ABSTRACT
Contents 19.1 Introduction ....................................................................................................................385 19.2 Intestinal LAB ............................................................................................................... 386
19.2.1 Lactobacilli in the GI Tract ................................................................................ 386 19.3 Lactobacilli in the Gut: True Residents or Food-Derived Transients? ............................. 388 19.4 Lactobacilli in the Gut: Successful Adaptation ............................................................... 390 19.5 Streptococci: Forgotten LAB in GI Tract ........................................................................393 19.6 Conclusions and Perspectives ......................................................................................... 396 References ............................................................................................................................... 397
The LAB play a prominent role in the world’s food supply, having a leading part not only in the fermentation of dairy products, meats, and vegetables, but also in the production of wine, coffee, silage, cocoa, sourdough, and numerous indigenous food fermentations (Wood and Holzapfel 1995). In addition to their role in the food production, LAB are also associated with our mucosal surfaces, in particular with the gastrointestinal (GI) tract, and oral and vaginal cavities of humans and other mammals (Wood and Holzapfel 1995, and other chapters in this book). Therefore, because of their Generally Accepted As Safe (GRAS) and Qualified Presumption Safety (QPS) status and based on their common presence in daily human diets, LAB have received tremendous attention with respect to their potential health-promoting properties. Lactobacilli and bifidobacteria have been linked to human health since the late 1800s when Metchnikoff (1907) first proposed that LAB may have a beneficial effect on humans. Metchnikoff proposed that LAB in fermented milk could promote the development and maintenance of a healthy intestinal microbiota; in particular they could prolong human life by preventing putrefaction. In the 21st century, lactobacilli and bifidobacteria have an important position in the market of so-called functional foods, including probiotic products that contain “live microorganisms which when administered in adequate amounts confer a health benefit on the host” (FAO/WHO 2002). In this chapter we focus on the diversity and potential role of LAB in the human GI tract.
