METHOD FOR CULTIVATING MICROALGAL BIOMASS AND APPARATUS FOR THE IMPLEMENTATION THEREOF

Abstract

The invention relates to a process and equipment for cultivating and producing a biomass from microalgae, primarily plankton. A microalgal biomass is cultivated in a single bioreactor chamber in the shape of a vertically oriented parallelepiped. The culture mixture is illuminated by artificial light sources mounted on the inner side of one of the broad walls of the bioreactor chamber in horizontal rows throughout the height of the bioreactor chamber. The culture mixture is illuminated cyclically. Spray heads are mounted on the inner side of the opposite wall of the bioreactor chamber so that 4 spray heads are arranged symmetrically around each artificial light source. The pH value of the culture mixture is maintained in a range of 8.5-9.5 by the addition thereto of a lactic acid bacteria-containing solution at the beginning of each light cycle in an amount of 1-3 ml per litre of culture mixture, said solution having a pH value selected in a range of 4.0-5.0.

Claims

1. The method for cultivating microalgal biomass including mineral medium preparation, adding of microalgae strain stock culture, filling of the produced culture mixture into the system of successively mounted bioreactors in the form of light-transmitting chambers horizontally oriented, illumination of the culture mixture by vertically arranged artificial light sources, extraction of the produced suspension to the natural precipitation tank and subsequent extraction of the produced precipitated biomass as a target product, wherein prepared mineral medium has the following composition: ammonium nitrate (34% solution) 0.14 ml ammophos (15% solution) 0.10 ml ferrous chloride (1% solution) 0.15 ml cobaltous nitrate (0.1% solution) 0.10 ml copper sulphate (0.1% solution) 0.10 ml potable water 1000 ml cultivating the biomass in a single bioreactor chamber in the shape of a vertically oriented parallelepiped, illuminating the culture mixture by artificial light sources mounted on the inner side of one of the broad walls of the bioreactor chamber in horizontal rows throughout the height of the bioreactor chamber, illuminating the culture mixture cyclically, during all the cycles of microalgae cultivation maintaining pH value of the culture mixture in the range of 8.5-9.5 by the addition thereto of a lactic acid bacteria-containing solution at the beginning of each light cycle in an amount of 1-3 ml per litre of culture mixture, said solution having a pH value selected in a range of 4.0-5.0.

2. Method according to claim 1, wherein illuminating the culture mixture by artificial light sources within 4 light cycles, each of them consisting of 10 hours of illumination and subsequent 2 hours of no illumination, during illumination period the culture mixture temperature is maintained withing the range of 26-30° C., and during the period of no illumination—within the range of 24-26° C.

3. Method according to claim 1, wherein the culture mixture is filled into the bioreactor chamber above any horizontal row of light sources by a quantity equal to half of their center-to-center distance heightwise.

4. The microalgal biomass cultivation apparatus comprising successively mounted bioreactors in the form of transparent horizontal chambers, equipped with mixing means, connected to the ready microalgal biomass tank by a rundown line, the lactic-acid bacteria bioreactor connected at the outlet with microalgae bioreactors, medium preparation unit connected at the outlet with the microalgae bioreactors and lactic-acid bacteria solution bioreactor, artificial light sources in the form of electric lamps equipped with the cooling system, spray heads connected with the washing fluid preparation system, pumps and shutoff and control devices, wherein microalgae bioreactor chamber is in the shape of a vertically oriented transparent parallelepiped, artificial light sources are mounted on the inner side of one of the broad walls of the chamber in horizontal η rows perpendicular to it, spray heads are mounted on the inner side of the opposite wall of the bioreactor chamber so that 4 spray heads are arranged symmetrically around each artificial light source.

5. The apparatus according to claim 4, wherein it is equipped with programmable automatic system for control and monitoring the set parameters of temperature, volume, dosage, loading, unloading of solution and ready product.

6. The apparatus according to claim 4, wherein it comprises two or more bioreactors.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0043] The essence of the claimed group of inventions is supported by the drawings (FIG. 1-FIG. 3).

[0044] FIG. 1 illustrates a longitudinal section of the apparatus general view,

[0045] FIG. 2—section of the bioreactor chamber,

[0046] FIG. 3—section of the bioreactor chamber in plan view, Fig.

[0047] In accordance with the presented drawings (FIG. 1-FIG. 3) the apparatus comprises:

[0048] 1—bioreactor chamber,

[0049] 2—lactic-acid bacteria solution bioreactor,

[0050] 3—I&C board,

[0051] 4—process controller,

[0052] 5—immersion lamp, where [0053] 5.1—electric lamp, [0054] 5.2—lamp shell with flow channel,

[0055] 6—spray heads,

[0056] 7—solenoid valves for spray heads control,

[0057] 8—solenoid valve for stock culture/medium supply,

[0058] 9—peristaltic dosing pump for lactic-acid bacteria solution supply,

[0059] 10—motorized drainage valve,

[0060] 11—motorized ready product drain valve,

[0061] 12—treated source water pump,

[0062] 13—pump station with the washing fluid preparation system,

[0063] 14—stock culture pump,

[0064] 15—ready product pump,

[0065] 16—lamp cooling system circulation pump,

[0066] 17—direct-flow water heater,

[0067] 18—medium flow meter,

[0068] 19—nutrient solution preparation plant,

[0069] 20—ready product tank,

[0070] 21—bioreactor level transducer,

[0071] 22—three-way motorized control valve of the lamp cooling circuit,

[0072] 23—lamp cooling circuit heat exchanger.

EMBODIMENT OF THE INVENTION

[0073] The inventive method is implemented in the apparatus of the claimed design.

[0074] The apparatus operates as follows.

