Effetto delle condizioni di stress gastrointestinali sulla validità di batteri lattici di interesse salutistico

Many probiotic formulations are available on the market and sold in the form of food supplements that can improve physical health of the consumer. In fact, for many probiotic preparations, there are specific health claims, previously approved by EFSA, that are used to direct the consumer to their use in the prevention or treatment of different diseases. Therefore, in presence of a healthy effect stated, the formulation should contain particular probiotic strains, with appropriate amount of live and viable microorganisms, able to act in the intestine to relieve symptoms or assist the treatment of specific pathologies. Not surprisingly, among the criteria dictated by the appropriate use of the term "probiotic", there is the determination of the specific beneficial effect that the microorganism, or the pool of microorganisms, is able to give to the consumer. Another important evaluation criterion is represented by the ability to survive to the gastrointestinal transit, in order to arrive to the colon with high amount of live and viable microorganisms. However, unlike drugs, which are intensively inspected by the inspection authorities to ensure safe use and efficacy, probiotics are controlled less rigorously. As a result, it is much easier to take advantage of the existing legislative gap in this area, to bring to the market new probiotic products whose safety and efficacy have been often only slightly tested. In light of these circumstances, the first part of the PhD research was aimed to the identification of microorganisms composing different lactic acid bacteria based pharmaceutical formulations and the ascertainment of their ability to survive gastrointestinal (GI) stresses, the main requisite to produce beneficial effects. This evaluation, unlike what is reported in numerous studies available in literature, was conducted without a preliminary rehydration step, since their ingestion by the consumer, and the next step through the gastrointestinal tract, does not contemplate this condition. The next activity was focused on the evaluation of viability, after the conservation and simulated gastrointestinal transit, of some commercial probiotic strains integrated in a food matrix, in order to evaluate the protective capacity. From this point of view, food may be able to positively affect the survival of microorganisms in the gastrointestinal tract, thus playing an important role as a vehicle of probiotics in the diet. Their use can therefore become a winning approach from an economic and nutritional standpoint, as long as the food choice falls on matrices that are not only adequately present in consumers' diets, but also already have healthy interesting components and are appealing enough to the widest age range of people. In this context, our choice fell on dark chocolate. However, the results showed that this food matrix, although is rich in valuable ingredients from the nutritional, healthy and emotional point of view, can not be a preferential vehicle to protect the organisms during their passage through the intestine. From this consideration, in fact, derived one last activity: the assessment of the influence of each gastrointestinal stress factor on the survival of Lactobacillus rhamnosus strains isolated from food matrices, fecal samples and probiotics pharmaceutical formulations. That analysis furnished results particularly interesting not only with regard to the conditions that mostly affect the viability of the strains during transit but also to food-borne matrices (casein) that are able to play a substantial protective effect against the injuries caused by these conditions.