Journal of Biotechnology 61 (1998) 135 – 141 Characterization of exopolysaccharides produced by 19 halophilic strains of the species Halomonas eurihalina Victoria Be ´jar a, *, Inmaculada Llamas a , Concepcio ´n Calvo b , Emilia Quesada a a Exopolysaccharide Research Group, Department of Microbiology, Faculty of Pharmacy, Uniersity of Granada, 18071 Granada, Spain b Water Institute, Uniersity of Granada, Granada, Spain Received 23 September 1997; received in revised form 19 January 1998; accepted 23 January 1998 Abstract 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. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Halomonas eurihalina ; Exopolysaccharides; Halophilic bacteria 1. Introduction Bacterial growth is often accompanied by the production of exopolysaccharides (EPS), which have important ecological and physiological func- tions. Increasing interest is being generated in the study of these molecules because of their wide applications in food, pharmaceutical, petroleum and other industries (Dawes, 1990; Sutherland, 1990). Nevertheless, the strains used for the indus- trial production of EPS belong to a small number of taxa, such as Xanthomonas campestris (Evans et al., 1979), Pseudomonas (Jarman, 1979), Azoto - bacter (Jarman et al., 1978), Sphingomonas (Lobas et al., 1992), Alcaligenes (Sutherland, 1990), etc. There are still good prospects, however, for devel- * Corresponding author. E-mail: vbejar@platon.ugr.es 0168-1656/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S0168-1656(98)00024-8