Study On The Production Of Bioflocculant By E.cloacae W And The Characteristics Of Flocculating

Microbial flocculants due to its high activities, non-toxic and no secondary pollution advantages cause for concerning. There are, however, researchs and developments of microbial flocculants but low production rate, high cost , long production period, high cost of transportation and storage, easy metamorphic reason them can't be industrialized production and application. Screening high efficiency flocculant produce bacteria, with high yield, high activity, low cost and easy storage of the microbial flocculants become current researchers main goal. The sediments of heavy metal pollution as the source for strains screening and ultraviolet mutagenesis, get an easy to culture and produce high activity bioflocculant bacteria.Besides identify the bacteria and optimize its culture conditions, the components, physical and chemical propeties, flocculation properties and flocculation mechanisms of the bioflocculant which produced by the bacteria were researched.Several main conclusions are the followings:(1) Choose the sludge of industrial outfall and the active sludge of secondary sedimentation tank in municipal domestic sewage treatment plants, got 3 bacterial strains which have the produce bioflocculant that flocculating activity over 91%, through conventional separation methods, UV mutagenesis, prescreening and secondary screening. The stranins are Enterobacter sp., Bacillus subtilis and Aeromonas. The Enterobacter sp. which isolated from the sludge of estuary in XiaWan Port have the shortest processing cycle to produce bioflocculant, and the flocculating activity is the best, with 16S rDNA identify it is Enterobacter cloacae subsp. Cloacae. The GenBank login ID WAB1878.(2)The best culture condition for E.cloacae W produce bioflocculant:glucose and sucrose as united carbon source,ammonium sulphate and urea as united nitrogen source,carbon nitrogen ratio is 32:1,the CaCl₂ and K₂HPO₄ can boost the yield and activity of the bioflocculant;The optimum fermentation conditions:initial pH 7.0⁸.0, time 72 h, temperature 30±1℃, rotator ratio 120r/min, inoculum size 5%⁷% (v/v). Under the optimize condition the yield of bilflocculant produced by E.cloacae W is 4.82 g/L, the flocculating activity can be 98.5%.(3) The results of color reaction on sugars and protein of bioflocculant MBFE-61 indicated that the MBFE-61is an glycosioprotein contents hexose, proline or hydroxyproline but have no ketose, reducing sugars and aromatic aminoacids; the polysaccharide 80.74%(w%), protein or polypettide 17(w%) and relative molecular weight is 1.79×10⁵. The results of UV and IR spectrum prove that the MBFE-61 contents pentoside or valeric acid base, carboxyl, hydroxide radical, acid amide and pyranoside. The heat stability of MBFE-61 well, the flocculating activity can be over 93% as the temperature is 80℃.(4) Alkaline extraction is the best choice for MBFE-61, and the optimize condition to treat simulated wastewater are as follows, concentration of Cd²⁺ is10mg/L, dosage of MBFE-61 is 20 mg/L, rapid stirring 120 r/min and 3s, slow mixing 40 r/min and 3 min. Under the condition, remove ratio of turbidity and Cd²⁺ are 98.3% and 98.9%, respectively. The remove efficiency and order of ions in industrial wastewater of Xiawan Port are as follows: Cd²⁺> Fe³⁺> Pb²⁺> Zn²⁺> Ca²⁺,and 98.1%, 97.67%, 93.7%, 97.7% and 80% respectively.(5)The results of IR spectrum and SEM indicated that the flocculating mechanisms of MBFE-61 are charge neutrality, chemical chelation, chemicaladsorption and netting effect.