Physiological Characteristics and Immunomodulating Activity of Streptococcus macedonicus LC743 Isolated from Raw Milk

To develop a new starter culture for fermented milk, Streptococcus macedonicus LC743 was isolated from raw milk and its physiological characteristics were investigated. S. macedonicus LC743 showed good immunomodulating activity compared to the index LAB starters tested. The optimum growth temperature of S. macedonicus LC743 was 40oC, and it took 18 h to reach pH 4.34 under these conditions. S. macedonicus LC743 showed higher sensitivity to novobiocin in a comparison of 15 different antibiotics and showed the highest resistance to gentamycin. It also showed higher activities of leucine arylamidase and acid phosphatase. Moreover, it was comparatively tolerant to bile juice and acid and displayed high resistance to Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus with rates of 80.0%, 68.42%, and 81.54% respectively. These results demonstrate that S. macedonicus LC743 could be an excellent starter culture for fermented milk with a high level of immunomodulating activity.