TYPES OF FERMENTOR AIR LIFT FLUIDIZED BED FERMENTOR HOLLOW FIBER IN SITU-STERILIZABLE FERMENTOR

2. AIR LIFT
• This vessel design eliminates the
need for a stirrer system. A tall,
thin vessel is the best shape with
an aspect ratio of around 10:1 .
• Sometimes a “conical” section is
used in the top part of the vessel
to give the widest possible area
for gas exchange.
• The culture fluid is both mixed
and aerated by a stream of air,
which enters near the base of
the vessel.

3. • A hollow pipe or draft tube in the center of the vessel provides a “riser”
for the air (which is full of bubbles) to move upwards to the top of the
vessel.
• If a very large vessel is used, the hydrostatic head of the fluid provides a
pressurizing effect to the lowest region of the culture where the air
enters and so increases the dissolved oxygen concentration.
• The draft tube is usually double-walled to allow heating and cooling
using a thermocirculator system.
• When the aerated culture fluid reaches the top of the draft tube, it
“spills over” and begins to fall towards the bottom of the vessel via the
space between the outer wall of the draft tube and the inner wall of
the vessel.

4. • A large head space above the top of the draft tube allows for easy gas
transfer from the liquid to the gas phase, which causes the specific
gravity of the liquid to increase and so it descends to the bottom of the
vessel.
• The descending liquid returns to the base of the vessel where it is
regassed and begins to rise again.
• A common use of air lift fermentors is the growth of shearsensitive cells
such as plant and animal cultures. Also, the design has been used for
the production of large amounts of biomass as single-cell protein.

5. FLUIDIZED BED FERMENTOR
• Medium is recirculated via a pump; this can be easily adapted to give
a continuous/semicontinuous flow to allow the trapped cells to effect
chemical changes on constituents of the medium without being
washed out along with spent medium.
• This system is well suited to growth of animal cells on the smaller
scale and has large-scale application in effluent/decontamination
treatment plants.
• Solid-state fermentation is increasing in importance in several areas
of application.

6. • Here the substrate for growth is a solid, such as soil (or semisolid, e.g.,
fats). The substrate is rotated or mechanically mixed and temperature
control achieved by both air and water circulation.
• Applications include
the bio-remediation of soils to remove toxins or waste products
improving the efficiency of composting for agriculture
production of enzymes in solid fermentation

7. HOLLOW FIBER
• This is a similar idea but the cells are now embedded in fibers
contained in a cartridge that is bathed in circulating culture medium.
• An extension of this method is to use cartridges containing two
different bundles of fibers as a separation “membrane” between, e.g.,
a pair of fermentor vessels and allows dissolved gases and
metabolites to be exchanged without cells crossing the barrier.
• Application closely related to is
Micro-filtration

9. IN SITU-STERILIZABLE FERMENTOR
• The heating for the vessel is normally provided via a double jacket,
which can either be the full length of the vessel or cover just the
bottom third.
• The bottom section contains large (25 mm) port fittings for electrodes
and usually has some kind of steam-sterilizable sampling
device/harvest valve.
• The mechanical seal and drive shaft usually enter from the bottom on
this size of vessel.

10. • The vessel top plate has port fittings that use a membrane seal and
port closure.
• The steam for sterilization is either supplied from an in-house source
and used to heat the vessel jacket or can be raised electrically from a
separate steam generator.
• The medium in the vessel is heated to 121°C and often supplies the
steam for sterilization of the exit gas filter.