阅读说明：本技术 一种半连续发酵生产谷氨酸的方法及系统 (Method and system for producing glutamic acid by semi-continuous fermentation ) 是由 刘海涛 王均成 吕宝龙 李武红 于 2020-07-02 设计创作，主要内容包括：本发明属于发酵工程领域,公开了一种半连续发酵生产谷氨酸的方法及系统,种子培养；温敏谷氨酸菌种在30-32℃、pH7.0-7.1条件下培养制备种子液；发酵培养：种子液接入培养基中,采用半连续式发酵,在发酵过程中流加补料。本发明采用的利用温敏谷氨酸半连续发酵工艺能够延长谷氨酸产酸周期,避免了发酵液中谷氨酸积累对菌体的抑制作用,及提高发酵液中氧、营养素传递速率,与现有发酵工艺相比,能够整体缩短发酵周期,提高发酵效率,同时单罐发酵液谷氨酸含量得到了极大的提升。(The invention belongs to the field of fermentation engineering, and discloses a method and a system for producing glutamic acid by semi-continuous fermentation, which comprises seed culture; culturing temperature sensitive glutamic acid strain at 30-32 deg.C and pH7.0-7.1 to prepare seed solution; fermentation culture: inoculating the seed liquid into culture medium, fermenting in semi-continuous mode, and adding supplementary material during fermentation. The semi-continuous fermentation process of the temperature-sensitive glutamic acid can prolong the acid production period of the glutamic acid, avoid the inhibition effect of glutamic acid accumulation in fermentation liquor on thalli, and improve the transfer rate of oxygen and nutrients in the fermentation liquor.)

1. A method for producing glutamic acid by semi-continuous fermentation is characterized by comprising the following steps:

step one, seed culture; culturing temperature sensitive glutamic acid strain at 30-32 deg.C and pH7.0-7.1 to prepare seed solution;

step two, fermentation culture: inoculating the seed liquid into culture medium, fermenting in semi-continuous mode, and adding supplementary material during fermentation.

2. The method for producing glutamic acid by semi-continuous fermentation according to claim 1, wherein in the first step, the seed solution is subjected to three-stage seed expansion culture, and the inoculation volume ratio is 8% to 15%.

3. The method for producing glutamic acid by semi-continuous fermentation according to claim 1, wherein, in the second step,

when the volume of the fermentation liquor reaches 50-60% of the tank volume or the glutamic acid content is 14-17%, discharging the fermentation liquor for continuous fermentation;

when the volume of the fermentation liquor reaches 50-60% of the tank volume again or the glutamic acid content is 14-17%, discharging part of the fermentation liquor to a storage tank for continuous fermentation;

repeating the operation for 1-4 batches until the fermentation is finished.

4. The method for producing glutamic acid by semi-continuous fermentation according to claim 1, wherein in the second step, the fermentation culture temperature is: the fermentation temperature is 30-32 ℃ after 0-2h, 35-36 ℃ after 3-4h, and 37-38 ℃ after 5-25 h.

5. The method for producing glutamic acid by semi-continuous fermentation according to claim 1, wherein in the second step, the tank volume during fermentation is 5 to 15% of the total volume of the fermentation broth.

6. A system for producing glutamic acid by semi-continuous fermentation using the method of 1-5.

Technical Field

The invention belongs to the field of fermentation engineering, and particularly relates to a method and a system for producing glutamic acid by semi-continuous fermentation.

Background

At present: at present, the strains for industrially producing the glutamic acid are mainly temperature-sensitive mutant strains, and the fermentation process of the temperature-sensitive strains mainly changes the structure of a cell membrane by regulating the temperature to influence the activity of enzyme, so that the strains are converted into strains which are beneficial to continuously releasing the intracellular glutamic acid to the extracellular environment, and the feedback inhibition caused by the accumulation of the intracellular glutamic acid is removed to continuously synthesize the glutamic acid.

