Treatment method and application of corn steep liquor

Abstract

The invention provides a treatment method and application of corn steep liquor. The treatment method comprises the following steps: performing enzymolysis on corn steep liquor to be treated to obtain enzymatic hydrolysate; and mixing the enzymatic hydrolysate with a flocculating agent, and filtering to obtain corn steep liquor clear liquid. The method can solve the problem that a corn steep liquor treatment method in the prior art cannot reduce the content of inorganic phosphorus in corn steep liquor, and is suitable for the field of corn steep liquor processing.

Description

Technical Field

[0001] The invention relates to the field of corn slurry processing, and in particular to a corn slurry processing method and application. Background Art

[0002] Corn slurry is one of the main by-products of corn wet starch production, and the output of corn slurry is about 13% of the corn processing volume. According to statistics. Corn slurry is mainly used as an organic nitrogen source for fermentation, fiber feed and compound fertilizer. Corn slurry is rich in soluble sugars, proteins, polypeptides, amino acids, vitamins, inositol and other organic compounds and inorganic ions, and is a good nitrogen source for microbial fermentation. The protein content in corn slurry is about 40% (mass fraction), and a part of the protein combines with phytate to form a complex, which affects the digestion and utilization of protein. The protein in corn slurry cannot be directly utilized by microorganisms, and the protein and phytate phosphorus content will affect the post-extraction process of the product. Therefore, it is necessary to reduce the adverse factors in corn slurry, improve the quality of corn slurry, make full use of existing resources, turn waste into treasure, and reduce production costs.

[0003] CN103642857B discloses a production method of using corn slurry enzymatic hydrolysate for microbial oil fermentation. The method comprises enzymatic hydrolysing corn slurry with phytase and acid protease, and using the enzymatic hydrolysate instead of corn slurry as a culture medium for microbial oil fermentation to meet market needs.

[0004] Since corn steep liquor is hydrolyzed by phytase, phytic acid is converted into inorganic phosphorus and inositol pentaphosphate-inositol monophosphate, so that the inorganic phosphorus content in the enzymolysis solution is greatly increased, so if this enzymolysis solution is directly used as a culture medium for microbial fermentation, it will have an adverse effect on the fermentation and extraction of production. On the one hand, excessive inorganic phosphorus can affect the growth metabolism of microorganisms, high concentrations of inorganic salts can affect the osmotic pressure of cells, and excessive inorganic phosphorus can cause cell growth to be inhibited. It can also interfere with the metabolic balance inside the cell, affect energy conversion and the synthesis of ATP, and affect the formation of target metabolites, resulting in a decrease in fermentation efficiency or a deterioration in the quality of the target product. On the other hand, too high inorganic phosphorus can increase the difficulty in subsequent product extraction and purification processes. Too high inorganic phosphorus may form precipitation with metal ions such as calcium and magnesium in the fermentation medium, resulting in blockage of the membrane system and pipelines, and affecting the product impurity removal effect, and ultimately affecting product quality. However, the corn steep liquor treatment method in the prior art is difficult to reduce the inorganic phosphorus content in corn steep liquor, affecting the production process of corn steep liquor processing and the cost of production. Summary of the invention

[0005] The main purpose of the present invention is to provide a corn slurry processing method and application, so as to solve the problem that the corn slurry processing method in the prior art cannot reduce the inorganic phosphorus content in the corn slurry.

[0006] In order to achieve the above-mentioned purpose, according to the first aspect of the present invention, a method for treating corn slurry is provided, which comprises: enzymatically hydrolyzing the corn slurry to be treated to obtain an enzymatic hydrolyzate; and filtering the enzymatic hydrolyzate with a flocculant to obtain a corn slurry clear liquid.

[0007] Furthermore, the enzymatic hydrolyzate is mixed with a flocculant and stirred until the first solid appears and then the stirring is stopped; the first solid is allowed to settle and then filtered to obtain a corn syrup clear liquid.

[0008] Furthermore, the amount of flocculant added is 0.10-0.30% of the volume of the enzymatic hydrolyzate.

[0009] Furthermore, the flocculant includes one or more of polyaluminium chloride, aluminium hydroxide or polyferric chloride.

