Immobilization Effects of Wheat Bran on Enhanced Viability of Dairy Starters under Acid and Bile Salts Stresses

Abstract

Background and Objective: Survival of beneficial microorganisms in human gut faces many challenges. Immobilization on dietary fibers not only increases the viability of probiotic cultures, but also improves intestinal microbiota composition and decreases several diseases. Therefore, the objective of this study was to assess effects of wheat bran immobilization on survival of multiple species dairy starters under high acidity and bile salts conditions. Materials and Methods: Dairy starter association included lactic acid bacteria of Lactobacillus delbrueckii RKM 0850, Lactobacillus paracasei RKM 0852 and Lactobacillus. parabuchneri RKM 0854, acetic acid bacteria of Acetobacter syzygii RKM 0855, propionic acid bacteria of Propionibacterium freudenreichii subsp. shermanii PL and yeast of Kluyveromyces marxianus RKM 0853. Physical immobilization of the whole association was carried out using adsorption on 3% wheat bran. Results and Conclusion: Effects of acid and bile salts stresses on microbial association survival largely depended on the taxonomic affiliation, aeration rate and experiment media. Kluyveromyces marxianus RKM 0853 was highly resistant to pH 2.0-3.0 and addition of 0.5-15.0% of bile salts. Furthermore, Lactobacillus paracasei RKM 0852 and Acetobacter syzygii RKM 0855 were the most resistant microorganisms to bile salts and Lactobacillus delbrueckii RKM 0850 and Lactobacillus parabuchneri RKM 0854 included the best survival rates at low pH. Wheat bran immobilization promoted survival of the microbial association under stress conditions and prevented loss of viability by more sensitive species. These results are essential for understanding and improvement of stress tolerance in probiotic microorganisms of various taxonomies.