Progress to date
• Demonstrated Euglena growth on NO3- as well as on NH4+. Significance: Complicates the interpretation of the N-transformation reactions and their rates in the primary payload.
• Demonstrated Euglena growth on NH4+ produced by cyanobacteria in co-culture in 2 types of media. Significance: Euglena able to grow on NH4+ produced by other organisms (ground control data for potential contaminants in system – the current prototype CROP system is full of cyanobacteria).
• Colorimetric assays for the various nitrogen species produced variable results leading to the decision to use ion-chromatography for the ground controls and flight experiment. Significance: Changes the hardware, its configuration, as well as mass, power and volume in the payload.
• Decision finalized to use gas sensors to measure atmospheric gases in the primary payload instead of a gas chromatograph. Significance: Gas sensors are simpler and less prone to error and failure. It also impacts the hardware configuration as well as resulting in a reduction in the mass and power requirements.
• Using the ion chromatograph we are monitoring the concentration of the ammonium, nitrate, and nitrite in the system as well as net rate of the reactions from a batch of 20% synthetic urine run through the CROP system.
• Computer simulations of the microbial and nitrogen species changes in the Eu:CROPIS system were refined to better incorporate the data obtained from the CROP portion of the system.
• We constructed an additional test module that isolates each component of the system (i.e., greenhouse for Euglena, tomato growing section, trickling filter, etc.), such that they can function independently. This module is fitted with gas inlets/outlets and sampling ports so that we can control the atmosphere in the system. This allows us to test each system at various O2 levels in a controlled manner.
In the multi-modular test system running without tomatoes the addition of urea needs to be balanced with biomass production. To that end we have modified the system and improved the O2 production rate compared to the data obtained, improving the connection filter between the algae tank and the lava-tricking filter. In this improved system when it is flushed with 500 µl of urea it results in a significant reduction of oxygen but a much shorter time for oxygen recovery (build-up) in the system. Currently, the algae tank seems to be providing sufficient oxygen for the whole system. The O2 level is in the range of 4-5 mg/l oxygen in the filter circuit (before and about 2 h after urea supplement).
• We have improved the lighting program so that 100 different intensities can be tested. This will be important, because the light intensity needs to be adjusted to match the increasing cell density (algal growth is the prerequisite of oxygen production).
• Construction of the flight unit was completed this year and testing is ongoing in preparation for a March 2017 launch.
• Refined the computer simulation model by obtaining and incorporating more data from the laboratory studies of the CROP system.
• Minimize the gas leak rate from the laboratory system.
• Test integrated automated Eu:CROPIS system.