Action of β-galactosidase in medium on the Lemna minor (L.) callus polysaccharides

The callus culture of duckweed cultivated on medium containing different concentrations of p-galactosidase was shown to produce the following polysaccharides: pectin lemnan LMC, intracellular AG1, and extracellular AG2 arabinogalactans. The samples of lemnan with 46% galactose residue reduction and 9-46% increased galacturonic acid residue content were obtained at beta-galactosidase concentrations of 10(-3)-10(-1) mg/mL. The most substantial alterations in the sugar composition of pectin were found to occur in the fraction with a molecular mass of 100-300 kDa. Low concentrations of enzyme failed to influence the sugar composition of intracellular arabinogalactan, whereas high concentrations were shown to decrease the amount of arabinose residues in AG1 and to cause galactan formation. Extracellular galactan was found to be produced on the medium with 10(-1) and 1 mg/mL beta-galactosidase whereas extracellular arabinogalactan AG2 was shown to be biosynthesized without beta-galactosidase or at a beta-galactosidase concentration of 10(-3) mg/mL. Alterations in the sugar composition of polysaccharides were shown to be connected with the increasing activity of alpha-L-arabinofuranosidase and beta-galactosidase, and with the decreasing activity of intracellular polygalacturonase. (C) 2009 Elsevier Ltd. All rights reserved.