Elucidation of the mechanisms of chitosan-like bioflocculant production by Citrobacter strains and its higher production.

In the genus Citrobacter, at least four species, C. freundii, C. braaki, C. youngae, and C. werkmanni, can produce a chitosan-like polysaccharide consisting of N-acetylglucosamine and glucosamine from acetic acid in the cultures as a soluble form (Appl. Microbiol. Biotechnol., 97, 9569-9577, 2013). It is a polycationic polymer and can be used as an efficient flocculant for water treatment. The aim of this project is to produce this polysaccharide in a large quantity for the industrial use such as sludge dewatering and metal removal and recovery. For this purpose, we are trying to breed higher-producing strains by metabolic engineering based on the genome sequence.