The commercial production of microbial flocculants began in the 1990s. Because there is no secondary pollution, it is convenient to use and has an attractive application prospect. Such as Rhodococcus erythropolis and NOC-1 made from it. This microbial flocculant has strong flocculating activity and is widely used in the treatment of livestock wastewater, expanded sludge, and colored wastewater.

Microbial flocculants mainly include flocculants using microbial cell wall extracts, flocculants using microbial cell wall metabolites, flocculants using microbial cells directly, and flocculants obtained by cloning technology. The flocculant substances produced by microorganisms are glycoproteins, mucopolysaccharides, proteins, cellulose, DNA and other high-molecular compounds, with a relative molecular mass above 105.

Microbial flocculant is a safe, efficient, and naturally degradable new water treatment agent obtained by extracting and purifying microorganisms or their secretions using biotechnology. Because microbial flocculants can overcome the inherent defects of inorganic polymers and synthetic organic polymer flocculants, and finally achieve pollution-free emissions, the research of microbial flocculants is becoming an important topic in the world of flocculants.

Researchers of microbial flocculants have long discovered that some microorganisms, such as yeast and bacteria, have cell flocculation, but they have not paid much attention to it, and are only used as a method of cell enrichment. In the past ten years, cell flocculation technology has been widely used in continuous fermentation and product separation as a simple and economical biological product separation technology.

Microbial flocculant is a kind of macromolecular organic matter with flocculation function produced by microorganisms. There are mainly glycoproteins, mucopolysaccharides, cellulose and nucleic acids. From its source, it is also a natural organic polymer flocculant, so it has all the advantages of a natural organic polymer flocculant. At the same time, the research work of microbial flocculants has moved from purification and modification to the use of biotechnology to cultivate and screen excellent strains to obtain high-efficiency flocculants at a lower cost. Therefore, its research scope has surpassed traditional natural flocculants. The research scope of organic polymer flocculants. Microorganisms with the ability to secrete flocculants are called flocculant-producing bacteria.

The molecular weight, molecular structure and shape of the flocculant and its groups have an influence on the activity of the flocculant. Generally speaking, the higher the molecular weight, the higher the flocculation activity; the higher the flocculation activity of linear molecules, the more branched or cross-linked molecules, the worse the flocculation; the flocculant-producing bacteria are in the late stage of culture, and the watery water of the cell surface will increase. The activity of the flocculant is also higher. The surface structure and charge of colloidal ions in the treated water also affect the flocculation effect. Some reports pointed out that the presence of cations in water, especially Ca2+ and Mg2+, can effectively reduce the negative charge on the surface of the colloid and promote the formation of "bridging". In addition, the presence of high concentrations of Ca2+ can also protect the flocculant from degrading enzymes. Microbial flocculants have the advantages of high efficiency, safety, and no pollution to the environment, and they also have huge potential application value in the fields of medicine, food processing, and biological product separation.