DEVELOPMENT OF THE BIOTECHNOLOGY FOR OBTAINING A DIETARY SUPPLEMENT FROM THE SELENIUM-CONTAINING PROBIOTIC CULTURES LACTOBACILLUS ACIDOPHILUS 412/307 AND BIFIDOBACTERIUM BIFIDUM 1

The relevance of creating a new dietary supplement based on the selenium-containing cultures of lacto- and bifidobacteria was proven. We have chosen the optimal source of selenium – sodium selenite (Na 2 SeO 3 ), adding which to the cultivation medium of microorganisms ensures maximum accumulation of organic forms of selenium in the examined microorganisms. We have established the effect of concentrations of sodium selenite on an increase in the biomass of lacto- and bifidobacteria. Concentrations of Na 2 SeO 3 exceeding 8 µg/cm 3 cause the inhibition of growth in the lactobacilli biomass when compared with control. The growth of biomass of bifidobacteria is inhibited under the influence of the concentration of Na 2 SeO 3 above 5 µg/cm 3 . Applying the indicators of optical density, we determined values for a specific growth rate and the duration of generation of biomass of the examined microorganisms. The dynamics of selenium accumulation by the cultures Lactobacillus acidophilus 412/307 and Bifidobacterium bifidum I was studied. A direct dependence was established between the quantitative content of inorganic selenium in the environment of cultivation and the content of organic selenium in bacterial cells. Adding the concentration of sodium selenite equal to 0.5 µg/cm 3 provides for obtaining 105 µg of organic selenium per one gram of dry biomass of lactobacilli; this indicator for bifidobacteria is 97.5 µg/g. At a concentration of Na 2 SeO 3 equal to 20 µg/cm 3 , 4,698 µg of organic selenium is biotransformed in the biomass of lactobacilli and 3,149 µg –in the biomass of bifidobacteria. Based on the data derived, we have developed a technological scheme for obtaining the dietary supplement with the quantitative content of organic selenium at 202.5±1 µg/g. The content of lactobacilli was 1.0×10 9 CFU/cm 3 ; that of bifidobacteria – 1.2×10 8 CFU/cm 3


Introduction
At present, stresses, unsatisfactory conditions in the environment, disruption of nutrition lead to a decrease in the level of immune protection of people. This is the cause of chronic illnesses as it results in the deterioration of health and decreased labor performance [1].
Recent years have seen a wide popularity of the concept of functional food products, which implies development of theoretical provisions, as well as production, implementation, and consumption of functional foods. The concept of functional food first originated in Japan in the 80s of the twentieth century. The main components of functional products were determined to be nutritional value, pleasant taste, positive physiological effect.
Functional food products are intended for systematic use in the composition of food diet by all age groups of healthy people, which results in the improved state of health [2].
The products of functional purpose include those, which are obtained by increasing or decreasing the percentage of separate components of food: proteins, amino acids, lipids, vitamins, food fibers, micro-and macroelements, oligosaccharides, polyunsaturated fatty acids, alkaloids, isoprenes, cholines, probiotics, antioxidants [1,2].
One of the components, which can improve useful properties of functional foods is the microelement selenium. The priority pathways in which selenium is received by the human organism are alimentary -90 % with food, and 10 % − with water [3,4].
Selenium enters human body in organic form, with the products of plant and animal origin. However, an important problem, in Ukraine and other countries of the world, is the insufficient amount of the microelement selenium that the human body received from food products. The reason may be the use of synthetic fertilizers, unsatisfactory environmental situation, which leads to the acidification of soils and their contamination with industrial waste. As a result, the process of inorganic selenium accumulation by plants becomes more difficult. In the products of plant and animal origin selenium is in the form of selenomethionine and selenocysteine.
When penetrating the human body, the organic forms of selenium are built into proteins replacing methionine and cysteine and performing their functions. Selenium ions activate the redox enzymes glutathione peroxidase, glutathione reductase, cytochromes, participate in moving the electrons from hemoglobin to oxygen, and support the exchange of cysteine [4]. More than half of the total content of selenium in the body is in the form of selenoproteins. Antiviral, anti-apoptotic, antioxidant functions of selenium are associated with the expression of selenium-dependent enzymes. Selenomethionine, selenocysteine are non-toxic and can be consumed at higher-than-daily dosage of the microelement.
