Probiotics acid resistance

Probiotic bacteria differ on the basis of genus, species, and strains. Indeed, strains of the same species vary widely in traits such as expression of enzymes, types of inhibitors produced, carbohydrate fermentation patterns, resistance to acid and bile, ability to colonize the gastrointestinal tract, and clinical efficacy (Berg, 1996 Norat et al., 2002). Furthermore, the active principle has not always been associated with live bacteria, as some immune system modulation activities and macromolecular degradation have been linked to nonviable bacterial components such as enzyme activities or fermentation products (Huttner and Bevins, 1999). 

Gellan or xanthan gums are polysaccharides of microbial origin, obtained from Pseudomonas elodea and Xanthomonas campestris, respectively. Their mixture was reported to be extremely suitable to encapsulate probiotics in systems with high resistance in acidic environments. ... 

Probiotic bacteria have an enhanced viability and resistance to adverse environmental conditions for they are in the form of a biofilm on a phyto-carrier (Fig. 23.1). The pieparations contain enzymes cellulase, amylase, complex of proteases, lipase, as well as or nic acids, biologically active substances, vitamins, amino acids, immunoactive peptides - products of probiotics metabolism. The preparations comprise phyto-particles that are a cellulose microsoibent. 

The above-described scenarios imply that for the future, the selection of probiotics intended to be used in healthy people will require, as a mandatory step, the deep knowledge of the mechanism(s) of the desired beneficial action. To date, the selection criteria used (i.e., resistance to acid, to bile salts, adhesion to epithelial cells, etc.) will represent a pre-requisite in order to guarantee the survival of the bacterial cells into the gut and then to exert their beneficial action in that site. 

Viability probiotics must remain alive during production as well as in the specific delivery vehicle or carrier food. Moreover, probiotics should remain alive when passing through the upper GIT and be resistant to gastric acidity and bile acids before finally reaching the colon. 

To persist to the colon, probiotic strains must show a degree of resistance to gastric acid, mammalian enzymes and bile secretions. It may be of less importance if the mode of probiotic activity is stimulation of the immune system, where the requirement for cell viability and metabolic activity in the gastrointestinal tract is not as relevant. 

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