JP2017163936A - Device and method of culturing microorganisms - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently defoam the foam on the surface of a culture solution in a culture tank.SOLUTION: Microorganisms are cultured in a culture solution 90 in a culture tank 10. Substrate gas is supplied from a substrate gas supply part 14 to the culture solution 90. Ultrasound exposure means 30 exposes the foam 92 on the surface 91 of the culture solution 90 with ultrasound 39.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus and method for culturing microorganisms in a culture solution, and more particularly, to a culture device and a culture method suitable for eliminating bubbles on a culture solution or adjusting the amount of the foam.

Certain microorganisms are known to produce valuable organic substances such as ethanol from a substrate gas by fermentation (see the following patent documents and the like). This type of gas-utilizing microorganism is cultured in a culture solution. In general, examples of the culture tank include a stirring type, an air lift type, a bubble column type, a loop type, a filling type, an open pond type, and a photobio type. As the substrate gas, for example, a synthesis gas containing CO, H ₂ , CO ₂ or the like is used. Syngas is generated at steelworks, coal plants, waste disposal facilities, and the like. By supplying this synthesis gas to the culture tank, the gas assimilating microorganism is fermented.

US Pat. No. 8,658,415 US publication US2013 / 0065282 JP 2014-050406 A

In this type of culture apparatus, bubbles are easily formed on the liquid surface of the culture solution due to the supply of a substrate gas, a fermentation reaction, or the like. If the foam grows excessively, it may cause various problems such as foam entering the downstream gas processing section or the like via the exhaust gas line and causing failure or contamination. Bubble countermeasures are urgently needed.
As an antifoaming method, it is conceivable to add an antifoaming agent to the culture solution. However, the gas dissolution rate at the gas-liquid interface of the culture solution may decrease, and the efficiency of the gas fermentation reaction may decrease.
Further, it is conceivable to take out a part of the culture solution in the culture tank, return it to the upper end of the culture tank and spray it on the liquid level of the culture solution, but the structure becomes complicated.
Moreover, although it is possible to scrape a bubble by turning a foam cutting blade, the scraped bubble does not disappear.

In order to solve the above problems, an apparatus according to the present invention is a culture apparatus for culturing microorganisms in a culture solution,
A culture vessel containing the culture solution;
A substrate gas supply unit for supplying a substrate gas to the culture solution in the culture tank;
Ultrasonic irradiation means for irradiating the foam on the liquid surface of the culture solution with ultrasonic waves;
It is provided with.
A microorganism culturing method according to the present invention includes a culture step of culturing a microorganism in a culture solution in a culture tank,
A gas supply step of supplying a substrate gas to the culture solution;
An ultrasonic irradiation step of irradiating the foam on the liquid surface of the culture solution with ultrasonic waves;
It is provided with.

Foam is easily formed on the upper surface of the culture solution due to substrate gas supply or fermentation reaction. When this foam becomes excessive, the ultrasonic wave is irradiated to the foam from the ultrasonic wave irradiation means. The ultrasonic frequency and the like are adjusted according to the bubble diameter and the bubble component. Thereby, it is possible to efficiently defoam. Or the amount of foam can be adjusted.
It is preferable that the substrate gas is a synthesis gas, and the microorganism is an anaerobic gas assimilating microorganism that ferments and produces an organic substance from the synthesis gas.
Examples of the organic substance include alcohol such as ethanol and acetic acid.

It is preferable that the ultrasonic irradiation means includes an ultrasonic vibrator and a vibrator holding member that holds the ultrasonic vibrator above the liquid surface.
This can prevent the foaming of the culture medium from being promoted.
The ultrasonic transducer is only required to be arranged at least above the liquid level of the culture solution. An ultrasonic transducer | vibrator may be inserted in the inside of foam and an ultrasonic wave may be directly irradiated to foam. The ultrasonic transducer may be arranged above the foam so that the ultrasonic wave is applied to the foam using air as a propagation medium.
It is preferable that a ventilation portion is formed in the vibrator holding member.
If the gas containing the substrate gas component, fermentation by-product gas component, etc. rises from the liquid level of the culture solution, it can be guided upward from the vibrator holding member through the aeration portion, and can be reliably discarded.

The ultrasonic irradiation means may be fixed in position in the culture tank, and may be movable up and down with respect to the culture tank.
The culture apparatus may further include elevating means for elevating and lowering the vibrator holding member according to the height of the liquid level.
Thereby, the amount of foam can be adjusted reliably.

