Urine nitrification with a synthetic microbial community

Area of Science:

• Astrobiology
• Microbiology
• Environmental Science

Background:

• Long-term space missions require regenerative life support systems to recycle waste into resources.
• Converting astronaut urine into plant fertilizer is crucial for in-space food production.
• Synthetic microbial communities are preferred for controlled environments like space, but face challenges like salinity and organic compounds in urine.

Purpose of the Study:

• To compile and evaluate a synthetic microbial community for urine nitrification under space-relevant conditions.
• To assess the community's tolerance to salinity and its efficiency in removing ammonium and producing nitrate from urine.

Main Methods:

• A synthetic community comprising ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and ureolytic heterotrophs was constructed.
• Two reactors were used: one for salt adaptation of AOB and NOB, and another for testing the full community with synthetic and real urine.
• Nitrification rates, ammonium removal, nitrate production, and organic compound removal were measured.

Main Results:

• The AOB and NOB co-culture adapted to high salinity (up to 45 mScm^-1), maintaining significant ammonium removal rates.
• The complete synthetic community achieved notable nitrate production rates using both synthetic and real urine.
• Batch tests with real urine showed even higher nitrate production, though organic compound removal requires optimization.

Conclusions:

• The developed synthetic microbial community demonstrates potential for effective urine nitrification in space.
• Further optimization of organic compound removal is necessary for generating a high-quality nitrate fertilizer for space applications.
• This research supports the development of closed-loop life support systems for sustainable long-term space exploration.