Pectinasic enzymatic activity

Enzymes most frequently proposed to fruit juices producers are pectinases coming from Aspergillus. Pectinases are exocellular enzymes and are the main activities produced among numerous side activities type hemicellulases, glycosidases. The Table 1 gives the spectrum of enzymatic activities contained in three commercial preparations A, B and C. 

Pectin degradation requires fee combined action of various enzymatic activities. However, evaluation of fee contribution of individual pectinases in Suit juice extraction and clarification is rather complicated. Most commercial pectinolytic enzyme preparations are produced by fermentation wife filamentous fungi, mostly strains belonging to fee genus Aspergillus,. plication studies with mixtures of isolat enzymes obtained by fermentation or by means of fractionation of commercial enzyme preparations can be used to assess the importance of fee various individual enzymes. Subsequently, molecular biology and fermentation technology can be used to enhance specific desirable enzymatic activities. 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

The complex nature and interconnectivity of plant cell wall polymers preclude straightforward enzymatic digestion. There are dozens of enzyme families involved in plant cell wall hydrolysis, including cellulases, hemicellu-lases, pectinases, and lignin-modifying enzymes. The Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB) has classified cellulases and hemicellulases, like all enzymes, into different classes based on activity. Table 33.2 and Table 33.3, compiled from the IUBMB enzyme nomenclature database (http //www.chem.qmul.ac.uk/iubmb/ enzyme/), list the IUBMB enzyme classifications for cellulases and hemicellulases.153... 

Enzymatic reactions, activated by grape enzymes, are involved in cell wall degradation. They favor the dissolution of their vacnolar contents (Section 11.7.3). Commercial enzymatic preparations have recently been developed to activate these phenomena they have pectinase, cellulase, hemi-cellulase and protease activities of diverse origins (Amrani-Joutei, 1993). These enzymes seem to favor the extraction of skin tannins over skin anthocyanins. They act on the tannins linked to the polysaccharides of the cell wall, giving the enzymatic wine a more full-bodied character than the control wine. 

However, few researches have been reported on the mechanism of these non-specific enzymatic processes, and even then controversial views exist. On the one hand, Kittur et al.[33] first reported that a multiple functional pectinase isoform from Aspergillus niger co i A be responsible for chitosan degradation by pectinases,but on the other hand, some authors have purified hetero chitosanases or/and chitinases from several commercial proteases,which were charged with their chitosanolytic activity [51-53].Whereas,no reports have been focused on non-specific hydrolysis of cellulases and lipases before, although their utility were popular in chitosan hydrolysis[5,8,9,10,28-31,43] and several bifunctional cellulase-chitosanases have been reported to be secreted from bacteria [58,79,87]. 

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