I. Introduction

As is known, special technical systems are used to support human life in outer space, namely life support systems (abbreviated as SOE). Most often, these systems work either on resource reserves, or partially regenerating human waste. [1]

The creation of an autonomous space life support system is an extremely important, urgent and promising task for space exploration. A huge role in this is played by the development of SOEs, whose work is based on biological principles. One of them is an oxygen photobioreactor, the use of which in spacecraft is of particular interest. The creation of such equipment will be the first step towards the transition to autonomous biological life support systems.

The scientific novelty of the work consists in the development of a design sample of a photobioreactor that will be adapted to the conditions of space.

The use of such a photobioreactor to ensure the life of the crew in space could be more profitable than using the technical systems and life support systems that are familiar to us today. Firstly, it would make it possible to successfully solve the problem of maintaining the gas composition of the atmosphere of the spacecraft by using an air purification system from carbon dioxide and its oxygen enrichment based on biological regeneration methods, and would also solve the important task of providing additional food to the crew. Secondly, the installation of this bioreactor is environmentally appropriate.

Goals and objectives:

Objective: to develop a sample of a compact photobioreactor for use on autonomous space stations for the production of oxygen and protein mass.

Tasks:

1) Development of a technological scheme of an oxygen photobioreactor using a tubular bioreactor

2) Creation of a working sample (prototype) of a photobioreactor

3) Theoretical selection of components (equipment and materials) for the design of the prototype and design installation

4) Selection of microorganisms capable of producing oxygen and protein mass in the conditions of stay on the space station.

II. The main part

To implement the tasks set, an analysis of information from the relevant literature was carried out: engineering, biotechnological, chemical, as well as from patents and articles from authoritative sources (such as Roscosmos [1] and TsNIIMash [2]).

Also, for the convenience and efficiency of solving these tasks, the main areas of work were identified. So, the development of an oxygen photobioreactor sample was divided into three blocks:

Biological (Involves the analysis and selection of microorganisms – producers of biomass (protein mass) and oxygen; cultivation of microorganisms in space conditions in the installation of a photobioreactor)
Technical (Development and design of the photobioreactor technical installation)
Development and assembly of a prototype of a photobioreactor sample capable of demonstrating the principle of operation of the system.

1. Selection of microorganisms and the medium for their cultivation.

One of the first tasks in the work was the selection of microorganisms for cultivation in a photobioreactor. Here, thanks to the study of specialized literature, two suitable species of microalgae were identified: Chlorella vulgaris and Spirulina platensis.

The selection criteria were:

-growth and reproduction rate;

-performance;

- the content of protein, amino acids and vitamins;

- survival rate;

-relative simplicity and safety of cultivation.

Comparison:

Table 1. Comparison of microorganisms.

Chlorella vulgaris

Spirulina (Arthrospira) platensis

(Nordst.) Geitl.

Uniform distribution of cells in the medium

The absence in the structure of the cellulose cell wall characteristic of eukaryotic microalgae (in particular, Chlorella sp.) facilitates the digestion and assimilation of the biomass of these cyanobacteria

They are not demanding of carbon dioxide and nutrient medium

The medium should be highly alkaline

Does not require submission to the culture

carbon dioxide with the help of special technical means (it is enough to introduce a suspension saturated with carbon dioxide once a day)

It is important to stir spirulina from time to time (2-4 times a day)

No mechanical mixing of the suspension is required

Need the introduction of carbon dioxide

Contains all essential amino acids, surpasses

the nutritional value of soy protein is doubled

High survival rate in

conservation and reclamation

High calcium content (12 times more than in milk)

It is considered as producers of molecular hydrogen based on the bioconversion of solar energy, since hydrogen is a very promising and commercially available source of alternative energy

High reproduction rates (Every 12 hours, as a result of the rupture of the maternal shell, eight motorsports are born. Daughter cells instantly increase and repeat the process of division, which occurs indefinitely)

The growth rate of spirulina and its yield is 5-10 times higher than that of traditional crops; protein yield per unit area per unit time is ten times higher than that of soy (as an example of an organism producing a large amount of protein)

So, later, during the comparative analysis of microorganisms based on theoretical data, the choice was made in favor of chlorella.

This species is more optimal for cultivation in an oxygen photobioreactor for a number of reasons, namely:

• Undemanding strain in relation to the frequency of injection of a suspension saturated with carbon dioxide (once a day is enough), low demands in relation to the nutrient medium

• Uniform distribution of culture in the environment;

• There is no need for mechanical mixing of the suspension with the cultivated strain.

