Bile-resistant derivatives obtained from non-intestinal dairy lactobacilli

Our aim was to obtain derivatives of non-intestinal lactobacilli—commonly used in the dairy industry—able to grow under physiological concentrations of bile salts. Six resistant derivatives (five from Lactobacillus delbrueckii subsp. lactis and one from L. acidophilus) growing in the presence of 0.5% bile salts were obtained from 24 strains of L. delbrueckii subsp. bulgaricus, L. delbrueckii subsp. lactis and L. helveticus, and also one strain of L. acidophilus with low resistance to bile salts. Carbohydrate fermentation profiles remained unchanged but the rate of fermentation of several sugars was generally slower in bile-resistant derivatives. No significant differences with respect to the parent strains were observed for the cell-wall hydrophobicity, capacity to grow in milk and survival during frozen storage. Some bile-resistant derivatives were also resistant to low pH, but in other strains this capacity was acquired following progressive adaptation to low pH. Adaptation to bile salts and low pH might be valuable tools for increasing the survival under gastrointestinal conditions of non-intestinal lactobacilli used for the manufacture of dairy products.