Edible mushroom culture medium based on acid-modified biochar and preparation method of edible mushroom culture medium

Abstract

The invention relates to the technical field of edible mushroom cultivation, in particular to an edible mushroom cultivation medium based on acid modified charcoal and a preparation method of the edible mushroom cultivation medium. The method comprises the following steps: modifying mushroom dreg (SMS) biochar through phosphoric acid, remarkably optimizing the physicochemical properties of the mushroom dreg biochar, and mixing the mushroom dreg biochar with cottonseed hulls, wheat bran and the like to prepare the culture medium. The application can increase the specific surface area and micropore volume of the matrix, enhance hydrophilicity and adsorption capacity, improve the growth environment of oyster mushrooms, accelerate the growth rate of hyphae, increase the yield by 13%-16%, shorten the harvesting time by 2.5 days, ensure that the contents of heavy metals and metabolites meet the food safety standard, and improve the yield of the oyster mushrooms. And support is provided for mushroom residue resource utilization and oyster mushroom cultivation technology optimization.

Description

Technical Field

[0001] The present invention belongs to the field of agricultural waste resource utilization and edible fungus cultivation technology, specifically an edible fungus cultivation matrix based on acid-modified biochar and its preparation method Background Art

[0002] Optimizing and improving edible fungus cultivation substrates is crucial for improving mushroom yield, quality, and resource utilization efficiency. In recent years, with the widespread application of biochar in agriculture, its potential application in edible fungus cultivation substrates has gradually attracted attention. However, existing research on biochar in edible fungus cultivation substrates remains inadequate, particularly regarding biochar modification and its impact on substrate properties.

[0003] After searching, a renewable cultivation matrix, preparation method and application of edible fungi were disclosed with the publication number CN113597974B, and the publication date is August 26, 2022. This patent provides a renewable cultivation matrix comprising cottonseed hulls, sawdust, wheat bran and biochar, and realizes resource utilization by preparing biochar through waste mushroom bags. At the same time, it improves the physical and chemical properties of the matrix, increases the yield of edible fungi and shortens the cultivation cycle. However, the biochar used in this technical solution has not been modified, and its specific surface area is limited, the pore structure is not optimized enough, and the activity of the surface functional groups is insufficient, which may lead to the water retention, nutrient release capacity and mycelium colonization effect of the matrix failing to reach the optimal state. In addition, the pH value of unmodified biochar may not be suitable for the growth requirements of certain edible fungi varieties, limiting its scope of application.

[0004] A search revealed a grass-rot-type edible fungus cultivation substrate and its preparation method, with publication number CN103641639B, published on February 25, 2015. This patent provides a grass-rot-type edible fungus cultivation substrate using primary fungus husks, xylitol residue, wheat bran, and the like as primary raw materials, and promotes mycelial growth and reduces the contamination rate of foreign bacteria by adjusting the pH value and moisture content. However, this technical solution does not involve the use of biochar, and the physicochemical properties of the substrate (such as water retention, air permeability, and nutrient release capacity) still have room for improvement. In addition, the raw material composition of the substrate is relatively traditional and lacks innovation, making it difficult to meet the demand for efficient and environmentally friendly substrates in modern edible fungus cultivation.

[0005] The above issues indicate that existing edible fungus cultivation substrates still have certain deficiencies in terms of biochar modification, optimization of physical and chemical properties, and resource utilization. Therefore, the present invention provides an edible fungus cultivation substrate based on acid-modified biochar. This aims to significantly increase the specific surface area, pore structure, and surface functional group activity of the biochar through acid modification, thereby optimizing the substrate's water retention, air permeability, and nutrient release capacity, further improving the yield, quality, and cultivation efficiency of edible fungi, while also achieving efficient resource utilization of spent fungus bags. Summary of the Invention

[0006] This invention addresses the existing issues of direct disposal of mushroom residue (SMS), which can cause environmental pollution and has limited applicability as a biochar raw material. By developing a new edible mushroom cultivation substrate based on acid-modified biochar and its preparation method, this technology significantly optimizes the physical and chemical properties of SMS biochar through phosphoric acid modification. This technology can be applied to oyster mushroom cultivation, resolving the technical challenge of resourceful SMS utilization.