Nutrient medium and cultivation conditions:

In laboratory conditions, the strain is cultivated at a constant temperature of 36 ° C and an illumination intensity of 3 thousand lux, on a Tamiya nutrient medium, the sterilized solution of which can be stored in the refrigerator for up to 3 months.

Industrial production of microalgae biomass is carried out in liquid nutrient media.

Composition:

1)trace elements

H3BO3- 0.71 g.

MnCl2*4H2O-0.45 g.

ZnSO4*7 H2O -0.055 g.

MoO3- 4.41 mg.

NH4VO3-5.74 mg.

2) macronutrients

KNO3 (25% solution) - 20 ml

KN2PO4 (12.5% solution) - 10 ml

MgSO4 (12.2% solution) - 10 ml

FeSO4 x 7H2O (1% solution) - 1 drop

Sequence of actions:

1) Preparation of 2 mother liquor of trace elements (A and B):

To do this, weigh and then sequentially dissolve in 250 ml of distilled water 0.71 g H3BO3, 0.45 g MnCl2 x 4H2O, 0.055 g ZnSO4 x

7H2O - (solution A).

2) Weigh and sequentially dissolve 4.41 mg of MoO3, 5.74 mg of NH4VO3 - (solution B) in 250 ml of distilled water.

3) Prepare 1000 ml of tamiya medium by successively pouring the following volumes of masterbatch solutions into a 1 liter volumetric flask:

KNO3 (25% solution) - 20 ml

KN2PO4 (12.5% solution) - 10 ml

MgSO4 (12.2% solution) - 10 ml

FeSO4 x 7H2O (1% solution) - 1 drop

Solution A - 1 ml.

Solution B - 1 ml.

4) Bring the volume of the solution with distilled water to 1 liter.

5) Dilute the resulting concentrated tamiya medium 5 times: add 400 ml of distilled water to 100 ml of concentrated tamiya medium; or 800 ml of distilled water to 200 ml of tamiya medium, etc.

Seeding:

1) Sow the tamiya medium diluted 5 times with 5-10-day chlorella (up to light green staining; 200 thousand cells / ml).

2) Pour the prepared solutions of tamiya medium into flasks with a capacity of 1-2 liters. Ensure continuous air purging through the culture and a 12-hour lighting cycle with an intensity of 2000-3000 lux (temperature 18-20 ° C).

Recommendations for cooking:

1) The nutrient medium and salt solutions are prepared on distilled water and are not sterilized

2) To avoid the formation of sediment, the suspension of each substance is first dissolved in a small amount of water, and then the solutions are drained together in the above sequence and the water is topped up to the appropriate volume

3) Before the introduction of algae, the nutrient medium (100%) is diluted 2 times with distilled water (50%)

4) In the process of cultivation, the algae suspension is irradiated by the light of an incandescent lamp

5) Seeding of algae is carried out with an initial optical density of 0.020 ± 0.005. To do this, 15 ml of algae suspension filtered through 3-4 layers of gauze is introduced into 150 ml of 50% nutrient medium (Tamiya medium diluted with distilled water 2 times).

6) The crop is grown in a semi-stationary mode, which is achieved by daily sowing in a fresh environment. Such a cultivation regime allows maintaining a pure algae culture without observing the conditions of sterility

7) When preparing the nutrient medium, the sequence of reagents is observed.

8) After the introduction of each of them, the solution is thoroughly mixed

9) There should be no flakes, sediment or opalescence in the nutrient medium before adding a carbon dioxide solution

10) The introduced uterine culture of chlorella suspension is 20% of the volume of the container

Cooking technique:

Components of the medium (100% Tamiya medium, in g/l): KNO3 – 5.0 g/l;

MgSO4*7H2O – 2.5 g / l; iron citric acid – 0.003 g / l (dissolved by boiling); trace elements – 1.0 ml of solutions A and B.

Solutions A and B are prepared separately: solution A (H3VO3 – 2.86 g/ l;

MnCl2*4H2O – 1.81 g/l; ZnSO4*5H2O – 0.222 g/l), solution B (MoO3 – 17.64

mg/l; NH4VO3 – 22.96 mg /l, dissolve when heated).

The nutrient medium and solutions of all salts are prepared in distilled water. Then each solution is sterilized separately for 30 minutes. By boiling, cooled and tightly closed with a lapped stopper. Devices for growing algae culture in standard temperature and light conditions KV-03 47

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