MXPA00009878A - Membrane filtration - Google Patents

Abstract

The invention relates to a process for isolating a desired water-soluble product from a fermentation broth wherein the broth is circulated along a ceramic membrane, and wherein a trans-membrane pressure of at least 1.5 bar is applied, whereupon an aqueous solution containing the desired product traverses the membrane, and is subsequently collected. Advantageously, during this filtration process the temperature of the broth is maintained at 20 to 50°C, preferably at 30 to 45°C. According to the invention, a decreased process time and a higher capacity and efficiency of the filtration are obtained.

Description

FILTRATION BY MEMBRANE Field of the Invention The invention relates to a process for isolating a desired water-soluble product from a fermentation broth.

Background of the Invention Nowadays, fermentation processes to prepare chemical compounds - play an important role in increasing chemistry. Since this type of process is highly selective, environmentally attractive and leads to high productions in the product, even industrial preparations are carried out in this way. After the fermentation has been completed, the desired product needs to be isolated from the fermentation broth. Conventionally, this is accomplished by first separating the aqueous phase from the cellular material in a paste filtration step, followed by extraction or adsorption of the product from the filtrate. However, often said step of filtering in paste is accompanied by a REF .: 123 5 significant loss of the desired product. This is due to the fact that the filter cake can not be washed sufficiently, and that a large amount of the product remains in the filter cloth. In practice, it is observed that the efficiency and capacity of the filtration process depend strongly on the quality of the fermentation broth. In addition, the "dissolved" proteins and cellular debris present in the filtration broth are insufficiently removed from the fermentation broth phase when they are filtered in paste. This has the effect on the descending and subsequent processes, of suffering with protein contamination and thus, its capacity is diminished. In order to solve the above problems in the working procedure in fermentation broths, it has been proposed to make use of other filtration methods, such as membrane filtration. The membranes used for these purposes are usually polymeric membranes, such as polysulfone membranes. The advantage of membrane filtration is that by design, less product is lost and filtering is obtained. { permeate) more pure. The permeate contains significantly less protein and / or remnants of cellular material than the filtrate obtained in a conventional paste filtration technique. As a result, the extraction step can be carried out more conveniently and the overall efficiency of the process is increased. In the East German patent application DD-A-277 088, a process for isolating benzylpenicillin from a microbiological broth is described. The process involves a conventional pulp filtration step to remove the biomass and a subsequent ultrafiltration step, wherein the proteins present within the filtrate of the first filtration are separated. The product of the ultrafiltration is concentrated to 5% of its volume, and the desired benzylpenicillin is isolated from it, by means of extraction. A membrane filtration process for the filtration of a broth usually comprises three steps. In practice, particularly in a continuous process, the transition from one step to another can not be clearly discernible, frequently occurring when two or all of the steps are carried out at the same time. However, for the purpose of clarity, it is useful to establish this distinction. The first step is the concentration of the composition that will be filtered. Said step of concentration can be carried out properly, by circulating the broth along a membrane surface while maintaining a pressure gradient on the surface (often referred to as cross-flow filtration). In the second step, the concentrated product obtained washing during the cross-flow filtration, in a dialysis step. This means that the flow of a solvent is added to the circulation flow of the broth. In the case where the filtered product is a fermentation broth, this solvent will usually be water. In the third step, the filtered permeate obtained is further concentrated during the cross-flow filtration to a suitable point. In a process involving a membrane filtration step, it is necessary to control the retentive flow conditions (the filtration residue) along the membrane by applying a high transverse flow velocity (ie a velocity of linear flow, parallel to the plane of the membrane), in order to maximize the fluidity (capacity) of the process. However, in practice a large number of problems arise in trying to maintain a rapid flow of remnant after it has been concentrated. These problems are found particularly in the case of a broth of fermentation that has high contents (3-10%) of cellular waste and proteins that have to be filtered. Due to an increased viscosity, which is observed at high concentration factors, the axial pressure drop, which is a measurement for the energy required in the process, also increases. In large-scale applications, centrifugal pumps are applied and their capacity decreases as a result of the increased axial pressure drop. Due to the pseudoplastic nature of the materials involved under these conditions, the viscosity increases further, which in turn further amplifies the decrease in flow. Moreover, much heat is generated, which is not desired in cases where the desired product is unstable at high temperatures. Accordingly, in order to keep the temperature low and avoid degradation of the product, a large and expansive cooling device is necessary. Also, it is desired to minimize the time necessary to complete the filtration process, in order to avoid degradation and contamination of the desired product. The available measurements to minimize the filtration time are to increase the membrane surface of the filter, or to demand a specific capacity in increment. The specific capacity indicates that the desired amount of product permeates a certain surface area of the membrane per unit time (l / m2.h). This capacity can be increased by applying a high transmembrane pressure, which is the pushing force behind the filtration. A disadvantage of applying a high transmembrane pressure is that this often leads to a higher retention of the desired product, i.e., a large amount of product that does not permeate the membrane, which leads to an inefficient process. Moreover, the application of tubular polymer membranes in such cases can not be possible, since this type of membrane wears excessively under these conditions. It has been discovered in the present that the above problems can be solved in a surprising way, by using a ceramic membrane and by controlling the process conditions. The use of ceramic membranes has been reported in the prior art for use in various separations of desired products from a fermentation broth. In EP 0 522 517 Al, a microporous alumina membrane is used for the separation of methyl glucoside from a fermentation broth. In a first step the broth is concentrated, where after the methyl glucoside insoluble to the water is dissolved by means of adding methanol, where the methyl glucoside that contains the solution, passes through the membrane and thus the antibiotic is recovered. A similar technique is described in U.S. Patent 5,616,595 for the separation of cyclosporin A, from a fermentation broth. According to Russian patent publication 2090598, ceramic filter elements can be applied for the filtration of most of the elements in the production of wines.