Insufficient selenium intake by the human body may cause reduced immune protection level, weakness, skin diseases, ischemic heart disease, hypertension, arrested mental and physical development [5].
Creating food products enriched with organic forms of selenium, as well as dietary supplements based on it, is an important task. The use of such products makes up for the insufficient intake of selenium into the body.

Literature review and problem statement
At present, we can distinguish the following groups of functional products in Ukraine: breakfast cereals, dairy products, margarines and soft drinks, specialized foods. One of the important groups of functional foods are products with probiotic properties [2]. Probiotics are important components of the new products of functional purpose and dietary supplements [5].
Among the microorganisms with high probiotic properties most widely used in the food industry are representatives of the genera Lactobacillus, Bifidobacterium, Propionibacterium, Streptococcus. Specifically, the consortium of the genera Lactobacillus acidophillus DSM 20079 and DSM 20242, Bifidobacterium bifidum DSM 20082, DSM 20215, DSM 20239 and DSM 20456 with the addition of prebiotics serves as a component of dietary supplements [6].
Selenium-containing preparations, being developed now, can be used as dietary supplements, or as basic components to create products of functional purpose. One of such products is the preparation "Selenopropioniks" based on the selenium-containing culture of propionic acid bacteria Propionibacterium freudenreichii subsp. shermanii КМ 186. There are also preparations based on selenium-enriched yeast, in particular, Saccharomyces cerevisiae NCYC 1026, or the beer yeast of strain 8 AM (S.S. Chervona). Yeast have proven to be active accumulators of selenium, due to their high content of protein [7,8]. The dietary supplements were developed based on SeMet − selenium-containing amino acid. A positive effect of SeMet on the health of laboratory animals, including mice, was reported [9]. Adding selenomethionine to the diet of mice enabled the activation of the immune system by increasing the activity of natural killers and phagocytic activity of macrophages [9].
Creation of selenium-containing dietary supplements with improved functional properties is an important task. In our work, it implies the enrichment of symbiotic culture of probiotics with selenium.
The mechanism of probiotic action involves a probiotic dose of microorganisms finding its way to colon, after passing through the stomach and duodenum. In the parts of the colon the microorganisms-probiotics are attached to epithelial cells -the cells that line the inner surface of the intestine [10][11][12]. Probiotics feed on nutrients that are found in the large intestine and reproduce there. In the course of their life activity, they produce organic acids that stimulate the work of intestines and antagonistic effect relative to the pathogenic and conditionally pathogenic microorganisms [13]. Microorganisms synthesize vitamins of groups B and K, antibiotic-like substances [14]. They participating in the development of immunoglobulins of groups A1 and A2 and stimulate the phagocytic activity [15][16][17].
It is known that probiotics are capable of accumulating and biotransforming the inorganic forms of selenium (selenites, selenates) into organic (selenomethionine, selenocysteine) [18]. Characteristic of the organic forms of selenium obtained with the participation of different types of microorganisms is given in Table 1. Selenium, which is present as SeCys, SeMet in selenoproteins, is the protector against a number of diseases, including cancer, tiroidyn-dependent diseases, inhibits the development of pathogenic microorganisms, exhibits high antioxidant property. In medicine, organic selenium demonstrates high biological activity and low toxicity [19]. The daily need for organic selenium is, on average, 80-200 µg, in contrast to its inorganic forms, the daily need in which is 70-90 µg [20][21][22].
The process of transformation of inorganic forms of selenium by microorganisms is shown in Fig. 1.
Synthesis of selenocysteine is performed on specialized tRNA, which also include it in the growing peptide chain. The primary and secondary structure of selenocysteine-specific tRNA, tRNASec, differ from those in the standard tRNA in several aspects. Thus, the acceptor region contains 8 pairs of bases in bacteria, and 10 − in eukaryotic cells, and a longer T-loop [23,24]; in addition, tRNASec is characterized by the replacement of several rather conservative base pairs. First, tRNASec binds to serine using the enzyme of seril-tRNA ligase, however, the formed complex of Ser-tRNASec does not come into translation because it is not recognized by normal translational factors (EF-Tu in bacteria; and eEF1A in eukaryotic cells) [25,26]. The residue of serine, bound by tRNA, converts into the residue of selenocysteine by the enzyme selenocysteine synthetase.
