Abstract:Production of exopolysaccharide (EPS) using wastewater is an optimal approach to treating wastewater by turning it into resource and hence a hot pot in the study of EPS. To screen out a high-EPS-producing strain of Purple Phototrophic Bacteria (PPB), an in-lab experiment was carried out cultivating 11 strains of PPB in a kind of chemically composed medium and media of organic wasterwater composed of wastewaters from soybean-prosessing and corn starch production at different ratios, separately. In the end of the experiment, the media were analyzed for extraction of EPS and for comparison. Results show that the strains of PPB varied in EPS producing capacity and that organic wastewater was more conducive to EPS production than the chemical medium. After two cycles of comparison, Strain J4 was screened out to be the highest- EPS-producing strain. In the wastewater from soybean processing, Strain J4 produced as high as 140 mg g-1 cell dry weight of EPS and as a result, it reduced wastewater COD by over 90%. The analysis with Sephadex G-50 chromatography shows that the EPS produced by J4 is high in molecular weight and has a certain research value. To sum up, through the cultivation experiment, a strain of high-EPS-producing PPB, J4 was obtained, and was proved to be able to produce large volumes of EPS by organic wastewater, which could be used as a basis for finding and producing cheap polysaccharide materials.