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65DOI: https://doi.org/10.21323/2414-438X-2021-6-3-259-268 ©commons
Available online at https://www.meatjournal.ru/jour
Review article
AN EFFECT OF FOOD ADDITIVES Received 2.05.2021
Accepted in revised 14.09.2021
ON MICROBIOME Accepted for publication 25.09.2021
Vladimir Yu. Kornienko*, Mihail Yu. Minaev
V. M. Gorbatov Federal Research Center for Food Systems of Russian Academy of Sciences, Moscow, Russia
Keywords: food additives, sweeteners, microbiome, microbiota Abstract
The paper presents a review of available data about an effect of food additives on the human microbiome and lists the main physiological functions of the gut microbiome. The process of the human microbiome evolution is examined. The relationship between the emergence of a disease and the microbiome composition, as well as the main factors influencing the gut microbiome composition are described. The main food additives used today are listed, their key features are discussed and their structural formulas are given. The information about their effect on the human body through an influence on the microbiome composition is presented. The data on an effect of polysorbate 80, carboxymethylcellulose, sodium sulfite, nisin, potassium sorbate, sodium benzoate, sodium nitrate, essential oils, titanium dioxide and different sweeteners on the microbiome are analyzed. It is explained what microbial communities are suppressed and what communities gain advantages in multiplication when consumers eat food with one or another food additive. The consequences of alterations in the microbiome for the consumer's body are examined. Conclusions were made about the necessity of additional studies about an effect of food additives on the composition of the human microbiome.
Acknowledgements:
The authors thank Dmitry Shintyakov for the presented photo of the saccharine crystal.
tobacillus, Streptococcus, Bacteroides and Escherichia [11]. It is believed that the diet that includes increased consumption of legumes, cereals, fruit and vegetables is beneficial for the consumer's body [12,13]. There is a trend towards an increasing presence of artificial sweeteners in our diet [14]. Nowadays, an effect of food additives on the consumer's body has been comprehensively studied. However, food additives can also affect the body indirectly by influencing the gut microbiome [4,15]. Experiments on animals show that food additives can have an adverse effect on the colon and cardiovascular system [1]. It was demonstrated that food emulsifiers such as polysorbates and carboxymeth-ylcellulose can increase the intestine permeability, alter the microbiota composition, and facilitate penetration of Escherichia coli through epithelium [16].
In the Russian Federation, the use of food additives is regulated by Federal Laws № 29-FZ1, № 52-FZ2 and Technical Regulations of the Customs Union TR CU029/2012 "On the safety for food additives, flavorings and technological aids"3. The list of food additives permitted in Russia is approved by the Ministry of Health of the Russian Federation and the state control of their quality is performed by the Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing (Rospotrebnadzor).
1 Federal Law No. 29-FZ on food quality and food safety. (In Russian)
2 Federal Law No. 52-FZ on sanitary and epidemiological well-being of the population. (In Russian)
3 TR CU029/2012 Technical Regulations of the Customs Union "On the safety for food additives, flavorings and technological aids" Retrieved from https://docs.cntd.ru/document/902359401. Accessed April 15, 2021. (In Russian)
FOR CITATION: Kornienko, V. Yu., Minaev, M. Yu. (2021). An effect of food additives on microbiome. Theory and practice of meat processing, 6(3),
259-268. https://doi.org/10.21323/2414-438X-2021-6-3-259-268
Introduction
A type and diversity of consumed food significantly affect the human microbiome composition. Changes in the food composition can lead to alterations in the metabolic pathways and immune processes in the consumer's body [1]. The human gastrointestinal tract is inhabited by various symbiotic microorganisms. They colonize mainly the colon; with that, a ratio of the microbiome cells to cells of the host organism is 1:1 [2]. It is believed that microbiota is in the mutually beneficial relationships with its host taking part in various metabolic and immune processes [3]. The complex microbial ecosystem is closely linked with the host health [3,4]. Alterations in the gut microbiome composition can be associated with metabolic disorders, inflammation and even with neurological diseases [5,6]. The microbiome composition alters along the gastrointestinal tract forming specific regional communities [7]. It is agreed today that the microbiome composition includes, at least, 1000 species [8]. With that, Firmicutes and Bac-teroidetes are two predominant phyla representing Grampositive and Gram-negative bacteria colonizing the mammalian gastrointestinal tract. They account for 90% of total bacterial counts in the intestine [9]. A ratio between the number of members of these two phyla can vary depending on the individual peculiarities of the host organism, but total proportions are similar in the majority of people [10]. Among other members, the human microbiome also includes Fusobacteria, Verrucomicrobia, Actinobacteria, Proteobacteria and several species of archaea [9]. Moreover, researchers emphasize the importance of the presence of Bifidobacterium, Clostridium, Ruminococcus, Lac-
The available data on artificial sweeteners show disorders of the metabolic processes in rodents due to the disturbance in the microflora balance [17,18]. Therefore, it is important to study an effect of food additives on the gut microbiota composition [19]. Nowadays, there is limited knowledge about an effect of food additives on the human gut microbiota as available studies were carried out mainly on animal models [20].
Interrelation between the gut microbiome
composition and diseases
Disturbance of the balance in the gut microbiome composition is closely linked with the development of many human diseases, such as obesity, diabetes, cardiovascular and inflammatory pathologies [5]. It was shown that an increase in the number of Streptococcus and Enterobacteriaceae in the intestine is typical for the atherosclerotic cardiovascular diseases [21]. Also, the number of Faecalibacterium prausnitzii and Lactobacillus in patients with type 2 diabetes mellitus was significantly lower than in healthy individuals. The number of Bifido-bacterium was significantly higher than in healthy individuals [22]. Probably, imbalance of the gut microbiota composition influences the cancer development [1]. For example, the increased number of Bacteroides massilien-sis was observed in patients with prostate cancer, while the number of Eubacterium rectale and Faecalibacterium prausnitzii was lowered [23].
Metabolites of bacteria from the gut microbiome can be associated with human diseases. For example, arginine can be transformed into glutamate and then deaminated to gamma-aminobutyric acid, which as a neurotransmit-ter. Alterations in the expression of receptors of this neu-rotransmitter are linked to the development of anxiety and depression [24]. Another example is lysine, which can be metabolized with the formation of cadaverine, which increased level can be associated with ulcerative colitis [25,26]. However, it is necessary to note that in several cases, the above mentioned pathological mechanisms are a consequence of metabolic disorders.
Physiological functions of the gut microbiome
and its effect on the human health
The gut microbiome affects the physiological processes in the human body mainly through microbial metabolism. Microorganisms in the gastrointestinal tract can break down complex carbohydrates, proteins and some fats [1]. They are also capable of producing various enzymes that take part in metabolism [27]. The microbiome produces many metabolites that can enter blood and act throughout the whole body. Short-chain fatty acids, alcohols, ammonia, fatty acids, amines, sulfur compounds, phenols, indoles, glycerol derivatives, carbon dioxide and hydrogen are among such metabolites [1,27]. For example, the physiological functions of short-chain fatty acids are extremely important as they affect functioning of the epithelial cells
of the colon [28]. Also, microorganisms take part in ca-tabolism of amino acids and lipids [1].
