Purification and characterization of thermophilin T, a novel bacteriocin produced by Streptococcus thermophilus ACA-DC 0040

ACA-DC 0040 produced an antimicrobial agent, which was named thermophilin T, active against several lactic acid bacteria strains of different species and food spoilage bacteria, such as Clostridium sporogenes C22/10 and Cl. tyrobutyricum NCDO-1754. The crude antimicrobial compound is sensitive to proteolytic enzymes and α-amylase, heat-stable (100 °C for 30 min), resistant to pH exposure at pH 1-12 and demonstrates a bactericidal mode of action against the sensitive strain Lactococcus cremoris CNRZ-117. The production of bacteriocin was optimized approximately 10-fold in an aerobic fermenter held at constant pH 5.8 and 6.2. Ultrafiltration experiments with culture supernatant fluids containing the bacteriocin, and further estimation of molecular weight with gel filtration chromatography, revealed that bacteriocin in the native form has a molecular weight in excess of 300 kDa. SDS-gel electrophoresis of partially purified thermophilin T showed that bacteriocin activity was associated with a protein band of approximately 2.5 kDa molecular mass

Cell-wall-bound proteinase of Lactobacillus delbrueckii subsp. lactis ACA-DC 178: Characterization and specificity for beta-casein.

Lactobacillus delbrueckii subsp. lactis ACA-DC 178, which was isolated from Greek Kasseri cheese, produces a cell-wall-bound proteinase. The proteinase was removed from the cell envelope by washing the cells with a Ca(2+)-free buffer. The crude proteinase extract shows its highest activity at pH 6.0 and 40°C. It is inhibited by phenylmethylsulfonyl fluoride, showing that the enzyme is a serine-type proteinase. Considering the substrate specificity, the enzyme is similar to the lactococcal P(I)-type proteinases, since it hydrolyzes β-casein mainly and α- and κ-caseins to a much lesser extent. The cell-wall-bound proteinase from L. delbrueckii subsp. lactis ACA-DC 178 liberates four main peptides from β-casein, which have been identified

Characteristics of sheep and goat milks : Quality and hygienic factors for the sheep and goat dary sectors

International audienceAprès une présentation synthétique de l'industrie des laits de brebis et de chèvre sur le plan mondial, l'article expose les caractéristiques hygiéniques et technologiques de ces laits. Des recommandations relatives à l'application du code de l'hygiène pour les petits ruminants sont proposées, en relation avec la situation des filières industrielles des laits de brebis et de chèvre mais également en tenant compte de l'importance économique des productions artisanales et des pays en voie de développement

Characteristics of sheep and goat milks : Quality and hygienic factors for the sheep and goat dary sectors

International audienceAprès une présentation synthétique de l'industrie des laits de brebis et de chèvre sur le plan mondial, l'article expose les caractéristiques hygiéniques et technologiques de ces laits. Des recommandations relatives à l'application du code de l'hygiène pour les petits ruminants sont proposées, en relation avec la situation des filières industrielles des laits de brebis et de chèvre mais également en tenant compte de l'importance économique des productions artisanales et des pays en voie de développement

THE COMBINED USE OF WHOLE-CELL PROTEIN EXTRACTS FOR THE IDENTIFICATION (SDS-PAGE) AND ENZYME-ACTIVITY SCREENING OF LACTIC-ACID BACTERIA ISOLATED FROM TRADITIONAL GREEK DAIRY-PRODUCTS

A total of 148 strains of lactic acid bacteria from the ACA-DC Collection were examined in this study. They were all isolated from traditional Greek dairy products such as yoghurt and cheese and were assigned to the genera Enterococcus, Lactobacillus, Lactococcus, Leuconostoc and Streptococcus. By use of traditional phenotypic methods 65 strains were identified to the species level; the remaining 83 strains were partially characterised (genus level). The SDS-PAGE technique of whole-cell proteins was evaluated as an advanced tool for the identification of lactic acid bacteria. Therefore protein fingerprints were registered for all strains and compared to a large number of lactic acid bacteria reference strains stored in database format. In most cases the SDS-PAGE analysis confirmed the phenotypic identification results. With only a few exceptions, all partially characterised strains were identified to (sub)species level. In order to quickly reveal characteristics which could be important for their use as starter cultures in dairy fermentations, it is shown that the bacterial cell-free protein extracts could simultaneously be screened for peptidase and esterase activities using synthetic substrates. Obvious differences among the strains, the groups of strains as well as on the genus level were observed