CN114890823B - Method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation liquor - Google Patents
Method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation liquor Download PDFInfo
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Abstract
The invention relates to a method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation liquor, which aims to solve the problems of high cost for separating lactic acid and ammonium ions in the existing lactic acid fermentation liquor and environmental pollution and waste caused by unrecovered ammonium ions. The invention uses ammonia water as a neutralizer in the lactic acid fermentation process, the speed of neutralizing acid with ammonia water is higher than that of calcium carbonate, the pH adjustment is stable, and simultaneously, an inorganic nitrogen source is provided for the growth of bacterial strains, so that higher nitrogen fertilizer yield can be obtained. The invention is applied to the field of nitrogenous fertilizer preparation.
Description
Technical Field
The invention relates to a method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation liquor.
Background
The advantages of using ammonia to replace calcium carbonate for lactic acid fermentation in lactic acid fermentation are well known, but for the introduced ammonium, it is generally not considered to recover it as other substances co-enter the waste liquor. More than 95% of lactic acid is extracted by combining ultrafiltration and electrodialysis or ion exchange resin, wherein the electro-dialysis or ion exchange resin can better separate ammonium ions in ammonium lactate to obtain purified lactic acid, but the equipment has lower repeated use rate and higher cost, and cannot realize large-scale popularization and application; the organic extraction process needs to treat the waste liquid containing the residual organic solvent after extraction, increases the treatment steps and the difficulty of waste liquid treatment, and simultaneously has the recovery rate of lactic acid lower than 90 percent. If the ammonium-containing waste liquid generated by the means is directly discharged, the water body is seriously affected. In general, the protein, bacterial cells and the like in the fermentation liquid can be removed well by membrane separation means such as ultrafiltration, and how to simply and efficiently separate lactic acid and ammonium ions is a key to reducing the purification cost.
Ammonium sulfate is an excellent nitrogenous fertilizer, can make branches and leaves grow vigorously, improves fruit quality and yield, and enhances the resistance of crops to disasters. The ammonia reacts with sulfuric acid to generate ammonium sulfate, and then the ammonium sulfate is crystallized and dried to obtain solid ammonium sulfate, so that the required temperature is high and the cost is high.
Disclosure of Invention
The invention aims to solve the problems of high cost for separating lactic acid and ammonium ions in the existing lactic acid fermentation liquid and environmental pollution and waste caused by the ammonium ions which are not recovered, and provides a method for preparing a nitrogen fertilizer by using sweet sorghum stalk L-lactic acid fermentation liquid.
The invention relates to a method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation liquor, which comprises the following steps:
1. crushing sweet sorghum stalks into filaments to obtain sweet sorghum stalk filaments;
2. preparing an L-lactic acid bacteria liquid and filling the liquid into a sterile watering can; the culture medium used for the L-lactic acid bacteria liquid is MRS liquid culture medium, activated L-lactic acid bacteria is inoculated in MRS, then anaerobic culture is carried out for 18 to 24 hours in an incubator with the temperature of 37 to 45 ℃, and the concentration of the bacteria liquid is controlled at 10 5 ～10 7 cfu/g；
3. Measuring the moisture content of the stalk filaments, and controlling the moisture content of the stalk to 68-75% by spraying L-lactobacillus bacteria liquid to obtain sweet sorghum residues to be fermented; filling sweet sorghum residues to be fermented into silage bags, filling the silage bags layer by layer, compacting the silage bags layer by layer, squeezing out excessive air, compacting the seal bags, and storing the seal bags at 20-25 ℃ in a dark place;
4. silage after storage is transferred into a fermentation tank, silage filling is carried out according to the total solid content of 5-10%, cellulase and magnesium sulfate are sequentially added into the silage, and L-lactic acid fermentation is carried out, so that fermentation liquor is obtained; regulating the pH of the fermentation liquor to 5.8-6.2; introducing nitrogen for 2-4h at a flow rate of 500mL/min, and fermenting for 48-72 h at a temperature of 37-45 ℃ and a rotating speed of 200-300 rpm;
5. after fermentation, carrying out solid-liquid separation on the fermentation liquor in a filter pressing mode to obtain a crude fermentation liquor;
6. removing impurities from the crude fermentation broth by adopting a membrane separation technology to obtain a purified L-ammonium lactate fermentation broth;
7. performing rotary evaporation on the L-ammonium lactate fermentation liquor, wherein the evaporation temperature is 65-75 ℃, concentrating the mass content of the L-ammonium lactate to 60-80%, then adding ethanol, then adding concentrated sulfuric acid, then filtering to obtain ammonium sulfate precipitate, and drying to constant weight at 80-105 ℃ to obtain the nitrogen fertilizer.
