Investigating the molecular mechanism of Bio denitrification by thiobacillus denitrificans in the presence of metal nanostructure in bioreactor

Nitrate is one of the inorganic anions derived from the oxidation of elemental nitrogen. Nitrate contamination of groundwater and surface water has become a critical problem. Therefore, achieving the new technologies for nitrate removal is necessary. The aim of this study was to investigate the molecular mechanism of bio denitrification by thiobacillus denitrificans in the presence of quantum dot metal-carbon nanoparticles (CQD-Fe0) in a bioreactor.

Fe0 nanoparticles were synthesized by the liquid-phase reduction method, also called the borohydride reduction method and for biocompatibility, uniform distribution, and non agglomeration, Fe0 was coated with carbon quantum-dot. Characterization of nanoparticles was determined by XRD, TEM, FESEM, and FTIR. The biological process of nitrate removal was investigated in the presence and absence of nanoparticles. The expression of nirS, narH and recA genes was also assessed using real-time PCR.

The FTIR spectrum confirmed the formation of CQD-Fe0 bonds. The average diameter of CQD-Fe0 nanoparticles was in the range of 29.31 to 38.32 nm. Denitrification in the presence of CQD-Fe0, with increasing temperature (35C°) was 73.43%. In discontinuous conditions, bio denitrification was obtained for CQD-Fe0 nanoparticles 79.8312%. In the bioreactor, biodenitrification, in the presence of CQD-Fe0 nanoparticles, 95% was obtained. Examination of gene expression showed that the expression of all three genes nirS, narH and recA in cells treated with nanoparticles significantly increased compared to the control group, which indicates the high impact of these nanoparticles on the bio denitrification of this microorganism. 

Therefore, with further experiments, it is hoped that removing nitrate with Nanoparticles Zero Iron (nZVI) from water resources would be possible.