[0010] Furthermore, the treatment method includes: mixing the enzymatic hydrolyzate with a flocculant and a coagulant aid and then filtering to obtain a corn slurry clear liquid; preferably, the flocculant includes one or more of polyaluminum chloride, aluminum hydroxide or polyferric chloride, more preferably polyaluminum chloride; preferably, the coagulant aid includes polyacrylamide; preferably, the amount of polyaluminum chloride added accounts for 0.10-0.25% of the volume of the enzymatic hydrolyzate; preferably, the amount of polyacrylamide added accounts for 0.020-0.030‰ of the volume of the enzymatic hydrolyzate.

[0011] Furthermore, the stirring time is 5 to 20 minutes.

[0012] Furthermore, the standing time is 20 to 60 minutes.

[0013] Furthermore, the enzymolysis includes a first enzymolysis and a second enzymolysis; preferably, the first enzymolysis includes mixing the corn slurry to be treated with a first enzyme for enzymolysis to obtain a first enzymolysis solution; preferably, the second enzymolysis includes mixing the first enzymolysis solution with a second enzyme for enzymolysis to obtain an enzymolysis solution; preferably, the first enzyme includes corn slurry hydrolase or phytase; preferably, the second enzyme includes a protease; preferably, the protease is an alkaline protease.

[0014] Furthermore, the temperature of the first enzymolysis is 40-60°C; the time of the first enzymolysis is 6-10 hours; the amount of the first enzyme added accounts for 3-10‰ of the volume of the corn slurry to be treated; the pH of the second enzymolysis is 8-9; the temperature of the second enzymolysis is 40-60°C; the time of the second enzymolysis is 3-8 hours; the amount of the second enzyme added accounts for 0.5-2‰ of the volume of the first enzymolysis solution.

[0015] In order to achieve the above object, according to a second aspect of the present invention, there is provided an application of the above corn steep liquor processing method in microbial fermentation and preparation of agricultural phosphate fertilizer.

[0016] By applying the technical scheme of the present invention, the corn slurry to be treated is subjected to the first enzymolysis and the second enzymolysis in sequence with a hydrolase and an alkaline protease, the phytic acid-protein complex in the corn slurry is destroyed, the phytic acid is converted into inorganic phosphorus, and the protein is enzymolyzed into small molecule peptides or amino acids. Then, by mixing and filtering the enzymolysis solution obtained after the two enzymolysis with a flocculant, the inorganic phosphorus and protein are removed, and a corn slurry clear liquid with a reduced inorganic phosphorus content can be obtained, thereby improving the purity of the corn slurry clear liquid, being applicable to the production of a variety of corn slurry processing techniques, and being conducive to the industrial development of corn slurry processing. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0018] As mentioned in the background technology, corn slurry is the main by-product of corn wet processing starch, which contains rich nutrients such as protein, growth factors and vitamins, and can provide organic nitrogen sources and growth factors for fermentation production. However, the protein in corn slurry cannot be directly utilized by microorganisms during the fermentation process, and corn slurry contains phytic acid, which combines with protein to form insoluble substances, resulting in low protein digestibility. In the post-extraction process, macromolecular substances such as protein and phytate will block ceramic membranes and nanofiltration membranes, affecting the normal extraction process. If the inorganic phosphorus content in corn slurry is too high, it will affect the chromatographic impurity removal effect and affect the product purity. Therefore, in this application, the inventor attempts to develop a new corn slurry treatment method, so that the inorganic phosphorus content in corn slurry is reduced, and the development of corn slurry processing technology is promoted, and thus a series of protection schemes of the present application are proposed.

[0019] In a first typical embodiment of the present application, a method for treating corn slurry is provided, the method comprising: enzymatically hydrolyzing the corn slurry to be treated to obtain an enzymatic hydrolyzate; and filtering the enzymatic hydrolyzate after mixing it with a flocculant to obtain a corn slurry clear liquid.

[0020] Corn steep liquor is rich in soluble sugars, proteins, polypeptides, amino acids, vitamins, organic compounds such as inositol, and inorganic ions, and is a good nitrogen source for microbial fermentation. However, the protein in corn steep liquor cannot be directly utilized by microorganisms and needs to be decomposed into small molecule polypeptides and amino acids. Moreover, corn steep liquor contains phytate, which is easily formed into insoluble substances in combination with protein, resulting in low protein digestibility. In the subsequent extraction process, macromolecular substances such as protein and phytate will block ceramic membranes and nanofiltration membranes, affecting the normal extraction process, so it is necessary to hydrolyze phytic acid. In the prior art, phytase and protease are often used to process corn steep liquor, and phytic acid and protein are enzymolyzed, but because corn steep liquor is hydrolyzed by phytase, phytic acid is converted into inorganic phosphorus and inositol pentaphosphate-inositol monophosphate, so that the inorganic phosphorus content in the enzymolysis solution is greatly increased, so if this enzymolysis solution is directly used as a culture medium for microbial fermentation, it will have an adverse effect on the fermentation and extraction of production.

