Preparation method and application of microbial flocculant

The invention discloses a preparation method of a microbial flocculant, which is characterized in that fermentation products of bifidobacterium longum and bacillus mucilaginosus are used as main active substances, and the preparation method comprises the following steps: 1) respectively inoculating the bifidobacterium longum and the bacillus mucilaginosus into an MRS liquid culture medium for aerobic culture; 2) uniformly mixing the fermented MRS liquid culture medium, then adding growth factors, carrying out shake culture, collecting a culture solution after the shake culture is finished, and filtering and removing thalli by using gauze to obtain fermentation liquor; and (3) performing primary centrifugation on the fermentation liquor, collecting supernate, concentrating the supernate by adopting a rotary evaporator at 40-50 DEG C to obtain concentrated liquor, adding ice bath acetone, standing for 6-12 hours, performing secondary centrifugation, collecting precipitates, standing for 30-50 minutes at-15--20