Characterisation of pectin subunits released by an optimised combination of enzymes

Pectins from sugar beet, lime and apple were degraded by a rhamnogalacturonan hydrolase associated or not with pectin methylesterases and side chain degrading enzymes (galactanase and arabinanase). The composition of the enzymatic mixture was optimised by following the reaction by viscosimetric means. The reaction products were fractionated by ion exchange chromatography. Treatment with all the enzymes released four fractions: (1) 227-247 mg/g of initial pectins and corresponded to neutral sugars from the side chains; (2,3) represented together 184-220 mg/g of pectins and corresponded to rhamnogalacturonan; (4) 533-588 mg/g of pectins and corresponded to homogalacturonan. Lime pectins have the shortest rhamnogalacturonan regions. The molar masses of homogalacturonans were in the range of 16,000-43,400 g/mol according to the origin of pectins, corresponding to degrees of polymerisation of 85-250. The mode of action of the enzymes used is also discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.