**5.1 History of probiotics**

The term probiotic was taken from the Latin word (pro) and the Greek word (bios), both of which means "for life." The probiotics theory was introduced in the early twentieth century, according to Zoumpopoulou et al. [31]. A German chemist known as Werner Kollath came up with the term "active chemicals which are important and required for the healthy growth and development of life" in 1953 and that was when probiotics were first introduced. Probiotics were also defined by Lilly and Stillwell in 1965 as "substances released by an organism that boost the growth of another organism." In 1992, Fuller, on the other hand, also came up with a definition that "probiotics are live microbial feed additive with great benefits to the host by enhancing gut microbial balance" [32]. All these concepts are linked to the belief that probiotics are beneficial to human health. Despite all the above definitions for probiotics, FAO/WHO in [3] described probiotics as "live microorganisms that, when administered in suitable proportions, impart a health benefit on the host," and this FAO/WHO definition for the term "probiotics" was the most generally accepted. However, the relationship of being beneficial to health was not overlooked in the FAO/WHO definition, implying that probiotics are extremely beneficial to human health.

The first food makers used bacteria and yeasts to ferment this milk into fermented dairy products, although they were unaware of the presence of these microorganisms [33]. Scientists such as Hippocrates and others considered fermented milk to be more than just a food product but also to have useful medicinal properties. This observation supported the fact that sour milk was, however, later prescribed for curing stomach and intestinal disorders [34]. Louis Pasteur found the microorganisms

*Lactic Acid Bacteria: Review on the Potential Delivery System as an Effective Probiotic DOI: http://dx.doi.org/10.5772/intechopen.111776*

responsible for the fermentation of this milk and other fermented products in the early 1900s, whereas Eli Metchnikoff (Russian scientist) was also the first to discover the positive influence of these microbes on human health [35]. As a result, he proposed his longevity without aging theory and linked it to the Bulgarian bacillus discovered by Stamen Grigorov (Bulgarian physician), and later suggested that lactobacilli might help mitigate the putrefactive effects of gastrointestinal metabolism that contributed to illness and aging [35]. He also stated that toxins produced by bacterial putrefaction in the large intestine and released into the circulation are the cause of aging.

"According to Metchnikoff, the intestinal bacteria' need for food allows humans to develop techniques to change the flora in our bodies and replace harmful microorganisms with healthy ones." This then explains in detail the "probiotic concept." Lactobacilli are considered probiotics by Metchnikoff (as opposed to antibiotics, which are damaging to the host's life), and probiotics may improve health and delay aging. Metchnikoff is based on these scientific theories in the development and expansion of the French dairy industry. The Pasteur Institute's Henry Tissier also isolated bacteria (now known as *Bifidobacterium bifidum*) from the feces of healthy breastfed newborns and advised recommending it to babies with diarrhea [23].

#### **5.2 Probiotic consumption**

Probiotic consumption is critical since they provide numerous advantages to the body, particularly the gastrointestinal tract (GIT). The most essential issue, however, is how it is introduced into the biological system. In the late 1960s, some viable probiotic strains such as Lactobacillus (some species) and *B. bifidum* "group" were introduced as cultures into dairy products in Germany due to their ability to adhere to and adapt to intestinal walls, as well as their useful property of producing mildly acidified products such as yogurts [36]. Though these fermented milky products were popular in Germany and were known as mild yogurts or "bio-yogurts," an alternative product known as acidophilus milk was also popular in the United States at the time (s). The incorporation of these probiotic strains into these fermented milk products and other commodities results in a variety of ways of administration and consumption into the human system, including meals, mostly fermented, and pharmaceutical items, such as capsules or microencapsulated form. According to Salminen et al. [37], if probiotic bacteria are a specified part of a food, Functional Food Science in Europe (FUFOSE) defines it as "live constituents of a food that exert beneficial effects on health."

Probiotic foods are always in demand in the general market because people are beginning to recognize their value; these foods currently account for between 60 and 70 percent of the overall functional food industry. This causes the dairy food sector to expand its market niche since a continual increase in dairy-type probiotic foods is noticed; nevertheless, nondairy items including vegetables, fermented meats, and fruit juices also contribute to the same amount of probiotic food products. Currently, there is no evidence that a high number of probiotics are harmful to human health; in some situations, they may even be quite useful and provide significant advantages to human health [38].

#### **5.3 Origin and sources of probiotics**

Probiotic bacteria have been discovered and isolated in a wide range of environments, including foods (fermented foods), animals, plants, and humans. These probiotics are found in these various sources for a variety of reasons, including their fermentative and preservation impact (mainly in foods), contribution to good health in the human ecosystem (in humans), and so on. According to Ayivi et al. [1], the Lactobacillus and the Bifidobacterium species are the most frequently used probiotics. These two LAB strains have been identified to dominate the human intestinal wall due to their high adhesion capacity and are also generally considered safe for use (GRAS). According to Quigley [39], these safe Lactobacillus strains are well suited for gastrointestinal supplementation because Bifidobacterium is a prominent constituent as far as the large intestine is concerned, whereas Lactobacillus also being a major inhabitant of the small intestine. Streptococcus thermophilus, nonpathogenic strains of *Escherichia coli, Enterococcus, Bacillus,* and yeasts such as *S. boulardii* are also bacteria strains that are as good as these lactobacilli and *Bifidobacterium* [1]. Together with other probiotics, some strains particularly *E. coli* provide health benefits such as efficiently treating constipation and other related gastrointestinal diseases [40].

One of the most common sources of these probiotics is yogurt, which contains diverse bacterial strains such as *L. bulgaricus* and *S. thermophilus*. Yogurts are frequently fortified with strains that have favorable health effects on the human system when consumed. *S. thermophilus* has probiotic qualities, according to Pieniz et al. [41], and thus, its fortification in yogurt products is highly important to induce health advantages to the body. The strains utilized, on the other hand, are chosen based on their ability to survive in the product throughout its shelf life as well as during their transit to the stomach and the rest of the GI tract, allowing them to reach the distal tract, where they largely exercise their function.
