There are certain stress factors whichneed to take into consideration when determine the strain survivability. Inmost cases, the probiotics need to reach the target site in a metabolicallyactive state with a sufficient amount for it to be effectively promoted thehealth benefits.
In the circumstance of oral intake, probiotics must survivethe physicochemical, enzymatic and microbial conditions throughout the GI tractin the human. The first hurdle is the acidic conditionin the stomach. The pH of stomach in normal adult is in the range of 1.
5 to 3.5F. Despite the fact that some foodmatrix can act as a buffer which allowed the probiotics to survive in thebroader range, the long digestion time may subject some microorganisms into theacidic environment F. Thus,it is essential to wisely choose the strain with higher resistance under such environments.The new method to ensure the survival of beneficial microorganisms is byencapsulation 18. The second hurdle is the bilesalts in the small intestine. Bile salts help promotethe intestinal homeostasis by monitoring the intestinal micro flora.
Thesalts are characterized as both hydrophilic and lipophilic. However, bile salts are antibacterial compounds that lysebacterial membranes, denature proteins, chelate iron and calcium, causeoxidative damage to DNA, and control the expression of eukaryotic genesinvolved in host defense and immunity F. Bacterial strain that can adjusted to the small intestinal bilesalts require to withstand the harsh environment by several physiological modificationswhich include cell envelope remodelling and corresponding the efflux systems tostress responses F.Lastly,the probiotics must survive and be able to colonize in the GI tract.
This processis influenced by two factors: the competition against the existing colonyinside the GI tract and the ability to adhere and develop vigorously ontothe gut wall. Even though, the environment in the largeintestine is less harsh comparing to the stomach acid and bile salts, it prerequisitesto compete with existing gut microbial for the available substrates. So, the probioticsshould reside with the micro flora to occupy a purposeful niche in theecosystem. After it can compete with the normal flora, it necessary for the microbesto adhere and grow on the epithelium.
Thesecharacteristics depend on the properties of cells wall which can be determinedby assess the hydrophobic nature using BATH assay and short term adhesion assayswith gut-derived mucins 20,6.