In this case, there forms a complex of Sec-tRNASec, which specifically binds to the alternative translational factor (SelB or mSelB (or eEFSec), which delivers it directly to the ribosome, translates mRNA for selenoprotein. The specificity of this transport is predetermined by the presence of an additional protein domain (in bacteria, SelB), or an additional sub-unit (SBP2 for eukaryotic mSelB/ eEFSec), which binds with the appropriate element of the secondary structure of mRNA, formed by the element SE-CIS emerges (Kurek E. et al.) [27].
Following the biotransformation in the bacterial cell, about 32 % of selenium are found in the membranes, 22 % are part of the cell wall, 52 % are included in the composition of amino acids and soluble proteins of protoplasm. 72 % of them are in the fraction of proteins and amino acids, 1 % is bound with lipids, and 27 % of selenium are in non-organic form [28].
Owing to their properties, probiotics are capable of improving the state of human health and serve as a cheap source of the organic forms of selenium. Microorganisms are the original biomatrices for organic selenium [25][26][27]. The method of obtaining organic forms of selenium from inorganic sources, using microorganisms, is energy-efficient and environmentally safe. Therefore, we consider research aimed at the creation of the biotechnology for obtaining the selenium-containing dietary supplement based on the symbiotic culture of probiotic microorganisms to be promising. In this case, it is advisable to choose, as the microorganisms to be studied, the cultures of lacto-and bifidobacteria with high probiotic properties, specifically Lactobacillus acidophilus 412/307 and Bifidobacterium bifidum I. This can be justified by the fact that the lacto-and bifidobacteria are normal inhabitants of the gastrointestinal tract. Bifidobacteria are one of the first microorganisms that penetrate the body of the newborn with mother's milk. They are the first to colonize the gastrointestinal tract, preventing the development of pathogenic and conditionally pathogenic microorganisms. Lactobacilli are characterized by acid resistance that helps them withstand conditions of passing the gastrointestinal tract. Data from the scientific literature indicate bacterial synergy between lacto-and bifidobacteria, which manifests itself in the improved capability for adhesion to GIT. In addition, the joint cultivation of lacto-and bifidobacteria creates favorable conditions for the accumulation of bifidobacteria, by bringing down the redox potential to the values required for their development.
Malnutrition, reduced level of immune protection cause disruption of the microbial balance of the intestine. This may be the reason for lowering the quantitative content of lactoand bifidobacteria in it. That is why one of the tasks of present research was the development of a dietary supplement from selenium-containing probiotics [5]. Useful action of the developed dietary supplement (DS) is based on a double positive effect exerted on the human body by the metabolites of microorganisms-probiotics and the organic form of selenium. Consuming the developed DS makes it possible to improve the levels of the body's immune protection, as well as the antioxidant protection of body cells, to remove the ions of heavy metals, all of which, taken together, provides a better state of health.

The aim and objectives of the study
The aim of present study was to develop a biotechnology of selenium-containing probiotics and a dietary supplement. Adding to the diet of the dietary supplement with a strictly controlled quantitative content of selenium in it would make it possible to compensate for the daily need of the microelement. To accomplish the aim, the following tasks have been set: -to select the preparations of inorganic selenium; -to explore kinetic parameters of the growth of microorganisms and the accumulation of organic form of selenium by the microorganisms-probiotics; -to devise a technological scheme for obtaining selenium-containing probiotics; -to examine basic microbiological and physical-chemical indicators of the resulting product.

Materials and equipment used in the experiment
We studied the following objects: the probiotic culture Lactobacillus acdophilus strain 412/307 borrowed from the Museum of the Department of Biochemistry, Microbiology and Physiology of Nutrition at ONAKhT (Ukraine), and Bifidobacterium bifidum Ithe preparation "Bifidumbacterin", manufactured by company Biopharma. We used sodium selenite Na 2 SeO 3 (TOV NVP Hemel, hch) as a source of selenium. The environment for the cultivation of lactobacilli was chosen to be MRS broth (proteosopepton; meat extract; glucose; yeast extract; Twin-80; sodium acetate; ammonium citrate) and the environment based on cheese whey (cheese whey, milk, sodium acetate; magnesium sulfate; corn extract). For the cultivation of bifidobacteria we have chosen corn-lactose medium (lactose; peptone; sodium citrate; potassium; sodium phosphate; ascorbic acid; corn extract; water).