[0021] For example, most of the inorganic phosphorus in corn slurry cannot be used by microorganisms, and too high a phosphorus concentration will affect the growth and metabolism of microorganisms, affect the formation of target metabolites, and lead to a decrease in fermentation efficiency. On the other hand, during the extraction process, excessive inorganic phosphorus forms precipitation with metal ions in the fermentation medium, causing blockage of ceramic membranes, nanofiltration membranes, and pipelines, increasing the difficulty of product extraction. At the same time, excessive inorganic phosphorus will cause corn slurry to be unfavorable for chromatographic impurity removal during the purification process, thereby affecting the purity of the final product.

[0022] The present application has developed a new treatment method capable of removing most of the inorganic phosphorus in corn slurry. The present application adds a flocculant to the enzymatic hydrolyzate obtained by enzymatic hydrolysis of the corn slurry to be treated, which is mostly protein decomposed, to remove inorganic phosphorus and the protein remaining after enzymatic hydrolysis, and achieves solid-liquid separation by filtration to obtain a corn slurry clear liquid with reduced inorganic phosphorus content. This corn slurry clear liquid can be used in fermentation experiments of different products, and the filtered residue can also be used as a raw material for agricultural phosphate fertilizer after drying, which reduces the cost of the process and is conducive to promotion in the industrialization process of corn slurry processing.

[0023] In a preferred embodiment, the enzymatic hydrolyzate is mixed with a flocculant and stirred until the first solid appears, and then the stirring is stopped; the first solid is allowed to settle and then filtered to obtain a corn syrup clear liquid.

[0024] In a preferred embodiment, the amount of flocculant added is 0.10-0.30% of the volume of the enzymatic hydrolyzate, including but not limited to 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29% or 0.30%.

[0025] In a preferred embodiment, the flocculant includes one or more of polyaluminium chloride, aluminium hydroxide or polyferric chloride.

[0026] In a preferred embodiment, the treatment method comprises: mixing the enzymatic hydrolysate with a flocculant and a coagulant aid and filtering to obtain a corn syrup clear liquid; the flocculant comprises one or more of aluminum hydroxide or polyferric chloride, more preferably polyaluminum chloride; preferably, the coagulant aid comprises polyacrylamide; the amount of polyaluminum chloride added is 0.10-0.25% of the volume of the enzymatic hydrolysate, including but not limited to 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, 0.65%, 0.66%, 0.67%, 0.68%, 0.69%, 0.70%, 0.71%, 0.72%, 0.73%, 0. .15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20% or 0.25%; preferably, the amount of polyacrylamide added accounts for 0.020-0.030‰ of the volume of the enzymatic solution, including but not limited to 0.020‰, 0.021‰, 0.022‰, 0.023‰, 0.024‰, 0.025‰, 0.026‰, 0.027‰, 0.028‰, 0.029‰ or 0.030‰. Among them, the effective ingredient content of the polyaluminium chloride in the embodiment of the present application is 30%, and the molecular weight of the polyacrylamide anion is 12 million. Those skilled in the art can flexibly select conventional commercially available polyaluminium chloride and polyacrylamide according to actual needs, and the effect of the present application can be achieved.

[0027] The inventors of this application screened the types of flocculants and found that if the phosphorus removal reagents commonly used in the prior art are used to treat the above-mentioned enzymatic hydrolyzate, the phosphorus removal effect is not ideal. Therefore, in the corn slurry treatment system, the removal of inorganic phosphorus cannot be achieved simply by adding commonly used phosphorus removal reagents, but requires the selection of flocculants suitable for the treatment system.

[0028] The present application preferably utilizes a combination of polyaluminium chloride as a flocculant and polyacrylamide as a coagulant aid, and controls the addition amount of the two within the above range. When the two perform a flocculation reaction on the enzymatic hydrolysate, the protein and inorganic phosphorus remaining in the enzymatic hydrolysate can be polymerized to form a first solid. The first solid containing most of the inorganic phosphorus and protein can be removed by a simple solid-liquid separation method, thereby improving the final corn slurry phosphorus removal effect and protein removal effect, and obtaining a corn slurry clear liquid with higher purity.

