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Updated: Aug 4, 2026

Electrochemically and Bioelectrochemically Induced Ammonium Recovery
Published on: January 22, 2015
Microbial production of ammonium ion from nitrogen
Researchers engineered a nitrogen-fixing mutant (SK-24) that excretes ammonia (NH4+). This breakthrough offers potential for microbial production of nitrogen fertilizer from fixed N2.
Area of Science:
- Microbiology
- Biochemistry
- Agricultural Science
Background:
- Nitrogen fixation is crucial for agriculture.
- Efficient ammonia assimilation is key for microbial growth.
- Genetic manipulation offers pathways to control nitrogen metabolism.
Purpose of the Study:
- To isolate and characterize a mutant capable of excreting fixed nitrogen as ammonia (NH4+).
- To investigate the biochemical mechanisms behind NH4+ excretion in engineered microbes.
- To assess the potential of these mutants for fertilizer production.
Main Methods:
- Isolation of a derepressed N2 fixation mutant (SK-24).
- Biochemical analysis of nitrogenase, glutamate synthase, and glutamate dehydrogenase activities.
- Measurement of NH4+ excretion rates and energy conversion efficiency.
Main Results:
- Mutant SK-24 excreted up to 20.2 µmol NH4+/mg protein/24 hr.
- Excretion resulted from constitutive nitrogenase synthesis and genetic blocks in NH4+ assimilation pathways.
- Parent strain asm-1 showed transient NH4+ excretion.
- Maximum energy conversion efficiency was approximately 5 glucose degraded per NH4+ formed.
Conclusions:
- Engineered mutants can efficiently excrete fixed N2 as NH4+.
- This process is driven by specific genetic modifications affecting nitrogen assimilation.
- Microbial production of NH4+ fertilizer is a viable prospect.
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