University of Isfahan Iranian Journal of Environmental Technology  2423-5776 2 1 2016 04 01 The conversion of nitrate in water to diatomic nitrogen gas by immobilized Pseudomonas stutzeri on vermiculite The conversion of nitrate in water to diatomic nitrogen gas by immobilized Pseudomonas stutzeri on vermiculite 1 9 21065 10.22108/ijet.2016.21065 EN Badri Fazeli M.Sc. of Microbiology, University of Isfahan, Iran Giti Emtiazi Professor of Microbiology, University of Isfahan, Iran Journal Article 2016 02 14 Denitrification is a reduction of nitrate by heterotrophic and autotrophic bacteria that may ultimately produce molecular nitrogen (N<sub>2</sub>) through a series of intermediate nitrogen compounds.Vermiculite is a hydrous phyllosilicate mineral (Mg, Fe<sup>+2</sup>,Fe<sup>+3</sup>)<sub>3</sub>[(Al,Si)<sub>4</sub>O<sub>10</sub>](OH)<sub>2</sub>·4H<sub>2</sub>O with several layers for bacterial immobilization. The goal of this study was removal of nitrate from water with vermiculite and bacterial bio-film. In this process, 2×10<sup>7</sup> of bacteria were trapped in one gram vermiculite with resting cells and growing cells and nitrate removal were compared by free cells. The data showed that the un-immobilized cell in resting state could only remove 45 mg nitrate in 5 days, however nitrate removal by resting cell on vermiculite was 180 mg in 10 days, while in free resting cells this removal was poor. The maximum removal of 450 mg nitrate occurred after 25 days with feeding of biofilm. The intermediate product of nitrate removal was nitrite and in all data, the end product was nitrogen. <strong> </strong> <strong>Highlights</strong> Immobilization of <em>P. stutzeri </em>in resting cell status,improved nitrate removal efficiency versus un-immobilized bacteria. Feeding the immobilized bacteria, improved nitrate removal efficiency. Vermiculite introduced as a beneficial support media for immobilization of bacteria. Denitrification is a reduction of nitrate by heterotrophic and autotrophic bacteria that may ultimately produce molecular nitrogen (N<sub>2</sub>) through a series of intermediate nitrogen compounds.Vermiculite is a hydrous phyllosilicate mineral (Mg, Fe<sup>+2</sup>,Fe<sup>+3</sup>)<sub>3</sub>[(Al,Si)<sub>4</sub>O<sub>10</sub>](OH)<sub>2</sub>·4H<sub>2</sub>O with several layers for bacterial immobilization. The goal of this study was removal of nitrate from water with vermiculite and bacterial bio-film. In this process, 2×10<sup>7</sup> of bacteria were trapped in one gram vermiculite with resting cells and growing cells and nitrate removal were compared by free cells. The data showed that the un-immobilized cell in resting state could only remove 45 mg nitrate in 5 days, however nitrate removal by resting cell on vermiculite was 180 mg in 10 days, while in free resting cells this removal was poor. The maximum removal of 450 mg nitrate occurred after 25 days with feeding of biofilm. The intermediate product of nitrate removal was nitrite and in all data, the end product was nitrogen. <strong> </strong> <strong>Highlights</strong> Immobilization of <em>P. stutzeri </em>in resting cell status,improved nitrate removal efficiency versus un-immobilized bacteria. Feeding the immobilized bacteria, improved nitrate removal efficiency. Vermiculite introduced as a beneficial support media for immobilization of bacteria. Denitrification Cell Immobilization Pseudomonas stutzeri Vermiculite Resting cell https://ijet.ui.ac.ir/article_21065_fd3c8cdc364d978d10330cb6fbf7a550.pdf