CN102603814B - Method for increasing crystalizing efficiency of xylose in xylose mother solution - Google Patents

Abstract

The invention belongs to the fields of biology and chemical industry, and particularly discloses a method for increasing the crystalizing efficiency of xylose in a xylose mother solution. The method comprises the following steps of: diluting the xylose mother solution; adding nutritional components; sterilizing; inoculating yeast for fermenting; removing glucose and galactose from the xylose mother solution; centrifugally separating yeast out of a zymotic fluid; filtering a clear zymotic fluid with a cross flow tube film; and removing a colloid contained in the zymotic fluid and fermentation metabolic products such as free proteins and the like produced in a fermenting process to obtain an ultra-filtered clear solution containing xylose and arabinose for use in subsequent production. The method has the advantages of simple steps, low treatment cost, high separating accuracy, good separating effect, great reduction in the subsequent treatment difficulty, great increase in product yield and suitability for wide popularization and application.

Description

A method for improving xylose crystallization efficiency in xylose mother liquor

(1) Technical field

The present invention belongs to the fields of biology and chemical industry, and in particular relates to a method for improving the crystallization efficiency of xylose in xylose mother liquor.

(2) Background technology

Xylose products are mainly white crystals made from corn cobs and bagasse through hydrolysis, purification, evaporation, crystallization, centrifugation, drying and other processes. They are widely used in light industry, food and chemical industries. The concentration of xylose mother liquor is about 60%, of which xylose is 40~50%, in addition, glucose is 15~20%, arabinose is 15~30%, galactose is 8~12%, due to the existence of these components, xylose mother liquor cannot Crystallized and sold only as a by-product.

Although it has been reported to use a simulated moving bed to purify the xylose mother liquor to produce xylose and arabinose (patent number 200710014175.8), and it has been produced on a large scale, the pretreatment of the xylose mother liquor is not thorough, and the galactose, colloid, Proteins, metabolites produced by yeast fermentation and broken bacteria cannot be completely removed, which brings great difficulty to decolorization and filtration. Due to the traditional vacuum drum filtration and plate-and-frame filtration process, the direction of liquid flow is consistent with the direction of filtration. Impurities such as colloids in the liquid will directly adhere to the filter medium quickly, blocking the filter medium and unable to remove all impurities in the liquid. Colloid and protein and other substances contained in the plate and frame filter decolorized fermentation broth, the average filtration capacity of filter cloth per square meter is 2~3m ³ , and then the filter cloth has to be replaced and cleaned; in addition, the vacuum drum filtration process It also needs to consume a large amount of filter aids such as diatomaceous earth, which increases the operating cost of filtration on the one hand, and on the other hand, filter aids can take away part of the material, increasing the loss of materials; finally, due to the xylose and galactose The distance between the HPLC chromatographic peaks is very close, and the galactose cannot be removed from the xylose component by using the simulated moving bed separation liquid, resulting in most of the galactose existing in the xylose component, which greatly reduces the purity of xylose, and the galactose The presence of xylose makes the yield of xylose crystallization about 30%.

(3) Contents of the invention

In order to make up for the deficiencies of the prior art, the present invention provides a method for improving the crystallization efficiency of xylose in xylose mother liquor with simple steps and high separation precision.

The present invention is achieved through the following technical solutions:

A method for improving xylose crystallization efficiency in xylose mother liquor, using xylose mother liquor as raw material, mainly includes the following steps:

(1) Dilute the xylose mother liquor to a concentration of 15~25%, add nitrogen nutrition accounting for 0.1~1% of the weight of the diluted solution, then adjust the pH value of the diluted solution to 4.0~4.5, and sterilize at 115~120°C After 30 minutes, cool down to 24~26°C and insert yeast strains, the inoculum amount is 12g of dry yeast per liter of dilution, and then ferment at 20~40°C;

(2) Centrifuge the fermentation broth, return the centrifuged supernatant to the fermenter, and pour the concentrated liquid into the yeast tank for storage;

(3) Filtrate the centrifuged supernatant through a cross-flow tubular membrane at 35-80°C, using an ultrafiltration membrane with a membrane pore size of 1000Da~0.1 micron, collect the ultrafiltrate into the ultrafiltrate tank, and ultrafiltrate the concentrate again After centrifugation, the feed liquid is recovered.

The invention dilutes the xylose mother liquor, adds nutrients, sterilizes, inoculates yeast for fermentation, removes glucose and galactose in the xylose mother liquor, centrifuges the fermentation liquor to separate the yeast, and filters the fermentation supernatant through a cross-flow tube membrane Treatment, removal of fermentation metabolites such as colloids contained in the fermentation broth and free protein produced during the fermentation process, and finally an ultrafiltrate containing xylose and arabinose is obtained for subsequent production.

