**3.3 Buttermilk as an additive in the composition of culture media for fermentative processes**

 Acidic bacteria (AB) are widely used in the production of fermented products. The use of buttermilk as a growth medium for probiotic lactobacilli has been reported. Probiotic foods are those that have probiotic bacteria in their formulation which, when given in sufficient quantities, promote health benefits for the user [5, 14]. The benefits are related to both the direct effect of probiotics and active metabolites produced during the fermentation process. These products should have between 106 and 107 CFU/mL of probiotics, being *Lactobacillus* and *Bifidobacterium* the most commonly used probiotics [14].

Although buttermilk presents a carbon source, there is a lack of nitrogen, which is necessary for the growth of AB. In this regard, an investigation used yeast extract as a source of nitrogen and obtained a good performance of the three strains tested in a medium containing buttermilk and yeast extract [15]. Another study, with a small concentration of yeast extract (0.3%), also perceived a good performance in the growth of *Lactobacillus* in buttermilk [16].
