We have a putative bacterial strain that we suspect can utilize CO2 as carbon source - As a negative control we would like to grow it in a CO2 free atmosphere on a petri dish - do you have any suggestions about removal of CO2 from the air. We taught of mixing O2 and N2 and blowing it in the anaerobic chamber, but that would require special equipment as we do not have compressed O2 in the lab. Is there any "CO2 absorber" available?
Thank you for your ideas!
Best,Martin
Of course, one of the simplest possibilities to scavenge carbon dioxide from the inlet air of the aerobic bioreactor, would be to bubble the finely dispersed air stream trough a 'milk of lime' column, i.e. containing a saturated aqueous solution of Ca(OH)2 with excess Ca(OH)2(s) in suspension. Calcium carbonate would form by reaction of carbon dioxide with calcium hydroxide: Ca(OH)2(aq) + CO2(g) → CaCO3(s)↓ + H2O(l). The precipitated calcium carbonate could further react with excess of CO2: CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq). The air stream would also become saturated in humidity for the temperature of the suspension. This approach might be directly applied for a pilot scale bioreactor.
Considering a Petri dish (aerobic) culture, I think that the dishes could be closed and sealed with paraffin in CO2 free air obtained as above. For further CO2 absorption, as some CO2 could, in principle, be liberated to the Petri dish atmosphere during the course of the experiment, one could consider to use the upper dish for the culture gel (inverted) while keeping some convenient CO2 scavenger (e.g. milk of lime) at the lower dish, but without contacting the culture media.
Carbosorb, marketed by Perkin Elmer, consists of solid pellets that bind carbon dioxide with a very high affinity. They are often used to trap radioactive CO2. If you have access to glass or plastic jars ('anaerobic jars') designed for anaerobic cultivation (e.g. with the GasPak system), you might put your plates in such a jar, fill it with air, stick in a sufficient amount of Carbosorb and close the jar. Good luck!
Thank you all for your answers. We actually figured out we have a so called Synthetic air in lab that is used in CG-MS machine so we try first with that!
How large is the bioreactor? The most practical solution depends highly upon the size and CO2 production rate. For small quantities, Drierite followed by solid sodium hydroxide would work well. For large volumes/concentrations, an absorber column with sodium hydroxide solution passing downward while the gas is flowing upward.
We frequently use synthetic air from gas bottles, which is composed of only oxygen and nitrogen, and it works well.
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