Rudiments of a nitrate assimilating bacterium in bioremediation

• The degree to which nitrate assimilating bacterium, Methylobacterium fujisawaense, can remove nitrate was studied.
• The effect of immobilization on the nitrate-assimilating ability of bacteria like M. fujisawaense was also analyzed.
• M. fujisawaense was found to be capable of 89–100% removal of Nitrate concentrations close to 10 mg L−1 NO3-N.

The microbial pathway of nitrate assimilation may have bioremediation potential in cases where the need for nitrate removal is paired with a desire to reuse the captured nitrogen in biomass form. In order to assess the nitrate bioremediation potential of Methylobacterium fujisawaense, both freely suspended cells and those immobilized on calcium alginate beads were assessed in aerobic test tube and batch reactor settings for their ability to reduce NO3-N. Nitrate removal results were as high as 100% for freely suspended cells after 96 h and 95% for immobilized cells also after 96 h. A statistical analysis of the first order kinetic/exponential decay trend found in both free cell and immobilized cell systems found no significant difference in overall nitrate removal rates between the two systems. These findings suggest that the organism is capable of a significant assimilation of NO3-N. The assimilating ability of M. fujisawaense is also not greatly altered by immobilization, a characteristic that adds to the list of its potential benefits in a bioremediation setting.