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Microbial pectinolytic enzyme specificity in agro-industrial processes

Pectin is one of the components of plant cell walls, occurring in some abundance in citrus fruit, for example, from which it may be extracted for use as a food ingredient. Conversely, pectin degrading enzymes may be used to remove particulate matter in clarification of juices and beverages as well as finding many other applications in the food industry. The project investigated the nature and function of these enzymes at the molecular level as well as with respect to industrial applications.

So far, progress with respect to overproduction of pectinolytic enzymes and identification of new pectinolytic genes/activities of both fungal and bacterial origin has been good. Many genes encoding pectinolytic have been engineered under the control of strong promoters. In the case of the fungal genes, the strong constitutive pyruvate kinase promoter was used; while in the case of bacterial genes, several strong inducible promoters were used. Considerable progress has been made in biochemical characterization of pectinolytic enzymes from fungi. Temperature and pH optima have been determined for all 3 enzymes. Kinetic analysis has been completed for some enzymes. Another approach adopted has been the study of inducers of enzyme synthesis. Two routes have been explored for the synthesis of artificial substrates and inhibitors. These routes proved not to be successful. Other routes are now being explored. Characterization of several pectinolytic enzymes, based on 3-dimensional structure analysis, is in progress. In order to assess the mode of action and activity of the pectinolytic enzymes on pectins of different degrees of esterification and amounts and nature of side chains, pectins were isolated from lemon, apple, sugar beet and orange.

Reported by

WAGENINGEN AGRICULTURAL UNIVERSITY
Dreijenlaan 2
HA Wageningen
Netherlands