PROTEINASE ACTIVITY OF PSEUDOMONAS-FLUORESCENS GROWN IN COLD MILK SUPPLEMENTED WITH NITROGEN AND CARBON-SOURCES

Extracellular proteinase activity varied when Pseudomonas fluorescens was grown at 7-degrees-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.