[0007] The present invention provides an edible fungus cultivation substrate based on acid-modified biochar, wherein the substrate comprises acid-modified mushroom residue biochar (AMMS). The acid-modified mushroom residue biochar is prepared by the following steps: first, drying the SMS to a moisture content of less than 5%, and then grinding it to a particle size of less than 1 mm; second, pyrolyzing the SMS in a quartz tube furnace under anaerobic conditions, with the pyrolysis temperature set at 500°C and a heating rate of 25°C / min. -1 The reaction pressure was maintained at 50-60 kPa for 3 hours. After the obtained biochar was cooled to room temperature, it was mixed with a 3.0 mol·L-1 H3PO4 solution at a mass volume ratio of 1:15, stirred for 1 hour and shaken for 12 hours. Finally, the modified biochar was washed to neutrality and dried to obtain acid-modified fungus residue biochar (AMMS).

[0008] Furthermore, the edible fungus cultivation matrix of the present invention is prepared by mixing acid-modified biochar with cultivation materials. The acid-modified biochar is added at a ratio of 5wt%, 10wt%, or 15wt%, and the cultivation materials include cottonseed hulls, wheat bran, and other conventional auxiliary materials. The matrix is ​​adjusted to a moisture content of 60%, placed in a polyethylene plastic bag measuring 18 x 45 cm, and sterilized at 105°C for 10 hours before being inoculated with Pleurotus ostreatus spawn.

[0009] In particular, the present invention significantly improves the physicochemical properties of SMS biochar by acid modification. The specific surface area and micropore volume of the acid-modified biochar are significantly increased compared to the unmodified biochar, wherein the specific surface area is increased by about 33 times, and the micropore volume is increased by more than 20%. The acid modification process introduces more hydroxyl (-OH), carbonyl (C=O) and carboxyl (-COOH), thereby enhancing the hydrophilicity and adsorption capacity of the biochar surface. Specifically, the acid modification increases the -OH stretching vibration absorption peak intensity of the biochar surface at 3400 cm -1 At 1600cm -1 More carbonyl functional groups are introduced. The presence of these functional groups provides active sites for nutrient ions and promotes the 2+ 、Mo 4+ , Ca 2+ , K + Mg 2+ Adsorption and sustained release of plasma.

[0010] Furthermore, the application of the acid-modified biochar of the present invention in edible fungus cultivation shows significant advantages. The matrix exhibits more stable moisture and pH values ​​during the cultivation process of oyster mushrooms, and its electrical conductivity is about 30% higher than that of the unmodified biochar treatment group. In terms of mycelium growth, the mycelium growth rate of the AMMS treatment group is significantly accelerated, and the mycelium bags can be fully grown 12-13 days after inoculation, which is about 4 days earlier than the unmodified biochar treatment group. In addition, the oyster mushroom yield of the AMMS treatment group is 13%-16% higher than that of the unmodified biochar treatment group, and the first harvest time is 2.5 days earlier.

[0011] The present invention removes ash and impurities from the pores of SMS biochar through acid modification, further exposing the pore structure and increasing the specific surface area. The acid modification process rearranges the oxygen-containing functional groups on the biochar surface, forming a stable carbon skeleton and thereby increasing the fixed carbon content. Simultaneously, acid modification introduces more polar groups, enhancing the biochar's adsorption capacity for nutrient ions. For example, the oxygen atoms in the carbonyl groups can form hydrogen bonds or electrostatic interactions with molecules containing lone pairs of electrons, thereby improving adsorption performance.

[0012] Furthermore, the present invention conducted safety validation on mushroom samples treated with AMMS. Nuclear magnetic resonance (NMR) analysis and atomic absorption spectroscopy revealed that the levels of heavy metal pollutants and metabolites in all treatment groups met national safety standards. This safety validation ensures the reliability of AMMS in practical applications and mitigates potential food safety risks.