In addition to the influence on metabolism, the gut microbiome is also important for formation of the human immunity, especially for the development and regulation of the immune system as the body develops [3,4]. The gut microbiome interacts with the immune system sending "signals" that facilitate the differentiation of the immune cells and immunity development. Moreover, it influences the antibody production, T-cell differentiation and enhancement of the phagocytic function of macrophages [29]. The gut microbiome also facilitates maintenance of the integrity of the intestinal epithelial cells [1,30].
Thus, the gut microbiome contains a large diversity of different bacterial genomes and can produce a wide range of metabolites. These metabolites and components of bacterial cells are important for the host organism as they are associated with the physiological development and maintenance of the innate and adaptive immunity.
Factors influencing the gut microbiome
composition
The diversity of the human gut microbiome is influenced by various factors such as intake of antibiotics, age, stress and climatic conditions [23]. Factors are divided into dietary and non-dietary [1]. As for non-dietary factors, age is one of the factors affecting the gut microbiota composition. For example, Clostridium and Bacteroides dominate in the gastrointestinal tract of elderly people, while the number of Bifidobacteria is reduced [31]. An effect of dietary factors on the microbiota has been widely studied [1-10]. It is shown that a diet rich in simple carbohydrates leads to multiplication of Proteobacteria and Firmicutes, while a diet rich in fats leads to a decrease in the intestinal microbial diversity. Food rich in animal protein and saturated fats promotes the development of Actinobacteria and Bacteroidetes in the intestine [32,33].
Therefore, changes in nutrition affect the gut microbi-ome diversity.
Evolution of the human gut microbiome
During the whole human life, the human gut mirobi-ome demonstrates continuous dynamic changes that are manifested in constant evolution and adaptation [34]. In the first month after birth, the gut microbiome diversity in infants is very low. By the sixth month, the composition and number of cells of the gut microbiota significantly increase due to an increase in the variety of consumed food [31]. With the cessation of breastfeeding, the nutrition structure changes and consumption of carbohydrates by microorganisms increases. More short-chain fatty acids and vitamins metabolized by microorganisms appear in food [34]. In the course of time, the gut microbiome dominated by Bifidobacteria in infants transforms into the gut microbiome of adults with domination of Firmicutes and Bacteroides [35]. At the age of 2.5-3 years, rapid increase
in the bacterial diversity is significantly retarded and the gut microbiome composition gradually achieves the adult condition by the age of 7-12 years [34].
Acesulfame potassium
Acesulfame potassium is also known as acesulfame (E950). It is an acidic cyclic sulfonamide derivative, which is 200 times sweeter than sucrose (Figure 1). The acceptable daily intake of acesulfame is 15 mg/kg body weight/ day; 95% of this amount is fully excreted in urine after passing through the human digestive system [36]. A study of an effect of acesulfame potassium on the gut micro-biota composition in mice showed that disorders of the metabolic pathways and intestinal microflora occurred after four weeks of its consumption. These disorders significantly differed depending on a gender. In male mice, the body weight significantly increased, the expression of the functional bacterial genes related to the carbohydrate and energy metabolism enhanced. In female mice, the body weight did not change significantly but several bacterial metabolites such as 2-oleoylglycerol, succinic acid and D-lactic acid were reduced. Moreover, the abundance of Oxalobacteraceae, Clostridium, Lactobacillus and Rumino-coccaceae decreased, while the abundance of Mucispirillum increased [37].
Figure 1. Structural formula of acesulfame potassium (a) and aspartame (b)
However, another study showed that acesulfame at doses equivalent to the human acceptable daily intake (ADI) did not significantly change the gut microbiome composition in mice. The abundance of Clostridium IV, Clostridium IVXa, Bacteroides and Firmicutes was the same in the experimental and control groups. [38]. Frankenfeld et al. [39] studied an effect of acesulfame potassium on the human gut flora. As a result, no significant differences were revealed between medians characterizing the number of bacteria in consumers and non-consumers of acesulfame. The ratio of Bacteroidetes to Firmicutes was also the same [1,39].
Aspartame
Aspartame (L-a-Aspartyl-L-phenylalanine methyl ester, E951) is 180 to 200 times sweeter than sucrose. Its acceptable daily intake (ADI) is 40 mg/kg body weight. The most part of aspartame is fully hydrolyzed in the intestine with formation of phenylalanine, methanol and aspartic acid [40]. Although many studies on aspartame safety for humans were carried out, little attention was given to an
effect of aspartame intake on the human gut microbiome composition [1]. Palmnas et al. [41] reported about an effect of low aspartame doses (5-7 mg/kg body weight/ day) on metabolism and the gut microbiota in rats with and without diet induced obesity. For example, aspartame intake led to an increase in Clostridium leptum and Entero-bacteriaceae, and an increase in the members of Roseburia was observed in rats with diet induced obesity. Compared to the control group, the gut microbiota composition in rats with obesity that consumed aspartame had the increased abundance of Roseburia, Bifidobacterium, Clostridium leptum and Enterobacteriaceae. Also, aspartame intake increased a level of circulated short-chain propio-nate and glucose, which may lead to hyperglycemia and insulin tolerance later on [1,41]. Suez et al. [38] analyzed an effect of aspartame on glucose metabolism and the gut mi-crobiota. The glycemic response was significantly higher in the group consumed aspartame than in the control group (p<0.001). According to the authors' opinion, the revealed glucose tolerance can be associated with alterations in the gut microbiota composition, including a reduction of the abundance of Clostridiales and an increase in the abundance of Bacteroides [1,38].
Frankenfeld et al. [39] showed that although there was no significant difference in the ratio of Bacteroidetes to Firmicutes between the group consuming aspartame and the control group, the overall bacterial diversity differed between the groups. For example, aspartame intake was associated with an increase in Actinobacteria, Deltaproteo-bacteria and Enterobacteriaceae [1,39].
Saccharin
Saccharin (E954) is a derivative of naphthalene. It is about 240-300 times sweeter than sucrose and is one of the first artificial sweeteners used in various foods (Figure 2). It is slowly absorbed by the intestine and its acceptable daily intake is 5 mg/kg body weight/day, which is the lowest level among all artificial sweeteners [42].
Figure 2. Structural formula of saccharin and a photo of its crystal grown in acetone
Suez et al. assessed an effect of saccharin on the blood glucose level and the gut microbiota composition in mice [38]. According to the authors' data, saccharin induced misbalance in the gut microbial community, including an increase in the abundance of Clostridiales and Bacte-roides and a decrease in the abundance of lactobacilli and
Firmicutes. The same researchers reported that no disorders related to glucose tolerance were revealed in mice after saccharin consumption. However, transplantation of the gut microbiome from the in vitro cultures subjected to an exposure to saccharin to other mice led to impaired glucose homeostasis [38].