The method uses sulfuric acid to acidify and separate ammonium lactate, the ammonium lactate reacts with sulfuric acid to generate ammonium sulfate, ammonium ions are better separated from lactic acid, and if the ammonium in the ammonium lactate fermentation liquid is recycled, the interference on subsequent lactic acid esterification and purification and the risk of secondary utilization of waste liquid can be reduced. Ammonium sulfate is dissolved in water and insoluble in ethanol, in the integral purification process, the extracted lactic acid solution is esterified with ethanol to form ethyl lactate, the ethyl lactate is extracted from water phase, the obtained ethyl lactate can be hydrolyzed to separate lactic acid and ethanol, and the separated ethanol can be recycled. The method reduces the water content in the lactic acid solution in advance, adds a proper amount of ethanol before acidification, reduces the solubility of ammonium sulfate, extracts the pure lactic acid solution by separating ammonium sulfate precipitate, does not add impurities additionally, does not increase complicated steps and equipment, reduces the cost generated by the equipment, and is suitable for large-scale application.
The invention has the beneficial effects that:
according to the invention, ammonia water is used as a neutralizer in the lactic acid fermentation process, the speed of neutralizing acid with ammonia water is higher than that of calcium carbonate, the pH value is regulated stably, the solubility of ammonium lactate is higher than that of calcium lactate, and meanwhile, an inorganic nitrogen source is provided for the growth of bacterial strains, so that higher yield of ammonium lactate can be obtained, more nitrogenous fertilizer can be obtained, and the recovery rate of ammonium sulfate can reach 100%. In addition, compared with the traditional lactic acid fermentation neutralization mode, the invention uses ammonia water to adjust fermentation pH, reduces pressure for the subsequent separation and purification process of L-lactic acid, does not generate waste gypsum, and reduces the risk of membrane blockage. For the recovery of ammonium ions, by adding ethanol before acidification, the solubility of ammonium sulfate can be greatly reduced at room temperature, the energy consumption is low, and the ammonium sulfate precipitates rapidly.
Drawings
The filled sweet sorghum silage bag of fig. 1;
FIG. 2 change in sugar in sweet sorghum silage over time; wherein 1 is reducing sugar, 2 is total sugar, and 3 is glucose;
FIG. 3 changes in L-lactic acid content and pH with time in sweet sorghum silage; wherein x is pH and y is lactic acid;
FIG. 4 continuous L-lactic acid fermentation after ensiling of sweet sorghum; wherein a is a control group, b is cellulase and c is Mg 2+ D is cellulose+Mg 2+ 。
Detailed Description
The first embodiment is as follows: the method for preparing the nitrogen fertilizer by utilizing the sweet sorghum stalk L-lactic acid fermentation liquor in the embodiment comprises the following steps:
1. crushing sweet sorghum stalks into filaments to obtain sweet sorghum stalk filaments;
2. preparing an L-lactic acid bacteria liquid and filling the liquid into a sterile watering can; the culture medium used for the L-lactic acid bacteria liquid is MRS liquid culture medium, activated L-lactic acid bacteria is inoculated in MRS, then anaerobic culture is carried out for 18 to 24 hours in an incubator with the temperature of 37 to 45 ℃, and the concentration of the bacteria liquid is controlled at 10 5 ～10 7 cfu/g；
3. Measuring the moisture content of the stalk filaments, and controlling the moisture content of the stalk to 68-75% by spraying L-lactobacillus bacteria liquid to obtain sweet sorghum residues to be fermented; filling sweet sorghum residues to be fermented into silage bags, filling the silage bags layer by layer, compacting the silage bags layer by layer, squeezing out excessive air, compacting the seal bags, and storing the seal bags at 20-25 ℃ in a dark place;
4. silage after storage is transferred into a fermentation tank, silage filling is carried out according to the total solid content of 5-10%, cellulase and magnesium sulfate are sequentially added into the silage, and L-lactic acid fermentation is carried out, so that fermentation liquor is obtained; regulating the pH of the fermentation liquor to 5.8-6.2; introducing nitrogen for 2-4h at a flow rate of 500mL/min, and fermenting for 48-72 h at a temperature of 37-45 ℃ and a rotating speed of 200-300 rpm;
5. after fermentation, carrying out solid-liquid separation on the fermentation liquor in a filter pressing mode to obtain a crude fermentation liquor;
6. removing impurities from the crude fermentation broth by adopting a membrane separation technology to obtain a purified L-ammonium lactate fermentation broth;
7. performing rotary evaporation on the L-ammonium lactate fermentation liquor, wherein the evaporation temperature is 65-75 ℃, concentrating the mass content of the L-ammonium lactate to 60-80%, then adding ethanol, then adding concentrated sulfuric acid, then filtering to obtain ammonium sulfate precipitate, and drying to constant weight at 80-105 ℃ to obtain the nitrogen fertilizer.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: in the first step, the thickness of the sweet sorghum stalk silk is 1-2mm. The other is the same as in the first embodiment.
