Proteinase Activity of Pseudomonas fluorescens Grown in Cold Milk Supplemented with Nitrogen and Carbon Sources

¹ Departamento de Nutrición y Bromatología III, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain

Extracellular proteinase activity varied when Pseudomonas fluorescens was grown at 7°C in UHT milk supplemented with different substrates. Addition of glutamine (5 mM) and glutamic acid (10 mM) reduced proteinase activity by 35 and 50%, respectively, and 6 mM galactose and 10 mM lactate supplements reduced activity to about one-half of that in the unsupplemented control. Glucose addition (9 mM) delayed the onset of proteinase production by 24 h compared with that for the control culture. These results suggest that the onset of proteinase production could depend on a repressor role of certain milk components or on a low energy status in Pseudomonas cells as a result of the exhaustion of the more easily used substrates. However, differences were not significant between intracellular concentrations of ATP for control and glucose-supplemented cultures.

Key Words: extracellular proteinase production • Pseudomonas • intracellular adenosine triphosphate • milk supplementation

Submitted on August 9, 1993
Accepted on November 1, 1993