Sucralose
Sucralose (E955) is a chlorinated disaccharide. Its sweetening ability about 320-1000 times higher than that of sucrose (Figure 3). The acceptable daily intake is 15 mg/kg body weight/day. With that, the most part of ingested sucralose is excreted in faeces (65-95%) [36]. Uebanso et al.
[43] reported that the number of Clostridium IVXa in faeces of mice given sucralose significantly reduced with an increase in the ratio of secondary/primary bile acids and a decrease in the level of luminal butyrate [43]. Bian et al.
[44] studied an effect of sucralose on the gut microbiome in male mice. The gut microbiota composition altered significantly after sucralose intake during six months. After three months, the abundance of Ruminococcus increased and that of Bacillales, Peptostreptococcaceae, Staphylococcus and Anaerostipes decreased. After six months, an increase in the abundance of Christensenellaceae, Clostridiaceae, Akkermansia, Roseburia and Turicibacter, and a decrease in the abundance of Erysipelotrichaceae, Dehalobacterium, and Streptococcus were observed [44].
Figure 3. A simplified scheme of sucralose production from saccharose as a result of the five-stage reaction
Sodium cyclamate
Sodium cyclamate (E952) is used as a sweetener in more than 50 countries, and its sweetness is 30-40 times higher than that of sucrose (Figure 4).
Figure 4. A scheme of sodium cyclamate production
However, the U. S. Food and Drug Administration (FDA) removed sodium cyclamate from the list of substances generally recognized as safe ("GRAS") in 1969 and fully prohibited it in 1970 [42]. It was found that sodium cyclamate can be metabolized to toxic cyclohexylamine under the action of the gut microbiota [1]. For example, the animal experiments showed that bladder cancer was found in rats fed with a mixture of cyclamate and saccharin [45]. However, correctness of these studies was subjected to question and the safety of sodium cyclamate was revised. In 1982, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) established the acceptable daily intake of 11 mg/kg body weight/day for sodium cyclamate
[1]. In the USA, the use of this substance is still prohibited. Subsequently, an effect of sodium cyclamate on the monkey gut microbiota was studied. Compared to the control group, total counts of coliforms and the presence of the microbial population including Bifidobacterium, Clostridium, Enterobacteriaceae, Veillonella and Bacteroidaceae did not have significant differences [46].
Neotame
Neotame (E961) is an artificial sweetener produced by reductive alkylation of aspartame. It is often used in combination with other sweeteners in sauces, fermented dairy drinks, lemon tea and soft drinks [1]. Although the structural formulas of neotame and aspartame are similar, neotame has higher sweetness, which is 7000-13000 times higher than that of sucrose (Figure 5).
Figure 5. Structural formula of neotame. The blue color shows
aspartame as part of neotame; this part of the molecule is responsible for sweet taste formation in this substance [49]
Both the FDA and European Food Safety Authority (EFSA) approved the use of neotame; with that, its acceptable daily intake (ADI) is 2 mg/kg body weight/day [47]. Neotame is quickly metabolized and is not accumulated in the body. Half of the consumed neotame does not enter blood and is excreted in faeces, while another half is excreted in urine as deesterified neotame. Up to now, there have been no reports about its toxicity for mice and other experimental animals [36].
Chi et al. [48] studied an effect of neotame on the gut microbiota in male mice. After four-week neotame consumption, a significant increase in Bacteroidetes and a significant decrease in Firmicutes were observed in the neotame-treated mice. Total microbial counts were significantly lower in the neotame-treated mice than in the control group [48].
Emulsifiers and their effect on the gut microbiome
Emulsifiers are substances having the surface activity that are capable of creating stable emulsions when mixing with other substances. They help improving the food structure and taste, extend product shelf life [1,50]. Some emulsifiers are present in food as a natural component, for example, surface active protein casein, while others are synthesized artificially, for example, substances such as carboxymethylcellulose and polysorbate 80. Over the last years, there has been a trend towards an increasing number of studies showing that food emulsifiers can af-
fect the gut microbiome, cause intestinal inflammation and facilitate the development of the metabolic syndrome [1,50,51].
Carboxymethylcellulose
Carboxymethylcellulose (CMC, E466) is an amorphous colorless substance, a weak acid. According to the classifier of food additives, it is assigned to the class of stabilizers; it imparts shape and viscosity to a product. Carboxymethylcellulose is a cellulose derivative obtained from cellulose upon its treatment with chloro-acetic acid and alkali. It can be seen from the presented chemical structures (Figure 6) that carboxymethylcellu-lose has the higher water solubility than the initial raw materials due to the presence of the polar carboxymethyl group; however, the polymer structure remains to be unchanged. The chemical, food and pharmaceutical industries use the carboxymethylcellulose sodium salt (cros-carmellose, E468), which aqueous solutions are viscous and have pseudoplasticity. The CMC sodium salt is an amorphous colorless substance with a molecular mass (30-25)*103, browning temperature 227 °C, carbonization temperature 252 °C. It is soluble in water, aqueous alkaline solutions, NH3, NaCl and solvents for cellulose; it is not soluble in organic solvents, mineral oils. When solving in water, the CMC sodium salt forms viscous transparent solutions.
Figure 6. A scheme for production of the carboxymethylcellulose sodium salt
Toxicological studies showed that mice and rats treated with CMC did not have any significant side effects over 100 weeks [52]. Carboxymethylcellulose is a polysaccharide, which is hard to hydrolyze and digest by the enzymes of the human gastrointestinal tract; therefore, its fermentation usually depends on the gut microbiota [1]. Carboxymethylcellulose can be fermented by the gut microflora into short-chain organic acids, such as lactic acid, succinic acid, formic acid, acetic acid, butyric acid and propionic acid. Swidsinski et al. [53] studied an effect of CMC on mice with deactivated IL-10 gene (IL-10 gene suppresses production of all pro-inflammatory cytokines). Bacterial overgrowth was observed in CMC-treated mice. The bacterial concentration in the ileum was higher than 108 CFU/ml (colony forming units/ ml). It was found that leucocytes migrated into the intestinal lumen in four out of seven CMC-treated mice. CMC intake caused a reduction in Eubacterium rectale in the ileum and jejunum, and also increased Bacteroides. The authors assumed that CMC intake can lead to the bacterial overgrowth and cause inflammation of the intestine in susceptible mice [1,53].
Viennois et al. [54] studied an effect of CMC on intestinal inflammation and alterations of the mouse gut mi-crobiota composition in colorectal cancer development. After CMC intake for 13 weeks, the mouse gut microbiome composition altered: the abundance of Proteobacteria and Firmicutes significantly decreased and the abundance of Bacteroidetes increased. With that, the levels of the marker of intestinal inflammation (lipocalin 2) were elevated. Several groups took part in the study and the frequency of tumor development also increased in a group treated only with CMC compared to the control group. The authors concluded that CMC intake promoted carcinogenic processes [1,54].
