Construction Of Bioflocculant-producting Microorganisms And Studies On The Characteristics And Preliminary Applications Of Bioflocculant MAC37

Microbial Flocculants (MBF) are extracted from bacteria, fungi and other microorganisms or their secretions by using biotechnology, as a kind of special substances which primarily consists of Polysaccharide, protein, glucoprotein, cellulose, nucleic acids and other macromolecules, they have good properties of flocculation and sedimentation. With the advantages of safe, high efficiency, nontoxicity, biodegradation and non-secondary pollution, people have attached much more important to this "green" water treatment agent.In this paper, we isolated some bacteria which are viable but non-culturable (VBNC) from soil and sewage treatment systems by adding resuscitation promoting factor (Rpf) to culture medium. Adopting Kaolin suspension as the active evaluation system, we selected some single strains with preferable flocculation activity from those bacteria. According to the principle of effective biotechnology (EM), multiple colonies with high flocculation efficiency were constructed through mixing culture of two strains. The optimal conditions of medium compositions, culture conditions and flocculating activity were studied to achieve the best flocculation efficiency. The main contents of multiple bioflocculants MAC37were measured through biochemical reactions and instrumental analysis. Meanwhile, the application of multiple micro-organisms fermentation in the acrylic emulsion wastewater was studied to explore the effect of multiple bioflocculant MAC37. The main results are summarized as follows:1. Using bacteria which are viable but non-culturable (VBNC), isolated from soil and sewage treatment system by adding resuscitation promoting factor (Rpf) to culture medium as source, we screened out four strains:M3, M7, M8and M11with high flocculating activity. The flocculating efficiency to Kaolin suspension was82.24%,78.29%and72.54%respectively. Through mixing culture of two strains, we constructed multiple colonies with high flocculation efficiency:Arthrobacter (M3) and Chryseobacterium (M7), the flocculating efficiency reached87.13%.2. Through mesuring the flocculating efficiency (FE) and the cell growth (OD660), the optimal medium compositions and culture conditions of multiple bioflocculant-producing microorganisms M3and M7were studied through single factor method. The results showed that the optimal medium compositions were starch1.5%,(NH4)2SO40.3%, FeCl20.1%, initial pH7.0; The optimal conditions for bioflocculant production were:the proportion of M3to M70.6:0.4, the total inoculum size6%(V/V), fermentation temperature28℃, fermentation time72h and shaking speed160r/min. Under these conditions, the flocculating efficiency reached96.27%.3. The flocculating active substances mainly distributed in the fementation supernatant, within the scope of the heating temperature60℃, the flocculating efficiency remained above92%. The preferable flocculating processes were as follows:in the flocculating systems of4g/L Kaolin suspension100ml, a final dosage of multiple micro-organisms fermentation and1%CaCl2were1.5ml and3ml, and the system pH was adjusted to8.0. Under these conditions, the flocculating efficiency of multiple bioflocculant to Kaolin suspension was above98.23%.4. Crude yellow powder of bioflocculants MAC37was obtained by purification and solidification of the fermentation liquid cultured under optimized conditions, and the production rate was1.02g/L. Qualitative and quantitative analysis showed that the main components of MAC37were14.5%polysaccharides and20.4%proteins. This result demonstrated that bioflocculants MAC37were polysaccharide substances containg a small amount of protein.5. Application of bioflocculants MAC37and polyaluminum chloride (PAC) in acrylic emulsion wastewater showed that:the bioflocculants MAC37have better treatment effect compared with PAC. The optimized flocculating processes were as follows:multiple micro-organisms fermention dosage was16ml/L, the coagulant1%dosage was40ml/L, the system pH was adjusted to8.0, and the mixing method was:first rapid stirred (230r/min-250r/min)1min, then medium speed (130r/min-150r/min)6min, and then slowly stirred (30r/min to50r/min)10min, after mixing, the flocculating and standing time was15min. Under the best flocculation conditions, the removal rate of turbidity, color and CODcr of the acrylic emulsion wastewater was92.57%,94.73%and92.12%respectively.These results indicate that bacteria M3and M7were resurrected culture by the use of Rpf, after compound culturing, bioflocculants MAC37with high flocculating efficiency were attained. The bioflocculants MAC37were polysaccharide substances containg a small amount of protein and had good treatment effects on the acrylic emulsion wastewater. This study provides some theoretical basis for the expansion of flocculating-featured micro-organisms sources.