RESPONSE OF LEUCONOSTOC-OENOS TO ENVIRONMENTAL-CHANGES

Malolactic fermentation, a spontaneous step in vinification, is freque ntly controlled by used of malolactic bacterial starters of Leuconosto c oenos. Strains isolated from fermenting wines and then submitted to industrial processes to obtain freeze-dried preparations lose their na tural adaptation to survive and to grow in wine. However, culture cond itions influence their adaptability as well as their survival after ex posure to stress. As the plasma membrane was considered as the primary target for the deleterious effects of the environment, the changes of its components after cell heating and incubation in hostile condition s were studied. The ratio of phospholipids to proteins of the membrane decreased significantly when cells were submitted to any kind of stre ss. Phospholipids decreased while the protein content increased up to fivefold. Only some membrane proteins were over-synthesized compared t o control cells. Seventeen protein bands were separated by gel electro phoresis of which three in particular were always over-expressed after the cells were shocked. Some also appeared when the cells entered the stationary phase. These results show that Leuc. oenos responded to en vironmental stresses by changing its membrane composition. Stress prot eins appeared whatever the nature of the shock. This phenomenon may be involved in the acquisition of resistance of Leuc. oenos to harsh con ditions in wine.