Exoprotease activity of Leuconostoc oenos in stress conditions

Abstract

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 l-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.