  According to the present invention, it is possible to efficiently defoam the foam on the liquid surface of the culture solution in the culture tank and adjust the amount of foam.

FIG. 1 is a longitudinal sectional view showing a schematic configuration of the culture apparatus according to the first embodiment of the present invention. FIG. 2 is a plan sectional view taken along line II-II in FIG. FIG. 3 is a longitudinal sectional view showing a state in which the upper part of the foam is defoamed in the culture apparatus. FIG. 4 shows a second embodiment of the present invention and is a longitudinal sectional view of the upper part of the culture tank.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
1 to 3 show a culture apparatus 1 according to a first embodiment of the present invention. As shown in FIG. 1, anaerobic gas assimilating microorganisms are cultured by a culture apparatus 1. As the gas assimilating microorganism, those disclosed in the above-mentioned patent documents and the like can be used. The gas assimilating microorganisms fermentatively produce valuable organic substances (target substances) from the substrate gas g. The target substance of the apparatus 1 is ethanol (C ₂ H ₅ OH).

As the substrate gas g, synthesis gas (syngas) containing CO, H ₂ , CO ₂ or the like is used. Although illustration is omitted, the substrate gas production facility in the present embodiment is configured as a waste treatment facility. Examples of waste include municipal waste, tires, biomass, wood chips, and plastic waste. The waste treatment facility is equipped with a melting furnace (waste incinerator). In the melting furnace, the waste is burned by high-concentration oxygen gas and decomposed to a low molecular level. Finally, a substrate gas g (synthetic gas) containing CO, H ₂ , CO _{2 and the} like is generated.
In addition, the required component of the substrate gas g can be appropriately selected according to the type of the gas-assimilating microorganism and the target substance. The substrate gas g may contain only one of CO and H ₂ .

The culture apparatus 1 includes a culture tank 10. The culture tank 10 has a loop reactor structure including a main tank part 11 and a reflux part 12. The main tank 11 has a cylindrical shape extending vertically (up and down). A culture solution 90 is accommodated in the main tank portion 11. Most of the culture solution 90 is water (H ₂ O), in which nutrients such as vitamins and phosphoric acid are dissolved. Gas-utilizing microorganisms are cultured in the culture solution 90. Furthermore, the culture solution 90 contains a fermentation product such as ethanol.

  The reflux part 12 has a tubular shape extending vertically in parallel with the main tank part 11. An upper end portion of the reflux portion 12 is connected to a side portion near the upper end of the main tank portion 11 to an intermediate portion. A lower end portion of the reflux portion 12 is connected to a bottom portion of the main tank portion 11. A circulation pump 13 is provided in the reflux unit 12.

A substrate gas supply nozzle 14 (substrate gas supply unit) is provided at the bottom of the main tank unit 11. The substrate gas supply nozzle 14 is constituted by, for example, an air diffuser. A substrate gas supply line 15 from the waste treatment facility is connected to the substrate gas supply nozzle 14.
An exhaust gas line 16 extends from the upper end of the main tank portion 11. Although not shown, the exhaust gas line 16 is provided with a rear gas processing unit such as a desulfurization apparatus.

  The culture liquid 90 is likely to form a foam 92 due to substrate gas supply, fermentation action, or the like. The foam 92 is composed of a large number of bubbles and floats as one group on the liquid surface of the culture solution 90 in the main tank 11.

  The culture tank 10 is provided with ultrasonic irradiation means 30 as a defoaming means for the foam 92. The ultrasonic irradiation means 30 includes a plurality of ultrasonic transducers 31 and a transducer holding member 32. A suspension pillar 33 is suspended from the top plate of the main tank portion 11 into the main tank portion 11. The vibrator holding member 32 is supported on the lower end portion of the suspension column 33. The vibrator holding member 32 has a disk shape, and its central portion is connected to the suspension pillar 33. The vibrator holding member 32 is disposed above the liquid level 91 of the culture solution 90. As shown in FIG. 2, the ultrasonic transducer 31 is formed with a plurality of vent holes 32 a (ventilation portions).

  As shown in FIG. 1, the space above the liquid level 91 in the main tank portion 11 is partitioned vertically by the vibrator holding member 32. The space portion above the vibrator holding member 32 and the space portion below the vibrator holding member 32 are communicated with each other through the vent 32a.

