Release and partial characterization of cell-envelope proteinases fromLactococcus lactis subsp.lactis IFPL 359 andLactobacillus casei subsp. casei IFPL 731 isolated from raw goat,s-milk cheese

Different methods of releasing the cell-envelope proteinase (CEP) fromLactococcus lactis IFPL 359 (Lc-CEP) andLactobacillus casei IFPL 731 (Lb-CEP) have been tested. Release of Lc-CEP was higher in Ca^2+-free buffer than in the presence of lysozyme and Ca^2+-. Lb-CEP was not soluble in Ca^2+--free buffer, making necessary the use of chelating agents such as ethylenediaminetetraacetate (EDTA) to attain release yields of 15–20%. Solubilizing the cell wall oflb.casei using lysozyme and mutanolysin improved CEP release yields, even in the presence of Ca^2+-. Two differently charged chromophoric peptides were degraded by whole cells and the soluble fractions studied at different hydrolysis rates in both the strains considered. Based on the specificity of these CEPs for the different substrates, the two proteinases can be placed in the same class as the CEP_I/III mixed-type variants that have been identified in lactococcal proteinases. In both strains ß-casein was hydrolysed more rapidly thanα _s-cascin.