A method for improving the production of sdf in edible mushroom waste

Abstract

The application discloses a method for improving SDF yield in edible mushroom waste, and belongs to the technical field of biological food. The edible mushroom waste is dried, crushed, sieved, filtered, and freeze-dried after water extraction at 60 DEG C for 4 hours to obtain residues; the residues are mixed with distilled water at a solid-liquid ratio of 1g:(10-14)mL, high-temperature sterilized, and edible mushroom water-extracted residues are obtained. 4% of Aspergillus niger and 8% of Saccharomyces cerevisiae are inoculated on the edible mushroom water-extracted residues, and fermentation is carried out for 2-3 days; the supernatant is collected by centrifugation, alcohol precipitation and centrifugation, and flocculent precipitate is collected; and SDF is obtained by freeze-drying. The method utilizes the synergistic modification of Aspergillus niger and Saccharomyces cerevisiae on the extracted edible mushroom residues, and the SDF yield after modification is obviously higher than that of single strain modification, high-quality and high-yield dietary fiber is obtained, technical support is provided for deep processing and utilization of edible mushroom processing by-products, and environmental pollution problems caused by waste burning or direct disposal are relieved.

Description

Technical Field

[0001] This invention belongs to the field of bio-food technology, specifically relating to a method for increasing the SDF yield in edible fungi waste. Background Technology

[0002] Mushroom residue, as an agricultural waste, is widely used to improve soil fertility as a material for remediating heavy metal and metalloid pollution, which leads to resource waste. Mushroom residue contains a large amount of dietary fiber, typically composed of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). Compared to IDF, SDF is widely used in food processing due to its better nutritional and physiological properties. The extracted mushroom residue can be reused through modification.

[0003] Currently, methods for modifying edible mushroom residue include physical, chemical, biological, or combinations of these approaches. Physical methods, such as mechanical degradation, may damage the structure of dietary fiber, affecting its physicochemical properties and physiological activity. Chemical methods generally use reagents such as acids and alkalis, controlling appropriate pH, reaction time, temperature, and reaction duration to cause the breakage of polysaccharide glycosidic bonds and expose more functional groups, thereby altering the functionality of dietary fiber. However, chemically modified dietary fiber has low purity and is prone to producing harmful components, causing inconvenience to subsequent food processing. Biological modification methods are relatively low-cost, mild, and less environmentally polluting, mainly focusing on the modification of single enzymes or strains. However, there is currently limited research on the synergistic modification of dietary fiber by biological methods, and existing methods all suffer from low SDF yield, with extraction rates generally below 10%. Therefore, a biological modification method that can improve SDF yield is needed. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for increasing the SDF yield in edible fungi waste, so as to solve the technical problems of low SDF yield and lack of research on functional properties obtained by existing biological modification methods of edible fungi residue.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a method for increasing the yield of SDF in edible fungus waste. The method involves artificially inoculating 4% Aspergillus niger and 8% yeast onto the water-extracted residue of edible fungi, fermenting for 2-3 days, collecting the supernatant by centrifugation, precipitating with alcohol by centrifugation, collecting the flocculent precipitate, and freeze-drying to obtain SDF.

[0007] Preferably, the yeast is *Saccharomyces cerevisiae*.

[0008] Preferably, the method for obtaining the water-extracted residue of edible fungi is as follows: the edible fungi waste is dried, crushed, sieved, water-extracted, filtered, and freeze-dried to obtain residue; the residue is mixed with distilled water and sterilized at 121°C to obtain water-extracted residue of edible fungi.

[0009] Preferably, the edible fungus waste is dried, pulverized, and then passed through a 100-mesh sieve.

[0010] More preferably, the ratio of residue to distilled water is 1g:(10-14)mL.

[0011] Preferably, the ratio of residue to distilled water is 1g:12.5mL.

[0012] Preferably, the edible fungus is the stem of a shiitake mushroom, an enoki mushroom, or an oyster mushroom.

[0013] Preferably, the fermentation time is 3 days.

[0014] Preferably, the fermentation temperature is 28–32°C.

[0015] More preferably, the fermentation temperature is 31°C.

[0016] Preferably, the supernatant is collected by centrifugation at 6000–8000 r / min.

[0017] Preferably, the alcohol precipitation centrifugation step is as follows: mix the supernatant and 95% ethanol at a volume ratio of 1:4 for 12 hours, and then centrifuge at 6000-8000 r / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention provides a method for increasing the yield of SDF (Salt-Derived Dietary Fiber) in edible fungi waste. Edible fungi waste is rich in dietary fiber and is typically used as feed, incinerator, or discarded directly, causing serious environmental pollution and waste. Using edible fungi waste as a food supplement to produce SDF can solve environmental pollution while increasing the value of byproducts. *Aspergillus niger* is used as a bioactive enzyme, capable of producing enzymes itself and also utilizing waste to produce high-value-added products. Yeast is used because it is easy to operate, mature in development, has strong fermentation capabilities, and a wide range of substrates, allowing for suitable and effective utilization of waste. Synergistic enzyme modification can efficiently and precisely locate the β-glycosidic bonds of dietary fiber, cleaving its long-chain molecules into multiple smaller molecules, exhibiting advantages such as specificity, high specificity, and environmental friendliness. Therefore, the synergistic modification of extracted edible fungi residue using *Aspergillus niger* and yeast is demonstrated through experiments that the SDF yield of combined modification with *Aspergillus niger* and yeast is significantly higher than that of single-strain modification, reaching a maximum of 14.82%. Furthermore, during the modification process, the molecular morphology of the byproduct IDF changed, significantly improving its water-holding capacity, oil-holding capacity, and swelling capacity. Therefore, this method can yield high-quality, high-yield dietary fiber, providing technical support for the in-depth processing and utilization of byproducts from edible fungi processing, while also mitigating environmental pollution caused by waste incineration or direct disposal.

[0020] Furthermore, when the selected yeast is Saccharomyces cerevisiae, the yield of SDF is even higher. Attached Figure Description

[0021] Figure 1 This is a standard curve for sugar content determination.

[0022] Figure 2 The relative molecular mass spectrum of SDF;

[0023] Figure 3 This is a monosaccharide composition diagram of SDF; where A is the monosaccharide standard, B is SDF, 1 is Rha, 2 is Fuc, 3 is Ara, 4 is Xyl, 5 is Man, 6 is Glc, 7 is Gal, 8 is GclA, and 9 is GalA.

[0024] Figure 4 The images show the scanning electron microscope (SEM) images of the IDF (indicating fibrous material) of the shiitake mushroom stem before modification at 1000x magnification, the images show the IDF of the shiitake mushroom stem before modification at 3000x magnification, the images show the IDF of the shiitake mushroom stem after modification at 1000x magnification, and the images show the IDF of the shiitake mushroom stem after modification at 3000x magnification.

[0025] Figure 5 The graph shows the effect of Aspergillus niger inoculum amount on SDF yield.

[0026] Figure 6 Figure showing the effect of brewer's yeast inoculum amount on SDF yield of shiitake mushroom stems;

[0027] Figure 7 Figure showing the effect of fermentation temperature on the SDF yield of shiitake mushroom stems;

[0028] Figure 8 The graph shows the effect of fermentation time on the SDF yield of shiitake mushroom stems.

[0029] Figure 9 This is a graph showing the effect of the feed-to-liquid ratio on the SDF yield.

[0030] Figure 10 Contour lines and response surface plots showing the effects of fermentation time and temperature on the SDF yield of shiitake mushroom stems; where A is the contour plot and B is the response surface plot.

[0031] Figure 11 Contour lines and response surface plots showing the effects of material-to-liquid ratio and fermentation temperature on the SDF yield of shiitake mushroom stems; where A is the contour plot and B is the response surface plot.

[0032] Figure 12 Contour lines and response surface plots showing the effects of material-to-liquid ratio and fermentation time on the SDF yield of shiitake mushroom stems; where A is the contour plot and B is the response surface plot.

[0033] Figure 13 The effect of inoculation with Aspergillus niger and Saccharomyces cerevisiae on the SDF yield of enoki mushroom waste and oyster mushroom waste is shown in the figure.

[0034] in, Figures 5-9 , Figure 13 In the case where p < 0.05, the different letters a, b, c, d, and e represent significant differences. Detailed Implementation

[0035] To enable those skilled in the art to understand the features and effects of the present invention, the following descriptions and definitions are only general descriptions of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in the event of any conflict, the definitions in this specification shall prevail.

