Exoprotease activity of Leuconostoc oenos in stress conditions

Exoprotease activity during 48 h of total energy and nutrient starvation was examined in Leuconostoc oenos X2L isolated from wine. Starved cells after 2 h of incubation at 30 °C in citrate buffer, 0.05 mmol 1−1 pH 5, showed greater extracellular proteolytic activity than at the onset of starvation. In the presence of 60 mg l−1 SO2 and 8% or 12% ethanol, the proteolytic activity was higher; 10 mmol l−1 Ca2+ and Mg2+ produced an increase in protease activity during starvation. Glucose and 2‐deoxyglucose (2‐DOG) were found to repress synthesis by 80% and 100%, respectively. Cyclic adenosine 3′‐5′‐phosphate increased the exoprotease activity and reverted the repression by glucose and 2‐DOG. De novo synthesis of proteins was required for the exoprotease activity by cells submitted to stress conditions. The absence of protease activity in the supernatant fluids from chloramphenicol‐treated cells indicated that the activity is a result of deliberate release and not of passive cell lysis.