A total of 37 samples were collected from different clinical cases (ear, blood, sputum, burns, cerebrospinal fluid and cystic fibrosis samples) and environments (water and soil samples)from different locations in Baghdad governorate. The total isolates obtained from these samples were 57 isolates,13 of them were identified as Pseudomonas spp. after detecting it's ability to grow on cetrimide agar. Biochemical tests were carried out on these 13 isolates. Results showed that 6 of these isolates were identified as Pseudomonas aeruginosa, furthermore it has been proved using Api 20 E system. The ability of these isolates in alginate production was examined. Results showed that P.aeruginosa H3 was the efficient one in alginate production, the productivity of alginate from this isolate was 1.2 g / L. Optimum conditions for alginate production by locally isolated P.aeruginosa H3 were studied. Results showed that the optimum conditions for alginate production were achieved using the production medium that contains 4% of date extract (as a carbon source), 1% of commercial baker's yeast (as a nitrogen source), 0.005% of KH2PO4 (as a phosphate source), at pH 7, the production medium was inoculated with 8×107 cell/100 ml and it was incubated at 37ْ C for 96 hrs. the productivity of alginate under these conditions was 8.5 g/ L. Alginate produced by P.aeruginosa H3 was purified by two steps, the first step included isopropanol precipitation and dialysis, the second was gel filtration through Sepharose CL-6B 200. The molecular weight of the purified alginate was determined using gel filtration technique through Sepharose CL-6B 200. The results showed that the approximate molecular weight of alginate produced by locally isolated P.aeruginosa H3 was 141,253 Dalton.
