Multiphase Bioreactor Design

be as high as 100 times the tank-averaged value. In the remainder of the vessel, the

local dissipation rate may fall to 0.25. In bubble columns and ALRs, energy dissipation
rates can be estimated using the following equations (Chisti, 1998):

(4)

(5)

where usr is the superficial gas velocity in the riser and Ad/Ar is the ratio of the
downcomer-to-riser cross-sectional areas. Equations 3–5 indicate that energy dissipation
rates are strongly dependent on impeller design and agitation rate in STRs, and on
aeration rate and vessel geometry on ALRs. In an unaerated STR, average energy
dissipation rates

Table 14.4 System geometry and operating details

for a train of commercial bioreactors (adapted from

Hashimoto and Azechi, 1988)

V (L) T (m) Ha (m) H/T (−) Agitation System D/T (−) N (rpm) πND (m s−^1 )

20 0.24 0.33 1.38 2 turbines 0.40 125–1250 0.63–6.28

300 0.55 0.95 1.73 2 turbines 0.36 15–150 0.16–1.57

2000 1.25 1.22 0.98 2 turbines 0.34 10–100 0.22–2.20

20 000 2.50 3.06 0.92 2 4-blade paddles (45°) 0.50 10–40 0.65–2.62
aassuming a maximum working volume of 0.75V.

Table 14.5 Representative energy dissipation levels

in bioreactors used for the cultivation of plant cell

suspension cultures

System Vessel/Impeller
configuration

Operating

conditions

Np(−) ε(W

kg−^1 )a

Reference

Catharanthus
roseus

11 L STR(10L wv)

helical ribbon impeller

D: 0.21 m

120 rpm

surface aerated

μa: 0.6 Ns m−^2

~2 0.7 Kamen et al.

(1992)

Catharanthus
roseus

3 L STR (2 L wv)

Rushton turbine

D: 0.045 m

150 rpm ~5 0.007b Meijer et al.

(1994)

Nicotiana
tabacum

3 L STR (2L wv)

marine propeller

D: 0.045 m

100 rpm ~0.45 0.0002b Ho et al.

(1995)

Papaver 300 L ALR Qg: 0.05 vvm N/A 0.11 Parket al

Multiphase bioreactor design 430