title: Influence of growth conditions on production of capsular and extracellular polysaccharides by Rhizobium leguminosarum.
abstract: The influence of growth rate and medium composition on exopolymer production by Rhizobium leguminosarum was studied. When grown in medium containing 10 g/l mannitol and 1 g/l glutamic acid, Rhizobium leguminosarum biovar trifolii TA-1 synthesized up to 2.0 g/l of extracellular polysaccharide (EPS), and up to 1.6 g/l of capsular polysaccharide (CPS). Under non-growing cell conditions in medium without glutamic acid, CPS synthesis by strain TA-1 could proceed to 2.1 g/l, while EPS-production remained relatively low (0.8 g/l). Maximal CPS-yield was 2.9 g CPS/l medium in a medium containing 20 g/l mannitol and 2 g/l glutamic acid. The EPS-deficient strain R. leguminosarum RBL5515, exo4::Tn5 was able to produce CPS to similar levels as strain TA-1, but CPS-recovery was easier because of the low viscosity of the medium and growth of the cells in pellets. With strain TA-1 in nitrogen-limited continuous cultures with a constant biomass of 500 mg cell protein/l, EPS was the most abundant polysaccharide present at every dilution rate D (between 0.12 and 0.02 h-1). The production rates were 50-100 mg/g protein/h for EPS and 15-20 mg/g protein/h for CPS. Only low amounts of cyclic beta-(1,2)-glucans were excreted (10-30 mg/l) over the entire range of growth rates.
authors.affiliation: Department of Microbiology, Agricultural University, Wageningen, The Netherlands.
authors.forename: M W
authors.initials: MW
authors.lastname: Breedveld
authors.forename: L P
authors.initials: LP
authors.lastname: Zevenhuizen
authors.forename: H C
authors.initials: HC
authors.lastname: Canter Cremers
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder
mesh_terms: D000643:Ammonium Chloride / Q000378:metabolism; D016667:Bacterial Capsules / Q000096:biosynthesis*; D001431:Bacteriological Techniques; D050260:Carbohydrate Metabolism; D003470:Culture Media; D005936:Glucans / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D016961:Rhizobium leguminosarum / Q000254:growth & development / Q000378:metabolism*
chemical_list: D003470:Culture Media; D005936:Glucans; D005971:Glutamates; D011135:Polysaccharides, Bacterial; D000643:Ammonium Chloride; D008353:Mannitol