CN1156691C - A sensor for on-line detection of methanol concentration in solution - Google Patents

Abstract

The invention discloses a sensor for online detection of methanol concentration in solution. The sensor includes: a tubular shell with a carrier gas tube in the middle, a semi-permeable membrane, a gas-sensitive electronic element, and a sieve plate. Insert the end of the sensor with the semi-permeable membrane into the fermenter, and the methanol in the liquid phase will pass through the semi-permeable membrane. Diffusion to the diffusion chamber, the carrier gas enters the diffusion chamber through the sieve holes on the sieve plate through the carrier gas tube, and mixes with the methanol that enters the diffusion chamber through the semi-permeable membrane, and the mixture of carrier gas and methanol is introduced into the gas-sensitive electronic component through the air guide tube, that is The concentration of methanol can be measured. The sensor of the present invention has a response time of less than 120 seconds, can meet the requirements of on-line detection and control, is not affected by fermentation conditions, and has a wide range of applications. It can be used in the fermentation of Trichosaccharomyces and Pichia pastoris, or for online detection and control of volatile organic gases such as methanol and ethanol in other solutions.

Description

A sensor for on-line detection of methanol concentration in solution

technical field

The invention relates to a sensor, in particular to a sensor for detecting methanol used in a fermentation process.

Background technique

In the fermentation of yeasts that use methanol as a carbon source, such as Hansenula, Torulopsis, Candida and Pichia, excessive methanol will inhibit cell growth and Therefore, it is necessary to control the concentration of methanol in the fermentation broth within an appropriate range by continuously feeding methanol. In order to avoid excessive methanol feed, it is necessary to detect the concentration of methanol in the fermentation broth online.

There are mainly two methods for the on-line detection of methanol concentration in the fermentation broth reported in the literature at present:

(1) Silicone tube measurement method, the principle is that methanol in the fermentation broth permeates through the wall of the silicone tube from the outside of the silicone tube, enters the silicone tube, is taken away by the carrier gas in the tube, enters the gas-sensitive electronic component, and generates an electrical signal (GuamaM.M. ., Lesnicki G.L., Tam B.M., et al. Biotechnol. Bioeng., 1997, 56: 279-286).

(2) Tail gas measurement method, the methanol-containing tail gas released from the fermentation tank enters the gas-sensitive electronic component to generate an electrical signal. (Katakura Y., Zhang W., Zhuang G., et al. J. Ferment. Bioeng., 1998, 86: 482-487).

However, the above methods have the following disadvantages:

The first method is limited by the diffusion rate of the silica gel tube wall, has poor real-time performance and serious lag (general response time exceeds ten minutes), cannot reflect the instantaneous methanol concentration change in the fermenter, and is difficult to adapt to the automatic control of methanol concentration;

The second method is susceptible to severe interference such as oxygen concentration, gas volume fluctuations, gas components, moisture, etc., and the signal stability is poor, and it is easy to cause sensor poisoning and failure.

Therefore above-mentioned method is unfavorable for industrialized application promotion.

Contents of the invention

The technical problem to be solved in the present invention is to disclose a sensor for on-line detection of methanol concentration in fermentation broth, so as to overcome the defects of slow response time, low sensitivity, weak anti-environmental interference ability and inconvenient industrial application in the prior art.

Technical concept of the present invention:

(1) In order to detect the instantaneous methanol concentration change in the fermenter online, it is necessary to increase the diffusion rate of methanol and shorten the response time of the sensor. Because methanol is easy to pass through materials such as polytetrafluoroethylene, silica gel, polyethylene by molecular diffusion, the present invention selects these materials as semipermeable membrane. Methanol in the fermentation broth can diffuse into the gas phase through the semipermeable membrane. The diffusion rate of methanol in a semipermeable membrane is mainly determined by the methanol concentration in the liquid phase.

(2) On the gas phase side, a selective gas-sensing electronic component is used to detect the concentration of methanol in the gas phase. The resistance of the electronic component changes with the concentration of methanol in the gas phase, and the concentration of methanol in the liquid phase can be calculated according to the diffusion model or by a cold model. A standard curve was made in the experiment, and the concentration of methanol in the fermentation broth was determined by comparing with the standard curve.

(3) The structural design of the sensor meets the needs of industrial use, can be sterilized at high temperature, and can be conveniently installed on the general interface of the fermenter.

Technical scheme of the present invention:

Sensors of the present invention include:

A tubular shell with a carrier gas tube in the middle;

a semi-permeable membrane arranged at the end of the carrier gas tube;

A sieve plate arranged in the carrier gas pipe and adjacent to the semi-permeable membrane, the cavity between the semi-permeable membrane and the sieve plate is a diffusion chamber;

An air guide tube arranged in the carrier gas tube, one end of which passes through the sieve plate and communicates with the diffusion chamber;

A gas-sensitive electronic component connected to the airway.

The above sensors work like this:

Insert the end of the sensor with a semi-permeable membrane into the fermenter, and the methanol in the liquid phase diffuses through the semi-permeable membrane to the diffusion chamber;

The carrier gas enters the diffusion chamber through the carrier gas tube through the sieve hole on the sieve plate, and mixes with the methanol that enters the diffusion chamber through the semi-permeable membrane. The purpose of setting the sieve plate is to improve the gas flow in the diffusion chamber, reduce back mixing, and prevent the diffusion chamber The gas inside is back-mixed with the gas in the carrier gas channel;

The mixture of carrier gas and methanol is introduced into the gas-sensing electronic components through the air guide tube. When the flow rate of carrier gas is constant, since the diffusion rate of methanol in the semipermeable membrane is mainly determined by the concentration of liquid phase methanol, the concentration of methanol in the diffusion chamber is closely related to that of liquid phase methanol. The concentration is directly proportional to the relationship. Therefore, the methanol concentration in the carrier gas indicated by the gas-sensing electronic element can accurately reflect the concentration of liquid-phase methanol, so that the concentration of methanol can be measured.

