Objective  Enhancement on the development and application of exopolysaccharides produced economically from photosynthetic bacteria fermentation was investigated.

  Method  A strain of polysaccharide-producing photosynthetic bacteria, HP1, was isolated from a shrimp aquaculture pond. Crude polysaccharides were prepared from fermentation broth and precipitated by ethanol. Using astragalus polysaccharides for comparison, effects of inclusion of the polysaccharides in feed on nutrients in the meat of Ophiocephalus argus fed for 30 d were examined.

  Result  The physiological and biochemical characteristics as well as 16S rDNA sequencing of HP1 identified it to be Rhodopseudomonas faecalis. The polysaccharides produced from HP1 fermentation had no significant effect on muscle pH (P>0.05), but significantly decreased the drip loss and muscle fiber diameter of the fish after the feeding (P < 0.05). In the meat, the crude protein did not differ significantly by the diet change (P>0.05), but the amino acids did (P < 0.05). Compared with control without polysaccharide addition in the forage, the contents of total, essential, and delicious amino acids in the fish muscles increased by 8.7%, 11%, and 9%, respectively, crude fats by 10.7%, EPA+DHA by 12.8%, and the ratio of n-3/n-6.

  Conclusion  It appeared that a diet included the exopolysaccharides not only improved the eating quality but also enhanced the nutritional value of O. argus with effects comparable to astragalus polysaccharides.