Variation in caseinolytic properties of six cheese related Lactobacillus helveticus strains

A large degree of strain variation was observed in caseinolytic properties of six cheese related Lactobacillus helveticus strains. Activity on intact alpha(s1)- and beta-casein was observed only after growth in milk and not in MRS. Totally 27 peptides from alpha(s1)- and 22 from beta-casein were identified from MS/MS fragmentation patterns. All six strains released peptides from the amino end of alpha(s1)-casein, and the bonds Ile(6)-Lys(7) and Gln(9)-Gly(10) were identified as primary cleavage sites. Strain variation in the activity on intact P-casein was observed and five of the six strains released peptides from the C-terminal region. The strains had very different activities and some strains had only trace activities. L helveticus CNRZ 32 had the highest activity towards alpha(s1)-casein while L. helveticus LHC2 had the highest activity towards beta-casein, and these two strains also produced unique peptides from both alpha(s1)- and beta-casein. (C) 2009 Elsevier Ltd. All rights reserved.