ABSTRACT
Lactic acid bacteria (LAB) are a heterogeneous family of microorganisms that can ferment a variety of carbohydrates primarily into lactic acid (Carr et al. 2002). Most of the LAB belongs to the order of Lactobacillales, a group of mainly Gram-positive, anaerobic, non-sporulating and acidtolerant bacteria. Biochemically, LAB include both homofermenters and heterofermenters (Kleerebezem et al. 2003). The former group produces primarily lactic acid through carbohydrate fermentation, while the latter group yields a variety of fermentation by-products including lactic acid, acetic acid, ethanol, carbon dioxide and formic acid (Leroy and de Vuyst 2004). LAB can be sub-classifi ed into seven phylogenetic clades: Lactococcus, Enterococcus, Oenococcus, Pediococcus, Streptococcus, Leuconostoc and Lactobacillus. The defi nition of LAB is biological rather than taxonomical, i.e., the LAB do not comprise a monophyletic group of bacteria. Today, it is known that LAB play a crucial role in the world food supply by performing the main bioconversions in fermented dairy products, meats and vegetables. LAB are also used in the production of wine, coffee, silage, cocoa, sourdough and numerous indigenous food fermentations (Leroy and de Vuyst 2004). LAB are indigenous to food-related habitats including plant (fruits, vegetables and cereal grains) and milk environments. In addition, some LAB species are also member of the fl ora of the mouth, intestine and vagina of the mammalian (Vaughan et al. 2005). Isolates of the same species are often obtained from plant, dairy and animal habitats, implying wide
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distribution and specialized adaptation of these species to these diverse environments.
