FR2588271A1 - Installation and process for continuous aerobic or anaerobic fermentation - Google Patents

Abstract

The installation according to the invention comprises a fermenter 1 of the pulsed column type equipped with plates 5, which are capable of containing an inoculated culture medium 2, means 11 for continuously feeding the medium with nutrient substrate, means 15 for feeding the culture medium with neutralising agent, means for homogenising the culture medium comprising a device 33 for generating pulses in the culture medium as well as means 53 for continuously extracting the fermentation products. This installation can be used for the production of proteins, enzymes and monocellular organisms.

Description

INSTALLATION AND PROCESS FOR AEROBIC FERMENTATION OR
CONTINUOUS ANAEROBIC
The subject of the present invention is an installation for continuous aerobic or anaerobic fermentation and an anaerobic fermentation process using this installation. It advantageously applies in the field of biotechnology and in particular for the production of organisms. monocellular or micro-organisms (yeasts), the preparation of food products (wine, cheese), pharmaceuticals, chemicals and energy products as well as for the preparation of enzymes and proteins.

 When microorganisms produce ferments on an industrial scale and therefore, continuously, it is necessary to feed the microorganisms with feeder substrate (whey for example for the production of yeasts), to ensure the demand for substrate chemical, and in particular in oxygen, nitrogen or trace elements, to allow the growth of micro-organisms, to evacuate the heat produced during fermentation as well as to recover the products of fermentation, i.e. metabolites and / or microorganisms that have multiplied.

 Any defect or excess in the culture medium of nutrient substrate, chemical substrate, heat, or products of fermentation results in inhibition of fermentation and decreases yields. Each of the above operations must therefore be carried out in the best possible way in order to keep the fermentation yield constant.

 In currently known fermentation plants and processes, it is generally necessary to dilute the feed substrate in the culture medium, consequently entailing the treatment of a very large volume of liquid as well as an increase in the quantity of effluents discharged. . In addition, the installations currently used are relatively large and complex, resulting in high investment costs and relatively high energy consumption.

 The subject of the invention is precisely an installation and a process for continuous aerobic or anaerobic fermentation making it possible to remedy these various drawbacks.

 In particular, the installation according to the invention makes it possible to directly treat the nourishing media or substrates (whey for example) without prior dilution, regardless of the mode of operation, aerobic or anaerobic. The elimination of this dilution makes it possible to reduce the investment rates thanks to the use of a bulky care installation as well as a reduction in production costs due to the reduced volume of liquid and effLuents to be treated.

 Furthermore, the installation according to the invention makes it possible to ensure very high productivity and a high fermentation yield by continuously removing the metabolites formed.

 More specifically, the subject of the invention is an instatlation for continuous aerobic or anaerobic fermentation comprising a fermenter capable of containing a first phase, constituted by a culture medium seeded with microorganisms, means for supplying continuous of the first phase in neutralizing agent and in nourishing substrate, means of homogenization of the first phase and means of continuous extraction of the products of fermentation, characterized in that the means of homogenization include a device for generate pulsations in the first phase.

 By fermentation products, we must understand the metabolites produced by microorganisms, the gases formed, but also microorganisms. Indeed, microorganisms multiply constantly during fermentation.

 The fermentation plant of the invention can be used to produce metabolites and / or the microorganisms responsible for these metabolites.

 The pulsation which can be carried out mechanically or pneumatically makes it possible to perfectly homogenize the culture medium as well as to significantly increase the productivity. In addition, the use of pulses makes it possible, compared with the prior art, to reduce the energy consumption of the agitation station.

According to a preferred embodiment of
The installation according to the invention, the fermenter comprises a column internally lined with trays.

 In aerobic conditions, the presence of the trays allows, with that of the pulsation, to considerably increase compared to the prior art, the oxygen transfer necessary for the growth of microorganisms, by constantly increasing the exchange surface. gas-culture medium, and by contributing to the rupture and coalescence of the oxygen and gas bubbles formed during fermentation.

 In order to perfectly control the disengagement of the products (gas and liquid from the fermenter), this fermenter is advantageously equipped at its upper part with an expansion vessel.

 Furthermore, a system allowing the control of the foams formed during fermentation can advantageously be provided. This system consists of a regulated and automatic injection of surfactants without the risk of poisoning the culture medium. In the case of a dairy, silicone compounds can be used as surfactants.

 According to a preferred embodiment of the installation according to the invention, the homogenization means comprise means for circulating and recycling the first phase in the fermenter.