[0029] In a preferred embodiment, the stirring time is 5 to 20 min, including but not limited to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 min.

[0030] In a preferred embodiment, the standing time is 20 to 60 minutes, including but not limited to 20, 30, 40, 50 or 60 minutes.

[0031] In the present application, the enzymatic hydrolyzate is mixed with a flocculant and stirred within the above-mentioned stirring time range. During the stirring process, a large amount of alum flocs (the first solid) containing proteins and inorganic phosphorus that were not completely hydrolyzed during the enzymatic hydrolysis process will appear in the reaction system. After the stirring is completed, the system is allowed to stand until the alum flocs are completely settled. The liquid and solid in the reaction system at this time can be separated by simple filtering means, that is, the protein and inorganic phosphorus components are removed, and finally a corn pulp clear liquid with a reduced phosphorus content is obtained, which can be used for microbial fermentation later. The filtered residue can be used as a compound raw material for phosphate fertilizer after drying. The process is simple, the cost is low, and there is no waste discharge, which is in line with the concept of green development.

[0032] In a preferred embodiment, the enzymatic hydrolysis includes a first enzymatic hydrolysis and a second enzymatic hydrolysis; preferably, the first enzymatic hydrolysis includes mixing the corn slurry to be treated with a corn slurry hydrolase for enzymatic hydrolysis to obtain a first enzymatic hydrolysis solution; preferably, the second enzymatic hydrolysis includes mixing the first enzymatic hydrolysis solution with an alkaline protease for enzymatic hydrolysis to obtain an enzymatic hydrolysis solution; preferably, the first enzyme includes corn slurry hydrolase or phytase, more preferably corn slurry hydrolase; preferably, the second enzyme includes a protease; preferably, the protease is an alkaline protease.

[0033] In the present application, the corn slurry to be treated is treated by using an enzyme, and the first enzyme can be selected from phytase or corn slurry hydrolase, both of which can destroy the protein-phytate complex in the corn slurry to be treated, and convert the phytate in the complex into inorganic phosphorus and inositol pentaphosphate-inositol monophosphate; the second enzyme is a protease, which can be selected from an acidic protease or an alkaline protease, and can hydrolyze the protein in the first enzymolysis solution into small molecule polypeptides or amino acids. Compared with the acidic protease, the alkaline protease has a better enzymolysis effect in the technical solution of the present application, and is more conducive to the subsequent reaction of the flocculant and the enzymolysis solution. The corn slurry hydrolase in the present application is a composite enzyme, with phytase as the main component and the remaining components as protease. Using corn slurry hydrolase as the first enzyme can reduce the amount of subsequent protease.

[0034] By utilizing the above-mentioned flocculant to react with the enzymatic hydrolysate, the un-enzymatically hydrolyzed protein, phosphorus and other substances are precipitated, and finally by simple filtration, the clarified corn slurry enzymatic hydrolysate, i.e. the above-mentioned corn slurry clear liquid, can be obtained, thereby achieving the purpose of removing inorganic phosphorus and protein in the corn slurry, and most of the protein is converted into amino acid nitrogen and amino acids, effectively solving the problems of membrane blockage and unclean chromatographic impurity removal caused by excessively high inorganic phosphorus content in the post-extraction process, or excessively high protein content affecting product extraction and quality.

[0035] In a preferred embodiment, the temperature of the first enzymatic hydrolysis is 40-60°C, including but not limited to 40°C, 45°C, 50°C, 55°C or 60°C; the time of the first enzymatic hydrolysis is 6-10h, including but not limited to 6, 7, 8, 9, 10h; the amount of the first enzyme added accounts for 3-10‰ of the volume of the corn slurry to be treated, including but not limited to 3‰, 3.5‰, 4‰, 4.5‰, 5‰, 5.5‰, 6‰, 6.5‰, 7‰, 7.5‰, 8‰, 8.5‰, 9‰, 9.5‰ or 10‰.

[0036] Controlling the temperature, time and amount of corn syrup hydrolase added in the first enzymatic hydrolysis within the above range is more conducive to the first enzymatic hydrolysis, improves the efficiency of the enzymatic hydrolysis, and enables the phytate in the corn syrup to be fully converted into inorganic phosphorus and inositol pentaphosphate-inositol monophosphate, thereby facilitating the subsequent second enzymatic hydrolysis and flocculant reaction.

