Bioreactor System ERT 314 Sidang 1 2011/2012
Chapter 3:Types of Bioreactors Week 4-5 Handouts : Chapter 13 in Doran, Bioprocess Engineering Principles
Background to Bioreactors The bioreactor is the heart of any fermentation or enzyme conversion process. Design of bioreactors is a complex task relying on scientific and engineering principles and many rules of thumb. The main function of a properly design bioreactor is to provide a controlled environment to achieve optimal growth and/or product formation in the particular cell system employed Usually the term fermenter is used in literature in stead of bioreactor, but both carries the similar meaning
Strategies for bioreactor design
Background to Bioreactors The performance of any bioreactor depends on many functions such as: 1. Biomass concentration must remain high enough to show high yield 2. Sterile conditions must be maintained for pure culture system 3. Effective agitation is required for uniform distribution of substrate and microbes in the working volume of the bioreactor 4. Heat transfer is needed to operate the bioreactor at constant temperature, as the desired optimal microbial growth temperature 5. Creation of the correct shear conditions High shear maybe harmful to the organism and disrupt the cell wall Low shear may also be undesirable because the unwanted flocculation and aggregation of the cells, or even growth of bacteria on the reactor wall and stirrer
Stirred tank reactor (STR) Airlift bioreactors Airlift pressure cycle Loop bioreactor Types of Bioreactor Immobilized cell reactors (ICR) Membrane reactors (MBR) Bubble column Photobioreactors Fluidized bed reactors Trickle bed reactors
Stirred tank bioreactor
A disposable bioreactor Immobilized bioreactor A pilot plant bioreactor
Photobioreactor
Bubble column Membrane reactor
Packed bed reactor Tricklebed reactor
Stirred tank reactor The most common type of bioreactor used in industry Typically 70-80% of total volume is filled with medium (WHY?) H:D ratio is important in designing bioreactor especially when aeration is required (WHY?)
Airlift bioreactors Mixing in airlift bioreactors usually accomplished without any mechanical agitation The bioreactors are used for tissue culture because the tissues are shear sensitive and normal mixing (aeration plus mechanical agitation) is not possible Their advantages are: Low shear showed low mixing in the bioreactors which they can be used for growing plant and animal cell Since there is no agitation, sterilization is easily maintained The pressure at the bottom of vessel will increase the solubility of oxygen as well as Kla value in large vessel with 60m liquid height Large vessels can be constructed, since their main mixing approach is aeration
Airlift bioreactors (cont d) There are form of airlift bioreactors In the usual form, air is fed into the bottom of a central draught tube through a sparger ring, reduced the liquid density in the tube relative to the annular space within the bioractor The flow passed up through the draught tube to the head space of the bioreactors, where excess air and CO2 disengage The degassed liquid then flows down the annular space outside the draft to the bottom of the bioreactor Cooling can be provided by either making the draught tube an internal heat exchanger or with heat exchanger in and external recirculation loop
Airlift pressure cycle bioreactors The gas is circulated by means of pressurized air Circulation is caused by the motion of injected gas through a central tube, with fluid recirculation through the annulus between the tube and the tower or vice versa
Loop Bioreactor A modified type of airlift system with gas and liquid flow patterns in which a pump transports the air and liquid through the vessel External loop is used, with a mechanical pump to remove the liquid Gas and circulated liquid are injected into lower through a nozzle
Bubble column Aeration and mixing are achieved by gas sparging, therefore less energy For production of Baker s yeast, beer and vinegar, wastewater treatment Generally cylindrical vessel with height greater than twice the diameter No internal structure except sparger Perforated horizontal plates installed in tall columns to break up and redistribute coalesced bubbles.
Membrane bioreactors Conventional membrane bioreactors process immerses membranes directly into highly concentrated mixed liquor suspended solids. MLSS contains high levels of dispersed, small particles comprised of inert and colloidal material. High membrane fouling environment, which results in low membrane flux rates, which require large membrane surface area
Membrane bioreactors (cont d)
Photobioreactors Photobioreactor is a device that houses and cultivates algae. It provides a suitable environment for algae growth, supplying light, nutrients, air, and heat to the culture.
Immobilized cell reactors (ICR) The air circulates over a film of microorganisms that grows on a solid surface For example, particulate biocatalysts are used for enzyme production and conversion of penicillin to 6- aminopenicillanic acid
Packed-bed bioreactor Used with immobilised/ particulate biocatalyts Medium fed either from top to bottom Aeration is accomplished in separate vessel
Fluidized bed bioreactors When packed beds are operated in upflow mode, the bed expands at high flow rates; chanelling and clogging of the bed are avoided Application wastewater treatment and vinegar production
Trickle bed bioreactor Another variation of packed bed where the fluid is sprayed onto the top of the packing and trickles down the bed Air is introduced at the base, because liquid is not continuous throughout the column, so air can moved easily around the packing Application aerobic wastewater treatment
Solid-state fermenter/bioreactor Solid state fermentations (SSF s) involve solid substrates at low moisture levels or water activities The water content of a typical submerged fermentation is >95% The water content of a typical solid state fermentation is typically between 40-80% SSF s are usually used for the fermentation of agricultural products or foods, such as rice, wheat, barley, corn and soybeans The low moisture levels of SSF s acts as a powerful selection pressure for the growth of mycelial organisms
Some Traditional Food Fermentations
Rotary-drum bioreactor
Common features of bioreactors Industrial bioreactors can withstand up to 3 atmospheres positive pressure They are equipped with lit vertical slight glass for inspecting the contents of reactor Side parts for ph, temperature and dissolved oxygen sensors A steam sterilization sample port Mechanical agitators are installed on the to or bottom of the tank for adequate mixing Foam breaker