THE PURIFICATION OF ENZYMATIC PREPARATIONS FOR OENOLOGY

The enzymatic preparations produced by some strains of non-genetically modified micro-organisms contain numerous enzymatic activities. These filamentous non-pathogenic fungus are isolated from the soil where they do contribute to the micro-flora. They are ubiquitous. The enzymatic activities spectrum can be explained by the adaptation of the micro-organism to its natural medium. The strains used for oenology, Aspergillus niger and Trichoderma harzianum, besides the activities for which they are grown (pectinases for Aspergillus niger, beta- 1,3- 1,6 glucananes for T. harzianum), contain other types of enzymatic activities, such as cellulases, beta-glucosidases, xylanases, galactanases and proteases, only to list the more known ones. Some activities are undesirable for the oenological applications. It is the case of cinnamyl-esterase (CE), that can be found in A. niger. As a consequence, it seemed fully justified to have preparations with low levels of CE activity, and even no CE activity at all. The fermentative conditions in the industry are chosen in order to favour the production of activities that could be defined as “main activities”. These activities do characterize the enzymatic preparation. The enzymatic spectrum of each preparation depends on the strain and on the culture conditions though. They are specific to each producer. In order to obtain preparations containing only one type of activity, it is necessary to use genetically modified micro-organisms (GMO). After presenting the strains and the fermentative conditions, this article will review the enzymatic activities responsible for the formation of volatile phenols in wines and the role that the purification plays on the undesirable enzymatic activities.