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The application of microbial extracellular polymers began in the 1960s, and since then there has been a remarkable increase in their commercial use. They are used in the food, textile, pharmaceutical, agricultural, paint and petroleum industries. Volcaniella eurihalina, a moderately halophilic eubacterium, produces an extracellular polysaccharide whose physical and chemical properties could be of interest for various industrial applications. The aim of this investigation is to analyze the different environmental parameters which influence the production of polysaccharide, and to study its chemical composition and the rheological properties of its solutions.

The formation, chemical composition and rheological properties of the exopolysaccharides (EPS) produced by 19 strains belonging to Halomonas eurihalina have been compared in two different culture media. Our aim was to screen several strains isolated from saline soils to select those producing maximum EPS yield and good rheological properties. We found that MY medium was best for the production of EPS in all the strains studied. Maximum EPS production was 1.6 g l − 1 with strain H212 grown in this medium. The pattern of the chemical composition of the polysaccharides was affected by the strain in question and by the culture medium. All EPS studied had an unusually high sulphate content. Furthermore, the exopolymer from strain H96 contained significant amounts of uronic acid. EPS from strain H96, cultivated in defined NH medium, behaved in an interesting way rheologically; when the pH of the polymer solution was decreased to 3.0 a gel with a viscosity of 30 000 cP formed.

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