[0037] In a preferred embodiment, the pH of the second enzymolysis is 8-9; the temperature of the second enzymolysis is 40-60°C, including but not limited to 40°C, 45°C, 50°C, 55°C or 60°C; the time of the second enzymolysis is 3-8h, including but not limited to 3, 4, 5, 6, 7 or 8h; the second addition amount accounts for 0.5-2‰ of the volume of the first enzymolysis solution, including but not limited to 0.5‰, 0.6‰, 0.7‰, 0.8‰, 0.9‰, 1‰, 1.1‰, 1.2‰, 1.3‰, 1.04‰, 1.5‰, 1.6‰, 1.7‰, 1.8‰, 1.9‰ or 2‰.

[0038] The present application controls the pH, temperature, time and amount of alkaline protease added of the second enzymatic hydrolysis within the above range, which can promote the second enzymatic hydrolysis to fully convert the protease in the first enzymatic hydrolysis solution into small molecule polypeptides or amino acids, thereby increasing the polypeptide and amino acid content in the final corn slurry clear liquid. The pH of 8 to 9 is the optimal pH range of the alkaline protease of the present application, and within this pH range, it is more conducive to the flocculation effect of the flocculant, further improving the removal rate of inorganic phosphorus, and obtaining a corn slurry clear liquid with reduced phosphorus content.

[0039] In a second typical embodiment of the present application, there is provided an application of any one of the above-mentioned corn steep liquor processing methods in microbial fermentation and the preparation of agricultural phosphate fertilizer.

[0040] The corn slurry clear liquid obtained by the method of corn slurry treatment of the present application can provide an organic nitrogen source for microbial fermentation, reduce the addition of nutrients such as yeast powder and phosphate during microbial fermentation, shorten the fermentation cycle, improve the conversion rate, and further improve the final fermentation yield. In addition, the present application performs secondary enzymolysis and flocculation treatment on corn slurry, and then performs solid-liquid separation after simple filtration, so that the unenzymolyzed protein and residual inorganic phosphorus can be removed, the inorganic phosphorus and protein content in corn slurry can be reduced, and the protein can be converted into polypeptides or amino acids. The process is simple, easy to operate, and has low requirements for equipment, which reduces the production cost of corn slurry phosphorus removal process; moreover, the filter residue solid obtained by filtration can be used as a raw material for agricultural phosphate fertilizer after drying, and there is no wastewater and waste gas emission during the whole corn slurry treatment process, which is more green and environmentally friendly and suitable for promotion to corn slurry processing technology.

[0041] The beneficial effects of the present application will be further explained in detail below in conjunction with specific embodiments.

[0042] The main components of corn steep liquor used in the following examples are: solid content 10.8%; amino nitrogen 2.67 g / L; free amino acid 5.82 g / L; pH 3.8; inorganic phosphorus 0.95 g / L, light yellow. Corn steep liquor hydrolase, alkaline protease and acid protease are all from Baiyin Sainuo Biotechnology Co., Ltd.; unless otherwise specified, the reagents used in the examples and comparative examples of this application are all conventional commercially available products.

[0043] Example 1

[0044] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0045] S2) adjusting the pH of the first enzymatic hydrolyzate to 9.0 using a sodium hydroxide solution, adding 1‰ of alkaline protease, and performing a second enzymatic hydrolysis at 50° C. for 5 hours to obtain an enzymatic hydrolyzate.

[0046] S3) Add 0.2% polyaluminium chloride and 0.025‰ polyacrylamide (anion) to the enzymatic solution, stir for 10 minutes, fully mix and react the enzymatic solution with the flocculant, and slowly generate insoluble suspended matter during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved through plate and frame filtration to obtain a clear and transparent corn slurry clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0047] Example 2

[0048] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0049] S2) adjusting the pH of the first enzymatic hydrolyzate to 9.0 using a sodium hydroxide solution, adding 1‰ of alkaline protease, and performing a second enzymatic hydrolysis at 50° C. for 5 hours to obtain an enzymatic hydrolyzate.

[0050] S3) Add 0.1% polyaluminium chloride and 0.02‰ polyacrylamide (anion) to the enzymatic solution, stir for 10 minutes, fully mix and react the enzymatic solution with the flocculant, and slowly generate insoluble suspended matter during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved through plate and frame filtration to obtain a clear and transparent corn slurry clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0051] Example 3

[0052] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0053] S2) adding 1‰ of acidic protease, performing a second enzymolysis at 50°C for 5h to obtain an enzymolysis solution.