An effect of CMC on the gut microbial diversity was also studied with the use of in vitro models. For example, Chassaing et al. [55] studied an effect of CMC on the intestinal ecosystem using an artificial model that simulated the intestinal mucosa (M-Shime). The M-Shime model is an in vitro model consisting of several glass vessels with regulated pH, which simulate the stomach, small intestine and different parts of the colon. For better simulation of the human intestinal tract covered with mucus, the "mucous environment" was created in M-Shime using mucins, which allowed studying various microbiota types [55,56]. During simulation of the colon microflora treated with 1% of CMC in M-Shime for 13 days, Bacte-roidaceae decreased, while Enterobacteriaceae and Proteobacteria increased. It was found that CMC treatment increased the flagellin gene expression. When microbiota treated with 1% of CMC was transplanted to C57BL/6 Rag-/- mice without microflora, alterations in the gut mi-crobiota composition similar to those in the artificial system M-Shime were observed [55,56].
However, it is still necessary to study how CMC is related to alterations in the gut microbiota composition and the development of intestinal inflammation. One of the possible pathogenic mechanisms can be a damage of the intestinal mucosa by CMC, which can lead to muco-sal inflammation [53]. Another potential mechanism can consist in CMC-induced increase in flagellin production, which, in turn, enhances the bacterial ability to penetrate into the mucus layer, and thereby, facilitates the overgrowth of gut bacteria and alters functional characteristics of the gut microbiota [50]. However, it is still necessary to investigate to what extent the above described pathogenic mechanisms can be extrapolated from artificial systems to the human body.
Polysorbate 80
In the USSR, polysorbates were synthesized for the first time in the All-Union Scientific Research Institute of Organic Intermediates and Dyes in 1958. Polysorbate 80 (Tween 80, P80, E433) is obtained by co-polymerization of sorbitol and its dehydrated monooleate with ethylene oxide. It is often used in the food industry as an emulsifier, solvent and stabilizer (Figure 7).
0
Figure 7. Structural formula of polysorbate 80
It can be seen from the presented formula that the polysorbate molecule actually consists of two parts: hy-drophilic (left) and containing a long hydrophobic "tail" (right). Such structure from the hydrophilic and hydrophobic parts is typical for many emulsifiers. For polysorbate 80, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) established the acceptable daily intake of 25 mg/kg body weight/day. Similar to carboxymethyl-cellulose (CMC), polysorbate 80 showed weak assimilation in the gastrointestinal tract and most part of it is excreted in faeces; however, it is known that it can increase serum levels of lipopolysaccharide in vivo, facilitate micro-bial invasion and lead to alterations in the gut microbiota composition [6]. Chassaing et al. [51] studied an effect of 1% polysorbate 80 solution on the gut microbiota, colitis development and metabolic syndrome in C57BL/6 mice and two lines of genetically modified mice (IL10 -/- and TLR5 -/-). The 12-week study showed that intake of poly-sorbate 80 did not have a significant effect on the mouse microbial community; however, it was found that polysorbate 80 reduced the thickness of the intestinal mucosa, facilitated the contact between bacteria and epithelial cells and did cause changes in the gut microflora. Polysorbate 80 also led to an increase in the intestinal permeability and increased levels of lipopolysaccharide and flagellin. In addition, these authors studied effects depended on the amount of polysorbate 80. Mice treated with 0.1% solution of polysorbate 80 had low indicators of inflammation and obesity; while mice treated with 0.5% solution of polysorbate 80 showed mild hypoglycemia [1,51].
Singh et al. [57] studied an effect of polysorbate 80 on the mouse gut microflora and development of the intestinal inflammation and liver dysfunction [57]. Compared to the control group, the number of Gram-positive bacteria significantly increased in mice consumed polysorbate 80, which, according to the authors' opinion, promoted the development of non-alcoholic fatty liver disease due to an influence of the gut microflora on the enterohepatic circulation of bile acids. It was found that the abundance of Bacteroides decreased and the abundance of Salmonella, Helicobacter, Clostridium increased. With that, Campylobacter jejuni, Salmonella spp. and Helicobacter spp. are associated with the development of inflammation. Mice treated with polysorbate 80 showed the shortened colon, damage of epithelial cells, reduction in the faecal level of short chain fatty acids, such as butyrate, propionate and acetate, as well as a significant decrease in expression of
proteoglycan mucin-2. Mice in a group received polysorbate 80 also demonstrated an increased level of the lipocal-in-2 content in colon and faeces, an increase in intestinal permeability and in the flagellin content. These markers are associated with chronic intestinal inflammation. Also, intake of polysorbate 80 increased expression in the liver of alkaline phosphatase by 40%, alanine aminotransferase and aspartate aminotransferase by 50%. Moreover, lipid droplets and steatosis related to the increased activity of liver enzymes were observed in the liver, which indicated liver damage [1,57].
Viennois et al. [54] studied an effect of polysorbate 80 on microbiota and intestinal inflammation in mice. In their study, Proteobacteria and Firmicutes significantly decreased and Bacteroidetes increased in mice received polysorbate 80 [1,54].
Although both polysorbate 80 and CMC increase expression of pro-inflammatory flagellin, an increase induced by polysorbate 80 occurs more slowly than that induced by CMC. Compared to CMC, which promotes the overgrowth of bacteria in mice and, therefore, affects the development of inflammation, polysorbate 80 increases bacterial translocation through mucosa [58].
Therefore, both CMC and polysorbate 80 can affect mi-crobiota in mice, increase its ability to penetrate the mucus layer, influence the signal pathways of cell proliferation and apoptosis, and lead to intestinal inflammation and disorder of metabolic homeostasis [1]. However, it is necessary to further investigate how these results obtained mainly on rodents can be extrapolated to humans.
Sodium sulfite
Sodium sulfite (E221) is a sodium salt of sulfurous acid and is used in foods to inhibit the microbial growth and stabilize color. In 1974, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) established the acceptable daily intake of 0.7 mg/kg body weight for sodium sulfite. Sodium sulfite is readily soluble in water and is a strong reducer; therefore, it is quickly oxidized in the air. Irwin et al. [59] studied an effect of sodium sulfite in different concentrations on four bacterial species residing in the intestine: Streptococcus salivarius, Lactobacillus ca-sei, Lactobacillus rhamnosus and Lactobacillus plantarum. Although the used media were suitable for the growth of all four species and the exposure time was short, sodium sulfite exerted the bacteriostatic and bactericidal effects against all four tested species at a concentration lower than the acceptable daily intake. Therefore, up to now, there are no data about an effect of sodium sulfite on the micro-biome of the human gut, which is an environment more complex than those in in vitro experiments.
Nisin
Due to the high antibacterial activity, especially against Gram-positive bacteria, nisin (E234) is the only bacte-riocin approved by JECFA as a food preserving agent.
