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Probiotics, Prebiotics and Synbiotics: Opportunities, Health Benefits and Industrial Challenges

Parmjit Singh Panesar1, Anil Kumar Anal2 and Rupinder Kaur1

1 Food Biotechnology Research Laboratory, Department of Food Engineering & Technology, Sant Longowal Institute of Engineering and Technology, Longowal-, 148 106, Punjab, India

2 Department of Food Agriculture and Bioresources, School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani, Thailand

1.1 Introduction

Ever since the "Theory of Longevity" was proposed by Elie Metchnikoff and was correlated with prolonged youth and healthy old age, the search for food components as well as nutrients that not only enhance health but also help prevent disease has expanded, as has understanding of their role. Over the past few decades a plethora of novel foods have indicated specific health benefits, and those foods have been termed "functional foods" (Anal 2019; Noomhorm et al. 2014). The functional foods concept applies to those food products that exhibit various health beneficial properties to the host, apart from nutrition; hence this has become a recent area of research worldwide (Rastall 2010). Since its introduction, the global market demand for these foods has enlarged and market size is predicted to increase from USD 150 billion in 2018 to USD 250 billion in the next few years. The major leaders in this market are the United States, Europe and Japan, whereas China, India, Latin America and some of the other Asian countries are emerging as the fastest growing market (Patel and Goyal, 2012). In recent years, the functional food concept has moved progressively towards the development of dietary supplements that may have a profound effect on the gut microbial composition and activities.

The human microbiota comprises approximately 1014 microbial cells, which are 10 times greater in number than the cells of the human body (Savage 1970). Among all the parts or surface of the human body, the gastrointestinal tract is one of the most heavily colonized organs, accommodating about 70% of all the microbes in the human body (Figure 1.1) and playing a crucial role in health and disease (Ley et al. 2006). Changes in the gastrointestinal ecosystem or an imbalanced gut microflora have been associated with the occurrence of several diseases, including inflammatory bowel disease, diarrhea, colon cancer and many others.

Figure 1.1 Human intestine and the number of microflora in the gut.

Source: Modified from Vyas, U. and Ranganathan, N. (2012). Probiotics, prebiotics, and synbiotics: gut and beyond. Gastroenterology Research and Practice, 2012: 872716.

Studies have revealed that several dietary supplements, such as probiotics and prebiotics, have a positive impact on the gut microbiota and can be used to combat various diseases. In addition, the synergistic combination of probiotics and prebiotics, known as synbiotics, is known to impart greater efficiency than probiotic or prebiotic supplements used in isolation. Further, combinations of synbiotics have shown therapeutic effects against various diseases, such as those of the gastrointestinal and respiratory tracts, allergy, diabetes and cancer (Dinleyici et al. 2013; Rayes et al. 2002). Various examples of probiotics, prebiotics and synbiotics are described in Table 1.1. In United States, several foods incorporating probiotics and prebiotics have been introduced to the market and novel techniques are being developed to enhance shelf life and consumer acceptability (Koirala and Anal 2021).

In this context, this chapter provides a comprehensive overview of probiotics and prebiotics as well as synbiotics. Their mechanism of action in the body and significant health beneficial applications are also discussed in detail.

1.2 Probiotics

The term "probiotic" originates from the Greek word meaning "for life". The term was first invented by Ferdinand Vergin in 1954 as "probiotika", denoting something observed to be favorable to the gut microflora (Vergin 1954).This term was further refined by Lilly and Stillwell in 1965 as "a product produced by one microorganism stimulating the growth of another microorganism" (Lilly and Stillwell 1965). Subsequently, the term was redefined by Fuller in 1989 as "non-pathogenic microorganisms which when ingested exert a positive influence on host's health or physiology" (Fuller 1989). The latest definition was formulated in 2002 by the Food and Agriculture Organization (FAO) and World Health Organization (WHO), and states "live strains of strictly selected microorganisms, which when administered in adequate amounts, confer a health benefit on the host" (FAO 2002).

Table 1.1 Examples of probiotics, prebiotics and synbiotics.

Sources: Based on Tadesse, S. (2012). Probiotics, prebiotics and synbiotics as functional food ingredients: production, health benefits and safety. Journal of Biologically Active Products from Nature , 2(3): 124-134 ; Pandey, K.R., Naik, S.R. and Vakil, B.V. (2015). Probiotics, prebiotics and synbiotics-a review. Journal of Food Science and Technology , 52(12): 7577-7587 ; Markowiak, P. and Slizewska, K. (2018). The role of probiotics, prebiotics and synbiotics in animal nutrition. Gut Pathogens , 10(1): 21 ; Mofid, V., Izadi, A., Mojtahedi, S.Y. and Khedmat, L. (2020). Therapeutic and nutritional effects of synbiotic yogurts in children and adults: a clinical review. Probiotics and Antimicrobial Proteins 12(3): 851-859.

The most common microbial strains are Lactobacillus rhamnosus, L. reuteri, L. casei, L. acidophilus, Bacillus coagulans, Bifidobacterium, etc. Probiotic products may comprise either a single strain or a combination of two or more strains (Chapman et al. 2011). As per the guidelines of the FAO, WHO and European Food Safety Authority (EFSA) on the selection of probiotic strains, the strains must satisfy safety as well as functionality criteria and technological usability. The safety of the strain is characterized by its origin and absence of association with pathogens and antibiotic resistance, whereas functional aspects include its survival in the gastrointestinal tract and its immunomodulatory properties. On the other hand, technological usability is related to its production and is correlated with its survival and maintenance of properties throughout the storage and distribution period (Lee 2009). In addition, in the USA, the microorganisms used for consumption must have a Generally Recognized As Safe (GRAS) status regulated by the FDA; in Europe the EFSA has introduced Qualified Presumption of Safety (QPS), which involves additional criteria for the safety of bacterial supplements (Anadón et al. 2006; Gaggìa et al. 2010).

1.2.1 Mechanism of Action

Probiotics play a significant role in the host, especially in the development of the microbiota, ensuring a balance between the pathogens and bacteria necessary for the normal function of the host (Schachtsiek et al. 2004). A few microorganisms, such as L. plantarum, L. reuteri, Bifidobacterium adolescentis and B. pseudocatenulatum, have been reported as natural producers of B-group vitamins (Li and Gu 2016), immunomodulators, increase the absorption of vitamins as well as minerals and allow the production of amino acids and organic acids (Nova et al. 2007). Apart from this, some probiotic microorganisms are known to generate enzymes such as esterase and lipase, and coenzymes (A, Q, NAD, NADP), and the products of bacterial metabolism have anticancerogenic, immunosuppressive and antibiotic properties (Ishikawa et al. 2005).

On the basis of molecular and genetic studies, the health beneficial properties of probiotic microorganisms involve four basic mechanisms: (i) antagonism through secretion of antimicrobial substances; (ii) competition with pathogens for adhesion to the epithelium and for nutrients; (iii) immunomodulation of the host; and (iv) inhibition of toxin production (Guillot 2003; Isolauri...