[0036] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0037] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0038] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0039] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0040] This invention provides a method for increasing the yield of SDF in edible fungi waste. The edible fungi waste is dried and pulverized, then water-extracted at 50℃–90℃ for 4 hours, filtered, and freeze-dried to obtain residue. The residue is mixed with distilled water at a material-to-liquid ratio of 1g:(10–14)mL and sterilized at 121℃ for 20 minutes to obtain edible fungi water-extracted residue. 4% *Aspergillus niger* and 8% *Saccharomyces cerevisiae* are artificially inoculated onto the edible fungi water-extracted residue, cultured at 28–32℃ for 2–3 days, and centrifuged at 6000–8000 r / min for 4–6 minutes to separate the supernatant and the lower fermentation layer. The collected supernatant is mixed with 95% ethanol at a volume ratio of 1:4 for 12 hours, then centrifuged at 6000–8000 r / min for 4–6 minutes. The flocculent precipitate is collected and freeze-dried to obtain SDF. The collected lower fermentation layer was freeze-dried to obtain IDF. This method can significantly improve the yield of SDF in water-soluble dietary fiber.

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0043] I. Obtaining high-yield SDF from edible fungi waste

[0044] Example 1

[0045] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 100mL of distilled water was added at a material-to-liquid ratio of 1:10. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0046] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 30℃ for 4 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected and freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, and after centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 11.16%.

[0047] Example 2

[0048] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 100mL of distilled water was added at a material-to-liquid ratio of 1:10. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0049] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 28℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected and freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, and after centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 9.13%.

[0050] Example 3

[0051] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 140mL of distilled water was added at a material-to-liquid ratio of 1:14. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0052] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 30℃ for 4 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 12.21%.

[0053] Example 4

[0054] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 120mL of distilled water was added at a material-to-liquid ratio of 1:12. After high-pressure steam sterilization, shiitake mushroom stem water-extracted residue was obtained.

[0055] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 30℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 14.12%.

[0056] Example 5

[0057] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 120mL of distilled water was added at a material-to-liquid ratio of 1:12. After high-pressure steam sterilization, shiitake mushroom stem water-extracted residue was obtained.

[0058] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 28℃ for 2 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 8.32%.

[0059] Example 6

[0060] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 120mL of distilled water was added at a material-to-liquid ratio of 1:12. After high-pressure steam sterilization, shiitake mushroom stem water-extracted residue was obtained.

[0061] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 32℃ for 4 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 11.82%.

[0062] Example 7

[0063] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 140mL of distilled water was added at a material-to-liquid ratio of 1:14. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0064] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 28℃ for 3 days. The resulting mixture in the Erlenmeyer flask was centrifuged at 8000 rpm for 5 min, and the lower fermentation layer was collected and freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, and after centrifugation at 8000 rpm for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 10.42%.

[0065] Example 8

[0066] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 100mL of distilled water was added at a material-to-liquid ratio of 1:10. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0067] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 32℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, centrifuged at 8000 r / min for 10 min, and the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 11.94%.

[0068] Example 9

[0069] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 140mL of distilled water was added at a material-to-liquid ratio of 1:14. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0070] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 32℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, centrifuged at 8000 r / min for 10 min, and the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 14.82%.

[0071] Example 10

[0072] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 120mL of distilled water was added at a material-to-liquid ratio of 1:12. After high-pressure steam sterilization, shiitake mushroom stem water-extracted residue was obtained.

[0073] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 32℃ for 2 days. The resulting mixture in the Erlenmeyer flask was centrifuged at 8000 rpm for 5 min, and the lower fermentation layer was collected and freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, and after centrifugation at 8000 rpm for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 12.31%.

[0074] Example 11

[0075] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 120mL of distilled water was added at a material-to-liquid ratio of 1:12. After high-pressure steam sterilization, shiitake mushroom stem water-extracted residue was obtained.

[0076] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 28℃ for 4 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 9.53%.

[0077] Example 12

[0078] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 140mL of distilled water was added at a material-to-liquid ratio of 1:14. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0079] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 30℃ for 2 days. The resulting mixture in the Erlenmeyer flask was centrifuged at 8000 rpm for 5 min, and the lower fermentation layer was collected and freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, and after centrifugation at 8000 rpm for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 10.91%.

[0080] Example 13

[0081] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 100mL of distilled water was added at a material-to-liquid ratio of 1:10. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0082] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 30℃ for 2 days. The mixed solution in the Erlenmeyer flask after fermentation was centrifuged at 8000 r / min for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF. The SDF yield was calculated to be 9.73%.