Description of the invention The present invention relates to a process for isolating a desired water-soluble product from a fermentation broth, wherein the broth is circulated through a ceramic membrane and where a transmembrane pressure of at least 1.5 bar is applied. , wherein until an aqueous solution containing the desired product crosses the membrane and is subsequently collected. The process according to the invention has the advantage that a very short time can be obtained of filtration without the known problem of a high retention of desired product. Thus, the present filtration process is highly efficient. Surprisingly, a high transmembrane pressure can be applied in a process according to the invention, without encountering a high retention of the desired product. As well, the temperature can be controlled very appropriately at a desired value, without leading to problems of viscosity and without leading to the cutting of the desired product which is often thermally unstable. Moreover, in a process according to the invention, it is not necessary to carry out a conventional filtration of the fermentation broth, before subjecting it to the membrane filtration, as has been described in DD-A-277 088. The broth of Fermentation can be obtained from any fermentation process. In said process, a suitable chain of microorganisms is fermented by adding a carbon source, a nitrogen source, other nutrients and air to the broth. The procedures and typical operation recipes can be found in the literature. After the fermentation process has been completed to a desired point, the broth may comprise cellular material as well as proteins and the desired product. Also, different pollutants It is preferred that the broth be obtained from a fermentation process in which an anti-infective compound has been prepared. Examples of said compounds. they are the ß-lactamases and compounds such as erythromycin and nystatin. Examples of the β-lactamases in this respect are β-lactamases wherein the β-lactamase nucleus is attached to an appropriate side chain, such as penicillin G, penicillin V, adipyl-7-aminocephalosporanic acid, cluvulanic acid, Cephalosporin C, Ampicillin, Amoxicillin, Cefalexin, Cefaclor and Cefadroxil. Possibly, ß-lactamase nuclei are also suitable, such as 6-aminopenicillanic acid (6-APA), 7-aminocephalosporanic acid (7-ACA), 3-chloro-7-aminodesacetoxydes-methylcephalosporanic acid (3-Cl, 7). -ACCA), 7-aminodesacetoxides-sporic acid (7-ADAC) and 7-aminodesacetoxycephalosporanic acid (7-ADCA). Fermentation broths obtained through processes for the preparation of penicillin G, penicillin V, cephalosporin C, acyl-7-aminodesacetoxycephalosporanic acid or acyl-7-aminocephalosporanic acid are mostly preferred. It has been found that a filtering process of one of these fermentation broths significantly benefits from the advantages of the invention. Even though many of these wines Fermentation comprises thermally unstable products, it has been found that in a process according to the invention, these thermally unstable products can be isolated from a broth, without a significant loss of the product. The membrane that is used according to the invention is a ceramic membrane. This means that it comprises an inorganic material. Preferred materials are metal oxides, such as α-alumina, α-alumina and zirconia. The use of membranes of these materials leads to highly efficient filtration processes, where only small amounts of the desired product are lost, if they are, and where the desired product is obtained with a very high purity. Preferably, a ceramic membrane is used, which has an average pore size of 4 to 100 nm, more preferably 20 to 50 nm. It has been found that the use of a membrane having a pore size within these ranges leads to an efficient and highly selective membrane filtration process. During the circulation of the broth along the membrane (cross-flow filtration), it will concentrate, in both increased amounts of the Fluids present within the broth permeate through the membrane. An appropriate point of concentration is 1.5 times, preferably 2 times. Said concentration can be performed more advantageously at elevated temperatures, preferably at a temperature higher than 20 ° C, more preferably higher than 30 ° C. The maximum limit of the temperature during the concentration, will