Characterisation and preliminary lipid-lowering evaluation of Lactobacillus isolated from a traditional Serbian dairy product.

We investigated the potential probiotic properties of indigenous lactic acid bacteria (LAB) isolated from Serbian homemade cheese. Seventeen LAB strains were isolated and characterised using standard protocols. One of the strains showed several probiotic properties: survival at low pH and in bile salts solution, antimicrobial activity, susceptibility to antibiotics and adhesion to hexodecane. DNA analysis identified the isolate as Lactobacillus casei, hereafter named L. casei 5s. The lipid lowering effect of L. casei 5s was evaluated in vivo using a hyperlipidemic rat model. Orally administered L. casei 5s significantly decreased the elevated total serum cholesterol and triglycerides, and attenuated macro vesicular steatosis in the liver. Moreover, L. casei 5s improved the intestinal microbial balance in favour of lactobacilli, while decreasing the number of Escherichia coli cells. The bacteria were re-isolated and identified from the surface of the intestinal mucosa and from the faecal samples of treated animals, indicating adhesiveness and colonisation ability. The results of an acute oral toxicity study in mice and the absence of translocation to other organs demonstrated the safety of the strain. In conclusion, L. casei 5s demonstrated promising probiotic potential and might be a good candidate for more detailed investigations.

Superoxide dismutase biosynthesis by two thermophilic bacteria.

Some high-molecular weight antioxidant defense system components of two thermophilic bacteria isolated from spa waters of Serbia (Yugoslavia) and identified as Bacillus stearothermophilus and Thermothrix sp. were studied. In addition to superoxide dismutase (SOD; EC 1.15.1.1), qualitative analyses demonstrated the presence of catalase (EC 1.11.1.6), peroxidases and oxidases in both bacterial strains. Cell-free extracts were subjected to nondenaturing polyacrylamide gel electrophoresis (PAGE) and SOD activity in the eluates of the corresponding bands was examined in the presence of several specific inhibitors. A slight decrease of SOD activity observed in the presence of 0.3 M potassium cyanide and its complete insensitivity to hydrogen peroxide (5 mM) and sodium azide (20 mM) action suggest that the enzyme occurring in the two thermophiles represents Mn SOD. A high SOD activity recorded in cell-free extracts strongly recommends these two bacterial strains as potential producers of this important antioxidant defense system component at industrial scale.