[0083] Example 14

[0084] 1000g of shiitake mushroom stem waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain shiitake mushroom stem residue. 10g of shiitake mushroom stem residue was added to a 250mL Erlenmeyer flask, and 100mL of distilled water was added at a material-to-liquid ratio of 1:12.5. After high-pressure steam sterilization, shiitake mushroom stem water extraction residue was obtained.

[0085] The obtained shiitake mushroom stem water extract residue was inoculated with 4% Aspergillus niger and 8% Saccharomyces cerevisiae and fermented at 31°C for 3 days. The mixed solution in the Erlenmeyer flask after fermentation was centrifuged at 8000 rpm for 5 min, and the lower fermentation layer was collected, freeze-dried to obtain IDF. 95% ethanol (1:4, v / v) was added to the supernatant for 12 h, centrifuged at 8000 rpm for 10 min, and the flocculent precipitate was collected and freeze-dried to obtain SDF. The physicochemical properties of the SDF obtained in Example 14 were analyzed:

[0086] (1) The sugar content was determined using the phenol-sulfuric acid method. The result was calculated from the mass of the standard glucose and its measured absorbance. Figure 1 The standard equation is: y = 4.2890x - 0.0107, R 2 =0.9946. Substituting the SDF absorbance value into the above standard equation, the sugar content of SDF was determined to be 67.92 ± 3.23%.

[0087] (2) The relative molecular mass of SDF was determined by the HPGPC method. Figure 2 The relative molecular mass spectrum of SDF shows that SDF is a dietary fiber with uniform molecular weight. The relative molecular mass of SDF is calculated to be 458.52 ± 7.33 kDa.

[0088] (3) The monosaccharide composition of SDF was determined by GC. The results of the SDF analysis were normalized to perform qualitative and quantitative analysis of its monosaccharide composition. The retention times of the SDF chromatogram were compared with those of a mixed standard monosaccharide chromatogram. The results showed that SDF consisted entirely of Xyl, Man, Glc, and Gal, with calculated molar ratios of 1.07:1.20:7.55:1. The contents of glucose, xylose, and mannose increased, while the content of galactose decreased. Fermentation increased the contents of Glc, Xyl, and Man, and decreased the content of Gal. Figure 3 This is a monosaccharide composition diagram of SDF.

[0089] (4) Analysis of the molecular morphology of IDF in shiitake mushroom stem residue before and after modification. Figure 4The images are obtained using scanning electron microscopy (SEM). IDF samples before and after modification were observed using SEM at magnifications of 1000x and 3000x. Before modification, the surface of the shiitake mushroom stem IDF (A1) was relatively smooth with few serrated structures. After magnification (A2), the surface showed few protruding fragments and a smooth structure. After modification, the surface of the shiitake mushroom stem IDF (B1) was uneven, with many irregular and curled fragments, indicating significant damage to the original structure. After magnification (B2), many protruding fragments were visible on the surface. This is because cellulase was produced during the modification process, primarily targeting the glycosidic bonds on cellulose polysaccharides. By degrading these bonds, the compact structure of the sample was disrupted, resulting in a dispersed state. This increased the contact area between water and oil and IDF, thereby improving the water-holding capacity, oil-holding capacity, and swelling capacity of IDF.

[0090] II. Investigating the effect of different parameters on SDF yield in the experiment

[0091] (1) Effect of Aspergillus niger inoculum size on SDF yield

[0092] After drying and crushing the waste from shiitake mushroom stems, the residue was passed through a 100-mesh sieve, water-extracted at 60℃ for 4 hours, filtered, and freeze-dried to obtain the residue. 10g of the residue was added to a 250mL Erlenmeyer flask, 100mL of sterile water was added, and the mixture was sterilized by high-pressure steam to obtain the water-extracted residue from shiitake mushroom stems.

[0093] The amount of Aspergillus niger added was adjusted to 2%, 4%, 6%, 8%, and 10% respectively, and added to bottles containing water-extracted residue from shiitake mushroom stems. The fermentation time was set to 3 days and the fermentation temperature to 30℃. SDF was extracted after fermentation and the yield was calculated. Figure 5 The effect of Aspergillus niger inoculum amount on SDF yield was investigated. It was found that the highest SDF content was obtained when the inoculum amount of Aspergillus niger was 4%.

