**1. Introduction**

The consumer's interest in a healthier lifestyle has led to the development of foods that meet nutritional and health needs and that at the same time are attractive, tasty, and with good acceptance in the market. Products that support positive health effects or ingredients with these characteristics, claimed or proven, are called "emitted foods" [1].

The relationship between food and health is one of the keys to disease prevention and well-being promotion. As a result, industries have started to enrich foods with specific ingredients, differentiating them about the benefits offered to health compared to foods in their traditional forms [2–4].

In the present century, the scientific literature reports functional foods as allies in the treatment of obesity [5], prevention of cardiovascular diseases [1], plasma cholesterol balance [6], and cancer prevention [7]. Among functional foods, the

literature reports prebiotics (added with non-digestible fibers), fortified (with vitamins, omega-3), altered (removing harmful components), and probiotics [8].

According to Resolution No. 19, of April 30, 1999, on the claim of functional property of food, it is that related to the metabolic or physiological role that the nutrient or non-nutrient has in the growth, development, maintenance, and other normal functions of the human organism [9]. Among the functional compounds most investigated by science, we have probiotics, which according to RDC n° 241, of July 26, 2018, are defined as live microorganisms that confer benefits to the individual's health [10, 11].

The word probiotic has a Greek derivation in which it means "for the sake of life", that term was first introduced by Lilly; Stillwel in 1965 to describe substances secreted by a microorganism, which stimulates the growth of another [12–14]. Fuller (1989) defined probiotics as a supplement composed of live microorganisms that benefit the host's health through the balance of the intestinal microbiota. The term probiotic can be complemented as a pure culture or composed of living microorganisms that supplied to man or animals benefit the host by stimulating the properties existing in the natural microbiota [15].

Probiotics, after ingested, must be able to survive the stress conditions present in the gastrointestinal tract, such as gastric juice, the presence of bile salts, and digestive enzymes, and maintain their viability and metabolic activity in the intestine to exert beneficial effects on the hosts. As for the technological challenges for the industrial production of cells, they must remain stable and viable at satisfactory levels throughout the product's validity period [16–18]. Based on this assumption, there is a recent and growing scientific interest in improving the stability, bioavailability, and shelf life of products with probiotic sources using nanotechnology as an enhancement technique, since nanostructured systems may be able to control stability, improve solubility, bioavailability, and controlling the release of bioactive compounds [19–21].

The reduction of materials to the nanoscale leads to new and exciting properties and the increase of the surface volume ratio, increasing its reactivity. This characteristic of nanoparticles has attracted commercial interest in the manufacture of nano-ingredients, supplements, and nutraceuticals. Several types of nanoparticles can be found in the literature, such as metallic, semiconductor, carbon-based, metallic, and polymeric oxides, which can be applied in various sectors, predominantly personal care, health care, and cosmetics. The benefits of nanotechnology in the food sector go through the entire food chain, starting from production to processing, transportation, security, storage, and delivery [22, 23]. Based on the above, we will cover in this chapter a review on the use of natural probiotics and nanomaterials, aiming to specify their advantages and methodologies of preparation and characterization.

#### **2. Natural probiotics**

Probiotics can be defined as food supplements that contain live microorganisms or microbial components that, when ingested in a certain number, have a beneficial effect on the health and well-being of the host [17].

Among these benefits include antimicrobial activity; control of pathogenic microorganisms [24]; lactose hydrolysis; modulation of constipation; antimutagenic and anticarcinogenic activity [25, 26]; reduction of blood cholesterol, improvement of patients with type 2 diabetes (insulin resistance) and obesity [27–29]; modulation of the immune system; improvement in inflammatory bowel disease; and suppression of *Helicobacter pylori* infection [30–32]. Some of these

*Natural Probiotics and Nanomaterials: A New Functional Food DOI: http://dx.doi.org/10.5772/intechopen.98984*

benefits are already well established, such as constipation and lactose hydrolysis modulation, while other benefits have shown promising results in animal models, requiring further clinical studies [33].

Probiotics can be incorporated into a wide variety of food products, mainly in dairy products, such as milk, ice cream, yogurt, and cheese. Its application has also grown in other types of foods, such as soy milk, mayonnaise, pates, meats, baby food, confectionery, sweets, cakes, and chewing gum [34–37].

The selection of probiotic bacteria is based on the following criteria: gender, origin (which must be human), stability against stomach acid and bile salts, the ability to adhere to the intestinal mucosa, the ability to colonize, at least temporarily, the human gastrointestinal tract, the ability to produce antimicrobial compounds and metabolic activity in the intestine [38–40].