And a third specific embodiment: this embodiment differs from the first or second embodiment in that: the activation method of the L-lactic acid bacteria in the second step comprises the following steps: inoculating L-lactic acid bacteria into MRS slant culture medium, and anaerobic culturing at 37-45deg.C for 16-24 hr. The other embodiments are the same as those of the first or second embodiment.
The specific embodiment IV is as follows: this embodiment differs from one of the first to third embodiments in that: the method for measuring the moisture content of the stalk silk in the third step comprises the following steps: weighing 10-50g of crushed sweet sorghum residue, uniformly dividing into 3 parts, putting into a dry and clean crucible, and recording the mass of the empty crucible and each part of sweet sorghum residue; placing the sweet sorghum stalk into a 105 ℃ oven for 2-3 hours until the weight is constant, then placing the sweet sorghum stalk into a dryer for cooling to room temperature, and weighing to calculate the moisture contained in the sweet sorghum stalk. The other is the same as in one of the first to third embodiments.
Fifth embodiment: this embodiment differs from one to four embodiments in that: in the fourth step, the pH is regulated by 1-3M ammonia water or 0.5-1M dilute hydrochloric acid. The others are the same as in one to one fourth embodiments.
Specific embodiment six: this embodiment differs from one of the first to fifth embodiments in that: and in the fourth step, the silage storage time is 4-8 days. The other is the same as in one of the first to fifth embodiments.
Seventh embodiment: this embodiment differs from one of the first to sixth embodiments in that: the addition amount of the cellulase in the fourth step is 0.01-0.05% of the weight of the sweet sorghum stalk, and the enzyme activity is 5000-10000U/g. The others are the same as in one of the first to sixth embodiments.
Eighth embodiment: this embodiment differs from one of the first to seventh embodiments in that: in the fourth step, the concentration of magnesium sulfate in the fermentation liquor is 0.5-4 mM/L. The other is the same as in one of the first to seventh embodiments.
Detailed description nine: this embodiment differs from one to eight of the embodiments in that: and in the seventh step, the mass content of the L-ammonium lactate is concentrated to 60-80% by a rotary evaporator. The others are the same as in one to eight embodiments.
Detailed description ten: this embodiment differs from one of the embodiments one to nine in that: in the seventh step, L-ammonium lactate fermentation broth: ethanol: the molar ratio of the concentrated sulfuric acid is 1:5:0.5-1. The other is the same as in one of the embodiments one to nine.
In the embodiment, the ethanol is absolute ethanol, and the mass concentration of the concentrated sulfuric acid is 90-98%.
The beneficial effects of the invention are verified by the following examples:
example 1: harvesting and physicochemical characteristic measurement of sweet sorghum stalks
The test sweet sorghum is planted in Daqing city of Heilongjiang province, soil preparation, fertilization and cultivation are started in 5 months, and the planted variety is warpThe sweet sorghum variety which is suitable for fermentation and is planted and screened in 3 years is numbered as 12Fs9005, the stem sugar brix% is 14-18, and the sweet sorghum variety is suitable for biological refining. Harvesting in the early 10 months, wherein the average plant height is 1.8-2.2 m and the biological yield is about 15kg/m when harvesting, and the sweet sorghum is not mature in the booting stage due to the large rainfall capacity of the Heilongjiang province in 2021 and the worse growth vigor than the former one 2 。
The harvested sweet sorghum is removed with roots and leaves, and the stalks are transported to the room for crushing on the same day, and crushed into filaments with the thickness of about 1-3mm. The crushing work is completed within 48 hours, so that the loss of sugar and the breeding of spoilage bacteria are reduced, and fresh crushed stalks can be stored in a refrigerator at the temperature of minus 20 ℃ to ensure the freshness of the stalks.
