The microbial biocompatibility to convert absorbed CO2 from an aqueous amine solution was quantified at 20 different concentrations (0 -500 mM) of methyl diethanolamine (MDEA). Batch reactors constructed in borosilicate serum bottles with rubber-butyl stoppers with a total volume of 117.2 mL were filled with 44 mL of an aqueous amine solution combined with a phosphate-buffered saline (PBS) solution. The PBS solution of 8 g L -1 of NaCl, 0.2 g L -1 of KCl, 1.44 g L -1 of Na2HPO4 and 0.24 g L -1 of KH2PO4 was added to each batch reactor to maintain isotonicity and provide a minor pH buffer capacity to compensate for the large pH changes during the microbial fixation of the absorbed CO2. Mass flow controllers (Brooks SLA 5850 series)