Probiotics and Postbiotics from Food to Health: Antimicrobial Experimental Confirmation

*Janet Cheruiyot Kosgey, Mercy W. Mwaniki and Fengmin Zhang*

## **Abstract**

The field of probiotics is up-and-coming, especially in management of microbial pathogens. Probiotics confer nutritional benefits, reduce inflammation and infection. Probiotics have also shown to be helpful in the management of microbial pathogens, which include bacteria, fungi, and viruses. To ernes this potential maximumly, there is a need for an elaborate screening system for new isolates. This entails; rigorous screening methods and thorough confirmatory systems. There is need also to come up with standard methods used to evaluate the probiotics mechanism of action both in vivo and in vitro. In summary, there is a need for a standard screening process for probiotic microorganisms that is reproducible. The aim is to ensure that, the candidate microbial cultures are not written off without proper investigations. This will also fasten the screening process and save time and resources wasted in pre-screening experiments.

**Keywords:** probiotics, screening methods, confirmatory methods, postbiotics, animal model, coculture

## **1. Introduction**

Fermentation is one of the oldest technologies used for food preservation. It involves converting carbohydrates to alcohol, carbon dioxide, and organic acids using microorganisms under anaerobic conditions. The fermentation process improves food by developing diverse flavors, aromas, and textures in food substrates. Also, it enriches food substrates with protein, essential amino acids, essential fatty acids, and vitamins. The primary mechanism of the preservation of foods is the production of acid, which lowers the pH to a level at which most of the spoilage-causing microorganisms cannot grow, hence prolonging the shelf life of such foods [1]. At present, various fermented foods are produced worldwide at household and industrial levels, in both small-scale and large commercial enterprises. Associated with fermentation are beneficial microorganisms known as probiotics. The vast majority of the probiotics are lactic acid microorganisms [2] to produce fermented dairy products.

Among the beneficial effects of probiotics include improved intestinal health, enhancement of the immune response, reduction of serum cholesterol, and cancer prevention [3–5]. There is also substantial evidence to support probiotic use in

treating acute diarrhoeal diseases, prevention of antibiotic-associated diarrhea, and improvement of lactose metabolism [6]. The range of food products containing probiotic strains is vast and still growing. And so is the list of beneficial effects. More so, with an increasing desire for quality life, preference for minimal use of chemicals, and the rising cost of healthcare. Natural products like probiotics is a promising alternative. Related to probiotics are prebiotics. Biogenics involves the use of beneficial bioactive substances produced by probiotic bacteria whose activities are independent of the viability of probiotic bacteria.

This book chapter focuses on the use of probiotics in the management of microbial pathogens, emphasizing the need to have a reproducible standard screening process both *in vivo* and *in vitro*. This will highlight areas in the used technologies that need harmonization, technologies for investigation and confirmation of the antimicrobial activities of probiotics, and finally, the future prospects of probiotics and antimicrobial agents.

#### **1.1 Mechanism of action of probiotics**

WHO/FAO defines probiotics as **"**live microorganisms that, when administered in adequate amounts, confer a health benefit on the host" [7, 8]. Prebiotics refer to the substrates that are selectively utilized by host microorganisms that result in conferring a health benefit to the host [8–11]. Furthermore, postbiotics entails the use of beneficial bioactive compounds produced by probiotic bacteria. The activity of postbiotics is independent of probiotic bacteria's viability [11]. The term synbiotics is where both prebiotics and probiotics are utilized simultaneously [11, 12].

The probiotics have myriad of mechanisms in which it protects against infection. These include; (1) they lower pH, (2) pathogen antagonism by producing antimicrobial compounds for example, bacteriocins and or other metabolic products, (3) competitive exclusion with the pathogen for binding sites and receptors sites, (4) competition for substrates that is, nutrients and growth factors, therefore, limiting resources, (5) stimulate immunomodulatory cells, (6) production of enzymes example, enzymes that neutralize toxins produced by pathogens (7) improve the barrier function of the intestinal mucosa, (8) modulate inflammatory responses, (9) aggregate with pathogens, (10) produce hydrogen peroxide (H2O2) a strong oxidizing agent that damage nucleic acids and proteins, (11) produce organic acids like lactic acid, acetic acid among others (12) produce CO2 thus creating anaerobic microenvironment (**Figure 1**) [3, 4, 13–16].

The probiotics are generally regarded as safe [17]. The few results obtained when probiotics are administered together with conventional drugs clinically are promising and include synergy with the drug, half dose of conventional drug needed, and faster healing [18–21]. Further research is needed in this area.

#### **1.2 Probiotics as antimicrobial agents**

Besides the health-improving benefits, the antimicrobial activity of probiotics has been well documented, with promising results against microbial pathogens. Probiotics have been deemed as the following most crucial immune defense systems according to WHO [7]. This is due to increasing antibiotic resistance to commonly prescribed antibiotics [22, 23]. There is a need, therefore, to come up with reproducible screening protocols for *in vitro*, *in vivo*, and clinical studies. Therefore, this book chapter will highlight protocols used in screening probiotics and postbiotics, cite their strengths and drawbacks, and point areas that need harmonization.

*Probiotics and Postbiotics from Food to Health: Antimicrobial Experimental Confirmation DOI: http://dx.doi.org/10.5772/intechopen.99675*

**Figure 1.** *Mechanisms in which probiotics protect against infection.*
