EXTRACELLULAR MATERIAL FROM LEUCONOSTOC-MESENTEROIDES SUBSP DEXTRANICUM MEDIATES THE AGGREGATION OF LACTOCOCCAL CELLS - IMPLICATIONS FOR THE ISOLATION OF SINGLE STRAINS

Cultures of Lactococcus lactis subsp. cremoris, originally derived fro m mixed cheese Starter cultures, were assessed as pure following singl e colony selection and subculturing, yet nevertheless gave rise, under stress conditions, to an isolate with the ability to ferment citrate. The isolate was characterized with respect to its citrate enzymology and lactose fermentation and was identified as Leuconostoc mesenteroid es subsp. dextranicum and assigned the strain number 663. The extracel lular material (ECM) from Leuc. mesenteroides subsp. dextranicum 663 w as characterized and found to contain carbohydrate, protein and phosph ate (30.9, 50.7 and 18.4%, by weight, respectively). Glucose was the m ost prominent sugar (39% by weight of total carbohydrate) with mannose , galactose and rhamnose being the other major monosaccharides. The EC M protein resolved into a large number of bands on SDS-polyacrylamide gel electrophoresis, the most prominent having molecular masses of 40 and 49 kDa. The ECM from Leuc. mesenteroides subsp. dextranicum 663 ca used aggregation of suspensions of lactococcal cells and may facilitat e intergeneric interactions and/or co-culture during cheese starter st rain isolation.