In order for the microorganism to be able to promote the aforementioned beneficial effects, a minimum intake of 108 –109 colony-forming units (UFC) per day is recommended [41]. In addition, the minimum concentration of live bacteria should not be less than 10 CFU/g of food since many cells die during passage through the gastrointestinal tract (TGI) [1, 42].

#### **2.1 Types of probiotics**

Specific probiotic strains give the benefits transmitted to health, and not by specific species or genus. However, that each strain is related to a specific benefit. In this way, no strain will provide all of the proposed benefits. For example, *Lactobacillus casei* lineage Shirota, in which evidence supports the view that its oral administration can assist in the digestion and absorption of nutrients and restore the normal balance of the intestinal microbiota [43]. Other relevant factors are the addition of mixtures of probiotic cultures instead of individual strains [44] and the number of viable cells of these microorganisms in the marketed product.

In a healthy adult intestine, the predominant microbiota is composed of healthpromoting microorganisms (**Table 1**), mostly belonging to the genera *Lactobacillus* and *Bifidobacterium* [45]. Other lactic acid bacteria with probiotic properties are:


#### **Table 1.**

*Main microorganisms used for their probiotic properties, in the form of drugs or added to foods.*

*Ent. faecalis*, *Ent. faecium,* and *Sporolactobacillus inulinus*, while the microorganisms *Bacillus cereus, Escherichia coli Nissle, Propionibacterium freudenreichii,* and *Saccharomyces cerevisiae* have been cited as non-lactic microorganisms associated with probiotic activities mainly for pharmaceutical or animal use [32, 33, 46].

Some individuals may experience little of the side effects related to the ingestion of probiotics due to the death of pathogens in the intestinal environment since they release toxic cellular products, a reaction called a "die-off reaction". In such cases, the use of probiotics should be persisted in order to improve symptoms. There is a slight increase in gas production, abdominal discomfort, and even diarrhea, which resolves over time [12].

#### **2.2 Mechanism of action**

Three possible mechanisms of action are attributed to probiotics: the suppression of the number of viable cells through the production of compounds with antimicrobial activity, competition for nutrients, and competition for adhesion sites. The second of these mechanisms would be the alteration of microbial metabolism by increasing or decreasing enzyme activity. The third would be to stimulate the host's immunity by increasing the levels of antibodies and increasing the activity of macrophages. The spectrum of activity of probiotics can be divided into nutritional, physiological, and antimicrobial effects [47, 48]. The direct modulation of the immune system may be secondary to the induction of anti-inflammatory cytokines or by the increase in the production of secretory IgA [45].

Despite the scientific evidence regarding the mechanisms of action of probiotics, there is still a lack in the literature on biochemical and molecular pathways that fully explain these effects, such as, for example, increasing the function of the intestinal barrier. Despite the scientific evidence regarding the mechanisms of action of probiotics, there is still a lack in the literature on biochemical and molecular pathways that fully explain these effects, such as, for example, increasing the function of the intestinal barrier [49].

Currently, the mechanisms of action of probiotics for anticarcinogenic effects have been studied. These are believed to occur through (1) inhibition of bacteria responsible for converting pre-carcinogenic substances (such as polycyclic aromatic hydrocarbons and nitrosamines) into carcinogens; (2) direct inhibition in the formation of tumor cells; and (3) the ability to bind and/or inactivate carcinogenic substances [25]. Several mechanisms of action have been suggested, including the stimulation of the host's immune response (by increasing phagocytic activity, IgA synthesis, and the activation of T and B lymphocytes), the binding and degradation of compounds with carcinogenic potential, qualitative changes and/or quantitative in the intestinal microbiota involved in the production of carcinogens and promoters (ex: bile acid degradation), production of antitumor or antimutagenic compounds in the colon (such as butyrate), alteration of the metabolic activity of the intestinal microbiota, alteration of the physical- colon chemicals with decreased pH and effects on host physiology [33, 50].

The use of probiotics represents a promising and rapidly growing area for the development of functional foods. Probiotic cultures are successfully applied to different food matrices. However, the development of non-dairy products represents a challenge for the industry, as each food matrix has unique characteristics, and it is necessary to optimize and standardize each type of product [51].

In this context, nanomaterials have been widely studied as a technique to improve the stability of these microorganisms and functional foods, protecting them from unfavorable environments, improving the uptake, absorption, and bioavailability of nutrients for the body (**Table 2**) [19].


#### **Table 2.**

*Immune mechanisms of action associated with probiotics.*
