A method for preparing yeast by culturing with corn starch sugar molasses as nitrogen source
By enzymatically hydrolyzing the protein in soilless corn starch residue and adding a buffer system and trace elements, the problem of yeast's inability to effectively utilize soilless corn starch residue has been solved, achieving efficient yeast growth and high-value utilization of corn starch residue, which is in line with the concept of green manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2026-05-18
- Publication Date
- 2026-07-24
AI Technical Summary
In existing technologies, yeast cannot effectively utilize the nutrients in soilless corn starch residue, which limits its deep processing and utilization, and the high ash content reduces its economic value.
The protein in corn starch residue was hydrolyzed into peptides and amino acids using an enzymatic method. K2HPO4, KH2PO4 and MgSO4 were added as a buffer system and trace elements, and glucose was used as a carbon source to cultivate yeast.
It improves the growth efficiency and enzymatic hydrolysis efficiency of yeast, realizes the efficient utilization of corn starch residue, enhances its economic value, and provides a cheap nitrogen source for yeast, which is in line with the concepts of green manufacturing and circular economy.
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Figure CN122445487A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the high-value utilization of soilless corn starch residue, specifically to a method for cultivating yeast using corn starch residue as a nitrogen source. Background Technology
[0002] Corn starch is the most important raw material for starch sugar production. The current mainstream enzymatic process route is as follows, and the filtration or pressure filtration process mainly adopts the soil filtration process of diatomaceous earth.
[0003] In the above-mentioned amylase-based sugar production process, corn starch undergoes liquefaction and saccharification, hydrolyzing into water-soluble oligosaccharides and monosaccharides. Since the corn starch raw material also contains a small amount of impurities such as protein and fat, these impurities coagulate upon heating into insoluble and relatively viscous corn starch residue. Therefore, diatomaceous earth filter aid is added to this saccharification liquid system, and then the residue is obtained through filtration processes such as plate and frame filtration or vacuum filtration. Because it contains inorganic filter aids such as diatomaceous earth, its ash content is relatively high. For example, the residue sample filtered by soil from Guangzhou Shuangqiao Co., Ltd. has a high ash content, reaching 40% to 46%. The remaining dry matter components are protein, fat, and a small amount of sugar and carbohydrates. The high ash content of this type of corn starch residue significantly reduces its economic and comprehensive utilization value. It is suitable for direct use as low-value compost, and the price for enterprises to sell it is low. As a raw material for feed processing, its addition ratio is not high. Moreover, if this corn starch residue is not treated in time, the large amount of protein, sugar, and water in it will make it extremely susceptible to microbial contamination, causing it to turn sour, smelly, and deteriorate. It can only be used as compost, and it may be necessary to pay someone to transport and dispose of it.
[0004] Corn starch residue has other uses. For example, Li Shaolei (Li Shaolei. Solid-state fermentation of corn starch residue to produce protein feed and live lactobacillus feed additive [D]. Jiangnan University, 2023) used microbial solid-state fermentation. Without adding carbon and nitrogen sources, he first used brewer's yeast to convert the reducing sugar in the residue into yeast protein, and then added Bacillus subtilis to degrade the protein into free amino acids to produce protein feed. The fermented products had bitter, sweet, fruity and slightly alcoholic flavors, which greatly improved the sensory quality of the feed. In order to utilize the protein in corn starch residue, Zuo Ying et al. (Zuo Ying, Zhang Ping, Cao Xuedan et al. Composition analysis of corn starch residue and optimization of protein extraction process by enzymatic hydrolysis [J]. Food Research and Development, 2015, 36(02): 93~97 / 101) used enzymatic hydrolysis of protein in corn starch residue and found that alkaline protease had the highest hydrolysis rate of protein in residue, which reached 39.77% after optimization.
