**2. Lactic acid bacteria as source of probiotics**

Etymologically the term probiotics is derived from the Greek "probios" which means "for life". In 1974 Parker [11] defined as probiotics "organisms and substances which contribute to intestinal microbial balance". Fuller in 1989 [12] defined as probiotic "a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance". Later the Food and Agriculture Organization / World Health Organization defined probiotic bacteria as "live microorganisms which when administered in adequate amounts confer a health benefit on the host" [13]. Since probiotics can colonize the gastrointestinal tract and exert their beneficial effect long term, without requiring continuous medical intervention, they have been used for a century to treat a variety of mucosal surface infections (gut, vagina), but their use decreased after the appearance of antibiotics. However, today, probiotics are considered as an alternative solution to antibiotics due to the increasing spread of antibiotic resistance and the need for treatment cost reduction [14].

Microorganisms considered as commercial probiotics are mainly of the Lactobacillus genus with over one hundred species recognized, for example: *L. acidophilus, L. rhamnosus, L. reuteri, L. casei, L. plantarum, L. bulgaricus, L. delbrueckii, L. helveticus* [15-17]. Lactobacilli are Generally Recognized As Safe (GRAS) organisms [18,19].

Probiotic bacteria are very sensitive to many environmental stresses, such as acidity, oxygen and temperature [20,21] and they must fulfill some functional and physiological aspects such as [21,22]: a) Adherence to the intestinal epithelium and colonization of the lumen of the tract. b) Ability to stabilize the intestinal microbiota. c) Counteracting the action of harmful microorganisms. d) Production of antimicrobial substances. e) Stimulation of the immune response.

There are subcategories of the general term probiotic [23,24] which are: a) Probiotic drugs: intended to cue, treat and prevent disease. b) Probiotic foods: food ingredients and dietary supplements. c) Direct-fed microbials: probiotics for animal use. d) Designer probiotics: genetically modified. Generally, foods containing probiotic bacteria fall in the category of functional foods [25].

### **2.1. Mechanism of action of probiotics**

590 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

pollution by the petrochemical industry [10].

**Figure 1.** Uses and Functional Ingredients of Lactic Acid Bacteria

**2. Lactic acid bacteria as source of probiotics** 

relation with human health.

considered to have "Qualified Presumption of Safety" QPS-status [9].

meats (salami), fermented vegetables (olives, sauerkraut), sourdough bread, etc [9]. The European Food Safety Authority (EFSA) has stated that several LAB strains can be

Moreover, nowadays, LAB play an important role in the industry for the synthesis of chemicals, pharmaceuticals, or other useful products (Figure 1). Also, the biotechnological production of lactic acid has recently reported that offers a solution to the environmental

This chapter will discuss recent applications of LAB as source of probiotics, starter cultures, antimicrobial agents, vitamins, enzymes and exopolysaccharides, especially those that can satisfy the increasing consumer's demands for natural products and functional foods in

Etymologically the term probiotics is derived from the Greek "probios" which means "for life". In 1974 Parker [11] defined as probiotics "organisms and substances which contribute to intestinal microbial balance". Fuller in 1989 [12] defined as probiotic "a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance". Later the Food and Agriculture Organization / World Health Organization defined probiotic bacteria as "live microorganisms which when administered in adequate amounts confer a health benefit on the host" [13]. Since probiotics can colonize the gastrointestinal Probiotics have multiple and diverse effects on the host. The main mechanisms of action of probiotic bacteria by which they improve mucosal defenses of the gastrointestinal tract include:


c. Immunomodulation: Specific strains of probiotics might influence the innate and the acquired immune system, thus playing an important role in human diseases. Probiotic bacteria may affect the epithelial cells, the dendritic cells, the monocytes / macrophages and the various types of lymphocytes (Natural killer cells, T-cells and T-cell redistribution) directly or secondarily [33,34]. This action of probiotics could be important for the elimination of neoplastic host cells [22]. Moreover, the effects of probiotics on B-lymphocytes and antibody production resulted in an increase in IgA secretion and the enhancement of response to vaccination [34]. Recently, it was also reported that probiotics can have positive effects on the respiratory system by preventing and reducing the severity of respiratory infections, because of an increase of IgA in the bronchial mucosa [35].

Lactic Acid Bacteria as Source of Functional Ingredients 593

17, 46, 47

17, 36

17, 36

48

50-52

Lactic Acid Bacteria Effects on human health References

pH of the gut and inhibits the

Reduces blood cholesterol.

against inflammation

development of pathogens (*Salmonella* 

block the generation of carcinogenic agents by reducing enzyme activities

microflora. Effective against bacterial

a. Infective diarrhea. The most studied gastrointestinal condition treated by probiotics is acute infectious diarrhea in infants. Children represent a main target of studies due to the importance of limiting the spread of diseases and decreasing the need of antibiotics (Aureli et al. 2011). Clinical trials with LAB derived probiotics (*L. rhamnosus* GG; *L. reuteri*; *L. casei*; *L. delbrueckii subsp. Bulgaricus*) support the efficacy of these probiotics in preventing diarrhea [14,49,53], due to their direct or indirect

b. Antibiotic associated diarrhea. A variety of probiotic bacteria, mainly lactobacilli have been used in the treatment and prevention of antibiotic associated diarrhea [55,56]. In a recent study *L. acidophilus* and *L. casei* seemed to be effective in reducing the risk of development of diarrhea [57]. Nevertheless, the results obtained were from pilot studies, so further investigation is needed to evaluate the

c. Clostridium difficile associated diarrhea. *C. difficile* is an opportunistic pathogen often responsible for diarrhea in vulnerable people. *L. rhamnosus* GG, has

d. Travelers diarrhea. Probiotics with Lactobacilli did not seem to be effective on such diarrhea, which is caused by bacteria, in particular enterotoxigenic E. coli [14,53]. e. Radiation induced diarrhea. Although there is little research on this subject,

probiotics seem to be promising in decreasing radiation diarrhea [53].

to decreased blood pressure

LAB derived probiotics have potential health benefits in the following situations:

*Lactobacillus acidophilus* Secretes lactic acid which reduces the

*spp*, *E. coli*).

*Lactobacillus johnsonii* Effective in inhibition of *H. pylori* and

*Lactobacillus plantarum* Produces short-chain fatty acids that

*Lactobacillus fermentum* Effective in restoration of a normal

vaginosis flora

*Lactobacillus reuteri* Reduces the duration of diarrhea 49

*Enterococcus faecium* Can reduce blood cholesterol leading

**Table 1.** Lactic acid bacteria derived probiotics and human health

interaction with the enterotoxins [54].

efficacy of probiotics on such disorders.

demonstrated positive effects on treated patients [14].

1. Diarrheal diseases:
