JPH05293000A - Fermentation in highly viscous system - Google Patents

Abstract

PURPOSE:To provide a method for controlling the aeration and agitation conditions in a biopolymer fermentation process containing fermentation liquid having gradually increasing viscosity, to improve the productivity of biopolymer and to supply just enough power for aeration and agitation in contrast with conventional process performing the agitation and aeration at constant rates without using an efficient controlling method. CONSTITUTION:The relationship between the viscosity of a fermentation liquid and the fermentation time in the biopolymer fermentation is shown in the figure. There is little variation of viscosity during the period I. In the period II, the aeration and agitation rates are increased corresponding to the abrupt increase of the viscosity. The aeration and agitation rates are maintained at constant levels in the period III in which the variation rate of viscosity is constant. The rate of viscosity variation decreases in the period IV and the aeration and agitation are unnecessary in the period. The aeration and agitation are controlled based on a continuously detected viscosity data according to a program including the above operation conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling biopolymer fermentation in which the viscosity of a fermentation liquor becomes high. More specifically, the concentration of the biopolymer as a product in the fermentation liquor is continuously detected to perform fermentation production. The present invention relates to a highly viscous fermentation method with improved properties.

[0002]

2. Description of the Related Art In the fermentation production of biopolymers such as polysaccharides, proteins, nucleic acids and lipids produced by microorganisms, the viscosity of the fermented solution often becomes very high with the progress of fermentation. In highly viscous fermentation such as fermentative production of these biopolymers, fluctuations in the viscosity of the fermentation liquor result in insufficient agitation and mixing to keep the growth environment of aerobic microorganisms uniform, and the oxygen supply rate decreases. , Fermentation productivity can be kept low. In order to eliminate such inconvenience, conventionally, in fermentative production of biopolymers, fermentation is performed while supplying a larger amount of oxygen than the supply amount for general aerobic microorganisms,
Fermentation is usually carried out with a constant aeration rate and stirring speed.

[0003]

Oxygen is required for the growth of aerobic microorganisms, but whether the production of biopolymers by the microorganisms does not necessarily require the same level of oxygen as the growth of the microorganisms. I doubt. However,
As described above, in the fermentation production of biopolymers, the amount of aeration and the stirring strength are often constant, and it is considered that wasteful energy is input.

The concentration of the biopolymer, which is a product, in the fermentation liquor is difficult to quantify in real time, and the fermentation conditions cannot be controlled while monitoring the production rate of the biopolymer, thus increasing the productivity. The current situation is that no measures have been taken for this. Therefore, the present invention provides a high-viscosity fermentation method with controlled aeration and stirring conditions capable of increasing productivity in order to improve the low productivity in high-viscosity fermentation such as biopolymer fermentation. With the goal.

[0005]

Means for Solving the Problems To achieve the above object, the present invention continuously detects a change in the viscosity of a fermented liquid in a highly viscous fermentation method in which the viscosity of the fermented liquid changes with time, and determines the amount of change. Is calculated over time, and the aeration amount and stirring strength are controlled based on the increase / decrease in the amount of change, which is a highly viscous fermentation method.

In the present invention, the reason for paying attention to the viscosity of the fermentation liquor is that in the biopolymer fermentation, the viscosity of the fermentation liquor increases with the progress of fermentation, and the concentration of the biopolymer as the product and the viscosity of the fermentation liquor are different. This is because there is a correlation. That is, the production rate of the biopolymer can be indirectly known by detecting the change in the viscosity of the fermentation liquid. Therefore, by knowing this viscosity change, and controlling the aeration rate to aerate the fermentation solution and the stirring strength to stir the fermentation solution so as to keep the production rate of the biopolymer, which is related to this viscosity change, high The present invention was thought to be able to be greatly improved and the present invention was achieved.

The invention is explained in more detail below on the basis of the drawings. FIG. 1 shows a configuration example of a fermentation control device. Reference numeral 1 denotes a fermenter, which is provided with a stirrer 4 for making the growth environment of microorganisms uniform. The fermenter 1 is covered with a jacket 3 so that it can be kept warm at a constant temperature.
An aeration device 5 for supplying air into the fermentation tank is arranged in the lower portion of the fermentation tank 1, and air whose flow rate is adjusted by a flow meter 8 is supplied. The value of the flow meter 8 is connected so as to be input to the arithmetic unit 13, an appropriate amount of air to be supplied by the arithmetic unit 13 is calculated, and the opening / closing of the solenoid valve 9 is instructed based on the calculated value. It is controlled to have an appropriate amount of air.

