No abstract

Excess growth of cyanobacteria in semiclosed water area caused by eutrophication induces coagulation inhibition in drinking water treatment processes. Thus, it is highly desirable to establish effective countermeasures against such coagulation inhibition by identifying the causative substances released by cyanobacteria. In this study, coagulation inhibitor proteins of Microcystis aeruginosa were screened using a phage display system and an aluminum-ionimmobilized affinity chromatography. From the results, algal proteins with a high level of metal-coordinating amino acids were identified as inhibitor proteins for the coagulation. One of the inhibitor proteins, a homologue of the metal sensor protein ArsR, showed strong inhibition of the coagulation of kaolin suspension with polyaluminum chloride (PAC). It was demonstrated that one of the mechanisms of the coagulation inhibition caused by M. aeruginosa is the inhibition of the cross-linking between aluminum clusters in PAC and suspended solids by the algal inhibitor protein.