title: Ammonium production during the nitrogen-fixing process by wild Paenibacillus strains and cell-free extract adsorbed on nano TiO₂ particles.
abstract: During the nitrogen-fixing process, ammonia (NH₃) is incorporated into glutamate to yield glutamine and is generally not secreted. However, in this study, NH₃- excreting strains of nitrogen-fixing Paenibacillus were isolated from soil. The ammonium production by the Paenibacillus strains was assayed in different experiments (dry biomass, wet biomass, cell-free extract, and cell-free extract adsorbed on nano TiO₂ particles) inside an innovative bioreactor containing capsules of N₂ and H₂. In addition, the effects of different N₂ and H₂ treatments on the formation of NH₃ were assayed. The results showed that the dry biomass of the strains produced the most NH₃. The dry biomass of the Paenibacillus strain E produced the most NH₃ at 1.50, 0.34, and 0.27 micrometer NH₃/mg biomass/h in the presence of N₂ + H₂, N₂, and H₂, respectively, indicating that a combined effluent of N₂ and H₂ was vital for NH₃ production. Notwithstanding, a cell-free extract (CFE) adsorbed on nano TiO₂ particles produced the most NH₃ and preserved the enzyme activities for a longer period of time, where the NH₃ production was 2.45 micrometer/mg CFE/h over 17 h. Therefore, the present study provides a new, simple, and inexpensive method of NH₃ production.
authors.affiliation: Faculty of Sciences, Department of Biology, Isfahan University, Isfahan, Iran.
authors.forename: Dariush
authors.initials: D
authors.lastname: Shokri
authors.forename: Giti
authors.initials: G
authors.lastname: Emtiazi
mesh_terms: D000327:Adsorption; D000641:Ammonia / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D053758:Nanoparticles / Q000737:chemistry*; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation; D056507:Paenibacillus / Q000302:isolation & purification / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012988:Soil Microbiology; D014025:Titanium / Q000737:chemistry
chemical_list: D000644:Quaternary Ammonium Compounds; C009495:titanium dioxide; D000641:Ammonia; D006859:Hydrogen; D014025:Titanium; D009584:Nitrogen