 In anaerobic conditions, the fermentation installation according to the invention is advantageously equipped with a supply line for a second phase in the fermenter, this second phase serving for the in situ extraction of the products of the fermentation and in particular metabolites produced by microorganisms.

In situ extraction of metabolites produced during anaerobic fermentation by
Microorganisms, leads to a considerable simplification of this fermentation process, an increase in productivity with a high fermentation yield, as well as an increase in the concentration of the nourishing medium (no prior dilution) and overall production.

 Advantageously, a settling tank can be provided to separate, in anaerobic mode, the first phase from the second phase. Likewise, a concentration device can be provided to separate the products of the fermentation of this second phase and in particular the metabolites produced by the microorganisms.

 The present invention also relates to a continuous anaerobic fermentation process using the installation described above. This consistent process of supplying a neutralizing agent and a nourishing substrate for a first phase, consisting of a culture medium containing microorganisms, and extracting the products of fermentation, is characterized in that the first phase with a second phase used to extract, in the fermenter, the metabolites produced by microorganisms during fermentation.

 The extraction of metabolites by the second phase in the fermenter can be carried out by circulating the first and second phases with cocurrent or against the current. This second solution has the advantage of considerably facilitating the separation of metabolites and microorganisms produced during fermentation and of simplifying the fermentation installation; in fact, these metabolites pass into the second phase and the microorganisms remain for fermentation in the first phase.

 In the case of a dairy, long chain aliphatic alcohols can be used as the second phase.

 In the installation and the process according to the invention, the physico-chemical parameters of the fermentation such as the temperature, the neutralizing agent, the nourishing substrate, the chemical substrate (oxygen, nitrogen, and trace elements), are adjusted by very precisely and automatically which reduces total operating costs.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given by way of illustration and without limitation, with reference to the appended figures, in which:
FIG. 1 schematically represents, according to a first variant, an installation according to the invention for aerobic fermentation,
FIG. 2 schematically represents, according to a second variant, an installation in accordance with the invention for aerobic fermentation,
FIG. 3 schematically represents an installation for anaerobic fermentation in accordance with the invention with co-current extraction of the products of the fermentation, and
- Figure 4 schematically shows an installation for anaerobic fermentation according to the invention with an extraction against the current of the fermentation products.

 In order to simplify and better understand the description, the parts of the installation unchanged in FIGS. 1 to 4 will bear the same reference and the parts of different structure but playing the same role will bear the same references preceded by d 'a number 1 of hundreds.

 In Figure 1, there is shown an installation for aerobic fermentation, that is to say requiring the presence of oxygen.

 This installation comprises a fermenter 1 designed to receive a culture medium 2, in the liquid state, containing microorganisms. This fermenter comprises a column body 3 preferably lined internally with perforated trays 5, regularly distributed over the entire height of the column body 3. The column body 3 of the fermenter has at its lower part a feeding zone 7 in products necessary for fermentation, and in particular in feed and chemical substrates necessary for the growth of microorganisms. The fermenter 1 also comprises in its upper part and surmounting the column body 3 an expansion vessel 9, serving in particular to disengage from the fermenter the products of fermentation such as metaboli, the gases produced by microorganisms and the microorganisms themselves.

 The installation according to the invention further comprises a supply line 11 for the feeder substrate (whey, for example) possibly enriched in chemical substrate (nitrogen, trace elements). This supply line 11 in substrate is equipped with a valve 13 used to regulate the feed rate of feed substrate in the culture medium 2. This pipe 11 opens into the supply zone 7 of the fermenter and in particular in the bottom of it.

 The installation for the fermentation also comprises a loop 15-18 for regulating the pH of the culture medium 2. This loop comprises a supply line 15 for a solution, generally basic and in particular a solution of NaOH or NH3 equipped with an electro-valve 16. The supply line 15 opens into the supply zone 7 of the fermenter. The opening and closing of the solenoid valve 16 are controlled, via a device 17 of the threshold comparator type, to the measurement of the pH of the culture medium carried out by a probe 18, housed in the column body 3 of the fermenter and immersed in the culture medium 2.

 Likewise, a loop 19-22 for regulating the oxygen pressure in the fermenter is provided.

This loop comprises an oxygen supply pipe 19 opening into the supply zone 7 of the fermenter 1. It is equipped with an electro-valve 20 whose closing and opening are controlled by a regulator 21 of the comparator type to threshold following the measurement of the oxygen pressure in the fermenter carried out by a probe 22 housed in the body 3 of the fermenter 1.