The water content of the crushed sweet sorghum stalks is measured according to national standard GB/T6435-2014; squeezing to obtain sweet sorghum juice, and measuring sugar brix by using a sugar brix meter; weighing 10-20g sweet sorghum residue, preparing leaching solution according to a ratio of 1:10, crushing the leaching solution by a high-speed juicer, and centrifuging at high speed by a centrifuge to obtain supernatant (centrifuging condition: 10000-12000rpm,8-10 min) for measuring soluble sugar, reducing sugar, glucose, L-lactic acid and pH value. Soluble sugar, reducing sugar content according to DNS method; glucose, L-lactate content was measured by a biological dual channel sensor (SBA-40E); the pH value is measured by a Metrele acidometer; the cellulose content was determined by potassium dichromate titration. All index determinations were repeated three times. The relevant physicochemical indexes of the sweet sorghum are shown in table one:
TABLE 1 physical and chemical characteristics parameters table of tested sweet sorghum
Example 2 preparation and storage of sweet sorghum silage
The water content of the tested sweet sorghum meets the optimal water content (65% -75%) of the silage raw material, so that the adding proportion of the microbial inoculum (commercial lactobacillus plantarum, GDMCC 1.191) is set to be 5% of the mass of the raw material. And (3) preparing sweet sorghum silage by using a vacuum bag with a plug, wherein each bag is filled with 400-500g of sweet sorghum residues, and 20-25mL of bactericide is sprayed. Firstly, placing weighed sweet sorghum stalk residues into a tray which is clean and dry; turning sweet sorghum residue with clean hands, and spraying a microbial inoculum at the same time to uniformly mix the sweet sorghum residue with raw materials; spraying a small amount of microbial inoculum in the pre-filled bag, putting the uniformly mixed sweet sorghum residues into the bag, putting the sweet sorghum residues layer by layer, pressing the sweet sorghum residues layer by layer, removing air in the raw materials, compacting the sweet sorghum residues again after filling, and packaging the sweet sorghum residues; the air in the bag is pumped out by a pump, as shown in fig. 1.
And placing the sweet sorghum silage bag in a constant temperature incubator at 25 ℃, covering the light-transmitting glass on the incubator, and carrying out shading storage. FIG. 2 shows the change of sugar content in sweet sorghum silage over time, and FIG. 3 shows the change of L-lactic acid content and pH value in sweet sorghum silage over time.
As is evident from fig. 2, the change trend of each sugar in the sweet sorghum silage is the same, the sugar is reduced in 0-2 days, the content reduction rate is increased in 2-8 days, and then the sugar is gradually stabilized, which means that the sugar is in a period of vigorous metabolism of the strain in 2-8 days, the sugar consumption is severe, and the metabolic activity of the strain is inhibited due to higher accumulation of lactic acid; as can be seen from FIG. 3, the pH value is reduced slightly within 0-2 days, the L-lactic acid content is increased slightly, and L-lactic acid is accumulated rapidly in silage within 2-8 days, and the L-lactic acid is in a stationary phase along with the great reduction of the pH value, and the pH value and the L-lactic acid are not changed obviously within 8-32 days, so that the metabolic activity of the strain is limited due to the lower silage pH value, so that the sugar consumption is weakened within 8-16 days, and the L-lactic acid content is accumulated slowly.
In conclusion, within 2-8 days of sweet sorghum silage, the growth situation of the endostrains is good, and a good acid environment is formed. At day 8 of silage, the total sugar content was reduced by about 25.35% and the lactic acid content was increased to 1.94%. Silage of the added strain, 74.65% of total sugar is retained, which is significant for subsequent continuous fermentation of L-lactic acid.
Example 3: feasibility test of continuous L-lactic acid fermentation after sweet sorghum silage
The sweet sorghum silage prepared in example 2 was stored at 20-25℃for 8 days, and 10-20g was used for physical and chemical index measurement. And directly inoculating the sweet sorghum silage into a fermentation tank to perform a feasibility test of continuous L-lactic acid fermentation. The blank control was treated without addition of the treatment group.
