placed in a constant-temperature and humidity chamber (20 °C, 65% RH) to balance the moisture content to 12%. Compressive strength parallel to the grain was measured by applying a loading speed of 10 mm/min in the direction parallel to the wood grain. According to the Chinese Standard GB/T 1936.2-2009 [25], a three-point bending test was performed on wood strip samples measuring 80 mm (L) × 7 mm (T) × 7 mm (R). The span between the devices adjusted to 46 mm, and the loading rate was set at 5 mm/min.

3.4.4. Microscopic Morphological Characterization

The surface and internal morphology of the samples were observed using a Primo Star iLED SEM (ZEISS Co., Ltd., Oberkochen, Germany). The accelerating voltage was set to 5.0 kV, and the samples were measured after spraying Pt on the sample surface using an ion sputtering apparatus [26].

4. Results

4.1. Inhibitory Effect of B. amyloliquefaciens on F. pinicola

As shown in Figure 1a, the PDA plate was completely covered by F. pinicola, with the mycelium stretching until the edge of the plate. The mycelium is white and villous, while the back of the colony exhibits a yellowish hue. After the plate confrontation, Figure 1b shows the colony produced by B. amyloliquefaciens AW3 is at a certain distance from the mycelium edge of the colony produced by F. pinicola, and the boundary of the inhibition zone was obvious. The results showed that the fermentation broth of B. amyloliquefaciens AW3 had an antagonistic effect on F. pinicola NE1 and could effectively inhibit the growth of F. pinicola. Figure 2 and Figure 3 show the results of decay on Korean pine wood treated with B. amyloliquefaciens bacterial liquid and filtered bacterial solution, respectively, after 90 days of decay on PDA medium. These results suggest that both B. amyloliquefaciens bacterial liquid and filtered bacterial solution have anti-corrosion effects on Korean pine wood.

4.2. Results of Mass Loss Rate

The degree of wood decay was assessed based on the mass loss rate of decayed wood. Wood-decay fungi decay wood by destroying the wood cell wall, and the reproduction of mycelium in the cell cavity requires a process. Until the decay period of 90 days, the average mass loss rate of wood blocks is 22.31% [27]. Based on the mass loss rate results of 22.31% after 90 days of decay, which meets the criteria of “naturally decay-resistant” (≤30%) specified in GB/T 13942.1-2009, it can be concluded that Korean pine is a naturally decay-resistant wood. After preservative treatment with Bacillus bacterial liquid and filter bacterial solution followed by 90 days of decay testing, the average mass loss rates of the wood blocks were 4.45% and 5.46%, respectively. The average mass loss rate of the Korean pine samples after preservation treatments was less than 10%, indicating that they were classified as strongly decay resistant (Grade I). This indicates that the Bacillus bacterial liquid and Bacillus filter bacterial solution significantly improved the wood’s resistance to decay.

4.3. Structural Characterization Results

Figure 4 and Figure 5 represent the X-ray diffraction (XRD) results of Korean pine wood treated with the Bacillus bacterial liquid and Bacillus filter bacterial solution for preservation. Three relatively distinct wood cellulose (101), (002) and (040) diffraction peaks were observed at 2θ diffraction peaks 17°, 22° and 34°. The peak positions of cellulose did not show obvious change even after 90-day decay, and the shapes of the wood cellulose diffraction intensity graphs were basically the same. However, the intensity of cellulose diffraction peaks decreased significantly after decay, which indicated that the cellulose structure was degraded during the decay process. The brown rot fungi can secrete cellulase to make the cellulose in the wood be decomposed, destroying the structure of the cellulose crystalline zone in regular arrangement, the hydrogen bonds within or between the chains of cellulose molecules were broken, and part of the cellulose crystalline zone was transformed into an amorphous zone, which led to the decrease in the proportion of the crystalline zone [28]. Compared with the control group, the treatment with Bacillus bacterial liquid and Bacillus filter bacterial solution showed that the position of the wood cellulose 2θ diffraction peaks remained unchanged, while the intensity of the (002) diffraction peaks slightly decreased but remained evident. This indicates that the Bacillus treatment had minimal effect on the structure of cellulose, and the crystalline structure of the wood remained largely intact.