[0013] The beneficial effect of the present invention is that the performance of SMS biochar is significantly improved through acid modification, making it more suitable for edible fungus cultivation. The acid-modified biochar not only solves the environmental problems of SMS waste, but also promotes the growth of oyster mushrooms by improving the physical and chemical properties of the matrix. Specifically, the oyster mushroom yield of the AMMS treatment group increased by 13%-16% compared with the unmodified biochar treatment group, and the economic benefit increased by about 12%. In addition, the matrix has a higher specific surface area and pore volume, which provides more attachment points for the mycelium, while enhancing the water retention and air permeability of the matrix. In summary, the present invention provides an effective strategy for the resource utilization of SMS and provides technical support for optimizing oyster mushroom cultivation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the structure of acid-modified biochar;

[0015] Figure 2 Comparison of FTIR spectra of original biochar (BC) and phosphoric acid modified biochar (PBC);

[0016] Figure 3 This is an analysis diagram of the effects of different treatments on the pore structure of biochar;

[0017] Figure 4 This is a comparison chart of mycelium growth rate and oyster mushroom yield;

[0018] Figure 5 This is a comparison of the growth of Pleurotus ostreatus under BMS and AMMS treatments;

[0019] Figure 6 This is a graph showing the effects of different treatments on the levels of heavy metal pollutants in mushrooms;

[0020] Figure 7 NMR spectra analysis of the effects of different treatments on mushroom metabolites;

[0021] The reference numerals are as follows:

[0022] BC: original biochar; PBC: phosphoric acid modified biochar; AMMS: acid modified residue biochar; BMS: mushroom matrix biochar; CK: control group without biochar; PB1, PB2, PB3: treatment groups with 5wt%, 10wt%, and 15wt% phosphoric acid modified biochar added, respectively; B1, B2, B3: treatment groups with 5wt%, 10wt%, and 15wt% original biochar added, respectively. DETAILED DESCRIPTION

[0023] The present invention provides an edible fungus cultivation substrate based on acid-modified biochar and its preparation method. Through specific implementation steps and experimental data analysis, its practical application effect in the cultivation of oyster mushrooms has been verified. The following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings.

[0024] The preparation process of acid-modified biochar is one of the core technical links of the present invention. First, the SMS is dried to a moisture content of less than 5%, and then dried in an 85°C oven for 6 hours to ensure complete dehydration. It is then crushed using a grinder and passed through a 1 mm sieve to obtain a raw material with uniform particle size. This processing step ensures the uniformity of the reaction during the subsequent pyrolysis process. Next, the dried SMS is placed in a quartz crucible and placed in a quartz tube furnace for oxygen-free pyrolysis. The pyrolysis conditions are set to a temperature of 500°C and a heating rate of 25°C·min -1 , reaction pressure 50-60kPa, duration 3 hours. After pyrolysis is completed, the obtained biochar is cooled to room temperature for use. Figure 3 As shown in the figure, by regulating the pyrolysis parameters, the pore structure of biochar was initially optimized, significantly increasing its specific surface area and fixed carbon content. To further enhance the performance of biochar, the cooled biochar was mixed with a 3.0 mol·L-1 H3PO4 solution at a mass volume ratio of 1:15, stirred on a magnetic stirrer for 1 hour, and then shaken for 12 hours. This step removed ash and impurities from the surface and pores of the biochar through acid modification, while introducing more oxygen-containing functional groups, such as hydroxyl, carbonyl, and carboxyl groups. The structural changes can be seen in Figure 1 The acid-modified biochar was washed repeatedly with deionized water until neutral, and finally dried at 105 °C for 12 h to obtain acid-modified bacterial residue biochar (AMMS). Figure 2 The FTIR spectra of original biochar (BC) and phosphoric acid modified biochar (PBC) are compared, indicating that acid modification significantly enhances the -OH stretching vibration absorption peak intensity and increases the absorption peak at 1600 cm -1 More carbonyl functional groups are introduced, and the presence of these functional groups provides active sites for nutrient ions, thereby improving the adsorption performance.