Its acceptable daily intake is 2 mg/kg body weight/day. Laukova et al. [60] used rabbits to study changes in the gut microbiota after continuous nisin intake for 28 days. They observed a significant reduction in pseudomonads, clos-tridiae, coliforms and coagulase-positive staphylococci. Ronan et al. [61] studied an effect of nisin in two different matrices (starch dough and starch gel) on the mouse intestinal microbiota. They found that the relative abundance of Bifidobacterium, and Gram-positive bacteria belonged to the Clostridium cluster XlVa was significantly lower in two groups fed with a diet containing nisin than in the control group [61]. However, it is necessary to study further how these alterations in the microbial community can affect human health.
Potassium sorbate, sodium benzoate and sodium
nitrite
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) established that the acceptable daily intake for sodium benzoate (E211), sodium nitrite (E250) and potassium sorbate (E202) is 5, 0.07 and 25 mg/kg body weight, respectively [1]. Hrncirova et al. [62] determined in the in vitro experiments an effect of combinations of sodium benzoate, potassium sorbate and sodium nitrite on bacteria isolated from human faeces. It was found that microflora was very sensitive to the antimicrobial food additives. Bacteroides coprocola was most sensitive. This microorganism is associated with Crohn's disease and ulcerative colitis. Clostridium tyrobutyricum was also sensitive to sodium nitrite. Lactobacillus para-casei and Bifidobacterium longum were most sensitive to sodium benzoate. These microorganisms can enhance antitumor immunity in vivo. Enterococcus faecalis was also sensitive to sodium benzoate, while Escherichia coli was most sensitive to potassium sorbate [62]. In another study, Hrncirova et al. [63] used mice colonized with the human gut microbiome to investigate an effect of food preserving agents on the gut microbiota. In their investigation, the second generation of mice, similar to the first one, received sodium benzoate (4.8 mg/kg body weight/ day), sodium nitrite (0.36 mg/kg body weight/day) and potassium sorbate (19 mg/kg body weight/day). Wildtype and Nod2-deficient C57BL/6 mice were included in this study. The experiment revealed a reduction of the overall microbial diversity, a decrease in Clostridiales
and an increase in Proteobacteria. The authors noted that Nod2-deficient mice were particularly susceptible to gut microbiota disruption. They also noted that an impact of preserving additives on the human gut microbiota can cause dysbiosis even at low doses [1,62,63].
Titanium dioxide
Food-grade titanium dioxide (E171) is used as a colorant in many food products [43]. With that, 17-36% of titanium dioxide particles in food products have the nano size (<100 nm) [64]. JECFA did not establish an acceptable daily intake level for titanium dioxide in foods due to the absence of toxicity [1]. However, the studies on animals showed that titanium dioxide nanoparticles can affect the gut microbiota composition, which raises concerns about the potential health risks associated with oral exposure to titanium dioxide nanoparticles [1,65].
Essential oils
Essential oils are volatile oil-like compounds with typical strong odor and taste. They are insoluble in water, mainly colorless or slightly colored liquids. The majority of essential oils consist of light fractions; therefore, they are quickly evaporated and do not leave "fatty" stains on paper. Essential oils are complex mixtures of terpenes, terpenoides and other aromatic and aliphatic compounds extracted with organic solvents or by distillation from various spices and herbs [66]. Essential oils are widely used as flavoring agents, but they also have the antibacterial activity (Figure 8). Thapa [67] studied 21 essential oils and found that 19 of them possessed the antimicrobial activity against, at least, one of the following microorganisms: Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumonia, Bacillus subtilis and Staphylococcus aureus [1,67].
It is known that essential oils can be added to feed for shrimps, broiler chickens, ducks and other animals [60,68,69]. Some essential oils are added into food as preserving agents and antioxidants, for example, thyme oil, cinnamon oil and clove oil [1].
Bento et al. [70] noted that the blend of cinnamon and thyme oils had a beneficial effect on the gut microbiome of monogastric animals and inhibited the growth of pathogens and opportunistic pathogens, for example, Salmonella spp. and Escherichia coli [70].
Figure 8. An effect of essential oils on colon microflora diversity in piglets The values of Shannon and Chao1 indices, as well as the total counts of the studied bacterial species are given. Con: the control group; EO: the experimental group [71].
Conclusion
In several cases, food additives exert a pronounced physiological effect. Theoretically, their influence on the body can have various features due to multiple classes of substances used as food additives and their subsequent metabolic transformation. With that, in case of a direct effect on the body, an action of food additives is well studied; however, it is studied insufficiently in case of indirect impact with participation of microbiome. Many studies demonstrate an importance of microbiome for the healthy functioning of the consumer's body. For example, it is known that the gut microbial composition affect immunity formation and production of different physiologically active substances.
As microbiome is an assembly of microorganisms, a researcher studying even one substance entering the body can encounter many metabolic pathways, in which various bacteria take part transforming the initial food additive into other substances. It is necessary to note that in several cases, genes responsible for encoding one or another metabolic enzyme can be on extra-chromosomal elements (for example, plasmids), which possibly would make prediction of metabolic pathways more difficult. Therefore, researchers can face a problem of explaining an effect on the human body of many minor metabolites even in investigation of one food additive. In this situation, machine learning can be used to process such volumes of data.