[0075] The apparatus is located in a translucent room, that ensures additional illumination or complete change-over to solar illumination pf algal suspension, where air conditioning system without atmospheric air admixture is used. Devices ensuring such processes as dosing, lighting, mixing, measuring, controlling, washing, drainage and emptying are located in individual I&C board 3.

[0076] Feed preliminarily purified from unintended impurities is supplied by the pump 12 to the direct-flow water heater 17, then—to the nutrient solution preparation plant 19. During the above steps the nutrient solution is prepared, which is divided into two production lines and used in the process of cultivation in the algal suspension bioreactor and also in producing the lactic-acid bacteria solution in the lactic-acid bacteria solution bioreactor 2.

[0077] Nutrient solution for the lactic-acid bacteria solution 2 is supplied by the pump 12 and controlled by the flow meter 18 and controller 4. Nutrient solution for producing algal suspension the bioreactor is supplied through the pressure line also by the pump 12 through the controller 4 operated solenoid valve 8. Bioreactor medium level is controlled by the level transducer 21 and controller 4 mounted in the board 3. Microalgal stock culture is supplied from the ready suspension tank 20 by the pump 14 through the stock culture filling solenoid valve 8 and controlled on the principle of medium supply. Lactic-acid bacteria solution supply is dosed by the dosing pump 9 with fixed capacity from the lactic-acid bacteria bioreactor 2 to the bioreactor 1 and is time controlled by the controller 4 mounted in the board 3. The bioreactor 1 is illuminated by the lamps 5 with fluid cooling jacket mounted inside the vessels. Each lamp is in the form of electric lamp 5.1 equipped with additional transparent shell 5.2 enveloping the electric lamp 5.1 case using the flow channel, wherein inlet and outlet are interconnected by the cooling system heat exchanger 23, cooling fluid supply line and rundown line. Cooling fluid is circulated by the pump 16 and controlled by three-way motorized control valve 22. Medium illumination time and periodicity are controlled by the controller 4 mounted in the board 3. Illumination lamps 5 ensure simultaneous illumination and maintaining the microclimate in microalgal suspension. After producing the ready product, the bioreactor 1 is drained through the ready product motorized ball cock 11 by means of the pump 15 to the ready suspension tank 20, then, the sections are washed by the spray heads 6 system. The spray heads are fed by means of the pump station 13 with the washing fluid preparation system for the chlorella bioreactors, bioreactor chamber is drained through the motorized ball cock 10.

[0078] The system of stationary spray heads connected at the inlets with the washing fluid preparation system mounted inside the bioreactor chamber, and washing fluid drain line of the bioreactor enable to wash and remove contaminations of the bioreactor chamber and lamps automatically without involving manual labour. Mounting of spray heads on the inner side of the bioreactor chamber wall opposite to the wall where light sources are mounted so that 4 spray heads are arranged symmetrically around each light source, that enables to wash almost complete surface of light sources. As a result of such arrangement of spray heads and optimal algorithm of washing the bioreactor 1 zones due to solenoid valves 7, not only the light source washing time is reduced, but also any possibility of infecting the bioreactor chamber with undesired bacteria is excluded. The said solutions enable to improve the apparatus productivity and target product quality due to preventing from infecting the culture with other algae spores.

The Best Example of the Method Implementation

[0079] The claimed method for producing microalgal suspension, in particular, food chlorella is implemented as follows.

[0080] The medium is preliminarily prepared using the program-controlled dosing pumps. The medium includes the following elements: N, P, Fe, , Co, on a per 1000 ml of water bases comprises 0.14 ml of ammonium nitrate (34% solution), 0.10 ml of ammophos (15% solution), 0.15 ml of ferrous chloride (1% solution), 0.10 ml of cobaltous nitrate (0.1% solution), 0.10 ml of copper sulphate (0.1% solution).

[0081] Then, the bioreactor chamber is filled with stock chlorella suspension up to the necessary volume and the required volume of medium with the above composition is added. The culture mixture is illuminated in the automatic bioreactor within four successive cycles, each of them consisting of 10 hours of illumination and subsequent 2 hours of no illumination with artificial light sources being Off, and during illumination period the bioreactor temperature is maintained within the range of 26-30° C., and during the period of no illumination—within the range of 24-2° C., that corresponds to developmental biology and promotes intensive growth and multiplication of microalgae cells. At that cultivation the culture reaches optical density of 1.4-1.8 D (440) (specified optical density). The cultivation is carried out subject to strict sanitary requirements for food products.

[0082] The produced suspension is poured from the bioreactor to the ready suspension tank, where chlorella is naturally precipitated within 30 days using natural diffused light, i.e. at normal lighting without artificial light sources. Upon completion of microalgae cultivation cycles, the light sources are washed, washing fluid is drained.

[0083] All the processes, namely, washing fluid draining, filling the bioreactor chamber with stock culture and medium, controlling the illumination cycles, maintaining the temperature conditions, dosing of carbon dioxide and cyclic mixing are performed automatically by the devices controlled by the programmable controller.

[0084] The produced suspension is poured from the bioreactor to the food chlorella natural precipitation transparent tank, where chlorella is naturally precipitated within 30 days using natural diffused light, i.e. at normal lighting without artificial light sources.

[0085] The best embodiment of the claimed group of inventions, with illumination optical density within the range (1.4-1.8) D, enables to produce ready product in 48 hours, 11 of which comprises 7-10 grams of microalgal wet mass, that ensures high quality of ready product. The known methods for microalgae cultivation enable to produce 3-5 g/l.

[0086] The claimed method for cultivating microalgal biomass enables to produce in the claimed device the high-quality ready product which could be used in food, microbiological and pharmaceutical industry.