Extraction and partial characterization of proteolytic activities from the cell surface of Lactobacillus helveticus Zuc2.

Proteolytic activities were extracted from a dairy Lactobacillus helveticus strain and partially characterized. A first cell envelope proteinase (CEP) was extracted using a high ionic strength buffer, both in the presence and in the absence of Ca2+. Moreover, cell treatment by 5 M LiCl allowed for the selective removal of the S-layer protein and CEP, suggesting an enzyme ionic linkage to the cell envelope similar to that observed for the Slayer structure. The enzyme specificity against alpha(s1)-CN (f1-23) showed unusual activity on the Lys3-His4 bond compared with other proteinases of the same species. A second proteinase appeared to be linked to the cell membrane because it was extractable only after membrane disgregation by detergents. Its specificity against CN fractions and alpha(s1)-CN (f1-23) was different from that of the first CEP; moreover, the measured activity was lower than that of CEP.

Serum cholesterol levels in axenic mice colonized with Enterococcus faecium and Lactobacillus acidophilus.

Hypocholesterolemic effect was shown in axenic, mono, bicolonized and conventional mice: the effect was different depending on probiotic properties of intestinal microorganisms. Contamination by Enterococcus faecium CX determined the highest effect: haematic cholesterol level decrease was 16.9% in females and 7.8% in males. In mice contaminated by Lactobacillus acidophilus N5 the decrease of haematic cholesterol levels was less and not relevant in mice contaminated by conventional microflora. Enterococcus faecium CX and Lactobacillus acidophilus N5 strains were able to grow in presence of bile salts, to colonize intestinal tract, to survive at gastric conditions and to assimilate cholesterol (E. faecium more than L. acidophilus). The authors consider the possibility to associate probiotic strains with these characteristics for the health of consumers.