Fermenting for 8 days with 2L fermentation volume, storing about 400g sweet sorghum silage in BIOSTATA fermenter, adding 1.6L sterile water, and adding commercial cellulase and magnesium sulfate; the addition amount of the commercial cellulase is 0.01-0.05% of the weight of the sweet sorghum stalk, and the enzyme activity is 5000-10000U/g; the concentration of magnesium sulfate in the fermentation broth was 0.5mM/L. Packaging the fermentation tank under aseptic conditions; connecting an acid-base neutralizer to a peristaltic pump, adjusting automatic control parameters, starting a fermentation tank and a heat preservation belt power supply, adjusting the initial pH value of a fermentation liquor to 5.8-6.1 by ammonia water, controlling the temperature to 37 ℃, stirring at 200-300rpm, and introducing N 2 2-3h; and observing through a monitoring screen, taking fermentation liquor at regular time, and measuring various parameters.
To verify the effect of cellulase and magnesium ions on L-lactic acid fermentation, three control experiments were selected, one with only commercial cellulase of the same mass, one with only magnesium sulfate of the same addition, and one with neither. The fermentation is carried out for 72 hours, and the change of the L-lactic acid content in the fermentation process is shown in figure 4
As is apparent from fig. 4, the increase of the L-lactic acid content was slow in the first 12 hours, because the microorganisms required time to recover due to the abrupt change of the pH of the fermentation environment, and then entered into the rapid L-lactic acid fermentation period, and at about 48 hours of fermentation, the L-lactic acid content reached the highest accumulation, and then entered into the stationary period, confirming that the fermentation process scheme of continuous fermentation after silage of sweet sorghum was viable.
Meanwhile, it is obvious that the addition of the cellulase is favorable for accumulation of L-lactic acid, and the L-lactic acid content is increased by 35.05% compared with that of a control group (neither of which is added); the magnesium ions are added to accelerate the recovery of microorganisms in the earlier stage of fermentation, the lactic acid production rate of the control group is 0.0155g/L/h in the first 12 hours, the cellulose addition treatment group is 0.1881g/L/h, and the magnesium sulfate addition treatment group is 0.2838g/L/h, so that the lactic acid production rate is obviously improved. The treatment group to which cellulose and magnesium sulfate were added had the highest lactic acid yield of 71.56g/L. This demonstrates that cellulase and magnesium ions have a pushing effect on L-lactic acid fermentation.
Example 4: sweet sorghum silage continuous L-lactic acid fermentation test
In order to solve the problem that the strain is recovered frequently and longer in the earlier stage of fermentation, the lactic acid production rate and yield are improved, and the strain GDMCC1.191 bacterial liquid is added for the first time.
The fermentation strain GDMCC1.191 was activated by MRS slant medium. Inoculating the activated strain into 150-300mLMRS liquid culture medium by using an inoculating loop, and performing anaerobic culture at 37-45 ℃ for 18-24 hours to prepare fermentation seed liquid for later use; the fermentation volume is 2-3L, and the fermentation seed liquid is 5-10% of the fermentation volume; about 400g of sweet sorghum silage is put into a BIOSTATA fermentation tank, commercial cellulase, magnesium sulfate and about 1.5L of sterile water are added, the addition amount of the commercial cellulase is 0.01-0.05% of the weight of the sweet sorghum stalk, and the enzyme activity is 5000-10000U/g. Packaging the fermentation tank under aseptic condition, wherein the concentration of magnesium ions in the fermentation liquid is 1mM/L; connecting an acid-base neutralizer to a peristaltic pump, adjusting automatic control parameters, starting a fermentation tank and a heat preservation belt power supply, adjusting the initial pH value of a fermentation liquor to 5.8-6.2 by ammonia water, controlling the temperature to 37-45 ℃, stirring at 200-300rpm, and introducing N 2 2-3h; observing through a monitoring screen, and adding the cultured fermentation seed liquid after each adjusting parameter is stable; the fermentation time is 48-72 hours.
Example 5: separation and purification of L-lactic acid fermentation broth
Example 4 after the end of the L-lactic acid fermentation, first the undigested sweet Gao Liangjing stalk was separated; using eight layers of sterile medical gauze, filtering the fermentation liquor, washing sweet sorghum filter residues with a small amount of sterile water for 2-3 times, squeezing water completely, and storing the sweet sorghum residues at-20 ℃ for soil remediation; filtering the separated filter residues by a membrane to remove microbial thalli, removing macromolecular organic matters such as proteins by ultrafiltration, decoloring by active carbon, and collecting filtrate which is the purified L-lactic acid fermentation liquor (L-ammonium lactate).
