Pullulans produced by strains of Cryphonectria parasitica -: II.: Nuclear magnetic resonance evidence

The structure of pullullan-like polysaccharides produced as exocellular material by different strains of Cryphonectria parasitica, the fungus responsible for chestnut tree cankers, was investigated with nuclear magnetic resonance (NMR) techniques. C-13, mono- and bidimensional H-1, and H-1-C-13 heteronuclear correlated NMR spectra (HSQC and HMBC) were recorded. Advanced analysis of the NMR spectra allowed the main resonance of the atoms in the maltotriose and in the maltotetraose repeat units of pullulan-like polysaccharides from C. parasitica to be recognised with confidence. In all cases investigated, the presence of large amounts of alpha-(1 -> 6) rnaltotetraose subunits was evidenced, in addition to the alpha-(1 -> 6) maltotriose subunits, corresponding to the repeating unit of pullulan produced by Aureobasidium pulludans and other fungi. The results were in agreement with other data from this laboratory, obtained with independent techniques. The belief that in 'pullulans' the maximum amount of alpha-(1 -> 6) maltotetraose subunits is about 7% can thus be considered as definitely outdated. (C) 2005 Elsevier Ltd. All rights reserved.