4

Notes

1. Types of bioreactor based on geometry and other design para-

meters could be bubble column, air-lift, fixed-bed column, and

stirred tank reactors. Dynamic method could not be correctly

applicable in high bioreactors with height more than 1 m due

to gas residence time in de-oxygenation step during nitrogen

hold-up.

2. Any microorganism other than E. coli can also be used to

determine the kLa measurement. However in this case, be

aware of choosing the right growth medium and physical con-

ditions that the microorganism requires.

3. Depending on types of microorganisms, other growth media

that provides macro and micro elements for cells can also be

selected for measurement of the kLa.

4. The sparger type of bioreactor could be porous or nozzle

beside orifice type.

5. Microorganisms transform substrates into biological products

with the advantages of mixing and consequently heat-mass

transfer mechanisms. To provide mixing, 6-blade Ruston tur-

bine impeller is used for bacterial production in this protocol.

Marine, paddle, anchor or helical ribbon types of impellers

could also be chosen in terms of microorganism types and

production purposes.

6. Be aware that the STR and LB medium are autoclaved sepa-

rately to ensure the loss of volume in the STR is minimized as a

result of evaporation.

7. When the growth medium is to be used, prepare it fresh or

prepare it not more than 3 days before the experiment and

store it in the refrigerator at +4 ^C until the measurement.

8. In the pH arrangement, diluted hydrochloric acid and sodium

hydroxide could be used if the pH of growth media is far away

from the range of 7.5–8.

9. The mixing condition for cells in broth culture is 150 rpm on

the shaker. The culture temperature is 37 ^C.

10. The viability of cells and whether there is any contamination

must be checked especially in the beginning of growth phase of

cells.

11. Make sure that the calibration of DO probe has been done.

Also check that all junction of bioreactor are closed except

aeration for sustaining batch operation.

12. The fermentation broth is assumed to be well mixed for deter-

mining the kLa from mass balance equations.

Volumetric Mass Transfer Coefficient Measurement

23