[0005] With the continuous development of science and technology and the advancement of food and chemical industry production technologies and equipment, Guangzhou Shuangqiao Co., Ltd. has designed and used advanced refining filtration equipment such as automated plate and frame filter presses, vacuum filter presses, horizontal screw centrifuges, and membrane separation devices. By improving the technical process and operation, the coagulated corn starch residue can be separated from the liquefied and saccharified corn starch without the need for adding inorganic filter aids such as diatomaceous earth (which were commonly used in the past). The resulting soil-free corn starch residue has a significantly lower ash content. According to data from Guangzhou Shuangqiao Co., Ltd., the original soil-based sugar residue had a dry basis protein, fat, ash, and reducing sugar content ranging from 10% to 17%, 15% to 25%, 28% to 46%, and 6% to 16%, respectively. The soil-free sugar residue produced at the new Nansha production base has a dry basis protein, fat, ash, and reducing sugar content ranging from 17% to 22%, 35% to 42%, 2% to 3%, and 10% to 15%, respectively. It is evident that by eliminating inorganic additives such as diatomaceous earth, the ash content of the latter is significantly reduced. At least as a feed ingredient, it can be directly added, and its nutritional value and the amount added are much higher than those of the former.
[0006] Although the composition analysis revealed that soilless corn starch residue contains proteins, reducing sugars, and other nutrients that yeast generally prefers, and in relatively high amounts, the preliminary experiments of this invention showed that yeast cannot effectively utilize the residue and its sugar and nitrogen nutrients for its own fermentation, reproduction, yeast preparation, and production. The deep processing of the residue and the efficient fermentation utilization of its sugar and nitrogen components have become a scientific, technological, and production problem that needs to be solved. Summary of the Invention
[0007] Compared to traditional soil-grown corn starch residue, soilless corn starch residue from companies like Guangzhou Shuangqiao Co., Ltd. consists mainly of protein, fat, and sugar in its dry solids, apart from water. Due to its significantly reduced ash content, its utilization value should be even greater.
[0008] To improve the utilization value of soilless corn starch residue in the corn starch sugar industry, this invention provides a method using soilless corn starch residue as raw material. The method primarily utilizes homogenization and enzymatic hydrolysis to hydrolyze the aggregated, denatured proteins in the residue into polypeptides and amino acid nitrogen for yeast cultivation and propagation. Enzymatic hydrolysis is employed to break down the proteins in the residue into smaller amino acids, thereby promoting yeast utilization of sugar nitrogen. Generally, factors affecting enzymatic hydrolysis include pH, temperature, time, and the amount of protease added. Therefore, this invention investigates the effects of these four factors on enzymatic hydrolysis and supplements the hydrolysates with appropriate carbon sources to cultivate yeast. Furthermore, since yeast growth requires a certain amount of phosphorus and trace elements, adding appropriate amounts of K₂HPO₄, KH₂PO₄, and MgSO₄ during the enzymatic hydrolysis stage is beneficial for yeast growth and proliferation, and the resulting buffer system helps maintain enzyme activity.
[0009] This invention provides a method for preparing yeast by culturing corn starch residue as a nitrogen source, comprising the following steps: 1) Weigh out corn starch residue, dissolve it, add K2HPO4, KH2PO4 and MgSO4, adjust the pH, homogenize under high pressure to make a residue solution, add an appropriate amount of alkaline protease, and start the enzymatic hydrolysis reaction. 2) After the enzymatic hydrolysis is completed, centrifuge, take the supernatant, add glucose to adjust the pH, and the culture medium is obtained. Sterilize the culture medium by high temperature and high pressure. 3) Inoculate the activated yeast into the above culture medium, culture it, and centrifuge it after it reaches the stationary phase. The precipitate is the fresh yeast obtained from the culture.
[0010] Preferably, in step 1), the corn starch residue is powdered from soilless corn starch residue after low-temperature drying and grinding.
[0011] Preferably, in step 1), the amount of K2HPO4 added is 1.00% in g / mL, the amount of KH2PO4 added is 0.10% in g / mL, and the amount of MgSO4 added is 0.05% in g / mL.
[0012] Preferably, in step 1), the amount of corn starch residue added to the sugar residue solution is 5% in g / mL.
[0013] Preferably, in step 1), the amount of alkaline protease added is 1% to 5% of the mass of corn starch residue.
[0014] Preferably, in step 1), the pH is adjusted to be controlled at 8.5~10.5; the temperature of the enzymatic hydrolysis reaction is 45~65℃, and the time is 2~10h.
[0015] Preferably, in step 2), centrifugation refers to centrifugation at a speed of 4000~5000 r / min for 10~20 min; high temperature and high pressure sterilization refers to sterilization at 115~121℃ for 20~30 min.
[0016] Preferably, in step 2), supplementing glucose means supplementing the glucose concentration to 7% in g / mL.
[0017] Preferably, in step 2), the pH is adjusted to be controlled between 5.5 and 6.5, and the pH is adjusted using a sulfuric acid solution.