[0094] (2) Effect of brewer's yeast inoculum amount on SDF yield of shiitake mushroom stems

[0095] After drying and crushing the waste from shiitake mushroom stems, the residue was passed through a 100-mesh sieve, extracted with water at 60℃ for 4 hours, filtered, and freeze-dried to obtain the residue. 10g of the residue was added to a 250mL Erlenmeyer flask, 100mL of sterile water was added, and the mixture was sterilized by high-pressure steam to obtain the water-extracted residue from shiitake mushroom stems.

[0096] The amount of brewing yeast added was adjusted and added to bottles containing shiitake mushroom stem water extract residue at proportions of 2%, 4%, 6%, 8%, and 10%. The fermentation time was set at 3 days and the fermentation temperature at 30℃. SDF was extracted after fermentation and the yield was calculated. Figure 6 The effect of the amount of Saccharomyces cerevisiae inoculated on the SDF yield of shiitake mushroom stems was investigated. It was found that the highest SDF content was obtained when the inoculation amount of Saccharomyces cerevisiae was 8%.

[0097] (3) Effect of fermentation temperature on SDF yield of shiitake mushroom stems

[0098] The waste from shiitake mushroom stems was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain residue. 10g of residue was added to a 250mL Erlenmeyer flask, 120mL of sterile water was added, and the mixture was sterilized by high-pressure steam to obtain water-extracted residue from shiitake mushroom stems.

[0099] The amounts of Aspergillus niger and Saccharomyces cerevisiae were 4% and 8%, respectively, and added to a bottle containing water-extracted residue from shiitake mushroom stems. The fermentation time was set to 3 days, and the fermentation temperatures were 26℃, 28℃, 30℃, 32℃, and 34℃. SDF was extracted after fermentation and its yield was calculated. Figure 7 The effect of fermentation temperature on the SDF yield of shiitake mushroom stems was investigated. It was found that at 26–28℃, the SDF content gradually increased with increasing temperature, while at 32–34℃, the SDF content gradually decreased. This may be because enzyme growth and function are inhibited by low and high temperatures.

[0100] (4) Effect of fermentation time on SDF yield of shiitake mushroom stems

[0101] The waste from shiitake mushroom stems was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain residue. 10g of residue was added to a 250mL Erlenmeyer flask, 120mL of sterile water was added, and the mixture was sterilized by high-pressure steam to obtain water-extracted residue from shiitake mushroom stems.

[0102] The amounts of Aspergillus niger and Saccharomyces cerevisiae were 4% and 8%, respectively, and added to a bottle containing water-extracted residue from shiitake mushroom stems. The fermentation time was adjusted to 1 day, 2 days, 3 days, 4 days, and 5 days, and the fermentation temperature was 30℃. After the fermentation was completed, SDF was extracted and its yield was calculated. Figure 8 The effect of fermentation time on the SDF yield of shiitake mushroom stems was investigated. It was found that the highest SDF yield was achieved after 3 days of mixed fermentation. This is likely due to the shorter time for the mycelium to function and the limited nutritional value of the shiitake mushroom stem residue. Therefore, a fermentation time of 2–3 days is more suitable.

[0103] (5) Effect of feed-to-liquid ratio on SDF yield

[0104] The waste shiitake mushroom stems were dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, the residue was filtered and freeze-dried to obtain the dregs. 10g of the residue was added to 250mL Erlenmeyer flasks, and 60, 80, 100, 120, and 140mL of sterile water were added respectively. After high-pressure steam sterilization, water-extracted shiitake mushroom stem residues with different contents were obtained.

[0105] The amounts of Aspergillus niger and Saccharomyces cerevisiae were selected as 4% and 8%, respectively, and added to bottles containing different amounts of shiitake mushroom stem water extract residue. The fermentation time was selected as 3 days and the fermentation temperature was 30℃. After the fermentation was completed, SDF was extracted and its yield was calculated. Figure 9 The effect of the material-to-liquid ratio on SDF yield was investigated. It was found that the SDF content first increased and then decreased, reaching its highest point at a ratio of 1:12. This is because while enzyme activity increases with increasing water content, excessive water also dilutes the enzyme and creates high humidity in the shiitake mushroom stem residue, leading to poor gas exchange and substrate clumping, thus decreasing the SDF content. Therefore, a ratio of 1:(10–14) was chosen.

