Study On The Culture Condition Of B.Subtilis And Characterization Of Its Microbial Flocculant

As a new type of water treatment flocculants, microbial flocculants has longbeen a research hot spot because of its efficient, non-toxic and no secondary pollutionfeatures. On the basis of predecessors’ experience and appropriate microbial sources,this research targeted screened out a strain of high efficient bioflocculant-producingmicroorganism, then studied its culture conditions, physical characteristics, as well asthe application conditions, actual wastewater treatment ability and chemicalcompositions, etc. of the flocculant produced by the strain. The main conclusions areas follows:First of all,16strains with flocculant activities had been screened out from theboichemical and domestic sludges which estracted form the Xiawang Port, sewagetreatment plant and West Mountain dry field. After further experiment, strain XH-5which produced bioflocculant has a flocculation activity up to91.1%) had beenselected for the subsequent study. Through the analysis of16S rDNA appraisal, thestrain XH-5was identified as Bacillus genus, whose Latin name is Bacillus subtilissubsp. subtilis; CICC10028.Next the results of the culture conditions improving experiment of B. SubtilisCICC10028which producing bioflocculant are as follows:20g of glucose,6.67g ofyeast extract,5g of MgSO₄·7H₂O，2g of KH₂PO₄，5g of K2HPO₄，0.5g of NaCl，0.01g of FeSO₄·7H₂O and1L of H₂O1are the ingredients of its culture medium;medium pH should be7.3to7.6, the inoculation was1%（v/v）, the best table speed130r/min and20h for its incubation time.Once more according to the optimization experiment of culture conditions, wecan find that the flocculant producing ability and its flocculation activity of B. SubtilisCICC10028will be largely suppressing if culture environment temperature rises toohigh, or the pH of its culture medium became too high or woo low; On the other hand,B. Subtilis CICC10028can have certain adaptability of low temperature, as well asdifferent carbon and nitrogen sources.Then The best flocculation system of microbial flocculant produced by B.Subtilis are as follows: add96mL of1g/L100mL kaolin clay turbid liquid and2.0mLof1g/L CaCl2in beaker, the optimal doses of MBFH5is of2mg/L, the pH valuesshould be at7-8, fast agitate at speed200r/min for1min, then slow agitate1min atspeed40r/min for5mins, lay aside for5mins. Under the optimum flocculating conditions, MBFH5flocculating rate increased from91.13%to95.38%. In actualindustrial wastewater treatment, the removal rate of COD、BOD、Zn、Fe、Ca、Cdis respectively76.8%,83.6%,97.2%,96.8%,97.2%and95.7%.In the end, the infrared spectrum shows that MBFH5has a lot of active points,the polar groups that determine MBFH5’s flocculating activity are hydroxyl radicals,aliphatic nitro and secondary alcohol polar group. In the routine range of40-70℃, theactivity of microbial flocculant MBFH5can maintain above90%, and can also bestable at more than80%when the pH levels keep form6to11.