4.4. Infrared Spectroscopic Results

Infrared spectra acquired to evaluate preservation effectiveness are shown in Figure 6 and Figure 7. Infrared spectra of the samples were scanned in the FTIR infrared scanning in the band of 500–4000 cm−1. The absorption peak at 3340 cm⁻¹ corresponds to the stretching vibration of the hydroxyl group (O-H) involved in hydrogen bonding, which is a characteristic peak representing cellulose and hemicellulose. Compared to the control group, the intensity of the absorption peaks at this position was significantly reduced in the samples after 90 days of decay, indicating that the treatment with F. pinicola had a substantial effect on the degradation of cellulose and hemicellulose. The decline in the preservative-treated samples was relatively small, indicating that the treatment with Bacillus bacterial liquid and Bacillus filter bacterial solution effectively slowed down the degradation of cellulose and hemicellulose. The peak located at 1024 cm−1 is related to the C-O group stretching vibration in cellulose and hemicellulose, and the intensity of this peak decreased significantly after 90 days of decay, indicating the degradation of cellulose and hemicellulose. However, the preservative-treated samples with the Bacillus bacterial liquid and Bacillus filter bacterial solution maintained a higher intensity of the absorption peak, suggesting that Bacillus preservation treatment effectively delayed the degradation of the polysaccharide structure in the wood. The characteristic peak at 2900 cm⁻¹ is related to the symmetric and asymmetric stretching vibrations of methyl and methylene (C-H) groups. After 90 days of decay, it can be seen clearly that the intensity of the absorption peak in the samples decreased compared to that of the control group, indicating that the structure of cellulose and lignin’s aliphatic components in the wood was damaged. The intensity of the absorption peak in the preservative-treated samples showed little change compared with the control group, suggesting that Bacillus treatment provides a certain degree of protection to the aliphatic structure in the wood. 1624 cm−¹ originated from the skeleton stretching vibration of the aromatic structure of lignin, and the absorption intensity of this peak did not change significantly after decay and generally maintained a certain degree of stability, with a weak degradation ability for lignin. F. pinicola is a brown rot fungus, and the above results demonstrate that its degradation of cellulose and hemicellulose is particularly pronounced. Brown rot fungi primarily degrade polysaccharides in wood, while lignin remains largely undegraded, which aligns with the degradation mechanism of brown rot fungi [29]. The treatment with Bacillus bacterial liquid and Bacillus filter bacterial solution significantly delayed the degradation of cellulose and hemicellulose, slowed down the oxidation of lignin, and reduced the formation of oxidation products.

4.5. Mechanical Property Testing Results

Wood decay severely impacts the mechanical properties of wood materials. The results of the compressive strength parallel to the grain (CS), modulus of rupture (MOR), and modulus of elasticity (MOE) of Korean pine wood that has been treated with Bacillus bacterial liquid and Bacillus filter bacterial solution are shown in Figure 8. Compared to the control group, the compressive strength parallel to the grain of the samples treated with F. pinicola for 90 days decreased by 79.13%. The compressive strength parallel to the grain of the samples treated with the Bacillus bacterial liquid and Bacillus filter bacterial solution at 0 days increased by 9.88% and decreased by 2.18%, respectively, compared to the control group. The compressive strength parallel to the grain of the preserved 90-day samples decreased compared to the preserved 0-day samples; however, it remained significantly higher than the value of the compressive strength parallel to the grain of the decayed 90-day samples. The MOR was reduced by 77.81%, and the MOE was reduced by 78.51% for 90 days of Korean pine decayed by F. pinicola compared to the control group. The MOR and MOE of the 90-day preservation sample have decreased compared to the untreated control (0 days) but are still much higher than the 90-day samples. The reduction in mechanical properties in decayed wood primarily results from the degradation of cellulose and hemicellulose, which weakens the wood’s strength and toughness. In the short term, Bacillus bacterial liquid may enhance the wood’s compactness by filling micropores or altering the wood’s surface properties. However, over time, the activity of the Bacillus bacterial liquid and the concentration of its antimicrobial metabolites decrease, resulting in a slight decline in the preservation effect. The Bacillus filter bacterial solution delayed wood degradation to some extent but exhibited less effective preservation compared to the direct Bacillus bacterial liquid treatment. Nevertheless, the filtered spore suspension still effectively slowed down the deterioration of mechanical properties and showed potential for preservation.

