FERMENTATION.pptx
- 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.