Effect of biosynthesis conditions on the chemical composition of the water-soluble polysaccharides of fast-growing rhizobia.

Abstract

Water-soluble polysaccharides of fast-growing Rhizobia strains were produced in three conditions of biosynthesis: cells growing in a yeast extract medium, cells growing in a mineral medium and cells resting. Under these three conditions, three strains of Rhizobium leguminosarum (L 1S, L2S, L3S), three strains of Rhizobium phaseoli (P2S, P7S, P8S), and two strains of Rhizobium trifolii (T7S, T15S) produced polysaccharides which were precipitated with one volume of ethanol and purified. These polysaccharides contained (in % w/w): glucose (51.7-64.8), galactose (8.9-14.7), glucuronic acid (14-23), and some pyruvic and acetic acids which varied with the conditions of polysaccharide production. The polysaccharides produced in the conditions cited above, by four strains of Rhizobium meliloti (M5N1, M11S, M1-5, L5-30) differed from those of R. leguminosarum, R. phaseoli, and R. trifolii. The polysaccharides of R. meliloti contained (in% w/w): glucose (63.7-74), galactose (8.2-11), no glucuronic acid (except for R. meliloti M11S: 1%) and some pyruvic, acetic and succinic acids which varied with the conditions of polysaccharide biosynthesis.