A better solution of the present invention is:

In step (1), the nitrogen nutrition is urea, ammonium chloride or ammonium sulfate, and the amount added is 0.3-0.5% of the weight of the diluent.

In step (1), the yeast strain is one or more of baker's yeast, brewer's yeast or Schizosaccharomyces pombe.

In step (1), during fermentation, the ventilation rate is 1:0.1-0.4, the stirring speed is 50-100 rpm, and the fermentation time is 48 hours.

In step (2), a disc centrifuge is used for the centrifugation of the fermentation broth.

In step (3), the pore size of the ultrafiltration membrane is 100,000 Da, the operating temperature is 35~40°C, the filtration pressure is 0.05~0.3MPa, and the average flux is 60L/m ² ·h.

In step (3), the cross-flow tubular membrane filtration includes circulation filtration and continuous filtration. During continuous filtration, the centrifuged liquid enters the membrane filtration equipment, and after a membrane filtration, the pre-membrane liquid continues to enter the second set of ultrafiltration membranes , and finally to the third group of ultrafiltration membranes, the ultrafiltrate is collected in the ultrafiltrate tank uniformly, the pre-membrane liquid is collected in the centrifuge front tank, and the next batch of feed liquid is mixed and then centrifuged and ultrafiltered again to maximize the use of feed liquid The purpose; during circulation filtration, the centrifuged supernatant enters the membrane filtration equipment, after a certain cycle time, the ultrafiltrated supernatant is collected in the ultrafiltrate tank, and the ultrafiltered concentrate is centrifuged again to recover the feed liquid.

On the basis of yeast fermentation and simulated moving bed purification of xylose mother liquor, the present invention seeks a method that can completely remove galactose, colloid, and broken bacteria and metabolites produced in the xylose mother liquor in the yeast fermentation process, and obtain relatively pure A mixture of xylose and arabinose.

The invention utilizes the cross-flow tubular membrane filtration process to make the fermented liquid pass through the cross-flow tubular membrane under a certain pressure, and collect the filtrate as the raw material for the next process. In the cross-flow tubular filtration process, the liquid flow direction and the filtration direction are perpendicular, the filtration direction is perpendicular to the membrane surface, and the liquid flow direction is parallel to the membrane surface; due to the rapid flow of the liquid, impurities such as colloids cannot stay on the surface of the filter medium. Even if the impurities are temporarily attached to the surface of the filter medium, the fast-flowing liquid can wash them away in time, so cross-flow filtration is not easy to block the filter medium. Due to the huge difference in molecular weight of the impurities contained in the xylose mother liquor, colloids and yeast The broken bacteria and metabolites produced during the fermentation process belong to macromolecular substances with a molecular weight of more than 100,000 or hundreds of thousands, while micromolecular substances such as xylose and arabinose have a molecular weight of about several hundred, so the colloid can be separated by using membrane equipment. Macromolecular substances such as xylose are intercepted, while xylose and other components can pass through the membrane and gather at one end of the filtrate. Since the present invention adopts cross-flow tubular membrane filtration, the fermentation broth passes through the membrane side at a high speed in a tangential direction, while the xylose Small molecules pass through in a direction perpendicular to the membrane, and macromolecules are trapped on the side of the fermentation broth of the membrane. Due to the scouring effect of the high-speed flow of the fermentation broth, the macromolecules cannot stay on the surface of the membrane, and it is not easy to block the pores of the membrane. After the membrane filtration process, the average filtration capacity per square meter of filter cloth can reach 8~10m ³ .

The invention has simple steps, low processing cost, high separation precision and good separation effect, greatly reduces the difficulty of follow-up processing, can greatly increase product yield, and is suitable for wide popularization and application.

(4) Specific implementation methods

Example 1:

Take 200ml of xylose mother liquor diluted to 20%, adjust pH to 4.3, add 1g of urea, sterilize and cool to room temperature. Inoculate 2.4 g of baker's yeast, add baker's yeast, and ferment in a shaker at 35°C. After 24 hours of fermentation, the concentration of the fermented liquid was 17.4%, the measured glucose content was 0.23%, and the galactose content was 12.32%. After 48 hours, the glucose content was 0, and the galactose content was 1.72%.