REFERENCES
1. Cao, Y., Liu, H., Qin, N., Ren, X., Zhu, B., Xia, X. (2020). Impact of food additives on the composition and function of gut mi-crobiota: A review. Trends in Food Science and Technology, 99, 295-310. https://doi.org/10.1016/j.tifs.2020.03.006
2. Sender, R., Fuchs, S., Milo, R. (2016). Are we really vastly outnumbered? Revisiting the ratio of bacterial to host cells in humans. Cell, 164(3), 337-340. https://doi.org/10.1016/j. cell.2016.01.013
3. Belkaid, Y., Hand, T. W. (2014). Role of the microbiota in immunity and inflammation. Cell, 157(1), 121-141. https://doi. org/10.1016/j.cell.2014.03.011
4. Kornienko, V. Yu. (2015). The skin microbiome: the relationship between changes in the microbial community and disease (literature review). Young scientist, 10 (90), 477-483. (In Russian)
5. Ding, R.X., Goh, W.R., Wu, R.N., Yue, X.Q., Luo, X., Khine, W.W.T. et al. (2019). Revisit gut microbiota and its impact on human health and disease. Journal of Food and Drug Analysis, 27(3), 623-631. https://doi.org/10.1016/jjfda.2018.12.012
6. Holder, M.K., Chassaing, B. (2018). Impact of food additives on the gut-brain axis. Physiology and Behavior, 192, 173-176. https://doi.org/10.1016/j.physbeh.2018.02.025
7. Martinez-Guryn, K., Leone, V., Chang, E.B. (2019). Regional diversity of the gastrointestinal microbiome. Cell Host and Microbe, 26(3), 314-324. https://doi.org/10.1016/j.chom.2019.08.011
8. Rajilic-Stojanovic, M., de Vos, W.M. (2014). The first 1000 cultured species of the human gastrointestinal microbiota. FEMS Microbiology Reviews, 38(5), 996-1047. https://doi. org/10.1111/1574-6976.12075
9. Eckburg, P. B., Bik, E. M., Bernstein, C. N., Purdom, E., Deth-lefsen, L., Sargent, M. et al. (2005). Microbiology: Diversity of the human intestinal microbial flora. Science, 308(5728), 16351638. https://doi.org/10.1126/science.1110591
10. Huttenhower, C., Gevers, D., Knight, R., Abubucker, S., Badger, J. H., Chinwalla, A. et al. (2012). Structure, function and diversity of the healthy human microbiome. Nature, 486(7402), 207214. https://doi.org/10.1038/nature11234
11. Backhed, F., Ley, R. E., Sonnenburg, J. L., Peterson, D. A., Gordon, J. I. (2005). Host-bacterial mutualism in the human intestine. Science, 307(5717), 1915-1920. https://doi.org/10.1126/sci-ence.1104816
12. Fomina, T.A., Kornienko, V.Y., Minaev, M. Yu. (2020). Methods of molecular diagnostics for fish species identification. Food systems, 3(3), 32-41. https://doi.org/10.21323/2618-9771-2020-3-3-32-41
13. De Filippis, F., Pellegrini, N., Vannini, L., Jeffery, I. B., La Sto-ria, A., Laghi, L. et al. (2016). High-level adherence to a mediterranean diet beneficially impacts the gut microbiota and associated metabolome. Gut, 65(11), Article 309957. https://doi. org/10.1136/gutjnl-2015-309957
14. Monteiro, C. A., Moubarac, J. ■£., Levy, R. B., Canella, D. S., Da Costa Louzada, M. L., Cannon, G. (2018). Household availability of ultra-processed foods and obesity in nineteen European countries. Public Health Nutrition, 21(1), 18-26. doi:10.1017/ S1368980017001379
15. Gokoglu, N. (2019). Novel natural food preservatives and applications in seafood preservation: A review. Journal of the Sci-
ence of Food and Agriculture, 99(5), 2068-2077. https://doi. org/10.1002/jsfa.9416
16. Levine, A., Sigall Boneh, R., Wine, E. (2018). Evolving role of diet in the pathogenesis and treatment of inflammatory bowel diseases. Gut, 67(9), 1726-1738. https://doi.org/10.1136/ gutjnl-2017-315866
17. Rodriguez-Palacios, A., Harding, A., Menghini, P., Himmel-man, C., Retuerto, M., Nickerson, K. P. et al. (2018). The artificial sweetener splenda promotes gut proteobacteria, dysbiosis, and myeloperoxidase reactivity in Crohn's disease-like ileitis. Inflammatory Bowel Diseases, 24(5), 1005-1020. https://doi. org/10.1093/ibd/izy060
18. Abou-Donia, M. B., El-Masry, E. M., Abdel-Rahman, A. A., McLendon, R. E., Schiffman, S. S. (2008). Splenda alters gut microflora and increases intestinal P-glycoprotein and cytochrome P-450 in male rats. Journal of Toxicology and Environmental Health - Part A: Current Issues, 71(21), 1415-1429. https://doi. org/10.1080/15287390802328630
19. Gerasimidis, K., Bryden, K., Chen, X., Papachristou, E., Verney, A., Roig, M. et al. (2020). The impact of food additives, artificial sweeteners and domestic hygiene products on the human gut mi-crobiome and its fibre fermentation capacity. European Journal of Nutrition, 59(7), 3213-3230. https://doi.org/10.1007/s00394-019-02161-8
20. Ben-Arye, T., Shandalov, Y., Ben-Shaul, S., Landau, S., Zagury, Y., lanovici, I. et al. (2020). Textured soy protein scaffolds enable the generation of three-dimensional bovine skeletal muscle tissue for cell-based meat. Nature Food, 1(4), 210-220. https://doi. org/10.1038/s43016-020-0046-5
21. Jie, Z., Xia, H., Zhong, S.-L., Feng, Q., Li, S., Liang, S. et al. (2017). The gut microbiome in atherosclerotic cardiovascular disease. Nature Communications, 8(1), Article 845. https://doi. org/10.1038/s41467-017-00900-1
22. Sedighi, M., Razavi, S., Navab-Moghadam, F., Khamseh, M.E., Alaei-Shahmiri, F., Mehrtash, A. et al. (2017). Comparison of gut microbiota in adult patients with type 2 diabetes and healthy individuals. Microbial Pathogenesis, 111, 362-369. https://doi. org/10.1016/j.micpath.2017.08.038
23. Conlon, M.A., Bird, A.R. (2014). The impact of diet and lifestyle on gut microbiota and human health. Nutrients, 7(1), 17-44. https://doi.org/10.3390/nu7010017
24. Bravo, J. A., Forsythe, P., Chew, M. V., Escaravage, E., Sav-ignac, H. M., Dinan, T. G. et al. (2011). Ingestion of lactobacil-lus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. Proceedings of the National Academy of Sciences of the United States of America, 108(38), 16050-16055. https://doi.org/10.1073/ pnas.1102999108
25. Portune, K.J., Beaumont, M., Davila, A.M., Tomé, D., Blachi-er, F., Sanz, Y. (2016). Gut microbiota role in dietary protein metabolism and health-related outcomes: The two sides of the coin. Trends in Food Science and Technology, 57, 213-232. https://doi. org/10.1016/j.tifs.2016.08.011
26. Pugin, B., Barcik, W., Westermann, P., Heider, A., Wawrzyn-iak, M., Hellings, P. et al. (2017). A wide diversity of bacteria from the human gut produces and degrades biogenic amines.
