Release of the Cell-Envelope-Associated Proteinase of Lactobacillus delbrueckii Subspecies lactis CRL 581 Is Dependent upon pH and Temperature

ESPECHE TURBAY, B.; SAVOY DE GIORI, G.; HEBERT, E.M.

JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

AMER CHEMICAL SOC

Año: 2009 vol. 57 p. 8607 - 8611

0021-8561

The cell envelope-associated proteinase of Lactobacillus delbrueckii subsp. lactis CRL 581 (PrtL) has an essential role in bacterial growth, and contributes to the development of the organoleptic properties of hard cheeses and to the release of bioactive health-beneficial peptides from milk proteins. In this study, the effect of environmental pH on PrtL production by L. delbrueckii subsp. lactis CRL 581 in a chemically defined medium and the influence of pH, temperature and Ca++ ions on PrtL activity, stability and release from the cell envelope were analyzed. The maximum PrtL activity levels were observed in the middle of exponential growth phase, the values at constant pH of 5.5 and 6.0 being higher than those observed at pH 4.5 and 5.0. At pH 4.5 PrtL remained mainly associated to the cell envelope, whereas at pH values of 5.5 or higher approximately 40% of PrtL was found in the medium. In addition, PrtL activity was stable for 24 h at 4 and 25°C and its release at 4, 25 and 40°C was time-dependent. PrtL activity, stability and release were independent of the presence of Ca++ ions in the medium. These results indicated that at pH and temperature conditions found during the manufacture of hard cheeses, PrtL would remain active either bound to the cell or released in the supernatant contributing to the organoleptic characteristics and health beneficial effects of the fermented milk products.