FR2549851A1 - Device permitting the regulation of dissolved gas concentrations in fermentation - Google Patents

Abstract

Dissolved gas concentrations play an important part in cell regulation mechanisms; rate of growth and production of metabolites largely depend thereon. The aim of the invention is therefore to control the gas exchanges by working in a reactor which is virtually closed for the gaseous phase. To meet this objective the gaseous phase will be: - on the one hand, recycled into the aqueous phase by virtue of a recirculating device - on the other hand, recycled wholly or partially to a device permitting the fractionation of the gaseous phase into its constituents and the optional addition of desired gases. Figure 1 shows a plant in which the process according to the invention can be implemented in the case of an aerobic fermentation where it is desired to control the dissolved oxygen and carbon dioxide at the same time.

Description

 The subject of the present invention is an improved device for regulating the gases dissolved in the fermentation of cell culture.

 The dissolved gas concentrations play an important role in the mechanisms of cell regulation, growth rate and production of metabolites largely depend on it.

 If we take the example of aerobic fermentation to satisfy the oxygen demand of the culture, we are forced to blow large quantities of gas (air, oxygen-enriched air, or pure oxygen), then it becomes impossible! regulate the concentration of dissolved carbon dioxide. The impossibility of regulating the concentration of dissolved carbon dioxide comes from the fact that the reactor operates in an open reactor for the gas phase and that carbon dioxide is a product of metabolism. The result of this tool-making situation is impossible to regulate oxygen and dissolved carbon dioxide concentrations at the same time.

The object of the invention is therefore to control gas exchanges by working in a practically closed reactor for the gas phase. To achieve this objective the gas phase will be
- on the one hand recycled in the aqueous phase thanks to an aircraft recir cul device
- On the other hand recycled in whole or in part on a device allowing the gaseous phase to be divided into its constituents and the possible addition of desired gases.

 FIG. 1 represents an installation in which the method according to the invention is capable of being implemented in the case of aerobic fermentation in which it is wished to regulate oxygen and dissolved carbon dioxide at the same time.

This installation includes
1) a device A for enriching the gaseous phase with oxygen, this device being able for example to consist of columns filled with zeolites making it possible to separate the oxygen from the other gases of the air; this device can also be shortened by direct supply to the reactor of pure oxygen obtained by conventional voSe.

2) a reactor B also called a fermenter characterized by the fact that it contains a liquid medium, called culture medium in which it is desired to control the concentration of dissolved oxygen and carbon dioxide, and a gaseous phase partly gaseous and partly emulsified in the liquid phase. The gas-liquid emulsion is obtained by means of a stirring device characterized in that it is constituted
- either by a self-aspirating turbine with or without a directing cylinder aspirating and emulsifying the gas phase in the liquid phase
- either by a device for recirculating the culture medium through a suction venturi and emulsifying the gas phase in the culture medium
- either by recirculation of the gas phase after recompression to create a system emulsifying the gas phase and the liquid phase (gas-lift system)
- Either by recirculation of the gas phase after recompression and injection by a conventional aeration and stirring device.

 3) a device for separating carbon dioxide (C) constituted either by a system of membranes making it possible to separate carbon dioxide from the gas mixture, either by a device for specific solubilization or neutralization of carbon dioxide, or by an adsorption device on carbon dioxide zeolites.

 The gaseous phase is partly extracted from the fermenter using a suitable device and fractionated on device C, the fraction of the gaseous phase recycled on device C is determined so as to maintain the concentration of carbon dioxide in the phase gas at a given value on the recycling circuit also includes a carbon dioxide injection system, the request of which may prove necessary at the start of fermentation. As the microbial growth develops, in the example given there is consumption of oxygen and release of carbon dioxide. To compensate for the consumption of oxygen, oxygen or oxygen-enriched air is introduced into the reactor and the recycled gas to separate the carbon dioxide on the device C.

The proposed device can easily be automated thanks to the information given either
- by two sensors in the gas phase, one with oxygen and the other with carbon-carbon, the oxygen and carbon dioxide concentrations are then kept constant in the gas phase.

 - By two sensors in the aqueous phase, one with dissolved oxygen and the other with dissolved carbon dioxide, the oxygen and dissolved carbon dioxide concentrations are then kept constant by adapting the oxygen and carbon dioxide concentrations in the gas phase.

 Of course the present invention is not limited to the embodiments described and shown, it is capable of numerous variants accessible to those skilled in the art without departing from the spirit of the invention. 'invention. Variants can be understood to mean other gas-liquid mixing devices, other gas separation devices, other compositions of gas mixtures, or combinations of different variants applied to aerobic or anaerobic microbial cultures or to cell cultures. animal or vegetable, cultures in solid and semi-solid media or on supports with enzymatic bioconversions.

Claims (5)

 1.- Device for regulating the concentrations of dissolved gas in a bioreactor used in aerobic or anaerobic fermentation and in culture of animal or plant cells. Characterized in that  - a gas flow is taken from said bioreactor  - this gas is recycled on a separation device to remove the excess gases produced during the reaction  - the gas consumed is introduced  - We work practically in a closed reactor for the gas phase which is recycled in the bioreactor.  2.- Device according to claim 1 characterized in that the device for emulsifying l) a gaseous phase in the liquid phase is obtained by a self-aspirating turbine with without the guiding cylinder, by recycling after recompression of the gas phase and use in a gas-lift device, by recycling after recompression of the gas phase and use in a conventional stirring aeration device.  3.- Device according to any one of claims 1 and 2 characterized in that the gas phase fractionation device is done by a physical or chemical process.  4.- Device according to any one of claims 1-2-3 characterized in that the device can be used either to keep the composition of the gas phase constant, or to keep the dissolved gas concentrations constant.  5.- Device according to any one of claims 1-2-3-4 characterized in that the reactor consists of an enzymatic reactor or a reactor for culture on solid or semi-solid medium or on support.