Screening And Identification Of Bioflocculant-producing Bacteria And Optimization Research On Cluture Conditons And Technics

Microbial flocculants are safe and biodegradable macromolecular flocculants secreted by microorganisms. Their degradation products are harmless to the ecosystem and humans. The development of a new biodegradable bioflocculant with strong flocculating activity is attracting wide research interest.26 bacterial strains which can produce bioflocculant with high flocculating activity was screened from soil by means of the common bacteria screening and purification method. There are 4 bacterial strains numbered B6, CA1,CE1 and GA1 of these which can produce bioflocculant with flocculating rate above 80%. The bacterial strain GA1 has the best effect of decoloring and flocculating with flocculating rate above 96% of Gaoling suspension.These bacterial strains were identified according to its morphological, physiological and biochemical characters, as well as 16S rDNA sequence homology comparison. The results are as follows: The bacterial strain B6 which GenBank accession is DQ115363 is Pseudomonas putida and is named Pseudomonas putida B6; The bacterial strain CA1 which GenBank accession is DQ 190240 is Bacillus mojavensis and is named Bacillus mojavensis CA1; The bacterial strain CE1 is Bacillus subtilis and is named Bacillus subtilis CE1; The bacterial strain GA1 which GenBank accession is DQ166375 is Paenibacillus polymyxa and is submitted to CCTCC, its conserved number is CCTCC M 206017 and its name is Paenibacillus polymyxa GA1 CCTCC M 206017.The bacteria which can produce extracellular bioflocculant include A3, A4, CA1, CE1, D14, GA1 and SE17. The extracellular bioflocculant of these bacteria can be separated with 1∶1~1.5∶1 (volume ratio) acetone. The extracellular bioflocculant of A3 and GA1 were identified as polysaccharide, and the extracellular bioflocculant of CA1 and CE1 were identified as glycoprotein, and the extracellular bioflocculant of SE17 was identified as protein.The optimum component proportion of medium(g/L)of Pseudomonas putida B6 which is glucose 15, fructose 3, KH2PO4 1.0, K2HPO4 3.0, MgSO4 0.1, NH4NO3 0.8, (NH4)2SO41.5, yeast extra0.2, NaCl 0.1was obtained according to the orthogonal test. The optimum culture conditions are as follows: initial pH 8.0, temperature 30℃and agitation rate 160r/min.The optimum component proportion of medium(g/L) of Paenibacillus polymyxa...