Biodiversity of lactic acid bacteria and the effects on their cell surface proteinases.

Lactic acid bacteria are used in a wide range of food fermentations and play an important role in food industry. The development of molecular biology techniques has revealed a broad genetic diversity and has resulted in a new classification. Lactic acid bacteria associated with food belong to eleven genera: Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus et Weissella. This biodiversity is reflected in the properties of a protein assuming an identical fonction among these bacteria: the cell surface proteinase. This endoprotease is essential to a rapid bacterial growth in milk and is responsible for the first step of casein hydrolysis. A variation of the hydrolysis specificity towards caseins is observed among proteinases from lactococci and lactobacilli. The genetic diversify within Lactobacillus genus has generated proteinases with different mechanisms controlling their biosynthesis, their enzyme maturation and cell wall attachment.