Microbial Flocculant Optimization Of Culture Conditions And Alternative Media Research

Bioflocculant is a kind of macromolecular flocculant secreted by microorganisms. These kinds of microbial polymers are expected to be useful in flocculating wastewater due to their bio-degradability and the harmlessness of their degradation products toward humans and the environment. However, the bioflocculants identified so far in laboratories have not yet practically applied in industry because of their high cost and low productivity.In this study , a flocculant-producing bacteria ZY3 was screened from the Chinese medicine factory in the activated sludge, flocculation rate could reach 71.2% . Through the dyeing observation, it was considered as Gram-positive bacteria.To this strain's culture medium composition and the culture conditions were optimized , obtained the fermentation best carbon source is sucrose , the best nitrogen source is (NH₄)₂SO₄ ; the culture medium best formula is : sucrose 6.5 g , (NH₄)₂SO₄1.25g,KH₂P0₄ 2.45 g, K₂HP0₄ 0.9 g, MgSO₄·7H₂O 0.135 g, NaCl 0.25 g, H₂O500ml, the flocculation rate is the highest; the best culture condition is : theinitial pH 6.0 , the culture temperature 30℃, seed fluid of addition 5 ml , theflocculation rate gets to maximum when the strain grows at 24h , the flocculating material exists primarily in the fermentation fluid.It was confirmed feasible through the experiment using the Citrus Grandis Peel to substitute carbon source partly and nitrogen source completely, the flocculation rate could reach 61.54%. The substitutive medium formula : sucrose 3.9 g , Citrus Grandis Peel 2.6 g , KH₂P0₄ 2.45g, K₂HP0₄ 0.9 g, MgSO₄·7H₂O 0.135g, NaCI 0.25g, H₂O 500ml.Preparation of the substitutive media cultivating flocculant-producing bateria, changing flocculation's external conditions , it is obtained , when flocculant dosage of 1.5ml, CaCl₂ dosage of 3ml, flocculation reaction system pH value of 8, inversion number of times 20 times , the flocculation effet is best . The flocculant under high temperature flocculation changed not obviously and has certain heat resistance.By ethanol precipitation method extraction and purification of flocculant , obtains the pure white powderly material . The flocculation material is mainly polysaccharide and the flocculation mechanism is mainly " adsorption bridging role " through the preliminary analyses of UV and IR atlas.The application effect test indicated that, the flocculant from bacterium ZY3, has certain decolorization ability for simulated indigo dye wastewater , is good to the soil suspending liquid's turbidity elimination rate , is big to activated sludge's settling property improvement, and has certain elimination ability for simulated organic wastewater's COD.