 Furthermore, a temperature regulation loop 23-27 prevailing in the fermenter 1 is provided. This loop comprises a double envelope 27 surrounding the column body 3 of the fermenter, supplied with a hot or cold fluid depending on the thermodynamics of the reaction (water for example) by a supply line 23, opening at the base of the double envelope , equipped with a solenoid valve 24, the control of which is ensured by a regulator 25 according to the temperature measured in the fermenter by a probe 26, housed in the body 3 of the fermenter.

 According to the invention, the installation for fermentation comprises means for homogenizing the culture medium 2 contained in the body 3 of the fermenter 1. These means in particular comprise a device 29 for mechanical agitation generating pulsations in the medium of culture 2. The pulsations are produced in the feeding zone 7 of the fermenter.

A system for circulating and recycling the culture medium 2 in the fermenter 1 can also be used to perfect the homogenization of the culture medium 2. This system includes a pipe 31 recovering the culture medium 2 leaving the head of the body column 3 and opening into the feed zone 7 of the fermenter 1. On this pipe 31 is mounted a pump 33 making it possible to circulate the culture medium 2 from top to bottom, outside the fermenter 1 and therefore from the bottom up in The fermenter.

 In order to control the formation of foams during fermentation, a system can advantageously be provided for automatically introducing an additive such as a surfactant into the upper part of the expansion tank 9 of the fermenter 1. This system includes a foam level sensor 35 connected to a regulator 36, of the threshold comparator type, controlling the opening and closing of a solenoid valve 37 mounted on a line 38 for supplying the surface-active agent with the medium culture 2.

 The extraction of fermentation products and in particular of metabolites and microorganisms is carried out by overflowing through an evacuation orifice 39 formed in the expansion tank 9 of the fermenter. An outlet pipe 41 makes it possible to bring the liquid medium leaving the expansion tank into a separator 43 serving to separate, for example by ultrafiltration, the microorganisms from the spent medium in the nourishing substrate but containing the metabolites produced by the microorganisms. The microorganisms from the separator 43 are recovered in a pipe 45 and the medium containing the metabolites in a pipe 47.

 If necessary, the microorganisms conveyed in line 45 can be recycled in the feed zone 7 of the fermenter 1. In addition, the metabolites resulting from the fermentation can be separated from the spent medium as a substrate containing them in concentrating them for example by evaporation or distillation.

 In Figure 2, there is shown a variant of the installation for aerobic fermentation described above. The installation of FIG. 2 differs from that of FIG. 1 by the use of a heat exchanger 127, mounted on the recycling pipe 31 of the culture medium 2, as a regulated heating or cooling element of the culture medium. culture 2.

 In addition, the installation for the fermentation of FIG. 2 differs from that of FIG. 1 by the use, as a device for generating pulsations in the culture medium 2, of a pneumatic device comprising an inlet valve. 129 of a fluid (air for example), the opening and closing of which are impulse-controlled by an electronic circuit 130 of known type.

 Finally, the installation shown in FIG. 2 is further distinguished from that of FIG. 1 by the use of full plates 105 housed in the column body 3. These plates 105 have a diameter smaller than that of the column body 3 and are offset from each other for baffles, while allowing the passage of the different phases contained in the column body 3.

 We will now describe the operating mode of the installation according to the invention for aerobic fermentation, shown diagrammatically in FIGS. 1 and 2. The arrows represented in these figures indicate the direction of circulation of the various media.

 First of all, a feed substrate optionally enriched with a chemical substrate is loaded, and the body 3 of the fermenter 1, and in particular the feed zone 7, in fermentation strain; the feed substrate is undiluted. Then, the pump 33 is started in order to homogenize the culture medium 2 by circulating it. The culture or growth of microorganisms is started statically by regulating the pH, the oxygen demand and the temperature by the corresponding loops 15-18, 19-22 and 23-26.

 When the population of microorganisms in culture medium 2 is judged. sufficiently abundant, the fermentation is set in motion; the feeder substrate is introduced via the supply line 11 into the feed zone 7 of the fermenter, the flow rate of this substrate being adjusted as a function of a determined dilution rate of the culture medium 2. The maximum dilution rate of the substrate is related to the generation time of microorganisms.

 Similarly, the supply of surfactants through line 38 is carried out.

 The mechanical pulsation device 29 (Figure 1) or pneumatic 129 (Figure 2) is started. It makes it possible to ensure, in combination or with the plates 5 or 105, an intimate contact between the oxygen introduced into the fermenter 1 and the culture medium 2 and consequently a good transfer of oxygen to the nourishing medium.

