title: Physicochemical properties of extracellular (1-->4)-beta-D-glucuronan produced by the Rhizobium meliloti M5N1CS strain during fermentation: evidence of degradation by an exoenzyme activated by Mg2+.
abstract: The mutant Rhizobium meliloti M5N1CS (NCIMB 40472) produced a partially acetylated (1-->4)-beta-D-glucuronan during fermentation. The polysaccharide (EPS) extracted from broth during fermentation by microfiltration and ultrafiltration (using a 100 kDa cut-off membrane) was characterized by size exclusion chromatography. The weight-average molecular weight (Mw) of the EPS decreased from 7.5 x 10(5) to 5 x 10(5) between 27 and 75 h of fermentation. When MgSO4.7H2O (0.8 gl-1 per day) was present in the medium during the same period, the Mw of the EPS decreased to 1.5 x 10(5). Since EPS degradation was detected after microfiltration of the fermentation medium supplemented with magnesium, the Mw decrease of the EPS extracted during fermentation may be explained by enzymic degradation of the polymer activated by Mg2+ ions.
authors.affiliation: Laboratoire de Biotechnologie Microbienne, Université de Picardie Jules Verne, Amiens, France.
authors.forename: P
authors.initials: P
authors.lastname: Michaud
authors.forename: J
authors.initials: J
authors.lastname: Courtois
authors.forename: B
authors.initials: B
authors.lastname: Courtois
authors.forename: A
authors.initials: A
authors.lastname: Heyraud
authors.forename: P
authors.initials: P
authors.lastname: Colin-Morel
authors.forename: J P
authors.initials: JP
authors.lastname: Seguin
authors.forename: J N
authors.initials: JN
authors.lastname: Barbotin
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002850:Chromatography, Gel; D005285:Fermentation; D005966:Glucuronidase / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D011134:Polysaccharides / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000378:metabolism*; D014462:Ultrafiltration; D014783:Viscosity
chemical_list: D001426:Bacterial Proteins; D011134:Polysaccharides; C088556:mucoric acid; D005966:Glucuronidase; D008274:Magnesium