[0018] Preferably, in step 3), the inoculation involves inoculating the activated yeast at 2% of the culture medium volume, and culturing it at a temperature of 28-30°C in an incubator.
[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1) This invention effectively utilizes the by-products of the corn starch sugar industry, using corn starch sugar residue as a nitrogen-rich culture medium raw material to meet the nitrogen requirements of yeast, thus turning waste into treasure.
[0020] 2) The K₂HPO₄ / KH₂PO₄ added during the enzymatic hydrolysis stage constitutes a buffer system, which effectively neutralizes the acidic substances generated during the hydrolysis process, maintaining the solution pH within the predetermined alkaline range. This ensures that the alkaline protease maintains high activity throughout the reaction, making the hydrolysis reaction more efficient and thorough. Simultaneously, the alkaline protease is a metalloenzyme, and MgSO₄ can provide Mg... 2+ As activators, they directly bind to enzyme molecules, stabilizing their three-dimensional structure and participating in substrate binding and catalytic processes, thereby enhancing enzyme activity. Furthermore, these elements (P, K, Mg, S) are also crucial for subsequent yeast culture, making the hydrolysate a more nutritionally balanced culture medium, which is beneficial for yeast growth.
[0021] 3) This invention further develops inexpensive industrial by-products, reducing solid waste emissions, perfectly aligning with the concepts of green manufacturing and circular economy, and enhancing the value and sustainability of the entire industrial chain.
[0022] 4) This invention uses organic nitrogen and carbon sources as substrates to prepare yeast. The yeast has high safety and opens up a new way for the comprehensive utilization of by-products in the corn starch sugar industry. Attached Figure Description
[0023] Figure 1 This is a flowchart of the method for preparing yeast by using corn starch residue as a nitrogen source according to the present invention.
[0024] Figure 2 The growth curves of yeast in Examples 1-6 are shown. Detailed implementation method: To better understand the present invention, it will be further described below with reference to the accompanying drawings and specific embodiments. However, the implementation of the present invention is not limited thereto. The described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] During the preparation of starch sugar, the protein in corn starch is not effectively utilized and eventually accumulates in the sugar residue. Therefore, this invention targets the protein in corn starch sugar residue by enzymatic hydrolysis, and uses the resulting hydrolysate as a culture medium for yeast cultivation. Figure 1 A flowchart illustrating the method for preparing yeast using corn starch residue as a nitrogen source according to the present invention is shown. Figure 1 As shown, the enzymatic hydrolysis of corn starch residue and the cultivation of yeast using the hydrolysate mainly involve the following steps: 1) Dissolve corn starch residue, add K2HPO4, KH2PO4 and MgSO4, adjust the pH, homogenize under high pressure to make a residue solution, add alkaline protease to carry out enzymatic hydrolysis reaction; 2) After the enzymatic hydrolysis is completed, centrifuge, take the supernatant, add glucose to adjust the pH, and the culture medium is obtained. Sterilize the culture medium by high temperature and high pressure. 3) Inoculate the activated yeast into the above culture medium, culture it, and centrifuge it after it reaches the stationary phase. The precipitate is the fresh yeast obtained from the culture.
[0026] In the above method, the corn starch residue in step 1) is obtained by drying soilless corn starch residue at low temperature and grinding it into powder; in the residue solution, the addition amount of corn starch residue is 5% (w / v, g / mL), the addition amount of K2HPO4 is 1.00% (w / v, g / mL), the addition amount of KH2PO4 is 0.10% (w / v, g / mL), and the addition amount of MgSO4 is 0.05% (w / v, g / mL); the enzymatic hydrolysis pH is controlled at 8.5~10.5; the addition amount of alkaline protease is 1%~5% of the mass of corn starch residue, too low a pH results in insufficient enzymatic hydrolysis, and too high a pH does not significantly increase the amino acid nitrogen content. Meanwhile, the temperature of the enzymatic hydrolysis reaction is controlled at 45~65℃ and the time is 2~10h.
[0027] In step 2), centrifugation refers to centrifuging at 4000 r / min for 10 min, followed by high-temperature and high-pressure sterilization at 115℃ for 20 min, supplementing glucose to 7% (w / v, g / mL), and adjusting the pH of the resulting enzymatic supernatant with sulfuric acid solution (sulfate has the least inhibitory effect on yeast) to control the pH at 6.0.
