Influence of growth conditions on production of capsular and extracellular polysaccharides by Rhizobium leguminosarum

• Published in: Antonie van Leeuwenhoek 1993-01, Vol.64 (1), p.1-8
• Main Authors: BREEDVELD, M. W, ZEVENHUIZEN, L. P. T. M, CREMERS, H. C. J. C, ZEHNDER, A. J. B
• Format: Article
• Language: English
• Subjects: Ammonium Chloride - metabolism; Bacterial Capsules - biosynthesis; Bacteriological Techniques; Bacteriology; Biological and medical sciences; Carbohydrate Metabolism; Culture Media; Fundamental and applied biological sciences. Psychology; Glucans - metabolism; Glutamates - metabolism; Laboratorium voor Microbiologie; Mannitol - metabolism; Metabolism. Enzymes; Microbiological Laboratory; Microbiologie; Microbiology; Polysaccharides, Bacterial - biosynthesis; Rhizobium leguminosarum; Rhizobium leguminosarum - growth & development; Rhizobium leguminosarum - metabolism
• ISSN: 0003-6072; 1572-9699
• DOI: 10.1007/BF00870915

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.