Technological characterization of wild-type Lactococcus lactis strains isolated from raw milk and traditional fermented milk products in Turkey

The aim of this work was to detect technological characteristics of fifty strains of lactococci previously isolated in Turkey in order to use them as components of starter formulations. All the lactococcal strains were low acid producers from lactose except L. lactis subsp. lactis MBLL9. 22, 17 and 11 strains of L. lactis presented low, moderate and strong proteolytic activity, respectively. Three out of 50 strains (L. lactis subsp. lactis MBLL1, MBLL9 and MBLL57) were determined to be bacteriocin producers. The strains L. lactis subsp. lactis MBLL1 and MBLL9 were found to be lacticin 481-like producers, whereas MBLL57 was a nisin-like producer, according to their partial characterization data. L. lactis strains were tested against 61 lactic phages for their phage-resistance properties. Eleven strains exhibited a sensitive phenotype against different phages, whereas the remaining 39 strains were completely resistant to all phages. Among the L. lactis subsp. lactis biovar. diacetylactis strains, 5 strains were defined as high, 3 strains as medium and 7 strains as low-level diacetyl producers. L. lactis strains were found to have 1-10 plasmids with molecular weights from 1.9 to 29.2 kb.