Method for decolorizing a cellulose lactic acid fermentation broth

Abstract

The present application discloses a method for decolorizing cellulose lactic acid fermentation liquor. The lactic acid fermentation liquor of lignocellulose is removed from solid substances such as bacteria and lignin, and calcium peroxide is added to decolorize for 10-30 minutes at 10-30℃. The pH of the fermentation liquor is adjusted to 8-10 by calcium hydroxide, and calcium lactate precipitate is obtained by filtration or centrifugation. Then dilute sulfuric acid is added to dissolve the precipitate, and the pH is adjusted to 1-3. The solid substances are removed by centrifugation, and the fermentation liquor is passed through a prepared granular activated carbon column, and the transmittance T 430 of the effluent is greater than 99%, and the product recovery rate is greater than 97%. Compared with the traditional decolorization method, the present application has good decolorization effect, high product recovery rate, low decolorization temperature, simple operation, and avoids the influence of incomplete removal of powdered activated carbon on subsequent separation and purification steps.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of bio-chemical industry, and particularly relates to a decolorization method for a cellulose lactic acid fermentation broth separation and purification process. BACKGROUND

[0002] There are a large number of pigment molecules in a microbial fermentation broth, which are mainly derived from carbon sources and nitrogen sources in a culture medium and proteins, polypeptides and the like produced by microbial metabolism; the pigments not only affect unit operations of separation and purification, but also affect product color and purity. At present, decolorization methods for lactic acid fermentation broth mainly include activated carbon, ion exchange resin and nanofiltration decolorization methods. Among them, the activated carbon decolorization method is relatively mature, but still has many deficiencies. For example, when powder or granular activated carbon is used, the decolorization cost often accounts for more than 50% of the separation and purification cost. During use of the powder activated carbon, dust is large, operation is inconvenient, and part of the powder is too fine to be completely removed, affecting subsequent separation and purification steps; although the granular activated carbon is relatively convenient to operate, the decolorization effect is poor, the amount used is large, and the cost is high.

[0003] Compared with traditional grain fermentation, the cellulose fermentation for producing lactic acid increases a cellulose pretreatment and saccharification process, and the pigment content is more and the composition is more complex. A general decolorization scheme is to preliminarily decolorize the fermentation broth through a granular activated carbon column, and then decolorize it once again with powder activated carbon, so that the transmittance T 430 of the fermentation broth can reach 92% to 95%. After the fermentation broth is concentrated, the pigments are aggregated, the transmittance is reduced to below 90%, and the powder activated carbon needs to be used for decolorization once again so that the transmittance can reach more than 98%. This method needs to undergo three times of activated carbon decolorization, the process is complex, the time is long, the amount of activated carbon used is large, and the cost is high. Therefore, it is necessary to develop a high-efficiency and low-cost decolorization method. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a decolorization method for a cellulose lactic acid fermentation broth. The method not only can save the amount of alkali in the fermentation broth separation and purification process, but also can reduce the amount of activated carbon in the decolorization process; after decolorization, the transmittance T 430 of the fermentation broth is greater than 99%, and the product recovery rate is greater than 97%. The present application not only improves the product quality of lactic acid, but also greatly saves the cost of separation and purification.

[0005] In order to achieve the above-mentioned purposes, the present application adopts the following technical scheme

[0006] The present application provides a decolorization method for a cellulose lactic acid fermentation broth, which comprises the following steps:

[0007] (1) centrifuging a cellulose lactic acid fermentation broth to remove bacteria and lignin, and measuring the volume and lactic acid content;

[0008] (2) Add calcium peroxide, a decolorizing agent, to the fermentation broth and stir for a period of time at room temperature;

[0009] (3) Add calcium hydroxide to adjust the fermentation broth to alkaline;

[0010] (4) Filter or centrifuge to obtain calcium lactate;

[0011] (5) Add dilute sulfuric acid to obtain a lactic acid solution and calcium sulfate precipitate;

[0012] (6) Centrifuge to remove the solid;

[0013] (7) Pass the lactic acid solution through a column of granular activated carbon that has been prepared, and the effluent is directly used in the next step of the separation and purification process.