generally be for practical reasons of 50 ° C, preferably 45 ° C. In accordance with the invention, it has been found that the viscosity of the broth does not reach high unacceptable values. When the concentration factor is 2, the typical maximum values are 337 mPa.s at a cut of 100 s "1, 197 mPa.s at a cut of 500 s" 1 and 156 mPa. As a consequence, no additional and expensive equipment is required to carry out the circulation at a sufficient cross-flow rate.The cross-flow velocity may show a slight fluctuation during a process of according to the invention and reach values of 2-4 m / s, however, said speed is preferably maintained at a value of at least 5 m / s, more preferably at 6 m / s. said speed is 10 m / s, more preferably of 8 m / s. When said speed is chosen within the specified ranges, the filtration process has a very high capacity. It has now been proven that it is possible to maintain high speed, even when the concentration is carried out to a large extent. After the residue has been concentrated to the desired point, it is preferred to add water to the circulating broth (dialysis). Preferably, an amount of water is added in such a way that the broth is diluted 1.5-4 times, more preferably 2-3 times. By means of this addition of water to the waste, the production and consequently the efficiency of the filtration process is increased. In fact, quantities of the desired product in the waste can be recovered by means of this dilution step, which comprises the addition of water to the residue. A great advantage of the process of the invention is that a very short process time can be obtained, without the known problem of high retention of the desired product occurring. Thus, according to the invention, the transmembrane pressure is higher at 1.5 bar. Within the context of the invention, the transmembrane pressure is defined as the difference in the average of the side of the waste and the average pressure of the permeate side of the waste. the membrane. In a preferred embodiment, the transmembrane pressure is from 2.5 to 7.5, preferably from 4 to 6 bar. According to a highly preferred embodiment of the invention, the transmembrane pressure is initially less than the pressure specified above. The initial transmembrane pressures are chosen between 1 and 2.5 bar. The period of time during which this initial transmembrane pressure is applied is relatively short. In general, said period will not be greater than 10%, preferably not greater than 8% of the total filtration time. In most practical cases, depending on the amount of fermentation broth to be filtered, this period will be approximately 10 minutes. This modality has the advantage that significantly less faults occur on the part of the membrane than could eventually be desired, a high transmembrane pressure is applied from the beginning of the process. Because of this, the life time of the membrane is increased, that is, the period of time in which the same membrane can be used without having to clean it is increased. Also, the capacity of the filtration process is greater and the selectivity is greater. Without pretending to commit to the theory, it is believed that these Advantages are contained because the layer descends proteins on the side of the membrane residue, which is deposited during the initial period, where a low transmembrane pressure is applied. The input pressure of the waste within a process according to the invention, will vary depending on the stage in which it is during the process, between 1 and 8 bar. The axial pressure drop of the waste will also vary depending on the stage during the process, between 0 and 3.5 bar. The specific fluidity can vary from 200 1 / m2. h. up to 50 1 / m2. h. bar and back up to 1 / m2. h. bar during the course of the process. On the permeate side of the membrane, a continuous flow will usually be maintained in order to collect the permeate and in particular, the desired product present there. After the permeate has been collected, it can be advantageously concentrated. The preferred concentration points of the permeate are from 1.5 to 7, more preferably from 2 to 5 times. In order to recover the desired product present in the concentrated permeate, conventional working procedures will generally be carried out. An appropriate example of said working procedure is an extraction.

