In this study, exopolysaccharides (EPSs) production was investigated by growing strains of Pseudomonas aeruginosa G1 and Pseudomonas putida G12 in medium containing various carbon sources such as glucose, mannose, fructose, and xylose. EPS production (192 and 182 mg/L, respectively) of these strains grown in PAP medium with 2% glycerol (v/v) was used as control. The highest EPS production of the two strains was found in the xylose containing medium. The effect of different concentrations [2-6% (w/v)] of xylose on EPS production of both strains was also studied. The maximum EPS yield (368 mg/l(-1)) of the strain G1 was recorded in 3% (w/v) xylose, while the highest yield EPS yield (262 mg/L(-1)) of the strain G 12 was recorded in 2% (w/v) xylose. The monosaccharide compositions of EPS produced by the two strains were analyzed by HPLC. Strain G1 [2% (w/v) glycerol] was found to compose of neutral sugars (92.0%), acetylated amino sugars (8.0%), while strain G1 [3% (w/v) xylose] contained neutral sugars (99.2%), acetylated amino sugars (0.8%). However, the composition of strain G12 [2% (w/v) glycerol] was neutral sugars (96.8%), acetylated amino sugars (3.2%) and the strain G12 [2% (w/v) xylose] was found to contain neutral sugars (96.1%), acetylated amino sugars (3.9%). (C) 2007 Elsevier Ltd. All rights reserved.