[0028] Step 3) Inoculation refers to inoculating the activated yeast at 2% of the culture medium volume, culturing at 30°C, and placing it in an incubator for cultivation.
[0029] The yeast used in the following examples is Angel Yeast, a high-activity dry yeast for brewing.
[0030] Example 1 Weigh 5% (w / v, g / mL) of corn starch residue and dissolve it in water. Add 1.00% (w / v, g / mL) K₂HPO₄, 0.10% (w / v, g / mL) KH₂PO₄, and 0.05% (w / v, g / mL) MgSO₄, adjust the pH to 8.5, and homogenize under high pressure to prepare a residue solution. Add 1% (w / v, g / mL) of alkaline protease from the corn starch residue and hydrolyze at 45℃ for 2 hours. After hydrolysis, centrifuge and determine the amino acid nitrogen content of the supernatant. Add glucose to the supernatant to bring the concentration to 7% (w / v, g / mL) and adjust the pH to 6.0 to obtain the culture medium. Autoclave at 115℃ for 20 minutes. Inoculate 2% (w / v, g / mL) of activated yeast into the culture medium and incubate at 30℃. After about 22 hours, the culture reaches the stationary phase. Centrifuge the precipitate to obtain fresh yeast and determine the yeast biomass.
[0031] Example 2 Weigh 5% (w / v, g / mL) of corn starch residue and dissolve it in water. Add 1.00% (w / v, g / mL) K₂HPO₄, 0.10% (w / v, g / mL) KH₂PO₄, and 0.05% (w / v, g / mL) MgSO₄, adjust the pH to 10, and homogenize under high pressure to prepare a residue solution. Add 1% (w / v, g / mL) of alkaline protease from the corn starch residue and hydrolyze at 45℃ for 2 h. After hydrolysis, centrifuge and determine the amino acid nitrogen content of the supernatant. Add glucose to the supernatant to bring the concentration to 7% (w / v, g / mL) and adjust the pH to 6.0 to obtain the culture medium. Autoclave at 115℃ for 20 min. Inoculate 2% (w / v, g / mL) of activated yeast into the culture medium and incubate at 30℃. After about 22 h, the culture reaches the stationary phase. Centrifuge the precipitate to obtain fresh yeast and determine the yeast biomass.
[0032] Example 3 Weigh 5% (w / v, g / mL) of corn starch residue and dissolve it in water. Add 1.00% (w / v, g / mL) K₂HPO₄, 0.10% (w / v, g / mL) KH₂PO₄, and 0.05% (w / v, g / mL) MgSO₄, adjust the pH to 10, and homogenize under high pressure to prepare a residue solution. Add 1% (w / v, g / mL) of alkaline protease (by weight of corn starch residue) and hydrolyze at 50℃ for 2 h. After hydrolysis, centrifuge and determine the amino acid nitrogen content of the supernatant. Add glucose to the supernatant to bring the concentration to 7% (w / v, g / mL) and adjust the pH to 6.0 to obtain the culture medium. Autoclave at 115℃ for 20 min. Inoculate 2% (v / v) of activated yeast into the culture medium and incubate at 30℃. After about 22 h, the culture reaches the stationary phase. Centrifuge the precipitate to obtain fresh yeast and determine the yeast biomass.
[0033] Example 4 Weigh 5% (w / v, g / mL) of corn starch residue and dissolve it in water. Add 1.00% (w / v, g / mL) K₂HPO₄, 0.10% (w / v, g / mL) KH₂PO₄, and 0.05% (w / v, g / mL) MgSO₄, adjust the pH to 10, and homogenize under high pressure to prepare a residue solution. Add 1% (w / v, g / mL) of alkaline protease from the corn starch residue and hydrolyze at 50℃ for 4 h. After hydrolysis, centrifuge and determine the amino acid nitrogen content of the supernatant. Add glucose to the supernatant to bring the concentration to 7% (w / v, g / mL) and adjust the pH to 6.0 to obtain the culture medium. Autoclave at 115℃ for 20 min. Inoculate 2% (v / v) of activated yeast into the culture medium and incubate at 30℃. After about 22 h, the culture reaches the stationary phase. Centrifuge the precipitate to obtain fresh yeast and determine the yeast biomass.