The ultrasonic vibrator 31 is held by the vibrator holding member 32. The ultrasonic transducer 31 has, for example, a vertical bar shape. Both end portions of the ultrasonic transducer 31 protrude above and below the transducer holding member 32. The lower end portion of the ultrasonic transducer 31 is located away from the liquid level 91.
As shown in FIG. 2, a plurality of ultrasonic transducers 31 are arranged in a distributed manner in the plane of the transducer holding member 32.

As shown in FIG. 1, a transducer drive source 34 is connected to the ultrasonic transducer 31. As shown in FIG. 3, an ultrasonic wave 39 is radiated from the ultrasonic vibrator 31 by the energy supplied from the vibrator driving source 34. For example, the ultrasonic wave 39 is radiated horizontally from the ultrasonic vibrator 31 in the direction of the surrounding 360 °. Preferably, the ultrasonic wave 39 is radiated from both the lower part and the upper part of the ultrasonic vibrator 31 than the vibrator holding member 32, and more preferably from the almost full length region of the ultrasonic vibrator 31. Is done.
Note that the ultrasonic wave 39 may be emitted from the ultrasonic transducer 31 in a local direction.
It is preferable that the ultrasonic wave 39 is not emitted downward from the ultrasonic vibrator 31, that is, to the culture solution 90.
The frequency, amplitude, and the like of the ultrasonic transducer 31 can be appropriately set according to the bubble diameter, the bubble component, and the like of the foam 92.

A culture method using the culture apparatus 1 will be described.
<Culture process>
The gas-utilizing microorganism is cultured in the culture solution 90 in the culture tank 10.
<Circulation process>
The culture solution 90 is circulated between the main tank unit 11 and the reflux unit 12 by the circulation pump 13.
<Gas supply process>
The substrate gas g from the waste treatment facility is supplied from the substrate gas supply nozzle 14 to the culture solution 90 in the main tank 11.
<Fermentation process>
The gas assimilating microorganisms fermentatively produce valuable organic substances such as ethanol from the substrate gas g.
<Gas discharge process>
A gas containing a substrate gas component, a fermentation byproduct gas component and the like is released from the liquid surface 91 of the main tank portion 11. This gas enters the space above the vibrator holding member 32 through the vent 32a. Further, it can be sent from the exhaust gas line 16 to the subsequent gas processing section.
<Purification process>
A part of the culture solution 90 is taken out from the culture tank 10, sent to a distiller (not shown), and distilled. Thereby, valuable organic substances such as ethanol can be extracted.

<Foam formation process>
In the culture solution 90 of the main tank part 11, the foam 92 is easily formed on the liquid surface 91 by substrate gas supply, fermentation reaction, or the like.
When the foam 92 grows excessively, the lower portion of the ultrasonic transducer 31 from the transducer holding member 32 is eventually buried in the upper portion 92a of the foam 92 as shown in FIG.
<Ultrasonic irradiation process>
When the foam 92 becomes excessive, the ultrasonic vibrator 31 is ultrasonically vibrated by the vibrator driving source 34 and the ultrasonic wave 39 is emitted from the ultrasonic vibrator 31. This ultrasonic wave 39 is irradiated to the foam upper part 92a. As indicated by a two-dot chain line in FIG. 3, the foam upper portion 92 a (excess portion) can be extinguished (defoamed) by the action of the ultrasonic wave 39. As a result, the amount of foam 92 can be controlled.
As shown by a three-dot chain line in FIG. 3, the foam 92 may propagate upward from the vibrator holding member 32 through the vent 32a. The foam upper portion 92 a ′ can be defoamed by the ultrasonic wave from the ultrasonic transducer 31 above the transducer holding member 32.
As a result, it is possible to avoid the foam 92 from entering the rear gas processing section or the like via the exhaust gas line 16 and causing a failure or causing contamination.
By disposing the ultrasonic transducer 31 upward from the liquid surface 91 of the culture liquid 90, it is possible to avoid the ultrasonic wave being irradiated into the culture liquid 90 and the foaming being accelerated.

According to the defoaming method of this embodiment, it is not necessary to use an antifoaming agent, and fermentation reaction efficiency can be ensured.
The ultrasonic generation means 30 can simplify the structure as compared with the one that takes out a part of the culture solution in the culture tank and sprays it from the upper end of the culture tank, or the one that uses foam cutting blades.
Furthermore, according to the culture apparatus 1, as an incidental effect, the ultrasonic irradiation means 30 can be used for cleaning, degassing, etc. in the culture tank 10, and the culture preparation process can be shortened.

Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are given to the drawings for the same configurations as those already described, and the description thereof is omitted.
Second Embodiment
FIG. 4 shows a second embodiment of the present invention. In the ultrasonic irradiation means 30B of the culture apparatus 1B of the second embodiment, the suspension pillar 33 (FIG. 1) is omitted. Instead of this, a plurality of floats 35 (lifting means) are provided. These floats 35 are floated on the liquid surface 91 and support the vibrator holding member 32 and the ultrasonic vibrator 31 from below through the connecting pillar 36. The connecting column 36 is suspended from the vibrator holding member 32. A lower end portion of the connecting column 36 extends downward from the ultrasonic transducer 31. The float 35 is provided at the lower end of the connecting column 36. The float 35 is located below the ultrasonic transducer 31.
The vibrator holding member 32 and the ultrasonic vibrator 31 can be moved up and down in the main tank portion 11.

  When the height of the liquid level 91 changes, the float 35 is moved up and down following this. As a result, the vibrator holding member 32 and thus the ultrasonic vibrator 31 can be raised and lowered according to the height of the liquid level 91. Therefore, the distance from the liquid level 91 to the ultrasonic transducer 31 can be made substantially constant regardless of the height fluctuation of the liquid level 91. As a result, as shown by the two-dot chain line in FIG. The thickness of the upper foam 92 can be maintained substantially constant regardless of the height of the liquid surface 91.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the ultrasonic transducer 31 is not limited to directly irradiating the foam 92 with the ultrasonic transducer 31 in the state where the ultrasonic transducer 31 is embedded in the foam 92. The ultrasonic wave 39 may be irradiated. That is, the ultrasonic wave 39 may be irradiated vertically downward from the ultrasonic transducer 31 to the liquid surface 91 or vertically upward to the top of the culture tank 10. The ultrasonic wave 39 may be emitted from the ultrasonic transducer 31 in all directions including horizontal and vertical directions.
The culture tank 10 is not limited to the loop reactor type, and may be a stirring type, an air lift type, a bubble column type, a filling type, an open pond type, a photobio type, or the like.
A plurality of reaction vessels may be provided.
The substrate gas production facility is not limited to a waste treatment facility, and may be an iron mill or a coal plant.
As a modification of the second embodiment, the vibrator holding member 32 and thus the ultrasonic vibrator 31 may be moved up and down by a lift slider (lifting means). The height of the liquid level 91 may be detected by a sensor, and the height of the vibrator holding member 32 and thus the ultrasonic vibrator 31 may be adjusted by a lift slider based on the detection result.
The valuable organic material is not limited to ethanol, but may be butanol or acetic acid.

  The present invention can be applied to an ethanol generation system that synthesizes ethanol from carbon monoxide in syngas generated by, for example, incineration of industrial waste.

g Substrate gas 1, 1B Incubator 10 Culture tank 11 Main tank part 12 Reflux part 13 Circulation pump 14 Substrate gas supply nozzle (Substrate gas supply part)
15 Substrate gas supply line 16 Exhaust gas line 30, 30B Ultrasonic irradiation means 31 Ultrasonic vibrator 32 Vibrator holding member 32a Vent (vent)
33 Suspended pillar 34 Vibrator drive source 35 Float (lifting means)
36 connecting column 90 culture liquid 91 liquid surface 92 foam 92a, 92a 'foam upper part

Claims (5)

A culture apparatus for culturing microorganisms in a culture solution,
A culture vessel containing the culture solution;
A substrate gas supply unit for supplying a substrate gas to the culture solution in the culture tank;
Ultrasonic irradiation means for irradiating the foam on the liquid surface of the culture solution with ultrasonic waves;
A culture apparatus comprising:   The culture apparatus according to claim 1, wherein the ultrasonic wave irradiation means includes an ultrasonic vibrator and a vibrator holding member that holds the ultrasonic vibrator apart from the liquid surface. .   The culture apparatus according to claim 2, further comprising elevating means for elevating and lowering the vibrator holding member according to the height of the liquid level. A culture process for culturing microorganisms in a culture solution in a culture tank;
A gas supply step of supplying a substrate gas to the culture solution;
An ultrasonic irradiation step of irradiating the foam on the liquid surface of the culture solution with ultrasonic waves;
A microorganism culturing method comprising: The substrate gas is a synthesis gas;
5. The microorganism culturing method according to claim 4, wherein the microorganism is an anaerobic gas assimilating microorganism that ferments and produces an organic substance from the synthesis gas.

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