Nitrate removal from water via self-flocculation of genetically engineered bacteria

Excessive nitrate in waterbody, which usually leads to eutrophication, can be removed by microbial denitrification processes. However, denitrification rate is greatly constrained by the spatial separation of nitrate in the upper oxic water layer from the electron donors close to the anoxic sediment. Herein, we constructed a genetically engineered bacterium (GEB), by co-expressing MO2.1 from Moringa oleifera and FLO5 from Saccharomyces cerevisiae, to simultaneously adsorb and self-flocculate nitrate from water. The GEB could migrate 45.5% of the nitrate to the bottom layer in actual water. Expressed FLO5 is electrically neutral and could trigger bacterial flocculation under the mediation of extracellular polysaccharides. Certain cationic arginine sites in MO2.1 can form strong electrostatic adsorption with NO3-, achieving bacterial self-flocculation, sedimentation and nitrate removal. The construction of multifunctional GEB could realize waterbody nitrate migration and is important to studies on new functional bacteria, water purification technology as well as geochemical nitrogen cycle. (C) 2021 Elsevier Ltd. All rights reserved.