 The mechanical or pneumatic pulsation device also makes it possible to easily evacuate the excess oxygen and the gases formed during fermentation, as well as ensuring good heat transfer.

 The fermentation products, that is to say the metabolites and micro-organisms / are evacuated from the fermenter 1 by the outlet port 39, then are separated from the culture medium exhausted by the separator 43. l oxygen not consumed and the gases produced during fermentation escape from the top of the expansion tank 9.

 In Figure 3, there is shown an installation according to the invention for anaerobic fermentation and co-current extraction of the fermentation products.

 This installation comprises as before a fermenter 1 comprising a column body 3 equipped with solid or perforated trays, a lower part 7 forming the feed zone and an expansion vessel 9 surmounting the column body 3 and serving as a zone of disengagement from fermentation products.

 The installation also includes a regulated supply system 11, 13 for the substrate, a loop 15-18 for regulating the pH of the culture medium 2, a pipe 19 for supplying oxygen, a system 35-38 for controlling foam. , and a system 23-27 for regulating the temperature in the fermenter. This installation is provided according to the invention with a pulsed stirring system, for example mechanical 29, or possibly pneumatic allowing good homogenization of the culture medium 2.

 This installation also includes, a pipe 49 for supplying a solvent 50 opening into the feed zone 7 used for the extraction of the metabolites produced by the microorganisms inside the fermenter 1. This solvent 50 consists of a liquid immiscible with the culture medium 2. The supply of solvent 50 is controlled using a regulation system 51 fitted to the supply line 49.

 In this first variant of installation for anaerobic fermentation, the circulation of the culture medium 2 is ensured by a pump 133 mounted on a pipe 131 for supplying the culture medium 2 to the feed zone 7 of the fermenter 1. The solvent 50 dispersed in the culture medium 2 is entrained therewith in the fermenter. The extraction is said to be co-current, the culture medium 2 and the solvent 50 flowing in the same direction from bottom to top in the fermenter 1 and from top to bottom outside 2 and the solvent.

The culture medium 2 and the dispersed solvent 50 are removed from the fermenter through the orifice 39 formed in the expansion tank 9 and sent via your pipe 141 to a settling tank 55. The culture medium 2 containing the microorganisms is returned to the fermenter 1 using the pump 133 while the solvent 50, containing the metabolites produced by
The microorganisms is brought into a separator 57 via a line 59. The separator 57 of the evaporation or distillation device type makes it possible to separate the metabolites from the solvent 50. The metabolites resulting from the fermentation are recovered at the outlet of the separator 57 via a line 61 while the solvent 50 is recycled through the supply line 49 of said solvent in the fermenter 1.

 The settling tank 55 allowing the separation of the culture medium 2 from the solvent 50 can be equipped with a level probe 62 of the culture medium 2 connected to a level regulator 63 controlling the closing or opening of an electro- valve 64 equipping the line 133 for supplying the culture medium 2 to the fermenter 1.

 The medium depleted in nutrient substrate leaving the settling tank 55 or the surplus of culture medium is evacuated via a pipe 65.

 We will now give the operating principle of the installation for anaerobic fermentation shown diagrammatically in FIG. 3. The arrows represented in this figure indicate the direction of circulation of the various media.

 The undiluted feeder substrate and possibly enriched in chemical substrate, and the fermentation strain are first loaded in the body 3 of the fermenter and in particular in the feeding zone 7. The culture is started in static by regulating the pH and the temperature of the culture medium 2 by the corresponding loops 15-18 and 23-26 and by supplying oxygen to the medium. The pump 133 is put into operation and allows homogenization of the culture medium 2. Similarly, the regulation loop 62-64 of the level of culture medium 2 in the decanter 55 is forced. The supply of surfactants through line 38 is put into operation.

 When the population of microorganisms in culture medium 2 is deemed to be sufficiently abundant, the fermentation is set in motion. The oxygen supply is then cut off. The feed of feed substrate through line 11 and the supply of solvent 50 through line 40 are then carried out. The feed substrate and solvent flow rates are linked to the generation time of the microorganisms.

 Similarly, the pulsation device according to the invention, mechanical or pneumatic, is started. It ensures an intimate mixing between the two phases, that is to say between the solvent 50 and the culture medium 2, thus promoting the extraction of the metabolites produced During the fermentation by the solvent, the microorganisms remaining in the culture medium, as well as better evacuation of the gases formed during fermentation. These gases are discharged at the top of the expansion tank 9.