[0025] Another important component of the present invention is the preparation method for the edible fungus cultivation substrate. Acid-modified biochar is mixed at a ratio of 5wt%, 10wt%, or 15wt% with cultivation materials, including cottonseed hulls, wheat bran, and other conventional supplementary materials. During the mixing process, the substrate's moisture content must be strictly controlled, adjusting to 60% to meet the optimal growth requirements for oyster mushrooms. After uniform mixing, the substrate is placed into polyethylene plastic bags measuring 18 x 45cm, with each bag containing approximately 1.3kg of substrate. The bags are then sterilized in an autoclave at 105°C for 10 hours to thoroughly kill any bacteria and pathogens. After sterilization, the bags are cooled to room temperature and inoculated with oyster mushroom spawn at an inoculum rate of 10g per bag. The inoculated bags are placed in a mushroom house equipped with an intelligent monitoring system, with environmental conditions set to 22-25°C, 85%-90% humidity, 500 lux of light, and a carbon dioxide concentration below 0.1%. Each treatment group was replicated three times, each replicate contained 30 fungus bags, and a total of 270 fungus bags were used in the experiment.

[0026] Acid-modified biochar showed significant advantages in the cultivation of Pleurotus ostreatus. Figure 4 The results show a comparison of mycelial growth rates and oyster mushroom yields across different treatment groups. The AMMS treatment, supplemented with acid-modified biochar, demonstrated a significant advantage in mycelial growth, reaching full mycelial bags 12-13 days after inoculation, approximately four days earlier than the unmodified biochar treatment. This phenomenon is attributed to the high surface area and rich microporous structure of the acid-modified biochar, which provides more attachment points for mycelium while enhancing the substrate's water retention and aeration properties. Furthermore, the polar groups introduced during the acid modification process effectively promote the adsorption and slow release of nutrient ions, creating a more favorable environment for mycelial growth. In terms of yield, the PB1 and PB2 treatment groups showed 13%-16% higher oyster mushroom yields than the B1 and B2 treatments, respectively, and the first harvest was achieved 2.5 days earlier. This demonstrates that acid-modified biochar not only accelerates mycelial growth but also significantly improves the yield and quality of oyster mushrooms.

[0027] To further verify the effect of acid-modified biochar on the physicochemical properties of the substrate, the present invention systematically analyzed the substrate characteristics of different treatment groups. Figure 3 The effects of different treatments on the pore structure of biochar were demonstrated. The micropore volume and BET surface area of ​​the AMMS-treated group were significantly higher than those of the BMS-treated group. For example, the surface areas of the B3 and PB3-treated groups were 29 and 33 times those of the CK, respectively, fully demonstrating the optimization effect of acid modification on the pore structure of the biochar. Furthermore, changes in the substrate's moisture content and pH were monitored in real time during the experiment. Figure 5The results show a comparison of the growth of oyster mushrooms under BMS and AMMS treatments. The substrate with acid-modified biochar maintained stable moisture and pH values ​​throughout the two harvests, while the moisture content of the CK group dropped sharply from 70% at the first harvest to around 50% at the second harvest. This result indicates that acid-modified biochar significantly improved the water-holding capacity of the substrate, avoiding the adverse effects of moisture fluctuations on mycelial growth. Furthermore, the electrical conductivity of the AMMS-treated group increased by approximately 30% compared to the BMS-treated group, indicating that acid-modified biochar enhanced the availability of total water-soluble nutrients in the substrate, providing sufficient nutrient support for the rapid growth of oyster mushrooms.

[0028] Safety is one of the important considerations of the present invention. In order to evaluate the reliability of acid-modified biochar in practical applications, the present invention tested mushroom samples from different treatment groups for heavy metal contaminants and metabolites. Figure 6 The effects of different treatments on the levels of heavy metal pollutants in mushrooms were demonstrated, and the results showed that the levels of mercury, arsenic, lead, cadmium and tin were all within the national safety standards. Figure 7 NMR spectroscopic analysis of the effects of different treatments on mushroom metabolites revealed a high degree of similarity between the metabolomes of each treatment group and that of CK, indicating that the addition of acid-modified biochar did not significantly interfere with the metabolic processes of the mushrooms. These experimental results demonstrate that AMMS not only increases the yield of oyster mushrooms but also effectively ensures their safety, avoiding potential food safety risks.

