JPH04221751A - Sensor for measuring biomass - Google Patents

Abstract

PURPOSE:To provide a sensor to perform on-line measurement of biomass by means of a solution having holdup. CONSTITUTION:In an electrode for measuring biomass having an electrode surface forming double structure where an inner electrode is covered with an outer electrode, a sensor for measuring biomass is provided with an electrode for measuring electrostatic capacity having a solution entrance located in a level higher than that of the inner electrode and a mechanism to intermittently discharge solution in the electrode to the outside of the electrode.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for online measurement of the capacitance of a liquid in general. Specifically, the present invention relates to a sensor that enables on-line measurement of biomass even when hold-up of a culture solution occurs due to aeration and stirring during culturing of microorganisms in a culture apparatus or the like. Therefore, the present invention
Including bio-industry, medical, food industry, sewage and
It plays a very important role in fields such as wastewater treatment.

0002

[Prior Art] Bioreactors and culture devices that produce useful substances using various microorganisms, animal cells, plant cells, etc.
The biomass inside the biomass changes from moment to moment, and it is very important to measure the biomass in order to control the bioreactor and culture device and to know the internal state.

[0003] In bioreactors and the like, when measuring the concentration of microorganisms in a suspended solution for various microorganisms with small cell sizes, the microorganism concentration is measured based on various optical properties of the microorganisms in the culture medium. It is possible to some extent. However, in various measurement methods using light, non-living SS (
There are problems such as misidentification of biomass due to the presence of suspended solids (suspended solids), increased errors due to the color and bubbles of the measurement solution, and the complexity of the measurement mechanism. In such cases, cells must currently be collected from the reactor or culture device using a sampling method, which poses a high risk of bacterial contamination of the culture system, and the expensive culture medium must be discarded due to bacterial contamination. Therefore, there was a desire to improve culture efficiency. Furthermore, it is impossible to reflect information such as biomass in the online control of reactors and culture equipment, so there has been an emphasis on developing methods that can measure biomass online without sampling organisms. .

[0004]Recently, the present inventors installed electrodes in the culture apparatus to measure electrical conductivity (conductivity) and/or capacitance (
A method for measuring biomass online and in real time was invented by measuring the dielectric constant (patent application 1986-
No. 224018).

[0005] This measurement method enables online measurement of biomass in a reactor by measuring the capacitance in a solution containing biological cells using a pair of electrodes. It is based on the fact that there is a linear relationship between the capacitance value in the electric field and the cell concentration in the solution. After determining this relationship (calibration curve) in advance and calculating the cell concentration from the capacitance value, the amount of biomass in the reactor can be determined by multiplying by the amount of solution containing cells. In this case, it is assumed that the amount of the entire solution is actually constant. However, when stirring microorganisms and the like at high speed while aerating the solution, the apparent amount of solution increases because gas is contained in the solution. Generally, this phenomenon is caused by hold-up
up). Correspondingly, the cell concentration in the measurement electric field naturally decreases. Therefore, if the biomass in the reactor is estimated only from the measured capacitance value, the estimate will be lower than the actual value. In such a case, in order to calculate the amount of biomass in the reactor, it is necessary to separately determine the amount of the solution containing the gas, or to determine the capacitance value of the solution returned to the state without the gas. The present invention relates to a sensor that makes it possible to measure capacitance values online while realizing a state in which gas is excluded from a solution, and such a sensor has not been previously known and is novel. .

[0006]

[Problems to be Solved by the Invention] When measuring the biomass in a reactor by measuring capacitance, the biomass has been measured by assuming that the amount of solution containing cells is practically constant. However, when hold-up occurs, accurate measurement of biomass cannot be performed. The present invention relates to a sensor for on-line measurement of biomass in solutions with hold-up.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks.

