AN ADAPTATION STRATEGY TO IMPROVE THE PROTEOLYTIC ACTIVITIES OF LACTIC ACID BACTERIA ISOLATED FROM PICKLES

This study aimed to increase the proteolytic activity of 10 lactic acid bacteria (LAB) species isolated from pickles, which had low activity. For this purpose, a nine-step adaptation through the gradual addition of MRS Broth with peptone and a subsequent four-step adaptation through the gradual addition of MRS Broth with skim milk were applied. A slight improvement of the proteolytic activity following the gradual addition of MRS Broth with peptone was observed only in six LAB samples, of which Pediococcus ethanoliduras 513 showed the highest activity at the ninth step. At the 13 step corresponding to the last step of the skim milk adaptation, only L. buchneri 114, L. brevis 494, and L. plantarum 380 showed slightly higher activity compared to that at the ninth step. In conclusion, peptone and skim milk adaptations did not yield any industrially significant increase in the proteolytic activity of the 10 LAB strains isolated from pickles. An important increase was only obtained in the proteolytic activity of L. plantarum 380. Its initial activity of 0.095 mM pNA increased to 0.182 mM pNA and finally to 0.250 pNA at the ninth and 13 steps, respectively, but this increase is too small for industrial applications.