 The mixture of solvent 50 and culture medium 2 overflows the evacuation orifice 39 of the expansion vessel 9 in the direction of the settling tank 55. The culture medium 2 loaded with microorganisms is recycled by the pump 133 to the fermenter 1 in order to keep the population of microorganisms constant. This recycling of microorganisms makes it possible to avoid the addition of fresh strain after the initial seeding. The surplus of the culture medium as well as the medium exhausted in the nourishing substrate are evacuated via line 65.

 The extract from decanter 55, collected by line 59 is concentrated using the device 57 and the solvent 50, freed from the products of fermentation and in particular from metabolites, is reinjected into fermenter 1, via the supply line. 49.

 FIG. 4 shows an installation for anaerobic fermentation with a countercurrent extraction of the products of the fermentation.

 This installation differs from that of FIG. 3 mainly by a feed of feeder substrate between the body 3 of the fermenter and the expansion tank 9. The supply pipe 111 of the substrate is equipped with a regulation system 113. In in addition, the recycling of the culture medium 2 loaded with microorganisms in the fermenter 1 is ensured by a pipe 131 equipped with a pump 133.

 In this embodiment, the circulation of the culture medium 2 takes place against the flow of that of the solvent 50, that is to say from top to bottom in the fermenter 1 and from bottom to top out of the fermenter, as shown by the arrows shown. Furthermore, the expansion tank 9 acts as a settling tank used to separate the culture medium 2 from the solvent 50.

 This decantation-ion tank 9 is preferably equipped with a culture medium level detector 2 comprising a probe 67 connected to a regulator 68 controlling a solenoid valve 69 mounted on a bypass 70 of the medium recycling pipe 131 culture 2. The surplus of culture medium 2 is discharged through this line 70.

 At the outlet of the settling tank 9, a line 141 brings the solvent 50 loaded solely with metabolites to the concentration device 57 serving for the separation of these metabolites from the solvent.

As before, the solvent 50 is reinjected into the feed zone 7 of the fermenter.

 We will now describe the operating mode of the installation shown in FIG. 4.

 The feeder substrate, undiluted and possibly enriched, and the fermentation strain are first loaded into the column body 3 of the fermenter and in particular into the feed zone 7.

The culture is started statically by regulating the corresponding loops 15-18 and 23-26 of pH and temperature of culture medium 2 and by supplying oxygen to said medium. The supply of surfactants through line 38 is carried out.

Then, homogenization of the culture medium 2 is carried out by switching on the pump 133 recycling the culture medium 2 and forcing the regulation loop 67-70 of the level of the culture medium 2 in the expansion tank 9 playing the role of decanter.

 When the population of microorganisms in culture medium 2 is deemed to be sufficiently abundant, the fermentation is set in motion. The oxygen supply is cut off. The feeder substrate is sent via line 111 to the fermenter. Likewise, the solvent 50 is sent against the current of the substrate in the fermenter. The flow rates of the substrate and the solvent are a function of the generation time of the microorganisms.

 The mechanical or pneumatic pulsation device is also activated. It ensures an intimate mixture of the two phases (culture medium and solvent), promotes the extraction of metabolites, produced during fermentation, by solvent 50. The pulsation also allows better evacuation of the gases formed during fermentation , at the top of tray 9.

 The solvent 50 dispersed in the culture medium 2 circulates from bottom to top in the fermenter, coalesces in the expansion or settling tank 9 and overflows through the outlet orifice 39 towards the device 57 for separating the metabolites from the solvent.

 The culture medium 2 collected at the bottom of the fermenter 1 is recycled to the top of the body thereof using the pump 133 in order to keep the population of microorganisms in the fermenter constant and homogeneous. This recycling of microorganisms eliminates the addition of fresh strain after initial seeding. The surplus of culture medium 2 is discharged through line 70.

 The preceding description has been given for explanatory purposes, any modification without departing from the scope of the invention may be envisaged. In particular, the direction of circulation of the different media can be reversed.

The facility for aerobic fermentation
according to the invention (Figures 1 and 2) was used to
the production of biomass, that is to say microorganisms by processing whey or whey produced
dairies.

Annual French production amounts to millions of tonnes of this excessively polished product
glow (BOD 60000 ppm) which can be easily valorized by the production of proteins.