Example 2:

Take 200ml of xylose mother liquor diluted to 20%, adjust the pH to 4.7, add 1g of ammonium chloride, sterilize and cool to room temperature. Inoculate 2.4 g of baker's yeast, add baker's yeast, and ferment in a shaker at 35°C. After 24 hours of fermentation, the concentration of the fermentation broth was 17.8%, the measured glucose content was 0, and the galactose content was 6.828%. After 48 hours, the glucose content was 0, and the galactose content was 1.587%.

Example 3:

Pump the xylose mother liquor raw material into a ^30m3 fermentation tank, add process water to dilute to a concentration of 21.5%, and the dilution accounts for about 2/3 of the volume of the fermentation tank. Add potassium dihydrogen phosphate, ammonium sulfate and magnesium sulfate at a ratio of 0.4%, adjust the pH to 4.4, and sterilize at 115-120°C for 30 minutes. After the temperature drops to 35°C, inoculate 360kg of baker's yeast and start fermentation. The fermentation conditions are: temperature 35~38°C, pH 4.0~4.5, stirring speed 64 rpm, ventilation rate 1:0.2. After about 9 hours of fermentation, the concentration was 18.2%, the glucose content in the fermentation broth was determined to be 0.37%, and the galactose content was 12.54%. After 48 hours of fermentation, the glucose content was 0, the galactose content was 1.39%, and the fermentation ended. The fermentation broth is then put into a disc centrifuge for centrifugation. After the fermentation liquid is centrifuged by a disc centrifuge, the clear liquid is returned to the fermenter, and the thick liquid is transferred to the yeast tank for storage.

Example 4:

Xylose mother liquor fermentation broth 502kg, concentration 17.8%, temperature 34°C, filtration pressure 0.1~0.3MPa. The pore size of the membrane used is 100,000Da. After passing through the membrane equipment, 466.144kg of filtrate is obtained, the concentration is 17%, and it is transparent. The membrane average flow rate is 1447g/min. The pre-membrane solution is 31.52kg, with a solid content of 4.6%, viscous and opaque.

Example 5:

Take 100mL of membrane filtrate and fermentation centrifuge liquid respectively, the concentration is 21.5%, add 2g of activated carbon, incubate at 55~60℃ for 40min, and filter with filter paper. The cut-off filtration time was 16 minutes, and the volumes of the membrane filtrate and the fermentation supernatant were measured. The membrane filtrate was 85 mL, and the fermentation supernatant was 41 mL. The filtration efficiency was about doubled.

Claims (5)

1. improve a method for xylose crystalline efficiency in xylose mother liquid, be raw material with xylose mother liquid, it is characterized by, mainly comprise the steps:

(1) nitrogen nutrition accounting for diluent weight 0.1 ~ 1% is added after xylose mother liquid being diluted to the concentration of 15 ~ 25%, then the pH value of diluent is regulated to be 4.0 ~ 4.5, sterilizing 30 minutes at 115 ~ 120 DEG C, barms is accessed after being cooled to 24 ~ 26 DEG C, inoculum size is often liter of diluent 12g dry yeast, then ferments at 20 ~ 40 DEG C; Barms is one or more in bread yeast, cereuisiae fermentum or schizosaccharomyces pombe;

(2) fermented liquid is centrifugal, centrifugal clear liquid returns fermentor tank, and dope is squeezed into yeast tank and stored;

(3) filtered at 35 ~ 80 DEG C through cross flow tube type film by centrifugal clear liquid, adopt membrane pore size to be the ultra-filtration membrane of 100000Da, operating temperature is 35 ~ 40 DEG C, and filter pressure is 0.05 ~ 0.3MPa, and average flux is 60L/m ²h, ultrafiltration clear liquid is collected into ultrafiltration flow container, and ultrafiltration dope, again through centrifugal, reclaims feed liquid.

2. the method for xylose crystalline efficiency in raising xylose mother liquid according to claim 1, it is characterized in that: in step (1), nitrogen nutrition is urea, ammonium chloride or ammonium sulfate, and its add-on is 0.3 ~ 0.5% of diluent weight.

3. the method for xylose crystalline efficiency in raising xylose mother liquid according to claim 1, it is characterized in that: in step (1), during fermentation, air flow is 1:0.1 ~ 0.4, and stirring velocity is 50 ~ 100 turns/min, and fermentation time is 48h.

4. the method for xylose crystalline efficiency in raising xylose mother liquid according to claim 1, is characterized in that: in step (2), the centrifugal employing disc centrifuge of fermented liquid.

5. the method for xylose crystalline efficiency in raising xylose mother liquid according to claim 1, it is characterized in that: in step (3), described cross flow tube type membrane filtration comprises circulating filtration and continuous filtration.