Developing an Automated Off-Gas Sampling System to Obtain High-Resolution CO2 Fixation Data from Cyanobacterial Cultures

Cyanobacteria and its complex photosynthetic systems have been a prime target for synthetic biologists and their molecular engineering tools for the last couple of decades. However, characterizing meaningful carbon dioxide (CO₂) removal performance has always been a struggle within the field. It is proposed that measuring changes in CO₂ gas concentration within a dynamic system can be accomplished with a simple automated Arduino-powered system. The system employs solenoids in parallel (one for each outlet stream) which are then connected to one large manifold which feeds into a single IR-based CO₂ probe. Since CO₂ probes are expensive, this approach allows for sample multiplexing while remaining affordable. The development of such a system allows for high resolution growth experiments between different strains of cyanobacteria. This approach provides continuous data collection over the entire life cycle of each individual culture, allowing differences in total CO₂ fixation between strains to be readily determined. From a culture of PCC 6803, it was found that the peak mg of CO₂ fixed per day is around 92 mg CO₂/day. In the future, the system can be modified to fit other simple dynamic gas systems, as well as testing similar gas utilization/production capabilities of other organisms.