Often aerobatic fermentations give off CO₂ gas because the respiring cells produce CO₂ as glucose nutrient is converted to chemical energy. The conditions used to set k_La for O₂ transfer in the fermenter also establish the same hydrodynamic conditions for CO₂ transfer.

Consequently, the transfer rate of CO₂ from the liquid to the aeration gas is also described by this volumetric mass-transfer coefficient, k_La.

Consider that the k_La for O₂ in the fermenter is 300 h^-1. Scale the k_La for O₂ to k_La for CO₂ transfer using film theory, boundary layer theory, and penetration theory.