The advantage of sensor of the present invention is very obvious:

1. The response time of this sensor is less than 120 seconds, which is far superior to other measurement methods. It can meet the requirements of online detection and control.

2. The sensor is not affected by the ventilation rate, stirring speed and dissolved oxygen content of the fermenter.

3. The sensor has a wide range of applications, and can be used in the fermentation of yeasts such as Hansenula, Torulopsis, Candida and Pichia that use methanol as a carbon source, or in other solutions where methanol, ethanol, etc. can volatilize On-line detection and control of volatile organic gases.

Description of drawings

Fig. 1 is a schematic structural diagram of the sensor of the present invention.

Figure 2 is a comparison of the methanol concentration measured by the sensor on-line during the fermentation process and the methanol concentration measured off-line by gas chromatography in the sample after sampling.

Detailed ways

As can be seen from Fig. 1, the sensor of the present invention comprises:

A tubular housing 1 with a carrier gas tube 5 in the middle;

A semi-permeable membrane 2 arranged at the end of the carrier gas tube 5;

A sieve plate 3 arranged in the carrier gas pipe 5 and adjacent to the semi-permeable membrane 2, the cavity between the semi-permeable membrane 2 and the sieve plate 3 is a diffusion chamber 7;

An air guide tube 4 arranged in the carrier gas tube 5, one end of which passes through the sieve plate 3 and communicates with the diffusion chamber 7;

A gas sensitive electronic component 6 communicated with the air duct 4 .

According to the present invention, the surface area of said semipermeable membrane 2 is 3-500 square millimeters, and the thickness is: 0<thickness<1 millimeter. The material is methanol-permeable materials such as polytetrafluoroethylene, silica gel, and polyethylene. The volume of the diffusion chamber 7 is 1.5-2500 cubic millimeters. The distance between the semi-permeable membrane 2 and the sieve plate 3 is: 0 < distance < 30 mm, The air duct 4 has a diameter range of 0.1-5 mm, the opening diameter of the sieve plate 3 is 0.1-2 mm, and the opening rate is 0.5%-50%. The gas sensitive electronic component 6 is an organic gas sensitive resistor, which can be used The model produced by Japan Figaro Company is TGS822 resistor or similar products from other companies.

Example 1

During the fermentation process of recombinant Pichia pastoris, the sensor of the invention is used to detect the concentration of methanol in the fermentation liquid on-line. in:

The material of the semi-permeable membrane is polytetrafluoroethylene, the thickness is 0.5 mm, the surface area is 45 square mm, the diameter of the air duct is 1.1 mm, the diameter of the sieve plate is 8 mm, the aperture diameter is 0.8 mm, and the opening rate is 10%. The gas sensor is a resistor of the type TGS822 produced by Figaro Corporation of Japan. Firstly, water is filled in the fermenter, and methanol of different concentrations (0.1-1%, v/v) is added to make a sensor response standard curve, and then culture medium and the sensor are heat-sterilized in the fermenter and then fermented. The concentration of methanol in the fermentation broth was determined by comparing the response value of the sensor with the standard curve. From the 25th hour, methanol was added to the fermenter. Figure 2 is a comparison between the methanol concentration measured by the sensor on-line and the methanol concentration measured by gas chromatography off-line in the sampled sample during the fermentation process. As can be seen from the figure, the difference between the two Basically match. The deviation can be eliminated by correction. Therefore, the sensor can detect the concentration of methanol in the fermentation process of Pichia pastoris better in real time.

Claims (8)

1. A sensor for on-line detection of methanol concentration in solution, characterized in that the sensor comprises: A tubular casing (1) with a carrier gas pipe (5) in the middle; A semi-permeable membrane (2) arranged at the end of the carrier gas tube (5); A sieve plate (3) arranged in the carrier gas pipe (5) and adjacent to the semipermeable membrane (2), the cavity between the semipermeable membrane (2) and the sieve plate (3) is a diffusion chamber (7); An air guide tube (4) arranged in the carrier gas tube (5), one end of which passes through the sieve plate (3) and communicates with the diffusion chamber (7); A gas-sensitive electronic component (6) communicated with the airway tube (4); The material of the semipermeable membrane (2) is polytetrafluoroethylene, silica gel or polyethylene. 2. The sensor according to claim 1, characterized in that the surface area of the semipermeable membrane (2) is 3-500 square millimeters, and the thickness is: 0<thickness<1 mm. 3. The sensor according to claim 1, characterized in that the diffusion chamber (7) has a volume of 1.5-2500 cubic millimeters. 4. The sensor according to claim 1, characterized in that the distance between the semi-permeable membrane (2) and the sieve plate (3) is: 0<spacing<30 mm. 5. The sensor according to claim 1, characterized in that the diameter of the airway tube (4) is 0.1-5 mm. 6. The sensor according to claim 1, characterized in that the sieve plate (3) has an aperture diameter of 0.1-2 mm and an aperture ratio of 0.5%-50%. 7. The sensor according to claim 3 or 4, characterized in that the surface area of the semipermeable membrane (2) is 3-500 square millimeters, and the thickness is: 0<thickness<1 mm. 8. The sensor as claimed in claim 1, said gas-sensitive electronic element (6) is a kind of organic gas-sensitive resistor, adopting the model produced by Japan Figaro Company as TGS822 resistor.

Images