Phenotypic and genotypic characterization of lactic acid bacteria isolated from Azerbaijani traditional dairy products

Studied lactic acid bacteria (LAB) were isolated from two types of final ready-to-eat artisanal dairy products (cheeses-Agdas, Sheki and yogurts-Karabakh, Ganja and Baku) manufactured in Azerbaijan. The Agdas cheese belongs to the group of semi hard cheeses whilst the Sheki cheese belongs to hard cheeses. Both of cheeses were produced from cow's milk without the addition of the starter cultures. The Karabakh and Baku yogurts were produced from bovine's milk and the Ganja yogurt from buffalo's milk. Overall 378 isolates were collected from these dairy products and 296 of them were Gram-positive and catalase-negative. It was determined using biochemical tests and molecular methods that four species of LAB were mostly present in these cheeses: Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus paraplantarum and Enterococcus faecium while in yogurts, Lactobacillus delbrueckii subsp. lactis, Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Enterococcus faecium dominated. Five enterococci were producers of antimicrobial compounds

Contribution a l'etude des caracteristiques physico-chimiques des proteines des graines de tournesol (Helianthus annuus L.) et de colza (Brassica napus L.)

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Comparative analysis of beta-casein proteolysis by PrtP proteinase from Lactobacillus paracasei subsp paracasei BGHN14, PrtR proteinase from Lactobacillus rhamnosus BGT10 and PrtH proteinase from Lactobacillus helveticus BGRA43

Lactic acid bacteria contain different cell-envelope proteinases responsible for hydrolysis of caseins. Isolates of Lactobacillus paracasei subsp. paracasei BGHN14 and Lactobacillus rhamnosus BGT10 harbour PrtP and PrtR proteinases, respectively, whereas the PrtH proteinase of Lactobacillus helveticus BGRA43 is similar to that of Lb. helveticus CNRZ32. Mass spectrometry analysis of the major peptides isolated by reversed phase-high performance liquid chromatography allowed the identification of 25, 22 and 17 peptides after beta-casein hydrolysis by strains BGHN14, BGRA43 and BGT10, respectively. Regardless of the type of proteinase, beta-casein was hydrolyzed preferentially after hydrophobic residues and glutamines ( Q). PrtP and PrtR proteinases preferentially targeted the C-terminus of beta-casein. In the case of PrtH proteinase, most of the peptides obtained were cleaved from N-terminus of this casein. Nine identical peptides were identified after hydrolysis with PrtP and PrtR, three after proteolysis with PrtR and PrtH, and two after hydrolysis with all three proteinases studied

Molecular characterization of a novel bacteriocin and an unusually large aggregation factor of Lactobacillus paracasei subsp paracasei BGSJ2-8, a natural isolate from homemade cheese

Screening the collection of natural isolates from semi-hard homemade cheese resulted in isolation and characterization of strain Lactobacillus paracasei subsp. paracasei BGSJ2-8. The strain BGSJ2-8 harbors several important phenotypes, such as bacteriocin production, aggregation phenomenon, and production of proteinase. Bacteriocin SJ was purified by three-step chromatography. Mass spectrometry established molecular mass of the active peptide at 5372 Da. The auto - aggregation phenotype of wild-type (WT) strain was mediated by secreted aggregation-promoting factor (protein of molecular mass gt 200 kDa), probably acting in cooperation with other cell surface protein(s). Comparative study of WT and its spontaneous nonaggregating derivative revealed that aggregation factor was responsible for the observed differences in the bacteriocin and proteinase activities. Bacteriocin SJ activity and resistance to different stresses were higher in the presence of aggregating factor. In contrast, proteinase activity was stronger in the nonaggregating derivative