Conventionally, when calculating the airborne bacterial cell concentration by measuring capacitance, it is preferable to use a double shell electrode as shown in FIG. The reason for this is that since the measuring range is limited, it is less likely to be affected by noise from the outside world and stable measurements can be made. In FIG. 1, 11 refers to a double cylindrical electrode, 12 refers to an inner electrode, and 13 refers to an outer electrode. 14 is a support made of an insulator. The outer electrode 13 had a cylindrical shape with an open bottom surface, and four holes were formed in each of the side surface and the top surface.

However, with the above-mentioned biomass measurement electrode, since the cell concentration in a limited electric field is measured, when the cell concentration in the electric field decreases due to hold-up, the cell amount in the reactor decreases. will be shown. In order to avoid this, there may be a method of simultaneously determining the volume of the solution in a held-up state, or a method of measuring the capacitance in a state where gas in the measurement electric field is excluded.

[0010] The inventors of the present invention, after considering various aspects, came to the conclusion that the latter method is preferable for industrial measurement, and as a result of intensive research, they found that it is possible to realize the latter state. They succeeded in measuring the cell concentration in the solution where hold-up occurred online, and completed the present invention.

That is, the biomass measuring sensor according to the present invention has a biomass measuring electrode having a double structure on the electrode surface so that the outer electrode covers the inner electrode, and the solution inlet and outlet is above the inner electrode. The basic technical idea is to provide a capacitance measuring electrode and a mechanism for discharging the solution inside the electrode to the outside of the electrode.

The present invention will be explained in detail below with reference to FIGS. 2 and 3, which are one embodiment of a sensor according to the present invention. FIG. 2 is an external view of one embodiment of the sensor shape according to the present invention, and FIG. 3 is a sectional view thereof. The sensor according to the present invention is basically a double shell type in which an outer electrode 1 wraps an inner electrode 2. The structure is such that the solution can enter and exit the electric field formed by the pair of electrodes from the upper surface 3 of the electrodes. When a gas-containing solution enters the electrode 4, it becomes stationary and is not affected by the flow of the solution outside the electrode, so the gas in the solution escapes from the solution, and the capacitance of the solution without gas is measured. can. After the measurement, air that has passed through a sterilization filter is sent through a gas outlet 5 provided within the sensor, and the solution in the electric field is sent out to the outside. After discharging the solution, when the air supply is stopped, a new solution from outside enters through the entrance and exit port at the top of the sensor. By repeating this operation, it becomes possible to actually measure the cell concentration in a solution with holdup online and in real time. Usually, a fermenter is always equipped with an aeration device, so there is no need to introduce a new aeration device, and it is only necessary to provide a line branching from the aeration line. To send gas into the electrode intermittently, it is sufficient to simply install an on-off valve in this branched line, and this valve may be opened and closed automatically by a timer, or by a signal from a measuring instrument. good. In this sensor, a valve that opens when gas is discharged may be attached to the gas discharge port. Further, a valve that opens when the solution in the sensor is discharged may be attached to the outer electrode.

[0013] The above embodiment is an electrode for biomass measurement having a double structure on the electrode surface so that the outer electrode covers the inner electrode, and is characterized in that the solution inlet/outlet is provided above the inner electrode. A biomass measurement sensor consisting of an electrode for measuring capacitance, a mechanism for blowing gas into the electrode to discharge the solution inside the electrode to the outside of the electrode, and a device for intermittently inserting gas into the electrode. However, as a mechanism for discharging the solution inside the electrode to the outside of the electrode, in addition to the gas blowing mechanism described above (the gas blowing outlet 5 is not limited to the location shown in the figure, but can be placed at an appropriate location inside the electrode). Any means for moving and discharging the liquid can be used as appropriate, such as by providing a piston within the electrode (which may be provided at a certain location), by providing a piston within the electrode, or by compressing the electrode from the outside.

