Characterization of Lactococcus lactis strains isolated from ewe's milk and selection of potential cheese culture

Lactococcus lactis je jedna od najbolje opisanih bakterija mliječne kiseline te se često koristi kao komercijalna starter kultura u mliječnoj industriji. Primjena autohtonih sojeva ove bakterije u sirarstvu može utjecati na kvalitetu i sigurnost te razvoj specifičnih senzornih svojstava proizvoda. Pretpostavljeno je da pet sojeva Lc. lactis subsp. lactis M1-M5 izoliranih iz sirovog ovčjeg mlijeka posjeduju poželjne biokemijske i tehnološke značajke, čije dokazivanje je bilo predmet ovog istraživanja. Rezultati pokazuju da ni jedan od izolata ne stvara plin razgradnjom glukoze, svi pokazuju jednaku proteolitičku, lipolitičku i antimikrobnu aktivnost aktivnost te imaju visoki stupanj acidifikacijske sposobnosti. Tijekom izlaganja različitim uvjetima temperature, pH vrijednosti te koncentracijama soli rast je prisutan kod svih izolata od kojih Lc. lactis subsp. lactis M1 pokazuje najbolji rast. Svi izolati bi se mogli primijeniti kao potencijalne sirarske kulture, a obzirom na navedena odstupanja odabir sojeva trebao bi se temeljiti na tehnološkom procesu i organoleptičkim svojstvima željene vrste sira.Lactococcus lactis is one of the best described lactic acid bacteria and is commonly used as a commercial starter culture in the dairy industry. The use of indigenous strains of this bacterium in cheese production can affect the quality and safety, as well as the development of specific sensory characteristics of the product. Five strains of Lc. lactis subsp. lactis M1-M5 isolated from raw sheep milk are believed to possess desirable biochemical and technological properties, the demonstration of which was the subject of this study. The results show that none of the isolates produce gas by glucose degradation, all show the same proteolytic, lipolytic and antimicrobial activity and have a high degree of acidifying ability. During exposure to different temperature conditions, pH values and salt concentrations, growth is present in all isolates, of which Lc. lactis subsp. lactis M1 shows the best growth. All isolates could be used as potential cheese cultures and given the above variations, the selection of strains should be based on the technological process and organoleptic characteristics of the desired type of cheese