Production of a glucoglucuronan by a rhizobia strain infecting alfalfa. Structure of the repeating unit

The Rhizobium sp. T1 strain, which induces nodule formation on alfalfa and clover roots, produces, during growth, an extracellular polysaccharide comp osed of D-glucose and D-glucuronic acid noted glucoglucuronan. During the b acterial growth, the pH of the medium decreases slightly. The control of pH in the growth medium slightly reduces the glucoglucuronan production. Unde r the conditions tested in the present work, the weight-average molecular w eight of the polymers produced with or without pH control are similar: Mw a pproximate to 2 x 10(6); the repeating unit determined by chemical and NMR analyses corresponds to the disaccharide: --> 3)-beta-D-GlcpA-(1 --> 4)-bet a-D-Glcp-(1 -->. (C) 2000 Elsevier Science B.V. All rights reserved.