[0014] The fermentation broth in step (1) is derived from lactic acid fermentation of lignocellulose (corn stalks, corn leaves, corn cobs, rice straw, sugar cane residue, miscanthus, reed, wheat straw, etc.); the lactic acid content is measured by high performance liquid chromatography using an external standard method.

[0015] The centrifuge speed in steps (1), (4), and (6) is 7000-9000 rpm, and the centrifuge temperature is 10-30°C.

[0016] The amount of calcium peroxide used in step (2) is 0.1%-3% g / mL of the volume of the fermentation broth; the stirring time is 10-30 minutes.

[0017] The pH of the alkaline fermentation broth in step (3) is 8-10; the molar ratio of the amount of calcium hydroxide used to the amount of lactic acid is 50-80%.

[0018] The pH of the lactic acid solution in step (5) is 1-3, and the concentration of the dilute sulfuric acid is 1wt%-5wt%.

[0019] The pH values in steps (3) and (5) are measured using pH paper or a pH meter.

[0020] The decolorization temperature in step (7) is 10-30°C.

[0021] The granular activated carbon column is activated with dilute hydrochloric acid or dilute sulfuric acid before use; the concentration of the acid used for activation is 0.1wt%-5wt%, and the activation temperature is room temperature.

[0022] After use, the activated carbon column can be eluted with a hot dilute sulfuric acid solution to recover and reuse the pigment; the concentration of the dilute sulfuric acid is 0.1wt%-5wt%, and the elution temperature is 50-80°C.

[0023] The transmittance T of the lactic acid solution after decolorization using the activated carbon column in step (7) is greater than 99%, and the solution can be directly used in the next step of the separation and purification process. 430

[0024] ​The present invention, which uses calcium peroxide as a preliminary decolorizing agent, has the following advantages:

[0025] 1. The decolorization and alkalization steps can be performed in the same reactor, which is simple to operate;

[0026] 2. The calcium hydroxide produced during the decolorization of calcium peroxide is exactly the alkali used in the alkalization step, thus saving the amount of alkali used.

[0027] 3. Calcium peroxide does not produce other solids during decolorization. Compared with activated carbon decolorization, it omits the filtration and carbon removal process, making the process simpler.

[0028] 4. Decolorization can be carried out at room temperature with remarkable results. Compared with activated carbon decolorization (50℃~80℃), it saves energy and reduces costs; it also eliminates heating time and improves process duration.

[0029] 5. Calcium peroxide has a significant decolorization effect on fermentation broth. When using granular activated carbon columns for secondary decolorization, the activated carbon columns need to adsorb less pigment, resulting in a better decolorization effect.

[0030] The elution and reactivation of activated carbon columns are easier, and the number of recycling cycles can be increased.

[0031] 7. This invention also avoids the use of powdered activated carbon, reduces the difficulty of operation, and avoids the impact of incomplete removal by ultrafine powdered activated carbon on subsequent separation and purification steps. Detailed Implementation

[0032] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail. Unless otherwise specified, the methods of the present invention are conventional methods in the art.

[0033] Example 1

[0034] Five L of lactic acid fermentation broth made from sugarcane bagasse was centrifuged at 25°C and 8000 rpm to remove solids such as bacterial cells and lignin. The lactic acid concentration in the fermentation broth was determined to be 106.0 g / L by high-performance liquid chromatography (HPLC). Two L of the fermentation broth was transferred to a decolorization vessel. 3 g of calcium peroxide was added, and decolorization was performed for 20 minutes at room temperature. Calcium hydroxide was added to adjust the pH of the fermentation broth to 9, and centrifugation was performed to obtain calcium lactate solids. The calcium lactate solids were transferred to an acidification vessel, and 3 wt% dilute sulfuric acid aqueous solution was added to adjust the pH to 2. The solids were removed by centrifugation, and the solids were washed twice with 200 mL of deionized water. The washings were combined, and the centrifuged solutions were decolorized using a granular activated carbon column. A total of 2.1 L of the decolorized solution was collected, and its transmittance T was measured. 430 The recovery rate was 99%, the lactic acid concentration was 98.0 g / L, the lactic acid recovery rate was 97.1%, and the lactic acid loss rate was 2.9%.