[0054] S3) The pH of the enzymatic solution is adjusted to 9.0 by using sodium hydroxide solution, 0.2% aluminum hydroxide and 0.025‰ polyacrylamide (anion) are added to the enzymatic solution, stirred for 10 minutes, the enzymatic solution and the flocculant are fully mixed and reacted, and insoluble suspended matter is slowly produced during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved by plate and frame filtration, and a clear and transparent corn slurry clear liquid is obtained. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0055] Example 4

[0056] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0057] S2) adding 1‰ of acidic protease, performing a second enzymolysis at 50°C for 5h to obtain an enzymolysis solution.

[0058] S3) The pH of the enzymatic solution is adjusted to 9.0 by sodium hydroxide solution, 0.2% polyferric chloride and 0.025‰ polyacrylamide (anion) are added to the enzymatic solution, stirred for 10 minutes, the enzymatic solution and the flocculant are fully mixed and reacted, and insoluble suspended matter is slowly produced during the flocculation process. The solution is allowed to stand for 30 minutes, and the insoluble suspended matter is settled, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved by plate and frame filtration, and a clear and transparent corn slurry clear liquid is obtained. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0059] Example 5

[0060] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0061] S2) adjusting the pH of the first enzymatic hydrolyzate to 9.0 using a sodium hydroxide solution, adding 1‰ of alkaline protease, and performing a second enzymatic hydrolysis at 50° C. for 5 hours to obtain an enzymatic hydrolyzate.

[0062] S3) Add 0.2% aluminum hydroxide and 0.025‰ polyacrylamide (anion) to the enzymatic solution, stir for 10 minutes, fully mix and react the enzymatic solution with the flocculant, and slowly generate insoluble suspended matter during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved through plate and frame filtration to obtain a clear and transparent corn slurry clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0063] Example 6

[0064] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0065] S2) adjusting the pH of the first enzymatic hydrolyzate to 9.0 using a sodium hydroxide solution, adding 1‰ of alkaline protease, and performing a second enzymatic hydrolysis at 50° C. for 5 hours to obtain an enzymatic hydrolyzate.

[0066] S3) Add 0.2% polyferric chloride and 0.025‰ polyacrylamide (anion) to the enzymatic solution, stir for 10 minutes, fully mix and react the enzymatic solution with the flocculant, and slowly generate insoluble suspended matter during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved through plate and frame filtration to obtain a clear and transparent corn slurry clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0067] Comparative Example 1

[0068] Take 50L corn slurry, adjust the pH to 9.0 with sodium hydroxide solution, add 0.2% polyaluminium chloride, 0.025‰ polyacrylamide (anion), stir for 10 minutes, fully mix and react the enzymatic solution with the flocculant, and slowly produce insoluble suspended matter during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved through plate and frame filtration to obtain a clear and transparent corn slurry clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0069] Comparative Example 2

[0070] S1) taking 50 L of corn steep liquor, adding corn steep liquor hydrolase at 5‰, performing a first enzymolysis at 50°C for 8 h, and obtaining a first enzymolysis solution.

[0071] S2) The pH of the first enzymatic hydrolyzate is adjusted to 9.0 by using sodium hydroxide solution, 1‰ of alkaline protease is added, and the second enzymatic hydrolysis is carried out at 50°C for 5 hours to obtain an enzymatic hydrolyzate. The solid-liquid separation is achieved by plate and frame filtration to obtain a clear and transparent corn syrup clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0072] Comparative Example 3

[0073] S1) 50 L of corn steep liquor was taken, corn steep liquor hydrolase was added at a rate of 5‰, and enzymolysis was performed at 50°C for 8 h to obtain enzymolysis solution.

[0074] S2) The pH of the enzymatic solution is adjusted to 9.0 using sodium hydroxide solution, 0.2% polyaluminium chloride and 0.025‰ polyacrylamide (anion) are added, stirred for 10 minutes, the enzymatic solution and the flocculant are fully mixed and reacted, and insoluble suspended matter is slowly produced during the flocculation process. The solution is allowed to stand for 30 minutes, and the insoluble suspended matter is settled down. The upper layer is the corn slurry clear liquid after flocculation. The solid-liquid separation is achieved by plate and frame filtration, and a clear and transparent corn slurry clear liquid is obtained. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0075] Comparative Example 4

[0076] S1) taking 50 L corn steep liquor, adjusting the pH to 9.0 with sodium hydroxide solution, adding 1‰ alkaline protease, performing enzymolysis at 50°C for 5 hours, and obtaining an enzymolysis solution.

