1. Bioreactors must be capable of aseptic operation for long periods of time while meeting containment regulations. 2. They must provide adequate aeration and agitation to meet microbial metabolic needs without damaging cells or causing excessive foaming. 3. Power consumption should be minimized while temperature is controlled during sterilization and fermentation.

1. Bioreactors

2. Stir tank reactor

5. Fermentation function-Basics-design point of view
The vessel should be capable of being operated aseptically for a number of days and
should be reliable in long-term operation and meet the requirements of containment
regulations.
Adequate aeration and agitation should be provided to meet the metabolic
requirements of the microorganism. However, mixing should not cause damage to
the organism nor cause excessive foam generation.
Power consumption should be as low as possible.
A system of temperature control, both during sterilization and fermentation, should
be provided.

6. Mass transfer-Aeration
• Oxygen transfer in aerobic fermentation
• Sterile filtered air or oxygen-enters the fermenter through a sparger
system, and air flow rates for large fermenters rarely exceed 0.5–1.0
volumes of air per volume of medium per minute (vvm).
• Sparger generally located below the agitator for aeration in stirred
tanks

7. • Small bubbles-larger surface area to volume ratio-greater oxygen transfer
• Oxygen transfer is complex-phase change from gaseous to liquid-influenced by the given
factors
the prevailing physical conditions; temperature, pressure and surface area of air/oxygen bubbles;
 the chemical composition of the medium;
the volume of gas introduced per unit reactor volume per unit time;
the type of sparger system used to introduce air into the fermenter;
the speed of agitation; or
a combination of these factors.

8. • aerobic fermentations molecular oxygen must be maintained at optimal concentrations to ensure
maximum productivity.
• The two steps associated with an oxygen mass balance are the rate at which oxygen can be
delivered to the biological system (oxygen transfer rate, OTR) and the rate at which it is utilized by
the microorganisms (critical oxygen demand).
• The OTR is determined by the driving force, the oxygen gradient, and the resistance to oxygen
transfer.
Where C*-saturated dissolved oxygen (mmol/dm3), CL-oxygen concentration at time (mmol/dm3), KL
= mass transfer coefficient (cm/h), i.e. the sum of reciprocals for the residencies of oxygen transfer
from the gaseous to liquid phase; and a-gas–liquid interface area per liquid volume (cm2/cm3).

9. The driving force for oxygenation is the oxygen gradient (C* – CL).
In order for oxygen to transfer from the gaseous phase to an individual cell or site of reaction,
it must pass through several points of resistance:
 resistance within the gas film to the phase boundary;
 penetration of the phase boundary between the gas bubble and bulk liquid;
 transfer from the phase boundary to the bulk liquid;
 movement within the liquid;
 transfer to the surface of the cell;
 entry into cell; and
 transport to the site of reaction within the cell.

11. Baffles
Baffles are usually flat vertical plates whose width is about one-tenth
of the vessel diameter.
Normally, 4–6 baffle plates are fitted to the inside vessel walls to aid
mixing and mass transfer by increasing turbulence, preventing vortex
formation and eliminating ‘dead spaces’.

12. Cyclone Column Fermenter
Dawson (1974) developed the
cyclone column-for the growth of
filamentous cultures.

13. Photobioreactor

14. Membrane bioreactor