[0029] Economic benefit is an important indicator for evaluating the practical application value of the present invention. Through input-output analysis, it was found that the total benefit of the AMMS treatment group was about 12% higher than that of the BMS treatment group. This was mainly attributed to the fact that the acid-modified biochar significantly improved the yield and quality of the oyster mushrooms, while shortening the cultivation cycle. For example, the yield of the oyster mushrooms in the PB1 and PB2 treatment groups was 13%-16% higher than that in the B1 and B2 treatment groups, respectively, and the first harvest time was advanced by 2.5 days, which directly reduced production costs and improved market competitiveness. In addition, the preparation process of the acid-modified biochar is simple and low-cost, and is suitable for large-scale promotion and application in the edible fungus industry. Overall, the present invention not only realizes the efficient resource utilization of SMS waste, but also provides a scientific basis and technical support for optimizing the oyster mushroom cultivation technology.

[0030] In summary, the present invention significantly improves the performance of SMS biochar through acid modification, making it more suitable for edible fungus cultivation. The acid modification process optimizes the pore structure and surface functional groups of the biochar, significantly increases its specific surface area, micropore volume and adsorption capacity, provides more attachment points for the mycelium, and enhances the water retention and air permeability of the matrix. In actual applications, the yield of oyster mushrooms in the AMMS treatment group increased by 13%-16% compared with the unmodified biochar treatment group, and the economic benefits increased by about 12%. The content of heavy metal pollutants and metabolites in all treatment groups met national safety standards, ensuring the safety of the product. The present invention provides an effective strategy for the resource utilization of SMS and provides technical support for the sustainable development of the edible fungus industry.

Claims

1. An edible fungus cultivation substrate based on acid-modified biochar, characterized in that The matrix comprises acid-modified fungus residue biochar, which is prepared by the following steps: drying SMS to a moisture content of less than 5% and grinding to a particle size of less than 1 mm; placing the SMS in a quartz tube furnace for pyrolysis under anaerobic conditions, with a pyrolysis temperature of 500 degrees Celsius, a heating rate of 25 degrees Celsius per minute, a reaction pressure of 50 to 60 kilopascals, and a duration of three hours; cooling the obtained biochar to room temperature, mixing it with a phosphoric acid solution with a concentration of 3.0 mol per liter at a mass-to-volume ratio of 1:15, stirring for one hour and shaking for twelve hours; washing the modified biochar to neutrality and drying it.

2. The edible fungus cultivation substrate according to claim 1, wherein The addition ratio of the acid-modified fungus residue biochar is 5% by mass.

3. The edible fungus cultivation substrate according to claim 2, wherein The substrate further comprises cottonseed hulls and wheat bran as cultivation materials.

4. The edible fungus cultivation substrate according to claim 1, wherein The addition ratio of the acid-modified fungus residue biochar is 10% by mass.

5. The edible fungus cultivation substrate according to claim 4, characterized in that The water content of the matrix is ​​adjusted to 60 percent.

6. The edible fungus cultivation substrate according to claim 1, wherein The addition ratio of the acid-modified fungus residue biochar is 15% by mass.

7. The edible fungus cultivation substrate according to claim 6, characterized in that The substrate was placed in a polyethylene plastic bag with a size of 18 cm x 45 cm, sterilized at 105 degrees Celsius for 10 hours, and then inoculated with Pleurotus ostreatus spawn.

8. The edible fungus cultivation substrate according to claim 1, wherein The surface of the acid-modified bacterial residue biochar has hydroxyl, carbonyl and carboxyl functional groups.

9. The edible fungus cultivation substrate according to claim 8, characterized in that The specific surface area of ​​the acid-modified fungus residue biochar is increased by about thirty-three times compared to the unmodified biochar.

10. The edible fungus cultivation substrate according to claim 1, characterized in that The micropore volume of the acid-modified fungus residue biochar is increased by more than 20% compared to the unmodified biochar.

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