[0106] (6) Response surface methodology experiment

[0107] Response surface methodology was designed using Design-Expert software, and the experimental model was analyzed to obtain the optimal modification process. Referring to Tables 1 and 2, time, temperature, and feed-to-liquid ratio were designed as independent variables, and SDF yield was used as the response value. A three-factor, three-level response surface experiment was designed, and the results are shown in [Table 1]. Figures 10-12 The results showed that the order of influence of the three factors on the SDF yield was fermentation temperature > solid-liquid ratio > fermentation time. Validation experiments were conducted to obtain the optimal modification conditions for SDF use at a fermentation temperature of 30.79℃, a fermentation time of 3.01 days, and a solid-liquid ratio of 1:12.37. Considering the convenience of actual production and operation, three parallel experiments were conducted with the simultaneous addition of 4% Aspergillus niger and 8% Saccharomyces cerevisiae, at a fermentation temperature of 31℃, a fermentation time of 3 days, and a solid-liquid ratio of 1:12.5. The SDF yield was 14.73%, which is close to the software result of 14.91% in Table 3, indicating a good fit and verifying the correctness of the model. The IDF yield was 82.45%. Under the conditions of fermentation temperature of 31℃, fermentation time of 3 days, and solid-liquid ratio of 1:12.5, the SDF yields obtained after adding 4% Aspergillus niger inoculum and 8% Saccharomyces cerevisiae were 10.21% and 9.23%, respectively. This indicates that simultaneous inoculation with Aspergillus niger and Saccharomyces cerevisiae is more effective than single-strain inoculation, and can achieve a synergistic effect between the two strains.

[0108] Table 1. Factors and Levels in Response Surface Analysis

[0109]

[0110] Table 2. Experimental Design and Results of Response Surface Analysis

[0111]

[0112] Table 3. Results of Model Variance Analysis

[0113]

[0114] Note: "Prob>F" indicates the probability of no significant effect, "***" indicates extremely significant (p<0.001), "**" indicates highly significant (p<0.01), and "*" indicates significant (p<0.05).

[0115] In summary, an optimal quadratic polynomial mathematical model for the mixed fermentation of edible fungi waste by Aspergillus niger and yeast was established through single-factor experiments combined with response surface methodology. The main factors affecting SDF yield and their interactions were analyzed, and the fermentation was optimized to obtain the best modification conditions: fermentation temperature of 31℃, fermentation time of 3 days, and material-to-liquid ratio of 1:12.5.

[0116] (7) Investigating the effect of the combined action of Aspergillus niger and Saccharomyces cerevisiae on SDF yield

[0117] The following groups were set up: a double-strain group of enoki mushroom waste, a blank control group, a Aspergillus niger control group, and a Saccharomyces cerevisiae control group.

[0118] 1000g of enoki mushroom waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain enoki mushroom residue. 10g of enoki mushroom residue was added to a 250mL Erlenmeyer flask, and 125mL of distilled water was added at a material-to-liquid ratio of 1:12.5. After high-pressure steam sterilization, enoki mushroom water-extracted residue was obtained.

[0119] The method for setting up the dual-strain group is as follows: 4% Aspergillus niger and 8% Saccharomyces cerevisiae are inoculated into the water extract residue of the obtained enoki mushrooms and fermented at 31℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask is centrifuged at 8000 r / min for 5 min, the lower fermentation product is collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) is added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate is collected and freeze-dried to obtain SDF.

[0120] The blank control group was set up as follows: the obtained enoki mushroom water extract residue was fermented at 31℃ for 3 days. The mixed solution in the Erlenmeyer flask after fermentation was centrifuged at 8000 r / min for 5 min, the lower fermentation product was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF.

[0121] The control group for Aspergillus niger was set up as follows: 4% Aspergillus niger was inoculated into the water extract residue of enoki mushrooms and fermented at 31℃ for 3 days. The mixed solution in the Erlenmeyer flask after fermentation was centrifuged at 8000 r / min for 5 min, the lower fermentation product was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF.

[0122] The control group of Saccharomyces cerevisiae was set up as follows: 8% Saccharomyces cerevisiae was inoculated into the water extract residue of Enoki mushrooms and fermented at 31℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, the lower fermentation product was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF.

[0123] The SDF yield of each group was determined. The SDF yield of the double bacteria group was 6.77%, the SDF yield of the blank control group was 0.51%, the SDF yield of the Aspergillus niger control group was 2.90%, and the SDF yield of the Saccharomyces cerevisiae control group was 1.80%.