4.6. SEM Results

Figure 9 and Figure 10 show the results of SEM for Korean pine preservation treatment with the Bacillus bacterial liquid and Bacillus filter bacterial solution. In Figure 9a and Figure 10a, the natural Korean pine wood shows orderly alignment of longitudinal vessels, with intact vessel walls, smooth surfaces, and dense structure, with no visible fungal hyphae growth. Figure 9b and Figure 10b show the SEM pictures of longitudinal and transverse sections of 90d images of F. pinicola decaying Korean pine wood. On the surface of the sample, a layer of F. pinicola mycelium grew, and the internal tubular cells of the wood were irregularly arranged. Some of the tubular cell walls had collapsed and fractured, and filamentous structures were observed inside the specimen, indicating that the F. pinicola mycelium had already invaded the interior of the wood. The area marked by the yellow circle in Figure 9b shows that the mycelium of F. pinicola near the pit decays and there are large holes, and the mycelium spreads to adjacent cell cavities through the pit and spreads among cells. Figure 9c and Figure 10c are SEM images of longitudinal and transverse sections of samples preserved by Bacillus bacterial liquid for 90 days. The tracheid arrangement is relatively regular, and there are no obvious hyphae or other degradation characteristics. In Figure 9d and Figure 10d, show SEM images of longitudinal and transverse sections of the Bacillus filter bacterial solution samples preserved for 90 days. In Figure 10c,d, the Bacillus filter bacterial solution-treated samples show intact transverse cross-sections, with slight degradation visible in localized areas near the pits. The tracheid cross-section remained intact, and no obvious mycelium growth was observed. Compared with Figure 9d, the local area of pits showed slight degradation signs. Some fine deposits were present in the yellow circled areas in Figure 10c,d as particles or metabolites of the Bacillus bacterial liquid and Bacillus filter bacterial solution penetrating the wood surface. In summary, the wood structure of Korean pine was severely decayed and damaged after 90 days of decaying by the F. pinicola. After the antiseptic treatment of Bacillus bacterial liquid and Bacillus filter bacterial solution, the growth of mycelium of F. pinicola could be effectively inhibited, the decay process was significantly slowed down. Compared with the antiseptic treatment of Bacillus bacterial liquid, the antiseptic effect of Bacillus filter bacterial solution was slightly lower.

