Partial Purification and Characterization of the Main Autolysins from Lactococcus Lactis Subsp, Cremoris ATCC 9596

The purpose of this study was to purify and characterize the main autolysins from Lactococcus lactis subsp. cremoris ATCC 9596 (Mc5). After protein separation, hydrolysing activity tests of bacterial cell wall were used to show the presence of autolysin in Lactococcus strains. Its presence was more evident when using LiCl in the test buffer. Using a simple method, 49.5 kDa autolysin was partially purified. Results for different ratios with or without LiCl showed that the addition of Lactobacillus to Lactococcus largely influenced cell autolysis. Mixing Lactococcus and Lactobacillus strains in a 3:1 ratio during the exponential phase of growth increased autolysis. Maximum autolysis (96%) was obtained after 48 h at a 3:1 ratio. However, when Lactobacillus concentration increased, autolysis decreased without LiCl. Electron microscopy and optical spectro observations correlated well. New structures (i.e. polysaccharides and small circular cells (vesicles)) observed after 48 h of lysis suggested that nearly complete cell-wall degradation occurred.