Investigation of some bioactive properties of buttermilk fermented by mixed probiotic cultures

In this study, it was aimed to investigate some pysicochemical, microbiological, and bioactive properties of buttermilk fermented by different probiotic bacteria and yeast strains. For this purpose, the strains of Lactobacillus acidophilus, Lacticaseibacillus rhamnosus, Bacillus coagulans, Bacillus clausii and Saccharomyces boulardii were used for buttermilk fermentation. During fermentation, changes of microbial gowth of each strain, pH, total free amino acid content, and antioxidant activity (CUPRAC and DPPH) values were monitored. Antimicrobial acitivy of the fermented buttermilk samples was determined using the disc diffusion tecnique. As a result, the counts of L. acidophilus, L. rhamnosus, B. coagulans, and B. clausii were observed to increase by 2.13 log CFU/mL, 2.0 log CFU/mL, 1.32 log CFU /mL ve 1.24 log CFU/mL, during fermentation. The microbial growth of B. coagulans and B. clausii was found to be limited in buttermilk. An increase in the counts of S. boulardii wasdetermined as 3.56 log CFU/mL ve 2.78 log CFU/mL respectively, at the end of 48 hours of fermentation in mixed-culture fermentation with S. boulardii+B. coagulans and S. boulardii+B. clausii. Significant changes in the CUPRAC and DPPH antioxidant values of the fermented buttermilk samples were observed depending on the type of probiotic microorganism and fermentation time. In fermentation experiments with L. acidophilus and L. rhamnosus strains, the total free amino acid content in the buttermilk samples was found to change depending on microorganism strains while the highest total free amino acid content was observed in the buttermilk samples fermented by L. acidophilus. It was determined that all fermented buttermilk samples did not exhibit significant antimicrobial activity against Escherichia coli ATTC 25922 and Staphylococcus aureus ATTC 6538 strains. Based on the findings, it can be concluded the use of probiotic microorganims in buttermilk can be further provided through the optimization of probiotic culture levels and the application of different fermentation tecniques.