Study of the effects of temperature, pH and NaCl on the peptidase activities of non-starter lactic acid bacteria (NSLAB) by quadratic response surface methodology
M. Gobbetti et al., Study of the effects of temperature, pH and NaCl on the peptidase activities of non-starter lactic acid bacteria (NSLAB) by quadratic response surface methodology, INT DAIRY J, 9(12), 1999, pp. 865-875
The individual and interactive effects of temperature, pH and NaCl on the a
minopeptidase-types N and A and proline iminopeptidase activities of severa
l strains of non-starter lactic acid bacteria (NSLAB) were studied by quadr
atic response surface methodology. The effects on enzyme activities depende
d on the interactions among the independent variables, species, strains wit
hin species and type of activity. With few exceptions, the aminopeptidases
N and A and proline iminopeptidase activities of Lactobacillus casei sap. p
seudoplantarum and Lb. curvatus were strongly inhibited by the hostile chee
se-like conditions, while the peptidases of Lb. casei ssp. casei and especi
ally Lb. plantarum were tolerant or not affected by variations in pH and sh
owed the least sensitivity to NaCl or even a requirement for NaCl for the o
ptimal activity. Strains which maintained relatively high activity under ch
eese-like conditions were selected within the species. The proline iminopep
tidase of Lb. casei ssp, casei 2107 as well as Lb. plantarum 2788 and 2789
greatly tolerated the interactions among the independent variables. At 10 d
egrees C in the presence of 3.750% NaCl and independent of the pH, the PepN
activity of Lb. plantarum 2788 and 2789 was at least 33% of the maximum de
termined at pH 7.5 and 35 degrees C. Proline iminopeptidase activity was mo
st sensitive to the individual and interactive variations in temperature, p
H and NaCl. On the other hand, aminopeptidase-type A activity seemed to be
least sensitive to cheese-like conditions. (C) 2000 Elsevier Science Ltd. A
ll rights reserved.