5. Discussion

Bacillus is an ideal biocontrol bacterium. In this study, the prepared Bacillus bacterial liquid and Bacillus filter bacterial solution were utilized for the first time for the preservation of Korean pine wood. The results demonstrated that both methods effectively inhibited the decay of Korean pine wood and enhanced its resistance to wood-decay fungi. Notably, the preservative effect of the Bacillus bacterial liquid was superior to that of the Bacillus filter bacterial solution.
The results of the plate confrontation experiment indicated that the B. amyloliquefaciens AW3 had a significant inhibitory effect on F. pinicola, as evidenced by the slow growth of F. pinicola mycelium and the formation of inhibition zones. This phenomenon suggests that Bacillus can effectively inhibit the growth of F. pinicola, which may arise from producing antimicrobial substances, which aligns with the findings of To et al. and Manowan et al. [30,31]. After 90 days of decay by F. pinicola, the mass loss rate of the Korean pine wood significantly increased. The decay severely affected the mechanical properties of the wood, reducing its mechanical performance and causing significant changes in the chemical composition of the wood. The decay damaged the microstructure of the wood, particularly cellulose, which is consistent with the previous reports [32,33]. The reason for this result is that the brown rot of wood is a complex process, during which the main components of wood, such as cellulose and hemicellulose are degraded, resulting in a reduction in wood mass. In addition, decay fungi mainly enter the interior of the wood through the ray parenchyma and cell wall pits of the wood [34]. These channels allow the decay fungi to spread along the longitudinal direction of the wood, causing damage to the microstructure of the wood and a sharp decline in its mechanical properties [35]. During the decay process, the intensity of cellulose diffraction peaks in the wood significantly decreased, indicating that the crystalline cellulose was damaged during the decay process, and the originally ordered molecular chains were disrupted, reducing the intermolecular forces and increasing the intermolecular gaps. These changes affect the physical and mechanical properties of the wood, thereby affecting its service life and performance.
Based on mass loss rate analysis, plate confrontation experiments, XRD, SEM, mechanical tests, and FTIR spectroscopy, Bacillus bacterial liquid and Bacillus filter bacterial solution demonstrate significant advantages in wood preservation. Both methods synergistically prevent wood decay by antagonizing decay fungi, secreting degrading enzymes, forming biofilms, and enhancing decay resistance through extracellular metabolites. The preservative effect of Bacillus filter bacterial solution was slightly lower compared to that of Bacillus bacterial liquid preservative treatment. The Bacillus bacterial liquid contains Bacillus organisms and metabolites, and the organisms themselves are biologically active and can colonize the wood surface and secrete antimicrobial substances, which can form a protective layer on the surface of wood and further resist the erosion of external wood decay fungi [36]. However, relying only on metabolites, lacking the protective function of the bacteria itself, once the metabolites are depleted, the antifungal effect may be weakened. For long-term preservation, the Bacillus bacterial liquid is preferred. Both treatments, derived from natural bioactive compounds, are eco-friendly and offer a promising alternative to traditional chemical preservatives, with significant commercial potential.

6. Conclusions

To reduce environmental pollution and achieve long-term and effective prevention and control of Korean pine wood decay, this study systematically explored the application effect of B. amyloliquefaciens AW3 as a biological preservative in wood prevention. The plate confrontation experiments demonstrated that it effectively inhibited the growth of Fomitopsis pinicola and exhibited good antibacterial activity. The results of mechanical property tests, XRD, FTIR, and SEM all indicated that the Korean pine wood treated with Bacillus bacterial liquid and Bacillus filter bacterial solution showed significant improvements in various properties. Specifically, the average mass loss rate of the treated Korean pine wood was significantly reduced, mechanical strength was enhanced, the relative crystallinity of cellulose was increased, and the microscopic structure of the wood remained relatively intact without infestation of F. pinicola mycelium. In addition, the preservative effect of Bacillus bacterial liquid was superior to that of Bacillus filter bacterial solution, although both treatment methods could effectively inhibit wood decay. The research results indicate that B. amyloliquefaciens AW3, as an efficient and environmentally friendly biological preservative, has broad application prospects in the field of wood preservation.

Author Contributions

Conceptualization, J.S.; funding acquisition, Y.L. and D.Q.; methodology, Y.W. and D.Z.; project administration, Y.L. and D.Q.; supervision, Y.L. and D.Q.; visualization, J.S.; writing—original draft, J.S.; writing—review and editing, J.S., Y.W., D.Z., H.L., Y.L., J.L., and D.Q. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Fundamental Research Funds for the Central Universities (No. 2572018AB22) and the National Natural Science Foundation of China (No. 31570712).