The circulation pump 10 arranged in the circulation path is
A part of the fermented liquid 2 in the fermenter 1 is taken out, and the fermenter 1 is again used.
Works to return to. A viscometer 11 for continuously measuring the viscosity of the fermentation liquid 2 is arranged in the circulation path, and a process viscometer is used for the viscometer 11.
Further, the viscometer 11 is connected to an AD converter 12 for converting the measured viscosity from an analog value to a digital value, and the digital value converted by the AD converter 12 is calculated by the arithmetic unit 13. Connected to be input to.
The appropriate aeration rate and stirring strength calculated by the computing device 13 are
It is connected so as to be transmitted to the means 7 for changing the aeration amount and the stirring strength. The means 7 for changing the aeration amount and the agitation strength operates the motor 6 at an appropriate rotation, and rotates the agitator 4 so that the agitation and the aeration amount are appropriate.

The function (action) of the present invention will be described below. FIG. 2 is a graph showing a general change pattern of the relationship between the fermentation solution viscosity and the fermentation time in biopolymer fermentation. As shown in FIG. 2, the change in the viscosity of the fermentation liquor is roughly divided into four periods I, II, III and IV. The period I is a period in which there is almost no change in the viscosity of the fermentation broth (indicated by μ), and both the aeration amount (indicated by Q) and the stirring strength (indicated by N) may be small.

Period II is a period in which the amount of change in viscosity (indicated by Δμ) increases with time, and during this period, the viscosity of the fermentation liquor sharply increases, and the oxygen supply amount increases accordingly. Since it is necessary to ferment, the aeration amount Q and the stirring strength N are increased. Period III is a period in which the amount of change in viscosity Δμ is constant, and it is sufficient to give a certain amount of aeration amount Q and stirring strength N. At this time, as described above, oxygen may not be required so much for the production of the biopolymer, so that the aeration amount Q and the stirring strength N are controlled so as to be decreased.

A period IV is a period in which the amount of change in viscosity Δμ decreases, and is an end stage of fermentation in which the aeration amount Q and the stirring strength N are not required. However, the reason why the amount of change in viscosity Δμ decreases may be that the air flow rate Q and the stirring strength N are insufficient.
When the viscosity change amount Δμ decreases, the operation of increasing the aeration amount Q and the stirring strength N first precedes. The control of the highly viscous fermentation of the present invention will be described based on the control example of the flowchart shown in FIG. At the same time as starting the fermentation by setting the aeration amount Q and the stirring strength N to the initial values, a part of the fermentation liquid in the fermentation layer 1 is returned to the fermentation layer 1 again by the circulation pump 10 via the viscometer 11 and circulated. Let The viscometer 11 continuously starts measuring the fermentation liquid viscosity μ. The analog value of the fermentation liquid viscosity μ is converted into a digital value by the AD converter 12, and the converted digital value is input to the arithmetic unit 13. The arithmetic unit 13 calculates the viscosity change amount Δμ per unit time.

When Δμ = 0, nothing is output and the next fermentation liquid viscosity μ is waited for. When Δμ ≠ 0, the previous viscosity change amount Δμ _n-1 and the current viscosity change amount Δμ _n are compared. When Δμ _n = Δμ _n-1 , the air flow rate Q and the stirring strength N
Is reduced by a predetermined amount set in advance, and the process is terminated, and the process returns to the initial state of input of the measured value of the fermentation liquid viscosity μ.

When Δμ _n ≠ Δμ _n−1 , the ventilation amount Q and the stirring strength N are increased by a predetermined amount, and the next Δμ _{n + 1} is calculated.
When Δμ _{n + 1} <Δμ _n , the ventilation amount Q and the stirring strength N are reduced by predetermined amounts set in advance, and the process is ended. Δμ
_{When n + 1} > Δμ _n, the process ends as it is, and the fermentation solution viscosity μ
Return to the initial state of inputting the measured value of.