[0077] S2) Add 0.2% polyaluminium chloride and 0.025‰ polyacrylamide (anion) to the enzymatic solution, stir for 10 minutes, fully mix and react the enzymatic solution with the flocculant, and slowly generate insoluble suspended matter during the flocculation process. Let it stand for 30 minutes, wait for the insoluble suspended matter to settle, and the upper layer is the flocculated corn slurry clear liquid. The solid-liquid separation is achieved through plate and frame filtration to obtain a clear and transparent corn slurry clear liquid. The filter residue intercepted by the plate and frame can be used as a raw material for agricultural phosphate fertilizer after drying.

[0078] The amino acid nitrogen, amino acid and inorganic phosphorus contents of the corn slurry obtained by the treatment methods of the above-mentioned embodiments and comparative examples were measured. The test results are shown in Table 1. The results show that the corn slurry can be partially converted into polypeptides or amino acids by the treatment method of the present application, and the flocculation reaction can effectively remove macromolecular substances such as inorganic phosphorus and protein in the corn slurry.

[0079] Table 1

[0080] Amino nitrogen / (g / L) Amino Acid / (g / L) Inorganic phosphorus / (g / L) Corn Syrup 2.67 5.82 0.95 Example 1 5.62 15.67 0.15 Example 2 5.36 15.16 0.34 Example 3 3.24 10.44 1.83 Example 4 3.41 9.52 1.56 Example 5 5.36 15.21 1.78 Example 6 5.23 15.44 1.68 Comparative Example 1 2.74 5.95 0.34 Comparative Example 2 5.47 15.75 2.51 Comparative Example 3 2.70 5.98 0.87 Comparative Example 4 5.45 15.84 0.43

[0081] The corn steep liquor prepared by the method of Example 1 was used to prepare the seed culture medium and fermentation culture medium of L-valine. The specific formula is as follows:

[0082] Seed culture medium: corn steep liquor at 5.0 g / L and 10.0 g / L addition, glucose 10 g / L, diammonium phosphate 5 g / L, potassium dihydrogen phosphate 5 g / L, magnesium sulfate heptahydrate 0.2 g / L, ferrous sulfate heptahydrate 0.01 g / L, vitamin B 150 μg / L, and ammonia water to adjust the pH to 6.5-7.8.

[0083] Fermentation medium: corn steep liquor was added in amounts of 5.0 g / L and 10.0 g / L, glucose 160 g / L, diammonium hydrogen phosphate 20 g / L, potassium dihydrogen phosphate 5 g / L, ammonium sulfate 1 g / L, magnesium sulfate heptahydrate 0.9 g / L, ferrous sulfate heptahydrate 0.05 g / L, vitamin B1 500 μg / L, and the pH was continuously adjusted to 6.5-7.8 with aqueous ammonia.

[0084] The culture medium containing untreated corn steep liquor was used as the control group. The above seed culture medium and fermentation culture medium were used to culture the L-valine fermentation production strain, and the specific method was as follows:

[0085] Seed culture: Brevibacterium flavum M2019496 (the construction method of strain M2019496 is shown in patent application CN110643547 A) was used for L-valine fermentation production. The frozen strain in a glycerol tube was first inoculated into LB medium for activation culture, and cultured at 28±1°C and 180r / min for 24h to obtain seed solution.

[0086] Fermentation medium: The cultured seed liquid was transferred into a 5L fermentation tank, the culture temperature was 37°C, the air was isolated and anaerobic fermentation was carried out, the rotation speed was 300r / min, and the pH was 6.8.

[0087] The glucose content was determined using an SBA biosensor, and the L-valine content was determined using HPLC. The fermentation results are shown in Table 2, and the results show that when untreated corn slurry was added to the seed culture medium and the fermentation medium, the L-valine yield was 60.5g / L and the conversion rate was 50.1%. When 5.0g / L of corn slurry enzymolyte was added to the seed culture medium and the fermentation medium, the L-valine yield was 74.8g / L and the conversion rate was 61.7%. When 10.0g / L of corn slurry enzymolyte was added to the seed culture medium and the fermentation medium, the L-valine yield was 73.7g / L and the conversion rate was 60.8%, which was significantly higher than that of adding untreated corn slurry. When the fermentation broth with corn slurry clear liquid was extracted later, the flux of the ceramic membrane and the nanofiltration membrane was higher than that of the fermentation broth with untreated corn slurry. And the chromatographic impurity removal was more thorough, and the purity of the product obtained was higher.