The examined materials and equipment used in the experiment, the procedure for determining the indicators of the properties of samples are described in detail in paper [29].

Results of research into development of a seleniumcontaining dietary supplement
The initial stage of research implied finding a source of selenium adding which to the cultivation medium of microorganisms would determine its maximum biological availability for the microorganisms. The examples of existing sources of the inorganic forms of selenium, which can be used as a source for their accumulation by microorganisms, are: sodium selenite -Na 2 SeO 3 , selenic acid -H 2 SeO 4 , sodium selenite − Na 2 SeO 4 . We added to the cultivation media of microorganisms the sources of inorganic selenium in the amount of 5 µg/cm 3 . The dynamics of accumulation of the organic forms of selenium is shown in Fig. 2.
It was established that sodium selenite is better accumulated both by the culture Lactobacillus acdophilus strain 412/307 and the culture Bifidobacterium bifidum I.
Sodium selenite was subsequently used in the research and introduced it in the amount from 0.5 µg/cm 3 to 20 µg/cm 3 . The environment without added sodium selenite served as control.
Changes in the indicators of optical density in the process of cultivation of lactobacilli were determined at all stages of cultivation, Fig. 3. We found the relationship between the concentration of Na 2 SeO 3 and the accumulation intensity of microorganism biomass. Thus, at the concentrations of Na 2 SeO 3 equal to 0.5−5 µg/cm 3 the indicators of OD were not essentially different from control. An increase in the concentration of Na 2 SeO 3 to 8−20 µg/cm 3 led to a slowdown in the dynamics of accumulation of lactobacilli biomass compared with control.
The content of selenium in the cells of microorganisms directly depends on its concentration in the environment of cultivation. This is due to the lack of a mechanism that would limit its intake. Constant delivery of selenium to cells leads to its maximal accumulation in the organic form and in the form of nanostructures Se 0 . Part of the zero-valent selenium enters the cultivation environment providing for its pink coloration.
Increasing the concentration of selenium causes the acidification of pH of cytoplasm, reduces the protein content in the biomass and increases the concentration of carbohydrates and lipids, which, taken together, causes the stressed state of the cell. The consequences are the disruption of biochemical processes in the cell, which can lead to apoptosis. Indicators of specific growth rate and duration of generation in the process of cultivation of lactobacilli in MRS medium were determined based on the indicators of optical density, Table 2.
It was established that an increase in the concentration of sodium selenite in the environment of cultivation to 8−20 µg/cm 3 leads to a gradual delay in the indicators of specific growth rate and to the increase in the indicators of generation period. Indicators of optical density obtained in the process of cultivation of bifidobacteria in corn-lactose environment with sodium selenite are shown in Fig. 4. Indicators of specific growth rate and duration of bifidobacteria generation are given in Table 3.
We established the relationship between indicators of SGR and DG and the concentration of sodium selenite in the environment of cultivation. Thus, growing concentrations of Na 2 SeO 3 cause a delay in SGR and an increase in the DG values, which, accordingly, affects the yield of selenium-containing biomass.
During cultivation process of the biomass of lacto-and bifidobacteria we determined a change in the indicators of colony-forming units (CFU/cm 3 ) over time. A change in the indicators of CFU/cm 3 of the culture Lactobacillus acdophilus over time is shown in Fig. 5.
It was established that an increase in the concentrations of sodium selenite in the environment of cultivation to 8−20 µg/cm 3 leads to a decrease in the dynamics of accumulation of the selenium-containing culture of lactobacilli.
A change in the indicators of CFU/cm 3 of the culture Bifidobacterium bifidum over time is shown in Fig. 6.
It was established that the concentrations of sodium selenite in the range of 5−20 µg/cm 3 lead to the gradual suppression of the accumulation of biomass of the examined culture of lactobacilli.
Quantitative content of the selenium accumulated by the examined probiotic microorganisms is given in Table 4. Table 3 Indicators of specific growth rate and duration of generation The initial factor that characterizes the intensity of biomass accumulation by selenium was the indicators of intensity of luminescence of the examined samples. This phenomenon can be explained by the lack of a mechanism for regulating the level of intake of selenium into the bacterial cell. In this case, the amount of accumulated selenium is directly proportional to the amount of selenium introduced to the environment for the cultivation of microorganisms.