[0014]

Example 1 Xanthan gum fermentation was selected as an example of biopolymer fermentation in which the fermentation liquor has a high viscosity. The fermentation conditions are as follows. Strains used: Xanthomonas campestris IFO 13551 Medium: Synthetic medium containing glucose as a main component Fermentor: Aeration-stirring type fermenter with a preparation volume of 2 L, with temperature control jacket Fermentation temperature: 30 ° C Stirring speed: 50-500 rpm Aeration rate: 0 Xanthan gum fermentation was carried out under conditions of 0.5 to 1.5 vvm or more according to the flow chart shown in FIG. The control situation of the fermentation is shown in FIG.
In FIG. 4, the horizontal axis represents fermentation time, the vertical axis represents fermentation liquid viscosity μ,
6 is a graph showing the growth rate OD of a microorganism, the aeration amount Q, and the stirring strength N. The OD is an index showing the concentration of microorganisms and is the turbidity of the fermentation broth. As shown in FIG. 4, the ventilation amount Q and the stirring strength N are controlled extremely finely. By controlling in this way, the final fermentation solution viscosity μ is 3000
It reached a little less than cp.

On the other hand, as a comparative example, changes in the fermentation liquid viscosity μ and the growth rate OD of the microorganism with respect to the fermentation time are shown in FIG. 5 when the aeration amount Q and the stirring intensity N are constant at 1.0 vvm and 400 rpm, respectively. Shown in. Comparing Example 1 with Comparative Example, the fermentation liquid viscosity μ 90 hours after the fermentation was stopped is higher when the control according to Example 1 is performed, and the rate of increase in viscosity is also higher. Although not shown in the figure, the final xanthan gum concentration is 1.0% when the aeration amount Q and the stirring strength N are constant, and 1.4% in the fermentation in which the aeration amount Q and the stirring strength N are controlled. From the air flow Q
It was demonstrated that the productivity of xanthan gum is improved by controlling the stirring strength N and the stirring strength N.

Further, in the controlled fermentation as shown in FIG. 4, the aeration amount Q and the agitation strength N are decreased from when the growth rate OD of the microorganism reaches a steady state. Is smaller than the uncontrolled fermentation shown in FIG. As described above, it is understood that in xanthan gum fermentation, a large amount of oxygen is required for the growth of microorganisms, but oxygen is not required so much during the production of xanthan gum after the growth. In such a fermentation system, the effectiveness of the present control, in which the aeration and agitation power is supplied without excess or deficiency, is particularly effective.

[0017]

According to the present invention, the viscosity of the fermentation broth is continuously monitored, the amount of change in viscosity is calculated at regular intervals, and the aeration amount Q and the stirring strength N are increased in the direction of increasing the viscosity increasing rate.
By increasing or decreasing the amount, the production rate is kept at a maximum and the aeration and agitation powers are kept low.Therefore, the biopolymer productivity is high, and the aeration and agitation powers are input without excess or deficiency. Therefore, productivity can be improved in terms of energy consumption.

[Brief description of drawings]

FIG. 1 shows a configuration example of a fermentation control device.

FIG. 2 shows a general pattern of change in the relationship between fermentation liquid viscosity and fermentation time in biopolymer fermentation.

FIG. 3 shows a flowchart of control of high-viscosity fermentation of the present invention.

FIG. 4 shows the control situation of xanthan gum fermentation of Example 1.

FIG. 5 shows changes in the fermentation liquid viscosity μ and the growth rate OD of microorganisms with respect to the fermentation time when the aeration amount Q and the stirring strength N are constant in the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fermenter 2 Fermentation liquid 3 Jacket 4 Stirrer 5 Aeration device 6 Motor 7 Means to change aeration amount and stirring intensity 8 Flowmeter 9 Electromagnetic valve 10 Circulation pump 11 Viscometer 12 A-D converter 13 Computing device

Claims (1)

[Claims] 1. In a highly viscous fermentation method in which the viscosity of a fermentation liquor changes with time, a change in the viscosity of the fermentation liquor is continuously detected, the amount of change is calculated over time, and based on the increase or decrease in the amount of change. A highly viscous fermentation method, characterized by controlling the amount of aeration and the stirring strength.