Homogalacturonans from lime pectins exhibit homogeneous charge density and molar mass distributions

Two series of lime pectins with different degrees and patterns of methyl-esterification were successively fractionated by size exclusion followed by anion exchange chromatography. 'Homogeneous' populations with respect to molar mass and charge density were thereby obtained and their physico-chemical properties were investigated. Recovered fractions were characterised by a high galacturonic acid and a low neutral sugars content. The homogeneous population obtained for each pectin sample was treated with side-chain releasing enzymes (rhamnogalacturonan hydrolase, endo-β-(1→4)-d-galactanase, endo-α-(1→5)-l-arabinanase, α-l-arabinofuranosidase and β-d-galactosidase) and combinations of these enzymes. The reaction products were fractionated by anion exchange chromatography and their constitutive homogalacturonans were recovered. Each homogalacturonan was found homogeneous with respect to charge density and to molar mass (polydispersity index close to 1).