The data obtained allowed us to characterize the relationship between the quantitative content of organic sele-nium in the examined cultures of lacto-and bifidobacteria, the duration of cultivation, and the content of inorganic selenium in the cultivation environments. The obtained dependences for the cultivation of lacto-and bifidobacteria are shown in Fig. 7, 8.
where a, b, c, d, e, f, g, h are the numerical constants. These equations are continuous and differentiated over the entire period of change in parameters. That is why it is possible to find the values for parameters of the concentration and duration of cultivation of microorganisms that would provide for the largest production of organic selenium employing classic methods of optimization.
For lactobacilli, maximum accumulation of organic selenium in the biomass occurs in 25 hours at the concentration of sodium selenite in the environment of cultivation of 16 µg/cm 3 . For bifidobacteria, respectively, in 26 hours at the concentration of sodium selenite of 12 µg/cm 3 .
When creating a selenium-containing dietary supplement, it is important to take into consideration the quantitative content of organic selenium in the resulting product. The daily need for a given microelement is 70− 90 µg for women and men, respectively. It is known that the organic forms of selenium are much safer for the human body compared to the inorganic forms. That is why it is allowed to consume this form of selenium in the amount of up to 200 µg per day.
The next stage of the research involved creation of the dietary supplement "Selenobifilact", based on the symbiotic selenium-containing culture of microorganisms with probiotic properties. Characteristic of the resulting product is given in Table 5. Using a fluorometric method for studying the quantitative con-tent of organic selenium in the examined biomasses of microorganisms, it was established that adding even 1 µg/cm 3 of the inorganic form of selenium provides the resulting product with the content of organic selenium equal to 200 µg/g of dry biomass.
Technological scheme for obtaining the dietary supplement "Selenobifilact" is shown in Fig. 9.
Presented scheme describes the technology of obtaining the biologically active additive "Selenobifilact" based on the symbiotic selenium-containing culture Lactobacillus acidophillus 412/307 and Bifidobacterium bifidum I. Table 5 Physical-chemical parameters of the preparation "Selenobifilact"

Indicator Characteristic
Physical appearance Powder with crystalline or porous mass

Taste and flavor Specific
Color Beige Quantitative content of selenium, µg/g 202.5±1 Fig. 8. Dependence of mass of accumulated selenium (MSe) on the cultivation duration (t) and the concentration of inorganic selenium (Xse) for the culture of bifidobacteria Fig. 9. Technological scheme for obtaining the preparation " Selenobifilact"

Discussion of results of obtaining a seleniumcontaining dietary supplement
The first stage of research involved choosing the optimal source of inorganic selenium, adding which to the environment of cultivation of microorganisms would enable its active biotransformation by microorganisms into organic form. The examples of such inorganic forms of selenium were Na 2 SeO 3 -sodium selenite, H 2 SeO 4 -selenic acid, Na 2 SeO 4 -sodium selenate.
Inorganic forms of selenium were introduced to the environment of cultivation of microorganisms in the amount of 5 µg/cm 3 . It was established that the culture of lacto-and bifidobacteria are most active when biotransforming sodium selenite into organic form. By using the fluorometric method, it was established that the quantitative content of organic selenium in the culture Lactobacillus acidophilus was 370 µg/g, Bifidobacterium bifidum -355 µg/g.
To test the impact of increasing concentrations of sodium selenite on the dynamics of biomass accumulation of lactoand bifidobacteria, it was added to the cultivation medium of microorganisms in the amount from 0.5 to 20 µg/cm 3 .
Indicators of optical density (OD) make it possible to register a change in the amount of biomass of the examined microorganisms over the duration of cultivation. Samples in the amount of 5 cm 3 were taken to cuvettes at a distance of 1 cm 3 , every two hours. It was registered that the sodium selenite concentrations in the amount of 0.5−5 µg/cm 3 had not a significant impact on the process of biomass accumulation of microorganisms (the indicators derived were close to control). Increasing concentrations of Na 2 SeO 3 (8−20 µg/cm 3 ) caused a gradual slowdown in the process of accumulation of biomass of lactobacilli, at all stages of cultivation. The concentrations of Na 2 SeO 3 at the level of 0.5−3 µg/cm 3 did not exert any inhibiting effect on the dynamics of accumulation of bifidobacteria biomass. However, the concentrations of sodium selenite at the level of 5−20 µg/cm 3 did lead to inhibiting the process of accumulation of bifidobacteria biomass. The lowest indicators for OD were recorded in the sample containing sodium selenite in the amount of 20 µg/cm 3 (both in the cultures of lactobacilli and bifidobacteria).