Data Availability Statement

Data is contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Antagonistic Effect of B. amyloliquefaciens against F. pinicola. (a) F. pinicola was cultured on PDA; (b) B. amyloliquefaciens inhibits F. pinicola.
Figure 1. Antagonistic Effect of B. amyloliquefaciens against F. pinicola. (a) F. pinicola was cultured on PDA; (b) B. amyloliquefaciens inhibits F. pinicola.
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Forests 16 01030 g002
Figure 2. 90-day effect of B. amyloliquefaciens bacterial liquid on Korean pine wood preservation. (a) wood strip preservation group; (b) wood block anticorrosion group; (c) enlarged picture of the surface of anticorrosive wood block.
Figure 2. 90-day effect of B. amyloliquefaciens bacterial liquid on Korean pine wood preservation. (a) wood strip preservation group; (b) wood block anticorrosion group; (c) enlarged picture of the surface of anticorrosive wood block.
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Forests 16 01030 g003
Figure 3. 90-day effect of B. amyloliquefaciens filter bacterial solution on Korean pine wood preservation. (a) wood strip preservation group; (b) wood block anticorrosion group; (c) enlarged picture of the surface of anticorrosive wood block.
Figure 3. 90-day effect of B. amyloliquefaciens filter bacterial solution on Korean pine wood preservation. (a) wood strip preservation group; (b) wood block anticorrosion group; (c) enlarged picture of the surface of anticorrosive wood block.
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Forests 16 01030 g004
Figure 4. XRD of preservative treatment of B. amyloliquefaciens AW3 bacterial liquid. CK: control group (untreated group); BA−BL−0D: preservative treatment for 0 days; BA−BL−90D: preservative treatment for 90 days; D90: decayed 90 days.
Figure 4. XRD of preservative treatment of B. amyloliquefaciens AW3 bacterial liquid. CK: control group (untreated group); BA−BL−0D: preservative treatment for 0 days; BA−BL−90D: preservative treatment for 90 days; D90: decayed 90 days.
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Forests 16 01030 g005
Figure 5. XRD of preservative treatment of B. amyloliquefaciens AW3 filtered bacterial solution. CK: control group (untreated group); BA−FBS−0D: preservative treatment for 0 days; BA−FBS−90D: preservative treatment for 90 days; D90: decayed 90 days.
Figure 5. XRD of preservative treatment of B. amyloliquefaciens AW3 filtered bacterial solution. CK: control group (untreated group); BA−FBS−0D: preservative treatment for 0 days; BA−FBS−90D: preservative treatment for 90 days; D90: decayed 90 days.
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Forests 16 01030 g006
Figure 6. FTIR results of preservative treatment of B. amyloliquefaciens AW3 bacterial liquid. CK: control group (original sample); BA−BL−0D: B. amyloliquefaciens bacterial liquid preservative treatment for 0 days; BA−BL−90D: B. amyloliquefaciens bacterial liquid preservative treatment for 90 days; D90: decayed 90 days.
Figure 6. FTIR results of preservative treatment of B. amyloliquefaciens AW3 bacterial liquid. CK: control group (original sample); BA−BL−0D: B. amyloliquefaciens bacterial liquid preservative treatment for 0 days; BA−BL−90D: B. amyloliquefaciens bacterial liquid preservative treatment for 90 days; D90: decayed 90 days.
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Forests 16 01030 g007
Figure 7. FTIR results of preservative treatment of B. amyloliquefaciens AW3 filter bacterial solution. CK: control group (original sample); BA−FBS−0D: B. amyloliquefaciens filtered bacterial solution preservative treatment for 0 days; BA−FBS−90D: B. amyloliquefaciens filtered bacterial solution preservative treatment for 90 days; D90: decayed 90 days.
Figure 7. FTIR results of preservative treatment of B. amyloliquefaciens AW3 filter bacterial solution. CK: control group (original sample); BA−FBS−0D: B. amyloliquefaciens filtered bacterial solution preservative treatment for 0 days; BA−FBS−90D: B. amyloliquefaciens filtered bacterial solution preservative treatment for 90 days; D90: decayed 90 days.
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Forests 16 01030 g008
Figure 8. Mechanical performance test results. (a) CS of the samples treated with Bacillus bacterial liquid; (b) CS of the samples treated with Bacillus filter bacterial solution; (c) MOR of the samples treated with Bacillus bacterial liquid; (d) MOR of the samples treated with Bacillus filter bacterial solution; (e) MOE of the samples treated with Bacillus bacterial liquid; (f) MOE of the samples treated with Bacillus filter bacterial solution.
Figure 8. Mechanical performance test results. (a) CS of the samples treated with Bacillus bacterial liquid; (b) CS of the samples treated with Bacillus filter bacterial solution; (c) MOR of the samples treated with Bacillus bacterial liquid; (d) MOR of the samples treated with Bacillus filter bacterial solution; (e) MOE of the samples treated with Bacillus bacterial liquid; (f) MOE of the samples treated with Bacillus filter bacterial solution.
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Forests 16 01030 g009
Figure 9. Longitudinal SEM images of the sample under different magnifications: (a) original sample; (b) decayed 90−day sample; (c) 90−day samples were preserved by Bacillus bacterial liquid; (d) 90-day samples were preserved by Bacillus filter bacterial solution.
Figure 9. Longitudinal SEM images of the sample under different magnifications: (a) original sample; (b) decayed 90−day sample; (c) 90−day samples were preserved by Bacillus bacterial liquid; (d) 90-day samples were preserved by Bacillus filter bacterial solution.
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Forests 16 01030 g010
Figure 10. Transverse section SEM images of the sample under different magnifications: (a) Original sample; (b) decayed 90−day sample; (c) 90−day samples were preserved by Bacillus bacterial liquid; (d) 90−day samples were preserved by Bacillus filter bacterial solution.
Figure 10. Transverse section SEM images of the sample under different magnifications: (a) Original sample; (b) decayed 90−day sample; (c) 90−day samples were preserved by Bacillus bacterial liquid; (d) 90−day samples were preserved by Bacillus filter bacterial solution.
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Table 1. Corrosion resistance grade of natural wood.
Table 1. Corrosion resistance grade of natural wood.
GradeMass Loss Rate (%)
Strong decay resistance (Ⅰ)0–10
Decay resistant (Ⅱ)11–24
Slightly decay resistant (Ⅲ)25–44
Not resistant to decay (Ⅳ)>45
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MDPI and ACS Style

