JP2948675B2 - Cross-flow filtration method for recovering valuable materials in fermentation liquor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering a valuable substance in a fermented liquid from a fermented liquid produced in a fermentation step using bacterial cells or an extract containing protein-based valuables. It relates to a cross-flow filtration method.

[0002]

2. Description of the Related Art As a type of a cross-flow filtration method, an undiluted solution to be treated is circulated and supplied into a filter, and flows along a filter membrane of a filter housed in the filter.
During this time, the undiluted solution is allowed to permeate from the negative side of the filtration membrane to the other side by the pressure difference on both sides of the filtration membrane to be filtered, and a diluent in an amount corresponding to the filtrate discharged from the filter in the circulating feed liquid There is a cross-flow filtration method for recovering valuable substances in a fermentation liquor, which is performed by adding a solution. This filtration method is generally called a diafiltration method, and usually uses water as a diluent. Therefore, the cross-flow filtration method is also called a water addition method.

[0003] The cross-flow filtration method is for recovering valuable resources dissolved in a stock solution once in a solution state. During the filtration process, the concentration of the substance to be separated in the circulating feed liquid gradually increases, thereby increasing the filtration efficiency. A diluent is added to the circulating feed to avoid a decrease, and the concentration of the substance to be separated in the circulating feed is maintained at a substantially constant level, resulting in a decrease in filtration efficiency due to an increase in the concentration of the substance to be separated. It is intended to eliminate the above factors.

[0004]

However, in the conventional filtration method, ordinary water is used as a diluent. Therefore, when the undiluted solution to be treated has a high ion concentration, the filtration treatment is performed. In the process, the ion concentration of the circulating feed liquid gradually decreases and finally reaches an ion concentration corresponding to the water to be added, which is substantially zero or close to it.
Such a state will be significantly different from the ionic concentration of the undiluted solution which is the liquid to be treated, and if the properties such as the shape of the substance to be separated in the undiluted solution are greatly affected by the ionic concentration, the state during the filtration process The properties of the substance to be separated are sequentially changed to cause a problem in the separation by the set filter, and the filtration efficiency is remarkably reduced. Specific examples of the stock solution in which the substances to be separated are mixed include a fermentation solution produced in a fermentation step using cells. Therefore, an object of the present invention is to significantly improve the filtration efficiency in cross-flow filtration using such a fermentation solution or the like as a stock solution.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a fermentation solution or an extract containing a protein-based valuable material produced in a fermentation step using cells is used as a stock solution to be treated, and the stock solution is circulated and supplied into a filter. Then, it flows along the-side of the filter membrane of the filter accommodated in the filter, and during this time, the undiluted solution permeates from the-side of the filter membrane to the other side due to the pressure difference on both sides of the filter membrane and is filtered. In addition, in a cross-flow filtration method for recovering valuable resources in a fermentation liquor performed by adding an amount of diluent corresponding to the filtrate discharged from the filter to the circulating feed liquid, the diluent is used as a conductive material of the undiluted solution. It is characterized by employing a diluent having the same conductivity as the conductivity or a conductivity close to the conductivity of the same stock solution.

[0006]

According to the cross-flow filtration method of the present invention, the conductivity of the circulating feed solution is the same as or close to the conductivity of the undiluted solution, and the object to be separated is affected by the characteristic change due to the ion concentration. Instead, it retains properties similar to those of the stock solution. For this reason, in the filter set based on such characteristics, the set filtering function is exhibited as it is, and the filtering efficiency is not greatly reduced in the filtering process as in the conventional cross-flow filtering method of this type. In addition, the filtration efficiency can be significantly improved.

[0007]

EXAMPLE A cross-flow filtration method by a diafiltration method was carried out using a cross-flow filtration apparatus shown in FIG. . In the cross flow filtration device, the stock solution tank 11, the circulation pump 1
2. The first filter 13 and the second filter 14 are connected in series to each other to form a circulation path, and the stock solution tank 11 is diluted by an amount corresponding to the amount of filtrate flowing out in the filtration process. The liquid is sequentially added.

(1) Undiluted solution Enzyme: Dissolves alkaline protease having a molecular weight of 100,000 Substance to be separated: Microorganisms, containing 2.9 wt% concentration… However, dry conversion pH: 7.5 Conductivity: 10 mS / cm (2) Filtration conditions Filter: average A ceramic monolithic filter with a pore diameter of 0.1 μm and a length of 1000 mm with 19 through holes with a diameter of 4 mm
Each one by one using filtration area on each filter 13 and 14 ones: total 0.48 m ² circulation flow rate: 5 m / sec filtration differential pressure: 1 kg / cm ² circulating feed temperature: 30 ° C. (3) dilution sodium chloride Water: 0.6wt%, conductivity 11mS / cm City water: conductivity 0.2mS / cm

[0009] In these experiments, the addition ratio of the diluent, the enzyme permeability, and the corresponding enzyme recovery were measured and calculated and compared. The results are shown in Table 1 and each graph in FIGS. The addition ratio was calculated as the cumulative amount of the diluent added to the stock solution, and the permeation ratio was calculated as the permeation amount based on the enzyme concentration in the remaining stock solution in the circulating feed solution.

[0010]

[Table 1]

As apparent from Table 1 and FIGS. 2 and 3, when a saline solution having a conductivity close to the conductivity of the undiluted solution is employed as the diluent, the addition ratio of the diluent increases. However, the decrease in transmittance is small and the final recovery of the enzyme is about 96.
%, Whereas when city water is used as the diluent, which is significantly different from the conductivity of the undiluted solution, the transmittance decreases greatly as the diluent addition ratio increases, and the final recovery of the enzyme is about It was only 82%.

[0012] From this fact, by employing a diluent having a conductivity that is the same as or close to the conductivity of the undiluted solution, a decrease in the transmittance during the filtration process is suppressed, and the final recovery of the enzyme is reduced. It was found to increase.
Based on this fact, almost the same results can be obtained when using an aqueous solution of potassium chloride, a buffer solution such as phosphoric acid, citric acid, boric acid, etc. instead of the saline solution as the diluting solution for the stock solution. I learned. Although such facts have not yet been sufficiently elucidated, the enzyme exhibits a minimum mass state in the liquid having the conductivity of the stock solution,
It is presumed that as the conductivity decreases, the mass gradually becomes large, and as a result, the state of filtration is affected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a cross-flow filtration device used for carrying out the method of the present invention.

FIG. 2 is a graph showing changes over time in enzyme permeation rate and recovery rate when a saline solution is employed as a diluent.

FIG. 3 is a graph showing changes over time in enzyme permeability and recovery when city water is used as a diluent.

[Explanation of symbols]

11: stock solution tank, 12: circulation pump, 13, 14: filter.

Claims (1)

(57) [Claims] 1. A fermentation solution produced in a fermentation step using bacterial cells or an extract containing a protein-based valuable material is used as a stock solution to be treated, and the stock solution is circulated and supplied to a filter and stored in the filter. The filter solution is caused to flow along the-side of the filtration membrane, and during this time, the undiluted solution is allowed to permeate from the-side of the filtration membrane to the other side by a pressure difference between both sides of the filtration membrane, and is filtered. In a cross-flow filtration method for recovering valuable resources in a fermentation liquor performed by adding an amount of diluent corresponding to a filtrate discharged from a filter, the diluent has the same conductivity as that of the undiluted solution, A cross-flow filtration method for recovering valuable resources in a fermentation liquor, wherein a diluent having a conductivity close to the ratio is employed.