阅读说明：本技术 一种高纯度乳酸的生产工艺 (Production process of high-purity lactic acid ) 是由 董立华 梁泉喜 董卫涛 于 2018-08-23 设计创作，主要内容包括：本发明公开了一种高纯度的乳酸制备工艺,采用葡萄糖为原料,米根霉菌为发酵菌种,在菌种制备过程中,通过米根霉的菌丝使其自团聚形成米根霉菌小球达到自固化的效果,避免游离的菌丝大面积团聚阻碍物料传质,并且发酵过后菌种易与料液分离,分离后的菌种还可进行重复利用,重要的是采用米根霉菌发酵的乳酸产品光学纯度高,原料利用率高,结合多道后续纯化处理步骤,确保制品乳酸具有高纯度,且工艺简便,具有很高的经济价值,适用于工业生产。(The invention discloses a high-purity lactic acid preparation process, which adopts glucose as a raw material and rhizopus oryzae as a fermentation strain, wherein in the strain preparation process, hyphae of the rhizopus oryzae are subjected to self-aggregation to form rhizopus oryzae pellets to achieve the self-solidification effect, the large-area aggregation of the free hyphae is avoided to prevent the mass transfer of materials, the strain is easy to separate from a feed liquid after fermentation, and the separated strain can be recycled.)

1. A production process of high-purity lactic acid is characterized by comprising the following steps:

(1) preparing raw materials: injecting a proper amount of water into the seasoning tank, heating the water to 50 ℃, opening the stirrer, pouring glucose powder, dissolving and stirring uniformly, adjusting the pH value to be between 5.5 and 6.0, and transferring the solution into a sugar solution storage tank for later use;

(2) heating and sterilizing: sterilizing material conveying equipment and fermentation equipment by adopting high-temperature steam, starting a material transferring pump after the material conveying equipment and the fermentation equipment are sterilized, enabling the material to enter a fermentation tank through an injection pump, simultaneously introducing the high-temperature steam into the injection pump, and heating and sterilizing the material by the high-temperature steam;

(3) fermentation: cooling the sterilized equipment and materials in the step (2) to 45-48 ℃, inoculating the strain into a fermentation tank, starting fermentation, keeping the temperature in the fermentation tank at 45-50 ℃ and the pressure at 0.4-0.8 Mpa, and adding Ca (OH)₂The pH of the feed liquid is maintained to be 5.5-6.0 by the saturated solution, the glucose content in the feed liquid is detected, and when the glucose content is 0, the fermentation is finished;

(4) and (3) filtering and flocculating: filtering to remove strains after the fermentation in the step (3), recovering the strains for later use, adjusting the pH value of the filtrate, and adding a flocculating agent to flocculate impurities;

(5) plate and frame filter pressing: transferring the flocculated material obtained in the step (4) into a fermentation liquor storage tank, feeding the material into a plate-and-frame filter press by using a pump, removing flocculation residues under the feeding pressure of 0.4-0.5Mpa and the compaction pressure of 15-20Mpa, and transferring the plate-and-frame filtrate, namely calcium lactate, into a fermentation clear liquid storage tank;

(6) calcium lactate evaporation and concentration: pumping the calcium lactate obtained in the step (5) into an evaporator, starting a water ring vacuum pump for evaporation and concentration, and discharging the material into a calcium concentrated solution storage tank;

(7) acid hydrolysis: pumping the calcium lactate concentrated solution obtained in the step (6) into an acidolysis tank, feeding at the temperature of 75-80 ℃, and then adding sulfuric acid into the acidolysis tank for acidolysis;

(8) and (3) filtering: pumping the acidolysis solution after the acidolysis end point in the step (7) into a belt filter by using a vacuum pump, and filtering filtrate after calcium sulfate;

(9) and (3) decoloring: pumping the filtrate obtained in the step (8) into a decoloring tank, heating to 70-72 ℃, and adding activated carbon to decolor;

(10) plate and frame filter pressing: performing plate-and-frame filter pressing on the material decolorized in the step (9), filtering out active carbon in the material, and feeding filtrate into a decolorized clear liquid storage tank;

(11) ion exchange: sequentially passing the decolorized clear liquid obtained in the step (10) through a carbon column, a cation exchange column and an anion exchange column to remove impurities, and then entering an ion exchange liquid storage tank;

