Aims: The aim of the study was to characterize isolates of lactic acid bacteria from Beyaz cheese and to study some of their technologically important properties. Methods and Results: Seventy‐seven lactic acid bacteria isolated from Beyaz, a Turkish white‐brined cheese made from raw ewes’ milk without any starter, were classified by phenotypic criteria and sodium dodecyl sulphate‐polyacrylamide gel electrophoresis of whole‐cell proteins. Whole cells of Lactococcus lactis subsp. lactis and enterococci showed lipolytic and proteolytic activities. Strains were found that differed in terms of their acidifying and caseinolytic activity. Most of the enterococci isolates showed tyrosine decarboxylase activity; moreover, lactobacilli exhibited weak antibacterial activities against foodborne pathogens. Conclusions: Strains of lactic acid bacteria with interesting biotechnologically important properties may be found in Beyaz cheese. Significance and Impact of the Study: Lactic acid bacteria isolates with interesting biotechnological profiles may influence the quality and variety of dairy products, if they are used as starters, and their cheese‐making characteristics seem promising.

Thirty native (Turkish origin) strains of Streptococcus thermophilus and 24 strains of Lactobacillus delbrueckii ssp. bulgaricus were isolated and identified. These strains were examined for their technologically important properties such as acidification, proteolysis, acetaldehyde production and antimicrobial activity. By taking into consideration their phage resistant properties, two strains of S. thermophilus (St.7.7, and St.26.2) and one of L. bulgaricus , numbered as 2004, were found to have the potential to be starters for yogurt production.

In this study, 26 Streptococcus thermophilus phages were classified according to their structural protein patterns and DNA restriction fragment length polymorphism. Furthermore, sensitivities of natural and commercial S. thermophilus strains to S. thermophilus phages were investigated. All the natural strains were found to be resistant to the phages. The electrophoretic profiles of the structural proteins of S. thermophilus phages were identified according to the two common major bands at 30.6 and 27.3 kDa. Various restriction endonucleases were used to digest S. thermophilus phages that were differentiated into eight subgroups depending on the length of EcoRV digestion. A phylogenetic tree was designed using fragments of EcoRV digestion. The results showed that all phages derived from a common ancestor and some of them were differentiated from each other over time. PRACTICAL APPLICATIONSLike other microorganisms, it is necessary to identify and classify the phages in order to follow their evolutionary development. Besides, the characterization of these phages is also important for determining the rotation program of the culture in dairy factory. In this study, the phages isolated from different dairy products were identified and classified according to their properties.

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