Example 6: preparation of ammonium sulfate
The purified L-lactic acid fermentation broth of example 5 (concentration about 11.2 wt%) was transferred to a rotary evaporator at a temperature of 60-70℃and evaporated to a concentration of 25wt% of L-ammonium lactate solution in order to reduce the production of L-lactic acid self-aggregates. After the concentrated L-lactic acid solution is cooled, the L-lactic acid content is measured; 5 molar equivalents of absolute ethyl alcohol of L-ammonium lactate are added, 0.75 molar equivalents of concentrated sulfuric acid is added according to the content of the L-lactic acid, the sulfuric acid reacts with the L-ammonium lactate to generate ammonium sulfate and L-lactic acid, and the purpose of removing ammonium ions is achieved through the reaction, wherein the chemical reaction formula is shown in the formula 1. The ethanol in the solution causes ammonium sulfate to be stored in the solution in a precipitated state, ammonium sulfate precipitation is trapped on a membrane through membrane separation, the filter membrane is dried overnight at 80 ℃, the dried ammonium sulfate is scraped off, and the ammonium sulfate is stored in a dryer, thus completing the preparation of the ammonium sulfate.
C 3 H 7 NO 3 +H 2 O+0.75H 2 SO 4 →C 3 H 6 O 3 +0.25H 2 SO 4 +H 2 O+0.5(NH 4 ) 2 SO 4 (1)
To determine the effect of different concentration on ammonium sulfate yield, the following different treatments were used as controls:
a. concentrating the concentration of the L-ammonium lactate solution to 25wt%, and adding no absolute ethyl alcohol; b. ethanol is added, and the concentration of L-ammonium lactate is concentrated to 50wt%; c. no absolute ethyl alcohol is added, and the concentration of the L-ammonium lactate is concentrated to 50wt%; d. ethanol is added, and the concentration of L-ammonium lactate is concentrated to 75wt%; e. the concentration of L-ammonium lactate was concentrated to 75wt% without the addition of absolute ethanol. .
TABLE 2 relation between ammonium sulfate yield and water content of L-ammonium lactate fermentation broth
1: l-ammonium lactate: ethanol=5 (mol)
2: recovery (%) =100 x (actual yield/theoretical yield): the theoretical yield of ammonium sulfate is 70.62g
As can be seen from Table 2, the moisture content of the L-lactic acid fermentation broth, as well as the addition or absence of ethanol, is critical to the yield of ammonium sulfate. Ammonium sulfate can be rapidly precipitated in the presence of ethanol as a precipitate from the fact that ammonium sulfate is water-soluble and ethanol-insoluble. The water content of the L-ammonium lactate fermentation broth affects the solubility of ammonium sulfate, and the yield of ammonium sulfate increases with the decrease of water. Therefore, the evaporation concentration part should reduce the water content in the fermentation liquor as much as possible, so as to facilitate the subsequent removal of ammonium ions in the L-ammonium lactate and the precipitation of ammonium sulfate. The method for precipitating the ammonium sulfate by concentrating the L-ammonium lactate and adding the ethanol is a process which is convenient to operate and low in cost, and the obtained ammonium sulfate can be reused as a soil fertilizer for soil, so that the waste of resources is reduced.