Sun, J.; Wang, Y.; Zhao, D.; Li, H.; Li, Y.; Li, J.; Qi, D. Research on the Prevention and Control of Korean Pine Wood Decay by Bacillus amyloliquefaciens AW3. Forests 2025, 16, 1030. https://doi.org/10.3390/f16061030

AMA Style

Sun J, Wang Y, Zhao D, Li H, Li Y, Li J, Qi D. Research on the Prevention and Control of Korean Pine Wood Decay by Bacillus amyloliquefaciens AW3. Forests. 2025; 16(6):1030. https://doi.org/10.3390/f16061030

Chicago/Turabian Style

Sun, Jing, Yanan Wang, Dongpeng Zhao, Hao Li, Yuanchao Li, Jingkui Li, and Dawei Qi. 2025. "Research on the Prevention and Control of Korean Pine Wood Decay by Bacillus amyloliquefaciens AW3" Forests 16, no. 6: 1030. https://doi.org/10.3390/f16061030

APA Style

Sun, J., Wang, Y., Zhao, D., Li, H., Li, Y., Li, J., & Qi, D. (2025). Research on the Prevention and Control of Korean Pine Wood Decay by Bacillus amyloliquefaciens AW3. Forests, 16(6), 1030. https://doi.org/10.3390/f16061030

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