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In the last years, tannin biodegradation has been the subject of a lot of studies due to its commercial importance and scientific relevance. Tannins are molecules of low biodegradation and represent the main chemical group of natural anti-microbials occurring in the plants. Among the different kinds of tannins, ellagitannins represent the group less studied manly due to their diversity and chemical complexity. The general outline of this work includes information on tannins, their classification and properties, biodegradation, ellagic acid production, and potential applications. In addition, it describes molecular, catalytic, and functional information. Special attention has been focused on the biodegradation of ellagitannins describing the possible role of microbial enzymes in the production of ellagic acid.

Three extracellular pectinases were produced byAspergillus niger CH4 by submerged and solid-state fermentation, and their physicochemical and kinetic properties were studied. The highest productivities of endo- and exo-pectinase and pectin lyase were obtained with solid-state fermentation. The kinetic and physicochemical properties of these enzymes were influenced by the type of culture method used. All activities were very different in terms of pH and temperature optima, stability at different pH and temperature values and affinity for the substrate (K m values). In solid-state fermentation, all pectinase activities were more stable at extreme pH and temperature values but theK m values of endo-pectinase and pectin lyase were higher with respect to those activities obtained by the submerged-culture technique. The pectin lyase activity obtained by the submerged-culture technique showed substrate inhibition but the enzyme obtained by solid-state fermentation did not. Electrophoresis, using sodium dodecyl sulphate/polyacrylamide gel with enzymatic extracts obtained for both culture methods, showed the same number on protein bands but some differences were found in their electrophoretic position. The results obtained in this work suggest that the culture method (submerged or solid-state) may be responsible for inducing changes in some of the pectinolytic enzymes produced byA. niger.