Value of the indicators of specific growth rate (SGR) and duration of generation (DG) characterized the rate of accumulation of the examined biomass of microorganisms. It was established that at all stages of cultivation the concentrations of Na 2 SeO 3 in the amount of 8−20 µg/cm 3 led to a delay in SGR and increased DG of lactobacilli culture, while the concentrations of Na 2 SeO 3 from 5 to 20 µg/cm 3 resulted in a delay of SGR and an increase in DG of bifidobacteria culture.
In parallel with the indicators of OD, DG, and SGR we determined the number of colony-forming units of lacto-and bifidobacteria per 1 cm 3 of the cultivation medium. Indicators for CFU/cm 3 make it possible to register the number of live microorganisms in a culture. It was established that over the first 4 hours there occurred the adaptation of lacto-and bifidobacteria to the cultivation medium. From hour 5 to hour 15 hour, we observed a phase of exponential growth of microorganisms, which was characterized by the rapid accumulation of biomass of selenium-containing microorganisms. The phase of exponential growth was gradually replaced with the stationary phase. The indicators of CFU/cm 3 made it possible to register the process of suppressing the growth of biomass of lactobacilli in the samples with the concentration of sodium selenite of 8−20 µg/cm 3 and 5−20 µg/cm 3 . By using the fluorometric method, we established the relationship between the amount of sodium selenite in the cultivation medium and the number of biotransformed organic selenium in microorganisms. The resulting selenium-containing culture of lacto-and bifidobacteria was separated from cultivation environments (which contained part of undiluted selenium) using the centrifugation method (10 minutes at 10,000 rpm). The resulting selenium-containing biomass was washed with sterilized water from the remnants of undiluted selenium. Next, the biomass was added with a cryoprotective environment (milk, gelatin, sucrose) in the ratio of 1:1, and then it was lyophilically dried. Next, we selected 0.1 g of dry selenium-containing preparation and determined the amount of accumulated selenium. Using indicators of the intensity of luminescence, we determined the content of organic selenium in the dry biomass of lacto-and bifidobacteria. It was established that increasing concentrations of sodium selenite in environments cultivation led to an increase in the amount of organic selenium in microorganisms. Thus, maximum indicators of the quantitative content of organic selenium in the culture of lactobacilli at the level of 4,698 µg/g were registered in the sample containing sodium selenite in the amount of 20 µg/cm 3 . The maximum amount of organic selenium for bifidobacteria reached 3,149 µg/g in the sample containing Na 2 SeO 3 in the amount of 20 µg/cm 3 .
We have created a selenite-containing dietary supplement based on the symbiotic selenium-containing culture of lacto-and bifidobacteria "Selenobifilact". For this purpose, we introduced to the sterile corn-lactose environment a 0.1-% solution of sodium selenite in the amount of 1 µg/cm 3 . As a growth stimulant for the culture of bifidobacteria we used fructose (which was introduced in the amount of 1 %). The inoculum of 1-day culture of bifidobacteria was introduced in the amount of 5 %. The cultivation lasted for 15 hours, at 37 °C. Next, we added an environment for the cultivation of lactobacilli in the ratio of 1:1, and introduced inoculum of the 1-day culture of lactobacilli (in the amount of 5 %). The cultivation was carried out at 37 °C. Obtained selenium-containing symbiotic biomass of microorganisms was separated from the cultivation environment using the centrifugation method (10 minutes at 10,000 rpm). The biomass was washed with sterilized water in order to remove the undiluted selenium. Next, we added a cryoprotective environment and lyophilically dried it.
Selenium-containing preparations based on live lacto-and bifidobacteria enriched with selenium could be used in liquid forms and capsules, liquid preparations, yogurts enriched with selenium-containing preparations, suspensions, tablets.
The amount of organic selenium in received DS was 202,5±1 µg/g. The quantitative content of lactobacilli in it was 1.0×10 9 CFU/cm 3 ; and the number of bifidobacteria was 1.2×10 8 CFU/cm 3 .
We have developed a new technology for producing organic bioselenium in the composition of probiotic cultures, which makes it possible to obtain dry and liquid forms of the finished product.
