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

摘要

Technological characteristics of 50 strains of lactococci isolated previously from Turkish dairy products were investigated in order to test their suitability as components of dairy starters. All the lactococcal strains produced low yields of acid from lactose, with the exception of Lactococcus lactis subsp. lactis MBLL9. Of the 50 isolates studied, 22, 17 and 11 strains of L. lactis presented low, moderate and strong proteolytic activity, respectively. 3 of the 50 strains (L. lactis subsp. lactis MBLL1, MBLL9 and MBLL57) produced bacteriocin. Strains L. lactis subsp. lactis MBLL1 and MBLL9 produced lacticin 481-like bacteriocins, whereas MBLL57 was a nisin-like bacteriocin producer. L. lactis strains were tested against 61 lactic phages for their phage-resistance properties. 11 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, 3 and 7 strains were defined as high, medium and low-level diacetyl producers, respectively. L. lactis strains were found to contain 1-10 plasmids with mol. wt. from 1.9 to 29.2 kb.