[0035] Example 2

[0036] The 5 L of lactic acid fermentation broth with corn stalk as raw material was centrifuged at 25 °C and 8000 rpm to remove the bacterial cells and lignin and other solid substances. The lactic acid concentration in the fermentation broth was measured by high performance liquid chromatography to be 111.3 g / L, and 2 L of the fermentation broth was taken to a decolorization kettle. 3 g of calcium peroxide was added, and the decolorization was carried out at room temperature for 20 minutes. Calcium hydroxide was added to adjust the pH of the fermentation broth to 9, and calcium lactate solid was obtained by centrifugation. The calcium lactate solid was put into an acidification kettle, 3 wt% dilute sulfuric acid aqueous solution was added, and the pH was adjusted to 2. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. The washing liquid was combined with the centrifugation liquid, and the decolorization was carried out with a granular activated carbon column. The total volume of the decolorized solution collected was 2.2 L, and the transmittance T 430 was 99%, the lactic acid concentration was 98.1 g / L, the lactic acid recovery rate was 97.0%, and the lactic acid loss rate was 3.0%.

[0037] Example 3

[0038] The 5 L of lactic acid fermentation broth with corn stalk as raw material was centrifuged at 25 °C and 8000 rpm to remove the bacterial cells and lignin and other solid substances. The lactic acid concentration in the fermentation broth was measured by high performance liquid chromatography to be 111.3 g / L, and 2 L of the fermentation broth was taken to a decolorization kettle. 3 g of calcium peroxide was added, and the decolorization was carried out at room temperature for 20 minutes. Calcium hydroxide was added to adjust the pH of the fermentation broth to 9, and calcium lactate solid was obtained by centrifugation. The calcium lactate solid was put into an acidification kettle, 3 wt% dilute sulfuric acid aqueous solution was added, and the pH was adjusted to 2. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. The washing liquid was combined with the centrifugation liquid, and the decolorization was carried out with a granular activated carbon column. The total volume of the decolorized solution collected was 2.2 L, and the transmittance T 430 was 99%, the lactic acid concentration was 98.1 g / L, the lactic acid recovery rate was 97.0%, and the lactic acid loss rate was 3.0%.

[0039] Comparative Example 1

[0040] The 5 L of lactic acid fermentation broth with corn stalk as raw material was centrifuged at 25 °C and 8000 rpm to remove the bacterial cells and lignin and other solid substances. The lactic acid concentration in the fermentation broth was measured by high performance liquid chromatography to be 111.3 g / L, and 2 L of the fermentation broth was taken to a decolorization kettle. 3 g of calcium peroxide was added, and the decolorization was carried out at room temperature for 20 minutes. Calcium hydroxide was added to adjust the pH of the fermentation broth to 9, and calcium lactate solid was obtained by centrifugation. The calcium lactate solid was put into an acidification kettle, 3 wt% dilute sulfuric acid aqueous solution was added, and the pH was adjusted to 2. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. The washing liquid was combined with the centrifugation liquid, and the decolorization was carried out with a granular activated carbon column. The total volume of the decolorized solution collected was 2.2 L, and the transmittance T 43095%, lactic acid concentration 67.5 g / L, lactic acid recovery 91.7%, lactic acid loss 8.3%.

[0041] Comparative Example 2

[0042] 5 L of lactic acid fermentation broth using corn stalk as raw material was centrifuged at 25°C and 8000 rpm to remove the bacterial cells and lignin and other solid substances. The lactic acid concentration in the fermentation broth was measured by high performance liquid chromatography to be 99.0 g / L. 2 L of the fermentation broth was decolorized by a granular activated carbon column. The effluent was adjusted to pH 9 by adding calcium hydroxide, and calcium lactate solids were obtained by centrifugation. The calcium lactate solids were put into an acidification kettle, 3 wt% dilute sulfuric acid aqueous solution was added, and the pH was adjusted to 2. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. The washing liquid was combined with the centrifugate, and the temperature was raised to 60°C, and the solution was decolorized with powdered activated carbon for 1 hour. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. A total of 2.8 L of the decolorized solution was collected, and the transmittance T 430 93%, lactic acid concentration 65.7 g / L, lactic acid recovery 92.9%, lactic acid loss 7.1%.