Microbial Ecology in Health and Disease, 28(1), Article 1353881. https://doi.org/10.1080/16512235.2017.1353881
27. Oliphant, K., Allen-Vercoe, E. (2019). Macronutrient metabolism by the human gut microbiome: Major fermentation by-products and their impact on host health. Microbiome, 7(1), Article 91. https://doi.org/10.1186/s40168-019-0704-8
28. Morrison, D.J., Preston, T. (2016). Formation of short chain fatty acids by the gut microbiota and their impact on human metabolism. Gut Microbes, 7(3), 189-200. https://doi.org/10.1080 /19490976.2015.1134082
29. Hooper, L.V., Littman, D.R., Macpherson, A. J. (2012). Interactions between the microbiota and the immune system. Science, 336(6086), 1268-1273. https://doi.org/10.1126/sci-ence.1223490
30. Zhang, K.Y., Hornef, M.W., Dupont, A. (2015). The intestinal epithelium as guardian of gut barrier integrity. Cellular Microbiology, 17(11), 1561-1569. https://doi.org/10.1111/cmi.12501
31. Cresci, G.A., Bawden, E. (2015). Gut microbiome: What we do and don't know. Nutrition in Clinical Practice, 30(6), 734-746. https://doi.org/10.1177/0884533615609899
32. Eid, H.M., Wright, M.L., Kumar, N.V.A., Qawasmeh, A., Hassan, S.T.S., Mocan, A. et al. (2017). Significance of microbiota in obesity and metabolic diseases and the modulatory potential by medicinal plant and food ingredients. Frontiers in Pharmacology, 8(Jun), Article 387. https://doi.org/10.3389/fphar.2017.00387
33. Fang, B., Li, J.W., Zhang, M., Ren, F.Z., Pang, G.F. (2018). Chronic chlorpyrifos exposure elicits diet-specific effects on metabolism and the gut microbiome in rats. Food and Chemical Toxicology, 111, 144-152. https://doi.org/10.1016/j. fct.2017.11.001
34. Derrien, M., Alvarez, A.S., de Vos, W.M. (2019). The gut mi-crobiota in the first decade of life. Trends in Microbiology, 27(12), 997-1010. https://doi.org/10.1016/j.tim.2019.08.001
35. Ottman, N., Smidt, H., de Vos, W., Belzer, C. (2012). The function of our microbiota: Who is out there and what do they do? Frontiers in Cellular and Infection Microbiology, 2, Article 104. https://doi.org/10.3389/fcimb.2012.00104
36. American Dietetic Association. (2004). Position of the American dietetic association: Use of nutritive and nonnutritive sweeteners. (2004). Journal of the American Dietetic Association, 104(2), 255-275. https://doi.org/10.1016/j.jada.2003.12.001
37. Bian, X., Chi, L., Gao, B., Tu, P., Ru, H., Lu, K. (2017). The artificial sweetener acesulfame potassium affects the gut microbiome and body weight gain in CD-1 mice. PloS One, 12(6), Article e0178426. https://doi.org/10.1371/journal.pone.0178426
38. Suez, J., Korem, T., Zeevi, D., Zilberman-Schapira, G., Thaiss, C.A., Maza, O. et al. (2014). Artificial sweeteners induce glucose intolerance by altering the gut micro-biota. Nature, 514(7521), 181-186. https://doi.org/10.1038/nature13793
39. Frankenfeld, C.L., Sikaroodi, M., Lamb, E., Shoemaker, S., Gillevet, P.M. (2015). High-intensity sweetener consumption and gut microbiome content and predicted gene function in a cross-sectional study of adults in the United States. Annals of Epidemiology, 25(10), 736-742.e4. https://doi.org/10.1016/j.annepi-dem.2015.06.083
40. Butchko, H. H., Stargel, W. W., Comer, C. P., Mayhew, D. A., Benninger, C., Blackburn, G. L. et al. (2002). Aspartame: Review of safety. Regulatory Toxicology and Pharmacology: RTP, 35(2Pt 2), S1-93.
41. Palmnas, M.S.A., Cowan, T.A., Bomhof, M.R., Su, J., Reimer, R.A., Vogel, H.J. et al. (2014). Low-dose aspartame consumption differentially affects gut microbiota-host metabolic interactions in the diet-induced obese rat. PloS One, 9(10), Article e109841. https://doi.org/10.1371/journal.pone.0109841
42. Carocho, M., Morales, P., Ferreira, I.C.F.R. (2017). Sweeteners as food additives in the XXI century: A review of what is known, and what is to come. Food and Chemical Toxicology, 107, 302-317. https://doi.org/10.1016/j.fct.2017.06.046
43. Uebanso, T., Ohnishi, A., Kitayama, R., Yoshimoto, A., Naka-hashi, M., Shimohata, T. at al. (2017). Effects of low-dose non-caloric sweetener consumption on gut microbiota in mice. Nutrients, 9(6), Article 662. https://doi.org/10.3390/nu9060662
44. Bian, X., Chi, L., Gao, B., Tu, P., Ru, H., Lu, K. (2017). Gut mi-crobiome response to sucralose and its potential role in inducing liver inflammation in mice. Frontiers in Physiology, 8(Jul), Article 487. https://doi.org/10.3389/fphys.2017.00487
45. Oser, B.L., Carson, S., Cox, G.E., Vogin, E.E., Sternberg, S.S.
(1975). Chronic toxicity study of cylamate-saccharin (10:1) in rats. Toxicology, 4(3), 315-330.
46. Matsui, M., Hayashi, N., Konuma, H., Tanimura, A., Kurata, H.
(1976). Studies on metabolism of food additives by microorgan-
isms inhabiting gastrointestinal tract (IV): Fate of faecal flora in monkey administered orally sodium cyclamate and detection of sodium cyclamate assimilating bacteria in vitro by anaerobic culture. Journal of the Food Hygienic Society of Japan, 17(1), 54-58. https://doi.org/10.3358/shokueishi.17.54
47. JECFA. (2004). 3.1.8. Neotame. In evaluation of certain food additives and contaminants. Sixty-first report of the Joint FAO/ WHO Expert committee on food additives (JECFA), Rome, Italy. WHO technical report series no 922Geneva, Switzerland: World Health Organization (WHO). Retrieved from https://apps.who. int/iris/bitstream/handle/10665/42849/WH0_TRS_922. pdf?sequence=1. Accessed April 16, 2021
48. Chi, L., Bian, X., Gao, B., Tu, P., Lai, Y., Ru, H. et al. (2018). Effects of the artificial sweetener neotame on the gut microbi-ome and fecal metabolites in mice. Molecules, 23(2), Article 367. https://doi.org/10.3390/molecules23020367
49. Walters, D. E. (1995). Using models to understand and design sweeteners. Journal of chemical education, 72(8), 680-683.
