ABSTRACT
Dairy propionibacteria are food grade bacteria belonging to the Actinomycetales order. Actinomycetales are described as high GC (53 to 68 %) Gram-positive bacteria, known for their prolifi c production of small molecule natural products and adapted to various ecological niches including soil, decaying vegetation, humans and animals. Accordingly, propionibacteria can be isolated from various environments. All species of the Propionibacterium genus produce propionic acid as a main metabolic end-product of their obligatory fermentative metabolism. They are nonspore forming, non-motile, pleomorphic rods, anaerobic to aerotolerant and generally catalase positive. Taxonomic studies, in accordance with phenotypic traits, clearly distinguish two groups of propionibacteria species (Table 1): cutaneous and dairy propionibacteria.