[0034] Example 5 Weigh 5% (w / v, g / mL) of corn starch residue and dissolve it in water. Add 1.00% (w / v, g / mL) K₂HPO₄, 0.10% (w / v, g / mL) KH₂PO₄, and 0.05% (w / v, g / mL) MgSO₄, adjust the pH to 10, and homogenize under high pressure to prepare a residue solution. Add 2% (w / v, g / mL) of alkaline protease (by weight of corn starch residue) and hydrolyze at 50℃ for 4 h. After hydrolysis, centrifuge and determine the amino acid nitrogen content of the supernatant. Add glucose to the supernatant to bring the concentration to 7% (w / v, g / mL) and adjust the pH to 6.0 to obtain the culture medium. Autoclave at 115℃ for 20 min. Inoculate 2% (w / v, g / mL) of activated yeast into the culture medium and incubate at 30℃. After about 22 h, the culture reaches the stationary phase. Centrifuge the precipitate to obtain fresh yeast and determine the yeast biomass.
[0035] Example 6 Weigh 5% (w / v, g / mL) of corn starch residue and dissolve it in water. Add 1.00% (w / v, g / mL) K₂HPO₄, 0.10% (w / v) KH₂PO₄, and 0.05% (w / v, g / mL) MgSO₄, adjust the pH to 10.5, and homogenize under high pressure to prepare a residue solution. Add 5% (w / v, g / mL) of alkaline protease from the corn starch residue and hydrolyze at 65℃ for 10 h. After hydrolysis, centrifuge and determine the amino acid nitrogen content of the supernatant. Add glucose to the supernatant to bring the concentration to 7% (w / v, g / mL) and adjust the pH to 6.0 to obtain the culture medium. Autoclave at 115℃ for 20 min. Inoculate 2% (w / v, g / mL) of activated yeast into the culture medium and incubate at 30℃. After about 22 h, the culture reaches the stationary phase. Centrifuge the precipitate to obtain fresh yeast and determine the yeast biomass.
[0036] Method for determining the amino acid content of enzymatic hydrolysate: Take a volume V1 of the enzymatic hydrolysate, dilute it with water to V2, adjust the pH to 8.2, add 10 mL of formaldehyde solution, and titrate with 0.05 mol / L sodium hydroxide standard solution to pH 9.2. Record the volume V of sodium hydroxide standard solution consumed. Simultaneously, take an equal volume of water, first adjust the pH to 8.2 with sodium hydroxide standard solution, then add 10.0 mL of formaldehyde solution, and titrate with sodium hydroxide standard solution to pH 9.2. Use this as a reagent blank control. Calculate the amino acid nitrogen content: Amino acid nitrogen content (g / L) =
[0037] In the formula: V0 — The volume of sodium hydroxide standard solution consumed after adding formaldehyde in the reagent blank experiment, in milliliters (mL). V — The volume of sodium hydroxide standard solution consumed after adding formaldehyde to the enzymatic hydrolysis dilution solution, in milliliters (mL). V1 — The amount of enzyme hydrolysate used, in milliliters (mL). V2 — The final volume of the enzyme hydrolysis dilution solution, in milliliters (mL).
[0038] V3 — Total volume of the enzyme hydrolysate obtained by centrifugation, in liters (L).
[0039] Methods for yeast biomass determination: Shake the culture medium that has reached the stationary phase well. Measure a certain volume of the fermentation broth into a centrifuge tube that has been dried to constant weight. Centrifuge at 5000 rpm for 20 minutes. Discard the supernatant and wash thoroughly 2-3 times with an appropriate amount of deionized water. Place the washed bacterial sludge in a 105℃ forced-air oven and dry to constant weight. Accurately weigh the bacterial cell mass (g / L) using a 0.01% analytical balance.
[0040] The amino acid nitrogen content and yeast biomass of the enzymatic hydrolysate prepared in the above examples were determined by measurement and calculation, as shown in Table 1. Table 1. Amino acid nitrogen content of enzymatic hydrolysate and corresponding yeast biomass in the culture medium
[0041] As shown in Table 1, the yeast in Examples 1-6 of this invention all achieved good growth. For Examples 1-5, with the optimization of the enzymatic hydrolysis reaction conditions, the enzymatic hydrolysis rate of protein in the corn starch residue continuously increased, and the amino acid nitrogen content significantly increased. Correspondingly, the yeast biomass during the stationary phase of each culture medium also increased, indicating that the yeast can utilize the amino acid nitrogen in the enzymatic hydrolysate. In Example 6, the enzymatic hydrolysis conditions were too harsh, leading to partial decomposition of amino acid nitrogen and a decrease in its content. However, the numerous small-molecule nitrogen molecules allowed the yeast to rapidly utilize them for growth and proliferation.
