where kLa is the volumetric gas–liquid mass transfer coefficient (s−1), N the shaking
frequency (rpm), VL (mL) the working volume, d0 (cm) the shaking diameter and d (cm) the maximum shake flask diameter. The gas–liquid mass transfer was expected
to be strongly coupled with flask geometry (modification of the interfacial area a)
and agitation conditions (modification of both the liquid-side mass transfer coefficient
kL and the interfacial area a). For surface aerated culture systems, no general
function relating kLa to power dissipation was found in the literature. Indeed, the
structure of the free surface and thus the interfacial area was expected to change
dramatically with power dissipation.