[0088] Table 2

[0089] Medium type Fermentation cycle / (h) L-Valine / (g / L) Conversion rate / (%) Unprocessed corn syrup 63.0 60.5 50.1 Corn Steep Liquid (5.0g / L) 48.5 74.8 61.7 Corn Steep Liquid (10.0g / L) 47.3 73.7 60.8

[0090] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the present application utilizes corn slurry hydrolase and alkaline protease to perform secondary enzymolysis on corn slurry in turn, and adds flocculant to perform flocculation treatment on the secondary enzymolysis solution, and finally, after simple filtration and solid-liquid separation, most of the unenzymolyzed protein and residual inorganic phosphorus in the corn slurry can be removed, and finally, the corn slurry clear liquid with reduced inorganic phosphorus and protein content can be obtained, the process flow is simple, the operation is convenient, the equipment requirements are low, and the production cost is reduced while obtaining a better phosphorus removal effect; and the filtered residue solid can be used as a raw material for agricultural phosphate fertilizer after drying, and there is no wastewater and waste gas emission in the process of corn slurry treatment of the present application, which is more green and environmentally friendly and suitable for promotion to corn slurry processing technology. Finally, the corn slurry clear liquid obtained by the method of corn slurry treatment of the present application can provide an organic nitrogen source for microbial fermentation, reduce the addition of nutrients such as yeast powder and phosphate in the process of microbial fermentation, shorten the fermentation cycle, improve the conversion rate, and further improve the final fermentation yield.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for processing corn steep liquor, characterized in that: The processing method comprises: After enzymatic hydrolysis of the corn steep liquor to be treated, an enzymatic hydrolyzate is obtained; The enzymatic hydrolyzate is mixed with a flocculant and then filtered to obtain a corn steep liquor.

2. The processing method according to claim 1, characterized in that: The enzymatic hydrolysate is mixed with the flocculant and stirred until the first solid appears and then the stirring is stopped; The first solid is allowed to stand for sedimentation and then filtered to obtain the corn steep liquor.

3. The processing method according to claim 2, characterized in that: The added amount of the flocculant accounts for 0.10-0.30% of the volume of the enzymatic hydrolyzate.

4. The processing method according to claim 3, characterized in that: The flocculant includes one or more of polyaluminium chloride, aluminium hydroxide or polyferric chloride.

5. The processing method according to claim 4, characterized in that: The treatment method comprises: mixing the enzymatic hydrolyzate with the flocculant and the coagulant aid and filtering to obtain the corn steep liquor; Preferably, the flocculant comprises one or more of aluminum hydroxide or polyferric chloride, more preferably polyaluminum chloride; Preferably, the coagulant aid comprises polyacrylamide; Preferably, the amount of the polyaluminium chloride added is 0.10-0.25% of the volume of the enzymatic hydrolysate; Preferably, the added amount of the polyacrylamide accounts for 0.020-0.030‰ of the volume of the enzymatic hydrolysate.

6. The processing method according to claim 2, characterized in that: The stirring time is 5 to 20 minutes.

7. The processing method according to claim 2, characterized in that: The standing time is 20 to 60 minutes.

8. The processing method according to claim 1, characterized in that: The enzymolysis includes a first enzymolysis and a second enzymolysis; Preferably, the first enzymatic hydrolysis comprises mixing the corn steep liquor to be treated with a first enzyme for enzymatic hydrolysis to obtain a first enzymatic hydrolysis solution; Preferably, the second enzymolysis comprises mixing the first enzymolysis solution with a second enzyme for enzymolysis to obtain the enzymolysis solution; Preferably, the first enzyme comprises corn steep liquor hydrolase or phytase; Preferably, the second enzyme comprises a protease; Preferably, the protease is an alkaline protease.

9. The processing method according to claim 8, characterized in that: The temperature of the first enzymolysis is 40-60°C; the time of the first enzymolysis is 6-10 hours; the amount of the first enzyme added accounts for 3-10‰ of the volume of the corn steep liquor to be treated; The pH of the second enzymolysis is 8-9; the temperature of the second enzymolysis is 40-60°C; the time of the second enzymolysis is 3-8h; and the amount of the second enzyme added accounts for 0.5-2‰ of the volume of the first enzymolysis solution.

10. Use of the corn steep liquor treatment method according to any one of claims 1 to 9 in microbial fermentation and preparation of agricultural phosphate fertilizer.