Study of the effects of temperature, pH, NaCl, and aw on the proteolytic and lipolytic activities of cheese-related lactic acid bacteria by quadratic response surface methodology |
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Authors: | Marco Gobbettia Rosalba Lanciotti Maria De Angelis Maria Rosaria Corbo Roberto Massini Patrick Fox |
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Affiliation: | a Istituto di Produzioni e Praparazioni Alimentari, Facoltà di Agraria di Foggia, Università degli Studi di Bari, Via Napoli 71100, Foggia, Italy b Istituto di Microbiologia Lattiero-Casearia, Facoltà di Agraria di Perugia, S. Costanzo, Perugia, Italy c Department of Food Chemistry, University College Cork, Cork, Ireland |
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Abstract: | The individual and interactive effects of temperature, pH, NaCl, and aw on the proteolytic and lipolytic activities of Lactobacillus delbrueckii subsp. bulgaricus B397, Lactococcus lactis subsp. lactis T12, and Lb. plantarum 2739 were studied by quadratic response surface methodology. The effects on enzyme activities depended on the interactions among the independent variables, type of activity, substrate and, especially, species. The proteinase activity of strains B397 and T12 was affected differently by pH as individual or interactive terms depending on the type of substrate sl- or β-casein. The increase of NaCl concentration (2.5–7.5%) under cheese-like conditions had a negative effect on the proteinase activity of strain T12. The effect of NaCl was related to the corresponding decrease in aw. Aminopeptidases N and A, iminopeptidase and endopeptidase of Lc. lactis subsp. lactis T12 were strongly inhibited by pH 5–6 and NaCl concentration higher than 3.75%. The negative effects of these independent variables was in several cases enhanced by their interaction and/or by the interaction with the lowest temperatures. In contrast, the same peptidases of Lb. plantarum 2739 retained a high activity under the very hostile environmental conditions. Iminopeptidase and especially endopeptidase activities of strain 2739 were stimulated slightly by NaCl at concentrations up to 5%. Lipase/esterase activity of Lb. delbrueckii subsp. bulgaricus B397 was markedly inhibited under cheese-like conditions. |
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Keywords: | Cheese ripening Proteolytic enzymes Lipolytic enzymes Lactic acid bacteria Non-starter lactic acid bacteria Response surface methodology |
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