[0124] The following groups were set up: a double-strain group of oyster mushroom waste water, a blank control group, a Aspergillus niger control group, and a Saccharomyces cerevisiae control group.

[0125] 1000g of oyster mushroom waste was dried, crushed, and passed through a 100-mesh sieve. After water extraction at 60℃ for 4 hours, it was filtered and freeze-dried to obtain oyster mushroom residue. 10g of oyster mushroom residue was added to a 250mL Erlenmeyer flask, and 125mL of distilled water was added at a material-to-liquid ratio of 1:12.5. After high-pressure steam sterilization, oyster mushroom water-extracted residue was obtained.

[0126] The method for setting up the dual-strain group is as follows: 4% Aspergillus niger and 8% Saccharomyces cerevisiae are inoculated into the obtained oyster mushroom water extract residue and fermented at 31℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask is centrifuged at 8000 r / min for 5 min, the lower fermentation product is collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) is added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate is collected and freeze-dried to obtain SDF.

[0127] The blank control group was set up as follows: the obtained oyster mushroom water extract residue was fermented at 31℃ for 3 days. The mixed solution in the Erlenmeyer flask after fermentation was centrifuged at 8000 r / min for 5 min, the lower fermentation product was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF.

[0128] The control group for Aspergillus niger was set up as follows: 4% Aspergillus niger was inoculated into the water extract residue of Pleurotus ostreatus and fermented at 31℃ for 3 days. The mixed solution in the Erlenmeyer flask after fermentation was centrifuged at 8000 r / min for 5 min, the lower fermentation product was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF.

[0129] The control group of brewer's yeast was set up as follows: 8% brewer's yeast was inoculated into the obtained oyster mushroom water extract residue and fermented at 31℃ for 3 days. After fermentation, the mixed solution in the Erlenmeyer flask was centrifuged at 8000 r / min for 5 min, the lower fermentation product was collected, freeze-dried to obtain IDF, and 95% ethanol (1:4, v / v) was added to the supernatant for 12 h. After centrifugation at 8000 r / min for 10 min, the flocculent precipitate was collected and freeze-dried to obtain SDF.

[0130] The SDF yield of each group was determined. The SDF yield of the double bacteria group was 6.60%, the SDF yield of the blank control group was 0.34%, the SDF yield of the Aspergillus niger control group was 2.78%, and the SDF yield of the Saccharomyces cerevisiae control group was 2.03%.

[0131] The above-mentioned yield and the bar chart of enoki mushroom and oyster mushroom waste show that the SDF yield of the two-strain co-inoculation was significantly higher than that of other groups, further indicating that Aspergillus niger and Saccharomyces cerevisiae can synergistically improve the SDF yield.

[0132] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for increasing the yield of soluble dietary fiber in edible fungi waste, characterized in that, Edible fungus waste is dried, pulverized, sieved, water-extracted, filtered, and freeze-dried to obtain residue. The residue is mixed with distilled water at a material-to-liquid ratio of 1 g: 10-14 mL and sterilized at 121℃ to obtain edible fungus water-extracted residue. 4% Aspergillus niger and 8% Saccharomyces cerevisiae are artificially inoculated onto the edible fungus water-extracted residue, and fermented at 28-32℃ for 2-3 days. The supernatant is collected by centrifugation, precipitated with alcohol, and the flocculent precipitate is collected and freeze-dried to obtain soluble dietary fiber. The edible fungus is the stem of shiitake mushroom, enoki mushroom, or oyster mushroom.

2. The method for increasing the yield of soluble dietary fiber in edible fungi waste according to claim 1, characterized in that, Fermentation time is 3 days.

3. The method for increasing the yield of soluble dietary fiber in edible fungi waste according to claim 1, characterized in that, The fermentation temperature is 31℃.

4. A method for increasing the yield of soluble dietary fiber in edible fungi waste according to claim 1, characterized in that, Collect the supernatant by centrifugation at 6000~8000 r / min.

5. A method for increasing the yield of soluble dietary fiber in edible fungi waste according to claim 1, characterized in that, The steps for alcohol precipitation centrifugation are as follows: mix the supernatant and 95% ethanol at a volume ratio of 1:4 for 12 h, and then centrifuge at 6000~8000 r / min.

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