[Culture medium and grading culture technics for bioflocculant production by Paenibacillus polymyxa GA1]

A bacterial strain named GA1 which can produce bioflocculant with high flocculating activity was isolated from soil. The strain was identified as Paenibacillus polymyxa according to its morphological, physiological and biochemical characters, as well as 16S rDNA sequence (GenBank Accession number: DQ166375) similarity comparison. The results indicated that sucrose and yeast extract were the optimal carbon and nitrogen sources for bioflocculant production. Furthermore, the mass ratio of sucrose to yeast extract and the optimal sucrose concentration were ascertained. The optimum component proportion of medium (g/L) is sucrose 40.0, yeast extract 4.0, K2HPO4 5.0, KH2PO4 2.0, NaCl 0.1, MgSO4 0.2. The culture conditions including initial pH, temperature, agitation rate and inoculation quantity of strain GA1 were ascertained. Based on the relation of bacterium growth and bioflocculant production, grading culture was applied to bioflocculant production of GA1. The experimental result show that grading culture can keep high bioflocculant yield as well as shorten time of flocculant production.