(12) MVR evaporation and concentration: starting a vacuum pump and a steam compressor, starting steam, heating the system, evaporating and concentrating the ion exchange liquid obtained in the step (11), and pumping the concentrated liquid into a storage tank before the membrane;

(13) and (3) nanofiltration membrane filtration: adjusting the pressure difference between the feeding and the discharging to be less than or equal to 0.5Mpa, leading the concentrated solution obtained in the step (12) to pass through a nanofiltration membrane, filtering impurities, and leading the filtrate to enter a membrane post-tank;

(14) concentrating by a plate evaporator: pumping the filtrate obtained in the step (13) into a plate evaporator, wherein the feeding flow rate is 5.2-6.0m³Heating by steam, controlling the air inlet pressure of a heat pump to be 0.35-0.4Mpa, controlling the discharge density to be 1.14-1.20kg/L, controlling the discharge concentration to reach more than 80%, and pumping into a finished product storage tank;

(15) blending and canning: and (5) detecting the material concentration in the finished product storage tank in the step (14), pumping the finished product into a blending tank according to the requirement, blending and then canning.

2. The process for producing high-purity lactic acid according to claim 1, wherein the amount of glucose added in step (1) is adjusted according to the concentration required for production.

3. The process for producing high-purity lactic acid according to claim 1, wherein the fermentation strain in the step (3) is fermented by rhizopus oryzae, the rhizopus oryzae is granular rhizopus oryzae which is cultured and self-flocculated by hyphae, the volume of the inoculated mold solution is 10-15% of the total volume of the feed solution in the fermentation tank, and the ratio of the added yeast powder to the rhizopus oryzae is 0.15-0.2%.

4. The process for producing high-purity lactic acid according to claim 1, wherein the flocculant added in the step (4) is a chitosan flocculant, the pH of the adjusted feed liquid is 3.9-4.1, and the concentration of the flocculant is 50mg/m³The amount of the flocculant added was 50mg/m³And adding a flocculating agent and stirring for 4-6 min.

5. The process for producing high-purity lactic acid according to claim 1, wherein the evaporator in the step (6) is a triple-effect evaporator, the concentration process comprises feeding the triple-effect evaporator, then feeding the triple-effect evaporator into a first effect, starting steam to boil the materials, then feeding the triple-effect evaporator into a second effect, keeping the temperature above 75 ℃, and reaching the concentration end point when the concentration of the double-effect calcium reaches 20%.

6. The process for producing high-purity lactic acid according to claim 1, wherein Ca is decomposed when pH is 2 to 2.5 in the step (7)^2﹢The concentration of 0.25-0.5% is the acidolysis end point.

7. The process for producing high-purity lactic acid according to claim 1, wherein the color of the feed liquid in the step (9) is reduced to a color of less than Y-3.

8. The production process of high-purity lactic acid according to claim 1, wherein the ion exchange flow rate of the feed liquid in the step (11) is 7-12 m³/h，Fe^3﹢≤10PPm,Cl^﹣≤20PPm，SO₄ ^2﹣The color is less than or equal to 50PPm, and the color is less than or equal to 50APHA, namely the ion exchange is qualified.

9. The process for producing high-purity lactic acid according to claim 1, wherein the MVR evaporation concentration in the step (12) has a discharge density of 1.116-1.118 kg/L.

10. The process for producing high-purity lactic acid according to claim 1, wherein the water used for blending the materials in the step (15) is softened tap water, and the conductivity of the water is less than or equal to 20 μ s/cm.

Technical Field

The invention relates to the technical field of fermentation engineering, in particular to a production process of high-purity lactic acid.

Background

Lactic acid has many uses in industry, food, medicine, and the like, and is widely used as a preservative, an acidulant, and a reducing agent. In the production process of cans, sauces and beverages, lactic acid can replace preservatives such as benzoic acid, potassium sorbate and the like which have side effects on human bodies, and can be used as a sour agent of the foods; in the production process of the beer, the pH value can be adjusted by using lactic acid, so that the saccharification of raw materials can be promoted, and the growth of mixed bacteria can be inhibited; lactic acid has many important applications in medical applications, both as a disinfectant and as a carrier; the solution prepared from sodium lactate can be used for treating acidosis and hyperkalemia; the lactate substances can be used as a solvent of the medicine, increase the absorption of the medicine by human body, reduce side effects, and can also be prepared into a lubricant of a tablet, wherein the lubricant is prepared from polylactic acid and is widely applied clinically, such as a slow release capsule preparation, a biodegradable surgical suture, a biological implantation tablet and the like; in the chemical industry, lactic acid is the main raw material of biodegradable plastic polylactic acid; the lactic acid can also be used in the leather manufacturing industry to ensure that the leather is soft and fine and the fiber is glossy; lactic acid can also be used as a synthetic resin coating, an adhesive, a perfume and a cleaning agent for petroleum pipelines.

