and control. For example, online NADH and NADPH cofactor measurements have

been obtained, although still suffering from interferences. When analyzing virus

containing samples, precautions regarding biosafety might need to be taken (e.g., a

short temperature increase for virus inactivation).

5.6

CULTIVATION VESSELS AT SMALL AND LARGER SCALE AND

PROCESS VARIABLES

5.6.1

CULTIVATION VESSELS

Cultivation vessels, from well-plates and T-flasks to STR, are systems where the

substrates in the culture medium are converted into the desired product by bio-

chemical processes that take place inside the cells. They must provide the appro-

priate conditions for cell growth and product synthesis [50]. Different choices of

static and dynamic cultivation systems including bioreactors are available for ad-

herent and suspension growth adapted cells. This section presents an overview of

the cultivation vessels used for virus production, their major features, the impact of

some process variables and some considerations for their scale-up.

For adherent and suspension growth adapted cells different vessels at different

sizes are available (Figure 5.4). Static bioreactors or vessels provide a surface pre-

treated to confer specific surface properties for attachment of adherent cells through

some coatings over e.g., a polystyrene matrix [51]. Their scale-up is based on the

available cell culture surface [52]. Aeration takes place through the gas-liquid in-

terface by diffusion from the air contained in the vessel. Initially, in screw-capped

vessels, partial twist of the cap allowed some gas exchange to the outside of the

vessel. Today, this is done via membrane-filtered vent caps. Furthermore, notches for

dishes, gas-permeable membranes for multi-plates, and multitray stacked systems

T-Flask

Shake flask

Multi-layer T-Flask

Cell stack

PBBR

OSB

STR

Wave

Ambr15

RB

FIGURE 5.4 Overview of cultivation vessels for adherent (top) and suspension (bottom) cells.

RB: roller bottle; PBBR: packed bed bioreactor; STR: stirred tank bioreactor; OSB: orbital

shaken bioreactor.

102

Bioprocessing of Viral Vaccines