However, the prior glutamic acid fermentation production mainly adopts a fed-batch fermentation process, and although batch fermentation is simple and convenient to operate, in the whole production process, along with the extension of fermentation time, on one hand, glutamic acid in fermentation liquor is accumulated to form an inhibition effect, and the acid production efficiency of thalli is influenced; on the other hand, as the volume of the feed liquid in the fermentation tank is increased, the transfer rate of oxygen transfer and fed-batch nutrient is slowed down, and the acid production efficiency of the thalli is further influenced, so that the whole fermentation period is prolonged, and the production efficiency is reduced.

Through the above analysis, the problems and defects of the prior art are as follows:

(1) glutamic acid in fermentation liquor is accumulated to form an inhibiting effect, so that the acid production efficiency of thalli is influenced;

(2) with the increase of the volume of the feed liquid in the fermentation tank, the transfer rate of oxygen and fed-batch nutrients is slowed down, and the acid production efficiency of the thalli is further influenced, so that the whole fermentation period is prolonged, and the production efficiency is reduced.

The difficulty in solving the above problems and defects is:

the inhibition effect of glutamic acid accumulation formation is increased along with the progress of fermentation, the concentration of glutamic acid in fermentation liquor needs to be reduced for removing the inhibition effect, although the inhibition effect is removed by a method of separating glutamic acid from partial fermentation liquor by centrifugation, membrane filtration and other separation technologies and then returning fermentation thalli to the fermentation tank for continuous fermentation in the prior art, the technology is complicated to operate and easily causes bacterial contamination of the fermentation liquor.

On the other hand, in fed-batch fermentation, as the volume of the fermentation tank increases, the problems of low oxygen transfer and nutrient transfer efficiency due to high-volume fermentation can be alleviated by physical distribution means such as increasing oxygen supply and stirring, but the problems also cause increase in electric energy consumption and damage to the cells due to high shear at high stirring speed, which affects the fermentation efficiency.

The significance of solving the problems and the defects is as follows:

by the technical process, part of fermentation liquor is discharged intermittently in the fermentation process, the concentration of glutamic acid in the fermentation liquor is diluted on the basis of feeding and supplementing materials, the volume of the fermentation liquor is effectively reduced, and the problems of poor oxygen transfer and nutrient transfer effects and the like are solved. And the discharged fermentation liquor is directly separated and purified, so that the acid production efficiency of a single tank is integrally improved.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for producing glutamic acid by semi-continuous fermentation.

The invention is realized in such a way that a method for producing glutamic acid by semi-continuous fermentation comprises the following steps:

step one, seed culture: culturing temperature sensitive glutamic acid strain at 30-32 deg.C and pH7.0-7.1 to prepare seed solution;

step two, fermentation culture: inoculating the seed liquid into culture medium, fermenting in semi-continuous mode, and adding supplementary material during fermentation.

Further, in the first step, the seed liquid is subjected to three-stage seed amplification culture, and the inoculation volume ratio is 8-15%.

Further, in the second step, when the volume of the fermentation liquor reaches 50-60% of the tank volume or the glutamic acid content is 14-17%, discharging the fermentation liquor for continuous fermentation;

when the volume of the fermentation liquor reaches 50-60% of the tank volume again or the glutamic acid content is 14-17%, discharging part of the fermentation liquor to a storage tank for continuous fermentation;

repeating the operation for 1-4 batches until the fermentation is finished.

Further, in the second step, the fermentation culture temperature is as follows: the fermentation temperature is 30-32 ℃ after 0-2h, 35-36 ℃ after 3-4h, and 37-38 ℃ after 5-25 h.

Further, in the second step, the volume of the tank is 5-15% of the total volume of the fermentation liquor in the fermentation process.

Another object of the present invention is to provide a system for producing glutamic acid by semi-continuous fermentation using the above method.