Disclosure of Invention

In view of the above, the present invention provides a method for producing lactic acid by fermentation of glucose, wherein raw materials in a fermentation liquid are fully utilized, a fermentation period is shortened by controlling fermentation conditions, fermentation efficiency is improved, a product has higher purity by multiple post-purification processes, and strains can be repeatedly utilized, thereby increasing economic benefits.

In order to achieve the purpose, the invention adopts the following technical scheme:

a production process of high-purity lactic acid comprises the following steps:

(1) preparing raw materials: injecting a proper amount of water into the seasoning tank, heating the water to 50 ℃, opening the stirrer, pouring glucose powder, dissolving and stirring uniformly, adjusting the pH value to be between 5.5 and 6.0, and transferring the solution into a sugar solution storage tank for later use;

(2) heating and sterilizing: sterilizing material conveying equipment and fermentation equipment by adopting high-temperature steam, starting a material transferring pump after the material conveying equipment and the fermentation equipment are sterilized, enabling the material to enter a fermentation tank through an injection pump, simultaneously introducing the high-temperature steam into the injection pump, and heating and sterilizing the material by the high-temperature steam;

(3) fermentation: cooling the sterilized equipment and materials in the step (2) to 45-48 ℃, inoculating the strain into a fermentation tank, starting fermentation, keeping the temperature in the fermentation tank at 45-50 ℃ and the pressure at 0.4-0.8 Mpa, and adding Ca (OH)₂The pH value of the feed liquid is maintained to be 5.5-6.0 by the saturated solution, the glucose content in the feed liquid is detected, and when the glucose content is 0, the fermentation is finished;

(4) and (3) filtering and flocculating: filtering to remove strains after the fermentation in the step (3), recovering the strains for later use, adjusting the pH value of the filtrate, and adding a flocculating agent to flocculate impurities;

(5) plate and frame filter pressing: transferring the flocculated material obtained in the step (4) into a fermentation liquor storage tank, pumping the material into a plate-and-frame filter press by using a pump, removing flocculation under the feeding pressure of 0.4-0.5Mpa and the pressing pressure of 15-20Mpa, and transferring the plate-and-frame filtrate, namely calcium lactate, into a fermentation clear liquid storage tank;

(6) calcium lactate evaporation and concentration: pumping the calcium lactate obtained in the step (5) into an evaporator, starting a water ring vacuum pump for evaporation and concentration, and discharging the material into a calcium concentrated solution storage tank;

(7) acid hydrolysis: pumping the calcium lactate concentrated solution obtained in the step (6) into an acidolysis tank, feeding at the temperature of 75-80 ℃, and then adding sulfuric acid into the acidolysis tank for acidolysis;

(8) and (3) filtering: pumping the acidolysis solution after the acidolysis end point in the step (7) into a belt filter by using a vacuum pump, and filtering filtrate after calcium sulfate;

(9) and (3) decoloring: pumping the filtrate obtained in the step (8) into a decoloring tank, heating to 70-72 ℃, and adding activated carbon to decolor;

(10) plate and frame filter pressing: performing plate-and-frame filter pressing on the material decolorized in the step (9), filtering out active carbon in the material, and feeding filtrate into a decolorized clear liquid storage tank;

(11) ion exchange: sequentially passing the decolorized clear liquid obtained in the step (10) through a carbon column, a cation exchange column and an anion exchange column to remove impurities, and then entering an ion exchange liquid storage tank;

(12) MVR evaporation and concentration: starting a vacuum pump and a steam compressor, starting steam, heating the system, evaporating and concentrating the ion exchange liquid obtained in the step (11), and pumping the concentrated liquid into a storage tank before the membrane;

(13) and (3) nanofiltration membrane filtration: adjusting the pressure difference between the feeding and the discharging to be less than or equal to 0.5Mpa, leading the concentrated solution obtained in the step (12) to pass through a nanofiltration membrane, filtering impurities, and leading the filtrate to enter a membrane post-tank;