 In the example below, the production of the yeast Kluyveromycés Fragilis was studied in an installation with a volume of 80 liters using a feed substrate flow rate of 10 to 20 l / h, a pH of 3.5, a temperature of 30 "C, a rate of recycling of the culture medium 400 to 500 l / h, a pulse frequency of 30 to 100 cp / min. and a pulse amplitude of 1 to 10 cm. The yeast produced can then be used to make proteins.

 All the operating conditions studied and the results obtained are given in the table below.

In this table, the second line gives the lactose concentration in g / l of the feeder substrate or small tait, the latter being previously enriched with trace elements and nitrogen but not diluted; the VVM aeration rate corresponds to the air flow rate, per minute, relative to the reaction volume, and therefore to the oxygenation necessary for the growth of the yeast;
the renewal time or residence time corresponds to the hourly flow rate of the substrate relative to the reaction volume; the fifth line gives the amount of yeast obtained after drying thereof.

BOARD
TEST 1 2 3 4
Lactose concentration g / l 25 40 45 35
VVM ventilation rate (min 1) 1.8 1.8 1.9 2.0
Renewal time (h) 3.0 4.0 3.0 2.5
Dry matter at equilibrium 11 18.5 17.8 16.1 g / I
Productivity g / l / h 3.60 4.65 5.80 6.30

Claims (18)

 1. Installation for continuous aerobic or anaerobic fermentation comprising a fermenter (1) capable of containing a first phase (2), constituted by a culture medium seeded with microorganisms, means for continuously feeding the first phase (2) in neutralizing agent (15 d and in nourishing substrate (11, 111), means for homogenization (29, 129, 31, 131) of the first phase (2) and means for extraction (39, 43 , 55, 57) continuously from the fermentation products, characterized in that the homogenization means comprise a device (29, 129) for generating pulsations in the first phase (2).  2. Installation according to claim 1, characterized in that the fermenter (1) comprises a column (3) internally lined with trays (5, 105).  3. Installation according to claim 1 or 2, characterized in that the fermenter (1) comprises at its upper part an expansion vessel <9) used for disengagement of the products of fermentation.  4. Installation according to any one of claims 1 to 3, characterized in that means (35-38) for introducing, at the upper end of the fermenter (1), * an additive to control the foams formed during the fermentation are planned.  5. Installation according to any one of claims 1 to 4, characterized in that the homogenization means comprise means (31, 33, 131, 133) for circulation and recycling of the first phase (2) in the fermenter (1).  6. Installation according to any one of claims 1 to 5, characterized in that means (Z3-27, 1273 for regulating the temperature in the fermenter (1) are provided.  7. Installation for aerobic fermentation according to any one of claims 1 to 6, characterized in that an oxygen supply pipe (19) of the first phase (2) is provided, the oxygen constituting a second phase used for the growth of microorganisms.  8. Installation according to claim 7, characterized in that a separator (43) is provided for separating the products of the fermentation of the first phase (2).  9. Installation for anaerobic fermentation according to any one of claims 1 to 6, characterized in that a supply line (49) of a second phase (50) in the fermenter (1) is provided, this second phase (50) used for the extraction in the fermenter (1) of the products formed by the microorganisms during fermentation.  10. Installation according to claim 9, characterized in that a concentration device (57) is provided for separating from the second phase (50) the products formed by the microorganisms.  11. Installation according to claim 10, characterized in that a pipe (49> is provided for recovering the second phase (50) leaving the concentration device (57), this pipe forming the supply pipe of the second phase ( 50) in the fermenter (1).  12. Installation according to any one of claims 9 to 11, characterized in that a settling tank (55) is provided for separating the first phase (2) from the second phase (50).  13. Installation according to claim 12, characterized in that the settling tank is constituted by the expansion tank (9) of the fermenter (1).  14. Continuous anaerobic fermentation process in a fermenter (I) consisting in supplying neutralizing agent and nourishing substrate a first phase (2), constituted by a culture medium containing microorganisms, and in extracting the products from the fermentation, characterized in that the first phase (2) is brought into contact with a second phase (50) serving to extract, in the fermenter (1), the metabolites produced by the microorganisms during fermentation.  15. Method according to claim 14, characterized in that the first (2) and the second (50) phases are circulated in co-current.  16. Method according to claim 14, characterized in that the first (2) and the second (50) phases are made to flow against the current.  17. Method according to any one of claims 14 to 16, characterized in that the first (2) and the second (50) phases are separated by decantation.  18. Method according to any one of claims 14 to 17, characterized in that the metabolites of the second phase (50) are separated by concentration.