Claims (7)
1. A method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation liquor is characterized by comprising the following steps:
1. crushing sweet sorghum stalks into filaments to obtain sweet sorghum stalk filaments;
2. preparing an L-lactic acid bacteria liquid and filling the liquid into a sterile watering can; the culture medium used for the L-lactic acid bacteria liquid is MRS liquid culture medium, activated L-lactic acid bacteria is inoculated in MRS, then anaerobic culture is carried out for 18 to 24 hours in an incubator with the temperature of 37 to 45 ℃, and the concentration of the bacteria liquid is controlled at 10 5 ～10 7 cfu/g；
3. Measuring the moisture content of the stalk filaments, and controlling the moisture content of the stalk to 68-75% by spraying L-lactobacillus bacteria liquid to obtain sweet sorghum residues to be fermented; filling sweet sorghum residue to be fermented into silage bags, filling layer by layer, compacting layer by layer, squeezing out excessive air, compacting and sealing the bags, and storing for 8 days at 20-25 ℃ in a dark place;
4. silage after storage is transferred into a fermentation tank, silage filling is carried out according to the total solid content of 5-10%, cellulase and magnesium sulfate are sequentially added into the silage, and L-lactic acid fermentation is carried out, so that fermentation liquor is obtained; regulating the pH of the fermentation liquor to 5.8-6.2 by ammonia water with the concentration of 1-3M; introducing nitrogen for 2-4h at a flow rate of 500mL/min, and then adding L-lactobacillus solution for fermentation for 48-72 h under the conditions that the temperature is 37-45 ℃ and the rotating speed is 200-300 rpm; the addition amount of the L-lactic acid bacteria liquid is 5-10% of the fermentation volume;
5. after fermentation, carrying out solid-liquid separation on the fermentation liquor in a filter pressing mode to obtain a crude fermentation liquor;
6. removing impurities from the crude fermentation broth by adopting a membrane separation technology to obtain a purified L-ammonium lactate fermentation broth;
7. performing rotary evaporation on the L-ammonium lactate fermentation liquor, wherein the evaporation temperature is 65-75 ℃, concentrating the mass content of the L-ammonium lactate to 60-80%, then adding ethanol, then adding concentrated sulfuric acid, then filtering to obtain ammonium sulfate precipitate, and drying to constant weight at 80-105 ℃ to obtain a nitrogenous fertilizer; wherein the L-lactic acid bacteria are Lactobacillus plantarum.
2. The method for preparing nitrogen fertilizer by using sweet sorghum stalk L-lactic acid fermentation broth according to claim 1, wherein the thickness of the sweet sorghum stalk silk in the step one is 1-2mm.
3. The method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation broth according to claim 1, wherein the activation method of L-lactic acid bacteria in the second step is as follows: inoculating L-lactic acid bacteria into MRS slant culture medium, and anaerobic culturing at 37-45deg.C for 16-24 hr.
4. The method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation broth according to claim 1, wherein the method for measuring the water content of stalk filaments in the third step is characterized by comprising the following steps: weighing 10-50g of crushed sweet sorghum residue, uniformly dividing into 3 parts, putting into a dry and clean crucible, and recording the mass of the empty crucible and each part of sweet sorghum residue; placing the sweet sorghum stalk into a 105 ℃ oven for 2-3 hours until the weight is constant, then placing the sweet sorghum stalk into a dryer for cooling to room temperature, and weighing to calculate the moisture contained in the sweet sorghum stalk.
5. The method for preparing nitrogen fertilizer by utilizing sweet sorghum stalk L-lactic acid fermentation broth according to claim 1, wherein the addition amount of cellulase in the fourth step is 0.01-0.05% of the weight of sweet sorghum stalk, and the enzyme activity is 5000-10000U/g.
6. The method for preparing nitrogen fertilizer by using sweet sorghum stalk L-lactic acid fermentation broth according to claim 1, wherein the concentration of magnesium sulfate in the fermentation broth in the fourth step is 0.5-4 mM/L.
7. The method for preparing nitrogen fertilizer by using sweet sorghum stalk L-lactic acid fermentation broth according to claim 1, wherein in the step seven, L-ammonium lactate fermentation broth: ethanol: the molar ratio of the concentrated sulfuric acid is 1:5:0.5-1.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1594584A (en) * | 2004-07-09 | 2005-03-16 | 哈尔滨工业大学 | Method for preparing lactic acid and feedstuff concurrent with crop straw fermentation |
| KR20120060446A (en) * | 2010-12-02 | 2012-06-12 | 한국화학연구원 | Recovery method of highly pure lactic acid and alkyl lactate |
| CN106755143A (en) * | 2017-01-11 | 2017-05-31 | 南京工业大学 | A kind of method for extracting high-pure lactic acid continuous from lactic fermentation liquid |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1594584A (en) * | 2004-07-09 | 2005-03-16 | 哈尔滨工业大学 | Method for preparing lactic acid and feedstuff concurrent with crop straw fermentation |
| KR20120060446A (en) * | 2010-12-02 | 2012-06-12 | 한국화학연구원 | Recovery method of highly pure lactic acid and alkyl lactate |
| CN106755143A (en) * | 2017-01-11 | 2017-05-31 | 南京工业大学 | A kind of method for extracting high-pure lactic acid continuous from lactic fermentation liquid |
Non-Patent Citations (1)
| Title |
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| 赵秀红主编.无机盐对发酵过程中的影响.《高功能性大豆低聚糖的制备及功效研究应用技术》.辽宁科学技术出版社,2018,第43页. * |
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