[0043] Comparative Example 3

[0044] 5 L of lactic acid fermentation broth using corn stalk as raw material was centrifuged at 25°C and 8000 rpm to remove the bacterial cells and lignin and other solid substances. The lactic acid concentration in the fermentation broth was measured by high performance liquid chromatography to be 99.0 g / L. 2 L of the fermentation broth was decolorized by a granular activated carbon column. The effluent was adjusted to pH 9 by adding calcium hydroxide, and calcium lactate solids were obtained by centrifugation. The calcium lactate solids were put into an acidification kettle, 3 wt% dilute sulfuric acid aqueous solution was added, and the pH was adjusted to 2. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. The washing liquid was combined with the centrifugate, and the temperature was raised to 60°C, and the solution was decolorized with powdered activated carbon for 1 hour. The solid was removed by centrifugation, and the solid was washed twice with 200 mL of deionized water. A total of 2.8 L of the decolorized solution was collected, and the transmittance T 430 93%, lactic acid concentration 65.7 g / L, lactic acid recovery 92.9%, lactic acid loss 7.1%.

[0045] Compared with the comparative examples, the cellulose lactic acid fermentation liquor is decolorized by using the process of the application, the effluent light transmittance is high, and the lactic acid loss rate is low. The decolorization step and the alkalization step of the application can be in the same reactor, and the operation is simple; the by-product calcium hydroxide produced during calcium peroxide decolorization is exactly the alkali used in the alkalization step, which saves the amount of alkali; no other solids are produced during calcium peroxide decolorization, compared with the powder activated carbon decolorization method, the filtration process for removing carbon is omitted, and the process is more simple; the decolorization can be carried out at room temperature and the effect is outstanding, compared with the powder activated carbon decolorization method (50~80℃), energy is saved, cost is reduced; the heating time is also saved, and the process time is improved; the decolorization effect of calcium peroxide on the fermentation liquor is remarkable, when secondary decolorization is carried out by using a granular activated carbon column, the amount of pigment adsorbed by the activated carbon column is small, and the decolorization effect is good; the elution and reactivation of the activated carbon column are easier to use, and the recycling times are increased.

[0046] The above only describes the preferred embodiments of the application, and any equivalent changes and modifications made within the scope of the application should be included in the scope of the application.

Claims

1. A method for decolorizing a cellulose lactic acid fermentation broth, characterized by, The method comprises the following steps: centrifuging cellulose lactic acid fermentation liquor to remove bacteria and lignin, and measuring volume and lactic acid content; adding a decolorizing agent to the fermentation liquor and stirring in a reactor for a period of time; adding calcium hydroxide to adjust the fermentation liquor to be alkaline; filtering or centrifuging to obtain calcium lactate; adding dilute sulfuric acid to obtain a lactic acid solution and a calcium sulfate precipitate; centrifuging to remove solids; passing the lactic acid solution through a prepared granular activated carbon column, and measuring the light transmittance of the effluent; and using a hot dilute acid solution to elute the activated carbon column to recover and reuse the activated carbon. The decolorizing agent is calcium peroxide, and the calcium peroxide dosage is 0.1%-3% g / mL of the fermentation liquor volume.

2. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, characterized by, The lignocellulose raw material for lactic acid fermentation includes corn stalks, rice straw and sugarcane residue.

3. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, characterized by, When calcium peroxide is used for decolorization, the temperature is 10-30°C.

4. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, characterized by, After the fermentation liquor is alkalized, the pH is 8-10.

5. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, characterized by, The molar ratio of calcium hydroxide dosage to lactic acid is 50-80%.

6. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, wherein, The dilute sulfuric acid used in the acidification process has a concentration of 1wt%-5wt%, and the lactic acid solution has a pH of 1-3.

7. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, wherein, When an activated carbon column is used for decolorization, the temperature is 10-30°C.

8. The method of decolorizing a cellulose lactic acid fermentation broth according to claim 1, wherein, When the activated carbon column is eluted, the dilute acid used is a 1wt%-5wt% dilute sulfuric acid solution, and the elution temperature is 50-80°C.