50. Halmos, E.P., Mack, A., Gibson, P.R. (2019). Review article: Emulsifiers in the food supply and implications for gastrointestinal disease. Alimentary Pharmacology and Therapeutics, 49(1), 41-50. https://doi.org/10.1111/apt.15045
51. Chassaing, B., Koren, O., Goodrich, J.K., Poole, A.C., Sriniv-asan, S., Ley, R.E. et al. (2015). Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature, 519(7541), 92-96. https://doi.org/10.1038/na-ture14232
52. McElligott, T.F., Hurst, E.W. (1968). Long-term feeding studies of methyl ethyl cellulose ('Edifas' A) and sodium carboxymethyl cellulose ('Edifas' B) in rats and mice. Food and Cosmetics Toxicology, 6(4), 449-460. https://doi. org/10.1016/0015-6264(68)90135-1
53. Swidsinski, A., Ung, V., Sydora, B.C., Loening-Baucke, V., Do-erffel, Y., Verstraelen, H. et al. (2009). Bacterial overgrowth and inflammation of small intestine after carboxymethylcellulose ingestion in genetically susceptible mice. Inflammatory Bowel Diseases, 15(3), 359-364. https://doi.org/10.1002/ibd.20763
54. Viennois, E., Merlin, D., Gewirtz, A. T., Chassaing, B. (2017). Dietary emulsifier-induced low-grade inflammation promotes colon carcinogenesis. Cancer Research, 77(1), 27-40. https://doi. org/10.1158/0008-5472.CAN-16-1359
55. Chassaing, B., Van De Wiele, T., De Bodt, J., Marzorati, M., Gewirtz, A.T. (2017). Dietary emulsifiers directly alter human mi-crobiota composition and gene expression ex vivo potentiating intestinal inflammation. Gut, 66(8), 1414-1427. https://doi. org/10.1136/gutjnl-2016-313099
56. Lambrecht, E., Van Coillie, E., Van Meervenne, E., Boon, N., Heyndrickx, M., Van de Wiele, T. (2019). Commensal E. co-li rapidly transfer antibiotic resistance genes to human intestinal microbiota in the Mucosal Simulator of the Human Intestinal Microbial Ecosystem (M-SHIME). International Journal of Food Microbiology, 311, Article 108357. https://doi.org/10.1016/j.ij-foodmicro.2019.108357
57. Singh, R. K., Wheildon, N., Ishikawa, S. (2016). Food additive P-80 impacts mouse gut microbiota promoting intestinal inflammation, obesity and liver dysfunction. SOJ microbiology and infectious diseases, 4(1), Article 148. https://doi.org/10.15226/so-jmid/4/1/00148
58. Roberts, C.L., Keita, A.V., Duncan, S.H., O'Kennedy, N., So-derholm, J.D., Rhodes, J.M. et al. (2010). Translocation of Crohn's disease Escherichia coli across M-cells: Contrasting effects of soluble plant fibres and emulsifiers. Gut, 59(10), 1331-1339. https://doi.org/10.1136/gut.2009.195370
59. Irwin, S.V., Fisher, P., Graham, E., Malek, A., Robidoux, A. (2017). Sulfites inhibit the growth of four species of beneficial gut bacteria at concentrations regarded as safe for food. PloS One, 12(10), Article e0186629. https://doi.org/10.1371/jour-nal.pone.0186629
60. Laukovâ, A., Chrastinovâ, L, Plachâ, I., Kandricâkovâ, A., Sz-aboovâ, R., Strompfovâ, V. et al. (2014). Beneficial effect of lantibi-otic nisin in rabbit husbandry. Probiotics and Antimicrobial Proteins, 6(1), 41-46. https://doi.org/10.1007/s12602-014-9156-4
61. Gough, R., Rubio, R. C., O'Connor, P. M., Crispie, F., Brodkorb, A., Miao, S. et al. (2018). Oral delivery of nisin in resistant starch based matrices alters the gut microbiota in mice. Frontiers in Microbiology, 9(JUN), Article 1186. https://doi.org/10.3389/ fmicb.2018.01186
62. Hrncirova, L., Hudcovic, T., Sukova, E., Machova, V., Trckova, E., Krejsek, J. et al. (2019). Human gut microbes are susceptible to antimicrobial food additives in vitro. Folia Microbiologica, 64(4), 497-508. https://doi.org/10.1007/s12223-018-00674-z
63. Hrncirova, L., Machova, V., Trckova, E., Krejsek, J., Hrncir, T. (2019). Food preservatives induce proteobacteria dysbiosis in human-microbiota associated Nod2-deficient mice. Microorganisms, 7(10), Article 383. https://doi.org/10.3390/microorgan-isms7100383
64. Weir, A., Westerhoff, P., Fabricius, L., Hristovski, K., Von Goetz, N. (2012). Titanium dioxide nanoparticles in food and personal care products. Environmental Science and Technology, 46(4), 2242-2250. https://doi.org/10.1021/es204168d
65. Bettini, S., Boutet-Robinet, E., Cartier, C., Comera, C., Gaultier, E., Dupuy, J. et al. (2017). Food-grade TiO2 impairs intestinal and systemic immune homeostasis, initiates pr2eneoplastic lesions and promotes aberrant crypt development in the rat colon. Scientific Reports, 7, Article 40373. https://doi.org/10.1038/srep40373
66. Bakkali, F., Averbeck, S., Averbeck, D., Idaomar, M. (2008). Biological effects of essential oils — a review. Food and Chemical Toxicology, 46(2), 446-475. https://doi.org/10.1016Zj.fct.2007.09.106
67. Thapa, D. (2015). Studies on the influence of essential oils on human gut bacteria and colonic cells. Doctoral dissertation University of Aberdeen. Retrieved from https://ethos.bl.uk/OrderDe-tails.do?uin=uk.bl.ethos.655666. Accessed April 21, 2021.
68. Skoufos, I., Giannenas, I., Tontis, D., Bartzanas, T., Kittas, C., Panagakis, P. et al (2016). Effects of oregano essential oil and attapulgite on growth performance, intestinal microbiota and morphometry in broilers. South African Journal of Animal Science, 46(l), 77-88. https://doi.org/10.4314/sajas. v46i1.10
69. Abouelezz, K., Abou-Hadied, M., Yuan, J., Elokil, A.A., Wang, G., Wang, S. et al. (2019). Nutritional impacts of dietary oregano and Enviva essential oils on the performance, gut microbiota and blood biochemicals of growing ducks. Animal, 13(10), 22162222. https://doi.org/10.1017/S1751731119000508
70. Bento, M. H. L., Ouwehand, A. C., Tiihonen, K., Lahtinen, S., Nurminen, P., Saarinen, M. T. et al. (2013). Essential oils and their use in animal feeds for monogastric animals — effects on feed quality, gut microbiota, growth performance and food safety: A review. Veterinarni Medicina, 58(9), 449-458. https://doi. org/10.17221/7029-VETMED
71. Li, Y., Fu, X., Ma, X., Geng, S., Jiang, X., Huang, Q. et al. (2018). Intestinal microbiome-metabolome responses to essential oils in piglets. Frontiers in Microbiology, 9(AUG), Article 1988. https://doi.org/10.3389/fmicb.2018.01988
AUTHOR INFORMATION
Vladimir Yu. Kornienko — candidate of biological sciences, Senior Researcher, Laboratory of molecular biology and bioinformatics, V. M. Gor-batov Federal Research Center for Food Systems of Russian Academy of Sciences. 26, Talalikhina Str., Moscow, 109316, Russia. Tel.: +7-495-67695-11 (109), E-mail: unipraim@yandex.ru ORCID: https://orcid.org/0000-0001-9068-9814
Mihail Yu. Minaev — candidate of technical sciences, head of Laboratory of molecular biology and bioinformatics, V. M. Gorbatov Federal Research Center for Food Systems of Russian Academy of Sciences. 26, Talalikhina Str., Moscow, 109316, Russia. Tel.: +7-495-676-95-11 (109), E-mail: m.minaev@fncps.ru ORCID: https://orcid.org/0000-0002-0038-9744
All authors bear responsibility for the work and presented data.
All authors made an equal contribution to the work.
The authors were equally involved in writing the manuscript and bear the equal responsibility for plagiarism. The authors declare no conflict of interest.