[0014] In addition to using air as described above, oxygen may also be used as the gas to be introduced, and in some cases, various gases such as carbon dioxide, nitrogen gas, and other inert gases may be used alone or It is also possible to use them together. Next, the present invention will be explained in more detail with reference to Examples, but these are merely illustrative and do not limit or limit the present invention in any way.

[0015]

[Embodiment 1] FIG. 4 shows an example of a measurement system using the sensor (electrode) according to the present invention. In this system, the sensor 41 according to the present invention shown in FIGS. 2 and 3 is attached to the fermenter 42. do. The sensor 41 is connected to a capacitance measuring device 43. Air supplied from the compressor 44 is sent to the fermenter through a sterilization filter 45. The sterilized air can be supplied into the sensor after passing through the solenoid valve 46. By controlling the solenoid valve with a timer 47, air can be intermittently supplied into the sensor. The following measurements were performed using this system.

A fermenter (inner volume: 10 liters) was filled with 5 liters of medium, various amounts of baker's yeast were added, and the electric capacity was measured while stirring at an aeration rate of 0.4 vvm and 200 rpm. Note that no hold-up was observed in this state. Next, a hold-up state was generated in the solution by stirring at an aeration rate of 2 vvm and a stirring rate of 1000 rpm, and then capacitance was measured. After the measurement, 10 ml of the solution was sampled, the cell concentration was calculated by the dry weight method, and the relationship with the capacitance value was determined. Note that air was supplied into the sensor for 3 seconds at 30 second intervals. Capacitance measurements were taken immediately before air supply. The measurement results are shown in FIG. The vertical axis is the value obtained by subtracting the value measured in a solution containing no bacterial cells after determining the capacitance value at 1 MHz. The horizontal axis is the bacterial cell concentration determined by the dry weight method. The solid line (○) indicates mild culture conditions (aeration rate 0.4v).
vm, stirring speed 200 rpm), and the broken line (●) is the measurement result at an aeration speed of 2 vvm, stirring speed 100 Orpm.
These are the measurement results. There is practically no difference between the two, and it has become clear that biomass can be measured even when hold-up occurs in the solution in the fermenter.

[0017]

[Effects of the Invention] By using the sensor of the present invention, it is possible to conduct online measurement of the biomass in a solution in a hold-up state, which was difficult to measure in the past, which is a new and outstanding effect that was not possible before. It was raised. Therefore, according to the present invention, the concentration of microorganisms, animal cells, and plant cells can be measured non-destructively, and the concentration of microorganisms, animal cells, and plant cells can be measured non-destructively. The present invention can be widely used in various fields.

[Brief explanation of the drawing]

FIG. 1 is an example of a conventional double shell electrode.

FIG. 2 is an external view of an electrode according to the present invention.

FIG. 3 is a cross-sectional view of an electrode according to the invention.

FIG. 4 is an example of a measurement system using the electrodes according to the present invention shown in FIGS. 2 and 3.

5 is a graph showing the relationship between electric capacity and yeast concentration (determined by dry weight method) using the measurement system shown in FIG. 4. FIG.

[Explanation of symbols]

1 Outer electrode 2 Inner electrode 3 Top surface of electrode 4 Electrode 5 Gas outlet

Claims (3)

[Claims] Claim 1: A biomass measuring electrode having a double structure on the electrode surface so that the outer electrode covers the inner electrode, the capacitance measuring electrode having a solution inlet and outlet above the inner electrode. A sensor for measuring biomass, comprising: a mechanism for discharging a solution inside the electrode to the outside of the electrode; 2. The biomass measuring sensor according to claim 1, further comprising a mechanism for intermittently discharging the solution inside the electrode to the outside of the electrode. 3. A mechanism for intermittently discharging the solution within the electrode to the outside of the electrode comprises a mechanism for blowing gas into the electrode for discharging the solution within the electrode to the outside of the electrode, and a mechanism for intermittently discharging gas within the electrode. 3. The biomass measuring sensor according to claim 2, further comprising a device for inserting gas.