Carbon dioxide (one of the main greenhouse gases) can be used as a raw material in microbial electrosynthesis system (MES) for the production of valuable organic compounds. However, one of the major drawbacks associated with the MES is the mass transfer limitation of CO2 in the aqueous phase. In order to overcome this limitation, several operational strategies such as the increase of CO2 flow rate have been proposed. Therefore, the present paper assessed an H-type MES (H-Cell) carried out under CO2 pure gas supplied at 5, 10 and 20 mL min(-1), and a gas diffusion electrode (GDE) MES (VITO-Cell) under 5 and 20 mL min(-1). In both the MESs, the increase of the CO2 flow rate led to the improvement of inorganic carbon concentration, reaching until 1068 +/- 115 mg L-1 in VITO-Cell. Consequently, in H-Cell the maximum acetate production rate increased from 45 to 270 mg L-1 d(-1) when the CO2 flow varied from 5 to 20 mL min(-1). In VITO-Cell the maximum acetate production rate reached 85 mg L-1 d(-1) at 5 mL min(-1) CO2 flow rate due to a better gas-liquid mass transfer coefficient of CO2 provided by the GDE.