The developed preparation "Selenobifilact" could be used as a dietary food supplement. "Selenobifilact" contains a probiotic dose of the viable cells Lactobacillus acidophillus 412/307 and Bifidobacterium bifidum I that can colonize the intestine and restore its normal microbiota. Probiotic microorganisms in the process of their metabolisms synthesize lactic, acetic, propionic, butyric, capric acids providing for the antagonistic activity against pathogenic and conditionally pathogenic micro-organisms. Probiotics synthesize lysozyme, hydrogen peroxide, enabling the antimicrobial activity, as well as produce vitamins of groups B and K. DS contains the organic form of selenium, which makes up for the lack of selenium in the human body and ensures antioxidant, antimutagenic, anticarcinogenic effect.
We have conducted pilot medical-biological testing on outbred white mice. The selenium-containing preparation was introduced to the daily diet in the amount equal to 5 µg per day per one mouse. We found in the process of examination that the experimental group of mice, similar to control group, the wool cover of animals was dry, glossy, visible mucous is pale pink. We did not reveal in the course of the experiment any statistically significant changes in the body mass of mice from the examined group compared with control. Every 10 days, we took the samples of faeces from the examined animals. The quantitative content of lacto-and bifidobacteria was then determined. In the course of the experiment we noted a growth of the content of lacto-and bifidobacteria. We observed a growth of the content of lactobacilli by 1.5 orders of magnitude at the end of the experiments, in comparison with control group. The number of bifidobacteria increased by 2 orders of magnitude.
The result of present research is the developed biotechnology for obtaining the selenium-containing functional ingredientthe dietary supplement, which is a new generation of probiotics with enhanced antioxidant, antimutagenic, anti-cancer effect due to selenomethionine and selenocysteine biotransformed by microorganisms. In other words, the preparation "Selenobifilact" has a dual biological action, as a probiotic and a source of organic selenium.
We consider the shortcoming of present study the insufficient medical-biological research, planned to be undertaken during further experiments.
In the future, the technology for obtaining a dietary supplement will require additional production-technical research into designing and development of the technological scheme of the process in order to improve parameters of the technology.

We have chosen preparations of inorganic selenium.
In the process of adding the sources of inorganic selenium to the cultivation media of the examined microorganisms, it was determined that sodium selenite (Na 2 SeO 3 ) performs best in terms of accumulation and biotransformation. Adding Na 2 SeO 3 to the cultivation environments of lacto-and bifidobacteria ensured the resulting content of organic selenium in the biomass of lactobacilli in the amount of 370 µg, and in the biomass of bifidobacteria -355 µg. In the subsequent work, we used sodium selenite as a source of inorganic selenium.
2. We have studied kinetic indicators of the growth of microorganisms and the accumulation of organic forms of selenium by microorganisms-probiotics. The indicators that characterize a growth of the biomass are the indicators of optical density, specific growth rate, duration of generation, colony-creating units. It was established that the concentrations of Na 2 SeO 3 in the amount of 0.5−5 µg/cm 3 do not inhibit the accumulation process of lactobacilli biomass. Such concentrations for bifidobacteria are 0.5-3 µg/cm 3 . It was established that an increase in the concentrations of Na 2 SeO 3 in the cultivation environment causes an increase in the content of organic selenium in the derived biomasses of microorganisms. Thus, at a concentration of Na 2 SeO 3 equal to 0.5 µg/cm 3 , the amount of organic selenium in the biomass of lactobacilli was 105 µg/g of dry biomass, for bifidobacteria -97.5 µg/g. At a concentration of Na 2 SeO 3 equal to 20 µg/cm 3 , the quantitative content of organic selenium in the biomass of lactobacilli was 4,698 µg per 1 gram of dry biomass; for bifidobacteria -3,149 µg/g.
3. Based on the results obtained, we devised a technological scheme for obtaining the dietary supplement "Selenobifilact", based on the selenium-containing symbiotic culture Lactobacillus acidophilus and Bifidobacterium bifidum whose special feature is obtaining a comprehensive dietary supplement, which combines the probiotic and antioxidant properties. 4. We have investigated the microbiological and physical-chemical indicators of the obtained preparation. The quantitative content of lactobacilli in the preparation "Selenobifilact" was 1.0×10 9 CFU/cm 3 , that of bifidobacteria -1.2×10 8 CFU/cm 3 . The content of organic selenium was equal to 202.5±1 µg/g.