By combining all the technical schemes, the invention has the advantages and positive effects that:

firstly, the glutamic acid is directly separated and extracted from the fermentation liquor discharged by the invention, so that the procedure of filtering and returning the thalli to a fermentation tank for continuous fermentation is omitted, on one hand, the fermentation process is simplified, and on the other hand, the risk of bacterial contamination is avoided.

Secondly, only high-concentration sugar flows in the feeding process, compared with the whole culture medium, the feeding process is more convenient, the production cost is saved, and the fermentation period can be effectively controlled.

Thirdly, the intermediate discharging process is finished instantly at a high speed, so that the risk of contamination and the loss of fed sugar caused by long-time discharging are avoided.

Fourth, the feeding rate of the invention is controlled in such a way that the sugar concentration of the fermentation liquor is stabilized at a certain level (0.5%), and the feeding rate is controlled by the sugar concentration.

Fifthly, the volume of the fermentation liquor or the concentration of the produced acid is used as an index of batch discharging, so that the adverse effect of low dissolved oxygen concentration under high volume of the fermentation liquor on the fermentation produced acid is avoided, and the inhibiting effect of high-concentration glutamic acid in the fermentation liquor on glutamic acid bacteria can be avoided.

Sixth, the semi-continuous fermentation process using temperature-sensitive glutamic acid adopted by the invention can prolong the glutamic acid production period, avoid the inhibition effect of glutamic acid accumulation in the fermentation liquor on thalli, and improve the transfer rate of oxygen and nutrients in the fermentation liquor.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.

FIG. 1 is a flow chart of a method for producing glutamic acid by semi-continuous fermentation according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Aiming at the problems in the prior art and solving the problems of low acid production, low production efficiency and the like of the prior glutamic acid batch fermentation, the invention provides a method for producing glutamic acid by semi-continuous fermentation, and the invention is described in detail by combining the attached drawings.

The method for producing glutamic acid by semi-continuous fermentation comprises the following steps: after the seeds are subjected to enlarged culture, inoculating the seeds into a fermentation tank according to a certain volume ratio for fermentation, feeding and supplementing sugar in the fermentation process to ensure that the sugar concentration of the fermentation liquid is stable, discharging part of the fermentation liquid into a storage tank for separation and extraction when the volume of the fermentation liquid reaches a certain volume or the content of glutamic acid reaches a certain concentration, continuously fermenting in the storage tank, and repeating the steps for 1-4 batches to obtain the fermentation liquid containing the glutamic acid.

(1) Seed culture: culturing temperature sensitive glutamic acid strain at 30-32 deg.C and pH7.0-7.1 to prepare seed solution;

(2) fermentation culture: inoculating the seed liquid into a culture medium, performing semi-continuous fermentation, feeding in a material during fermentation, and discharging the fermentation liquid for continuous fermentation when the volume of the fermentation liquid reaches 50-60% of the tank volume or the glutamic acid content is 14-17%; when the volume of the fermentation liquid reaches 50-60% of the tank volume again or the glutamic acid content is 14-17%, discharging part of the fermentation liquid to a storage tank for continuous fermentation, and repeating the operation for 1-4 batches until the fermentation is finished.

The seed liquid is subjected to three-stage seed amplification culture, and the inoculation volume ratio is 8-15%;

the seed liquid is added in an amount of 10-15% by volume;

the fermentation culture temperature in the step (2) is as follows: the fermentation temperature is 30-32 ℃ after 0-2h, 35-36 ℃ after 3-4h, and 37-38 ℃ after 5-25 h;

when the volume of the fermentation liquor reaches 50-60% of the tank volume, discharging part of the fermentation liquor, and simultaneously taking 14-17% of glutamic acid content as a judgment parameter;

and (3) in the step (2), the volume of the tank in the fermentation process is 5-15% of the total volume of the fermentation.

The comparative example is fed-batch fermentation, no material is discharged in the fermentation process, and other fermentation conditions are the same as those of the example.