3.1 Mixing time characterisation
Mixing time is an important parameter for mammalian cell culture
processes. Inadequate mixing results in cells being exposed to different
environments within the reactor, which can have adverse consequences on
cell growth kinetics and productivity (Gogate, Beenackers, & Pandit,
2000; Alvin W. Nienow, 2006). Hence mixing should be optimised to
produce a homogenous cell culture environment whilst avoiding any
deleterious effects caused by potential hydrodynamic forces and bubble
bursting. Short mixing times (tm < 10s)
should provide the necessary homogeneity as well as ensuring a fast
response to any changes in operating conditions such as pH and
temperature (Amanullah, Buckland, & Nienow, 2004; Langheinrich &
Nienow, 1999; Silk, 2014). For fed-batch culture, efficient mixing is
particularly important to avoid formation of local nutrient gradients
(Enfors et al., 2001; Alvin W. Nienow, 2006).
Mixing times in the 5 L STR and 24-DSW were determined using the DISMT
method as described in section 2.1.