[0042] Figure 2 The growth curves of yeast in Examples 1-6 show that the yeast in each culture medium has obvious lag phase, logarithmic phase and stationary phase: the lag phase is 0-6h, the logarithmic phase is 6-20h, and the stationary phase is after 20h.
[0043] As can be seen from the above examples, under better enzymatic hydrolysis conditions, the yeast biomass obtained by cultivation is higher, and corn starch residue can be considered as a nitrogen source in the industrial production of yeast.
[0044] This invention transforms corn starch residue, a byproduct of the corn starch sugar industry, into a valuable resource. Enzymatic hydrolysis breaks down its large protein molecules into smaller nitrogen molecules, which can then be used as a nitrogen source for yeast cultivation. Furthermore, the addition of K₂HPO₄, KH₂PO₄, and MgSO₄ during the enzymatic hydrolysis process not only improves hydrolysis efficiency but also plays a significant role in yeast cultivation: phosphate, as a phosphorus source, is an essential element for the synthesis of key cellular substances such as nucleic acids and phospholipids; potassium participates in intracellular osmotic pressure regulation and substance transport; magnesium is a key component of ribosomes and is crucial for protein synthesis; and sulfur can synthesize sulfur-containing amino acids, which are also important components of proteins.
[0045] In summary, this invention utilizes corn starch residue, an industrial byproduct, to produce yeast through enzymatic hydrolysis by extracting its proteins. This not only achieves a significant leap in the value of corn starch residue but also provides a cheap raw material for yeast cultivation, perfectly aligning with the current concepts of green development and circular economy.
[0046] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing yeast by culturing corn starch residue as a nitrogen source, characterized in that, Includes the following steps: 1) Dissolve corn starch residue, add K2HPO4, KH2PO4 and MgSO4, adjust the pH, homogenize under high pressure to make a residue solution, add an appropriate amount of alkaline protease to carry out enzymatic hydrolysis. 2) After the enzymatic hydrolysis is completed, centrifuge, take the supernatant, add glucose to adjust the pH, and the culture medium is obtained. Sterilize the culture medium by high temperature and high pressure. 3) Inoculate the activated yeast into the above culture medium, culture it, and centrifuge it after it reaches the stationary phase. The precipitate is the fresh yeast obtained from the culture.
2. The preparation method according to claim 1, characterized in that, In step 1), the corn starch residue is powdered from soilless corn starch residue after low-temperature drying and grinding.
3. The preparation method according to claim 1, characterized in that, In step 1), the amount of K2HPO4 added in the sugar residue solution is 1.00% in g / mL, the amount of KH2PO4 added is 0.10% in g / mL, and the amount of MgSO4 added is 0.05% in g / mL.
4. The preparation method according to claim 1, characterized in that, In step 1), the amount of corn starch residue added to the sugar residue solution is 5% in g / mL.
5. The preparation method according to claim 1, characterized in that, In step 1), the amount of alkaline protease added is 1% to 5% of the mass of corn starch residue.
6. The preparation method according to claim 1, characterized in that, In step 1), the pH is adjusted to be between 8.5 and 10.5; the temperature of the enzymatic hydrolysis reaction is between 45 and 65°C, and the time is between 2 and 10 hours.
7. The preparation method according to claim 1, characterized in that, In step 2), centrifugation refers to centrifugation at a speed of 4000~5000 r / min for 10~20 min; high temperature and high pressure sterilization refers to sterilization at 115~121℃ for 20~30 min.
8. The preparation method according to claim 1, characterized in that, In step 2), the addition of glucose refers to supplementing the glucose concentration to 7% in g / mL.
9. The preparation method according to claim 1, characterized in that, In step 2), the pH is adjusted to be controlled between 5.5 and 6.5, and the pH is adjusted using a sulfuric acid solution.
10. The preparation method according to claim 1, characterized in that, In step 3), the inoculation involves inoculating activated yeast at 2% of the culture medium volume; the culture temperature is 28~30℃, and the culture is carried out in an incubator.