(14) concentrating by a plate evaporator: pumping the filtrate obtained in the step (13) into a plate evaporator, wherein the feeding flow rate is 5.2-6.0m³Heating by steam, controlling the air inlet pressure of a heat pump to be 0.35-0.4Mpa, controlling the discharge density to be 1.14-1.20kg/L, controlling the discharge concentration to reach more than 80%, and pumping into a finished product storage tank;

(15) blending and canning: and (5) detecting the material concentration in the finished product storage tank in the step (14), pumping the finished product into a blending tank according to the requirement, blending and then canning.

By adopting the scheme, the invention provides the lactic acid preparation process with higher raw material utilization rate, and the product lactic acid has higher purity through the multi-stage subsequent purification process, and the process is simple, convenient and controllable.

Preferably, the adding amount of the glucose in the step (1) is adjusted according to the concentration required by production.

Preferably, the fermentation strain in the step (3) is fermented by rhizopus oryzae, the rhizopus oryzae is granular rhizopus oryzae which is cultured and self-flocculated by hypha, the volume of the inoculated mold liquid is 10-15% of the total volume of the feed liquid in the fermentation tank, and the added yeast powder is 0.15-0.20% of the rhizopus oryzae.

The beneficial effects of the preferred technical scheme are as follows: the rhizopus oryzae needs to be immobilized to avoid the aggregation of a large amount of free hyphae to block the mass transfer of materials when the rhizopus oryzae is fermented to produce lactic acid, the rhizopus oryzae aggregated into small particles plays a self-curing role, the production efficiency of the lactic acid is ensured, the rhizopus oryzae particle strains are easy to separate from products and can be recycled, and the saccharomycetes and the rhizopus oryzae are added to jointly act, so that the fermentation speed is increased, the fermentation period is shortened, and the economic benefit is increased.

Preferably, the flocculant added in the step (4) is a chitosan flocculant, the pH of the adjusted feed liquid is 3.9-4.1, and the concentration of the flocculant is 50mg/m³The amount of the flocculant added was 50mg/m³And adding a flocculating agent and stirring for 4-6 min.

Preferably, the evaporator in the step (6) is a three-effect evaporator, the concentration process comprises feeding into the three-effect evaporator, then entering into the first effect, simultaneously starting steam to boil the material, then entering into the second effect, keeping the temperature above 75 ℃, and reaching the concentration end point when the concentration of the second-effect calcium reaches 20%.

The beneficial effects of the preferred technical scheme are as follows: the balance of the temperature, the concentration and the viscosity of the feed liquid is facilitated, the scaling of an evaporator and the browning of the feed liquid are prevented, and the evaporation efficiency is improved.

Preferably, Ca is added in the step (7) when the pH value reaches 2-2.5^2﹢The concentration of 0.25-0.5% is the acid hydrolysis end point.

Preferably, the color of the feed liquid is decolorized in the step (9) until the color of the feed liquid is less than Y-3.

Preferably, the ion exchange flow of the feed liquid in the step (11) is 7-12 m³/h，Fe^3﹢≤10PPm,Cl^﹣≤20PPm，SO₄ ^2﹣The color is less than or equal to 50PPm, and the color is less than or equal to 50APHA, namely the ion exchange is qualified.

Preferably, the discharge density of MVR evaporation concentration in the step (12) is 1.116-1.118 kg/L.

Preferably, the water for blending the materials in the step (15) is softened tap water, and the conductivity of the softened tap water is less than or equal to 20 mu s/cm.

According to the technical scheme, compared with the prior art, the invention discloses a high-purity lactic acid preparation process, glucose is used as a raw material, rhizopus oryzae is used as a fermentation strain, during the preparation process, the rhizopus oryzae mycelia are self-agglomerated to form rhizopus oryzae pellets to achieve the self-solidification effect, the situation that the mass transfer of materials is hindered by large-area agglomeration of free mycelia is avoided, the strain is easy to separate from a feed liquid after fermentation, the separated strain can be recycled, and importantly, lactic acid products fermented by the rhizopus oryzae have high optical purity and high raw material utilization rate, and a plurality of subsequent purification treatment steps are combined to ensure that the lactic acid products have high purity.

Detailed Description

The technical solutions in the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.