The Screening, Identification And Application Of A Bioflocculant-Producing

More and more attention has been attached to microbial flocculants for their advantages, which includes high efficiency, non-toxic and harmless, no secondary pollution, etc. To screen out predominant strain is the first step to get efficient microbial flocculants, and then research on the culture conditions and flocculation performance can do some help by playing a guiding role in their industrial application.33of pure strains were screened out from Cassava starch yellow pulp wastewater by means of the common bacteria screening and purification method, then5strains with flocculating activity were screened out through preliminary screening. And then through further screening, one high-efficiency microbial flocculent producing bacteria was screened out, which was named Klebsiellasp.M2after morphological features, physiological and biochemical reaction experiments and16s rDNA gene sequence analysis confirming the strain was Klebsiella.The strain M2culture condition was optimized and growth characteristics was researched by single factor experiment. The results showed that, the best culture medium type, medium initial pH range and table speed were Chavez medium,4-7and140r/min respectively. The best carbon source and nitrogen source for the strain M2were sucrose and KNO3. The strain M2is well adapted to both acid and alkali environment, it was good for the bacteria to produce flocculants in30℃, and good for bacteria somatic breeding in25℃. The flocculating activity of strain M2is distributed in bacteria itself. It had the advantages of easy to be stored, transported and used. And under optimal conditions flocculating rate of flocculation process for kaolin slurry can reach93.20%.Flocculation performance of strain M2-flocculant was studied by single factor experiment. Results of flocculation200mL kaolin suspension were as follows:The best dosage of microbial flocculants was2mL, the best dosage of coagulant aid CaCl2solution was4mL too. Ca2+was the appropriate flocculation aid. Poor thermal stability of the Strain M2flocculants may come from its protein structure. Preliminary research for application of strain M2flocculants showed that it could flocculate soil suspension fast, and made the flocculation particles large and tight, the flocculating rate could reach96%. It could effective flocculated Cassava starch wastewater, and the flocculating rate was63%, COD removal rate was66%. Strain M2can effectively use cassava starch wastewater as cheap medium.