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( Shokri Dariush ),( Giti Emtiazi ) 한국미생물 · 생명공학회 2010 Journal of microbiology and biotechnology Vol.20 No.8
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 μM 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 μM/mg CFE/h over 17 h. Therefore, the present study provides a new, simple, and inexpensive method of NH3 production.
Hosseini-Abari, Afrouzossadat,Emtiazi, Giti,Lee, Sang-Hyuk,Kim, Byung-Gee,Kim, June-Hyung Humana Press 2014 Applied biochemistry and biotechnology Vol.174 No.1
<P>Seeking for simple, rapid, and environmental-friendly routes to produce metal nanoparticles is quite attractive for various biotechnological applications. Biological synthesis method of silver nanoparticles has been found very promising due to their non-toxicity and simplicity. Here, the spores of Bacillus stratosphericus isolated from soil enriched with 30 % H2O2 were used for the production of silver nanoparticles. Furthermore, the possible mechanism of silver nanoparticle synthesis by the spores was elucidated for the first time. In this regard, dipicolinic acid (DPA) was shown to play a critical role as a nanoparticle-producing agent. UV-Vis absorption spectroscopy, X-ray diffraction technique, energy-dispersive spectroscopy, and transmission electron microscopy were used to characterize the nanoparticles. Unlike vegetative cells of B. stratosphericus, the spores and the purified DPA were capable of producing nanoparticles from silver nitrate (AgNO3). These biogenic nanoparticles, which were highly toxic against different pathogenic bacteria, showed mixed structures including spherical, triangular, cubic, and hexagonal with the approximate size between 2 and 20 nm in diameter. Our results illustrated the role of dipicolinic acid as a main factor for the synthesis of nanoparticles by the bacterial spores.</P>