A process according to the invention can be carried out either batchwise or continuously. This is preferably carried out in the form of a continuous process. The invention will be further clarified by means of the following non-restrictive examples.

Example 1 156 kg of a penicillin fermentation broth were fed from a liquefied feed tank to a membrane filtration system (MF). Said system comprised a Membranlox SCT 3P19 membrane having a surface area of approximately 0.9 m and an average pore size of 50 nm. The system was debunked and the filtering process was initiated under the following conditions: Temperature 21 ° C Feed tank of 2.5 m3 / h flow in circulation Feed cycle of 35 nrVh flow in circulation (The transverse flow velocity was 6 m / s.) After 65 liters of the permeate were removed (ct = 1.67 (concentration factor), ß = 0.4 (dilution factor)), the circulation flow of the filtration cycle had decreased to 17 m3 / h, which corresponds to a speed of 2.9 m / s. The permeate flow decreased to 70 l / m2h at a transmembrane pressure of 4 bar. The concentration factor was 1.67. No additional concentration was possible. The diafiltration was started keeping the constant a, the cross flow velocity was increased again to 5.5 m / s, the flow of the permeate remained constant at 72 l / m2.h. The dilution factor was 1.72. The total processing time was 250 minutes.

Example 2 154 kg of a penicillin fermentation broth were fed from a liquefied feed tank to the same membrane filtration system (MF) that was used in Example 1.

The system was debunked and the filtering process was initiated under the following conditions: Temperature 40 ° C Feed tank of 2.5 m / h flow in circulation Feed cycle of 35 m3 / h flow in circulation (The transverse flow rate was 6 m / s.) After 74 liters of the permeate were removed (a = 1.92, ß = 0.48), the circulation flow of the circulation filter was slowly reduced to only 26 m3 / h. The permeate flow decreased to 94 l / m2h at a concentration factor of 2.0 and a transmembrane pressure of 4 bar. Directly after starting the diafiltration, in which a was kept constant, the cross-flow velocity was again increased to 5.9 m / s and the permeate flow was controlled to be 110 l / m2.h. The dilution factor was 1.85.

The total processing time was 180 minutes.

Example 3 177 kg of a penicillin fermentation broth were fed from a liquefied feed tank to the same membrane filtration system (ME) that was used in Example 1. The system was debugged and the filtration process was initiated under the following terms: Temperature 36 ° C Feed tank of 2.5 m3 / h flow in circulation Flow cycle in circulation (The flow rate was 6 m / s.) After 90 liters of the permeate were removed (a = 2.04, ß = 0.51), the circulation flow was 6 m / s. The permeate flow of 511 m2 / h at the start of the concentration decreased to 124 l / m2h at the conclusion of the concentration. The concentration factor was 2.04 and the transmembrane pressure was 5 bar.

After starting the diafiltration, in which a was kept constant, the permeate flow increased very slowly and was controlled to be 255 l / m2.h. The transmembrane pressure slowly decayed to 3.8 bar at the conclusion of the process. The dilution factor was 2.02. The total processing time was 134 minutes.

It is noted that, with regard to this date, the best method known by the requested, to carry out the present invention, is that which is clear from the present, discovering the invention. Having described the invention as above, the content of the following is claimed as property.

Claims (1)

1. CLAIMS A process for isolating a desired water soluble product from a fermentation broth, chaerized in that the broth is circulated along a ceramic membrane and where a transmembrane pressure of at least 1.5 bar is applied, where until An aqueous solution containing the desired product penetrates the membrane and is subsequently collected. The process according to claim 1, chaerized in that the broth is concentrated during its circulation along the membrane, at a temperature between 20 and 50 ° C. The process according to claim 2, chaerized in that the temperature varies between 30 and 45 ° C. The process according to any of the preceding claims, chaerized in that the transverse flow velocity is from 5 to 10 m / s, preferably from 6 to 8 m / s. The process according to any of the preceding claims, chaerized in that The ceramic membrane comprises a material chosen from the group consisting of metal oxides. 6. The process according to any of the preceding claims, chaerized in that the ceramic membrane has an average pore size of 4-100 nm, preferably 20-50 nm. 7. The process according to any of the preceding claims, chaerized in that the transmembrane pressure is 2.5-7.5 bar, preferably 3-6 bar. 8. The process according to claim 7, chaerized in that the transmembrane pressure is initially from 1 to 2.5 bar. 9. The process according to any of the preceding claims, chaerized in that water is added to the circulating broth, once said broth has been concentrated 1.5 times, preferably 2 times. 10. The process according to claim 9, chaerized in that the amount of water that is added is such that the broth is diluted 1.5-4 times, preferably 1-3 times. The process according to any of the preceding claims, chaerized in that after having filtered the broth, a permeate is obtained, which is concentrated 1.5-7 times, preferably 2-5 times. The process according to any of the preceding claims, chaerized in that the fermentation broth is obtained from a fermentation process where an anti-infective compound is prepared. The process according to claim 12, chaerized in that the anti-infective compound is chosen from the group consisting of erythromycin, nystatin, adiply-7-aminocephalosporanic acid, penicillin G, penicillin V, cephalosporin C, and isopenicillin N.