baffles are sometimes placed in the draft tube. TOWER LOOP AIRLIFT FERMENTER. Tower loop airlift fermenters, also known as external loop airlift fermenters. Air Lift Fermenters, and Air Lift Bioreactors for BioProcessing – Microbial Cell Culture or Fermentation. Air lift bioreactors are an alternative to mechanically. In this article a modeling of a draft-tube airlift fermenter (ALF) based on perfect back- Since airlift fermenters (ALF) are characterized by large oxygen trans-.
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This article throws light upon the six types of bioreactors used in bioprocess technology. The six types are: A continuous stirred tank bioreactor consists of a cylindrical vessel with motor driven central shaft that supports one or more agitators impellers.
The shaft is fitted at the bottom of the bioreactor Fig. The number of impellers is variable and depends on the size of the bioreactor i. The aspect ratio of a stirred tank bioreactor is usually between However, for animal cell culture applications, the aspect ratio is less than 2. The distance between two impellers is approximately 1. Different types of impellers Rustom disc, concave bladed, marine propeller etc. In stirred tank bioreactors or in short stirred tank reactors STRsthe air is added to the culture medium under pressure through a device called sparger.
The sparger may airift a ring with many holes or a tube with a single airoift.
The sparger along with impellers agitators enables better gas distribution system throughout the vessel. The bubbles generated by sparger are broken down to smaller ones by impellers and dispersed throughout the medium. This enables the creation of a uniform and homogeneous environment throughout the bioreactor. There are many advantages airliff STRs zirlift other types. These include the efficient gas transfer to growing cells, good mixing of the contents and flexible operating conditions, besides the commercial availability of the bioreactors.
In the bubble column bioreactor, the air or gas is introduced at the base of the column through perforated pipes or plates, or metal micro porous spargers Fig. The bubble column bioreactors may be fitted with perforated plates to improve performance. The vessel used for bubble ffrmenters bioreactors is usually cylindrical with an airlfit ratio of i. In the airlift bioreactors, the medium of the vessel is divided into two interconnected zones by means of a baffle or draft tube.
The other zone that receives no gas is the down comer. The dispersion flows up the riser zone while the down flow occurs in the down comer. There fermdnters two types of airlift bioreactors. Internal-loop airlift bioreactor Fig. These bioreactors are simple in design, with volume and circulation at a fixed rate for fermentation. External loop airlift bioreactor Fig. These reactors can be suitably modified to suit the requirements of different fermentations.
In general, the airlift bioreactors are more efficient than bubble columns, particularly for more denser suspensions of microorganisms. This is mainly because in fermenterss bioreactors, the mixing of the contents is better compared to bubble columns. Airlift bioreactors are commonly employed for aerobic bioprocessing arlift. They ensure a controlled liquid flow in a recycle system by pumping. Due to high efficiency, airlift bioreactors are sometimes preferred e.
In general, the performance of the airlift bioreactors is dependent on the pumping injection of air and the liquid circulation. Two-stage airlift bioreactors are used for the temperature dependent formation of products.
Each one of the bioreactors is fitted with valves and they are connected by a transfer tube and pump Fig. The cells are grown in the first bioreactor and the bioprocess proper takes place in the second reactor. A pressure-cycle fermenter with large dimensions constitutes a tower bioreactor Aurlift. A high hydrostatic pressure generated at the bottom of the reactor increases the solubility of O 2 in the medium. At the top of the riser, with expanded top reduces pressure and facilitates expulsion of CO 2.
The medium flows back in the down comer and completes the cycle.
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The advantage with tower bioreactor is that it has high aeration capacities without having moving parts. Fluidized bed bioreactor is comparable to bubble column bioreactor except the top position is expanded to reduce the velocity of the fluid.
The design of the fluidized bioreactors expanded top and narrow reaction column is such that the solids are retained in the reactor while the liquid flows out Fig. These bioreactors are suitable for use to carry out reactions involving fluid suspended biocatalysts such as immobilized enzymes, immobilized cells, and microbial flocs. For an efficient operation of fluidized beds, gas is spared to create a suitable gas-liquid-solid fluid bed. It is also necessary to ensure that the suspended solid particles are not too light or too dense too light ones may float whereas to dense ones may settle at the bottomand they are in a good suspended state.
Recycling of the liquid is important to maintain continuous contact between the reaction contents and biocatalysts. This enable good efficiency of bioprocessing. A bed of solid particles, with biocatalysts on or within the matrix of solids, packed in a column constitutes a packed bed bioreactor Fig.
The solids used fermenterss be porous or non-porous gels, and they may be compressible or rigid in nature. A nutrient broth flows continuously over the immobilised biocatalyst. The products obtained in the packed bed bioreactor are released into the fluid and removed.
Bioreactors and Fermenters – Electrolab
While the flow of the fluid can be upward or downward, down flow under gravity is preferred. The concentration of the nutrients and therefore the products formed can be increased by increasing the flow rate of the nutrient broth.
Because of poor mixing, it is rather difficult to control the pH of packed bed bioreactors by the addition of acid or alkali. However, these bioreactors are preferred for bioprocessing technology involving product-inhibited reactions. The packed bed bioreactors do not allow accumulation of the products to any significant extent.
These are the bioreactors specialised for fermentation that can be carried out either by exposing to sunlight or artificial illumination. Since artificial illumination is expensive, only the outdoor photo-bioreactors are preferred.
Certain important compounds are produced by employing photo-bioreactors e. The different types of photo-bioreactors are depicted in Fig. They are made up of glass or more commonly transparent plastic.
The array of tubes or flat panels constitute light receiving systems solar receivers. The culture can be circulated through the solar receivers by methods such as using centrifugal pumps or airlift pumps. It is essential that the cells are in continuous circulation without forming sediments.
Further adequate penetration of sunlight should be maintained. The tubes should also be cooled to prevent rise in temperature. Microalgae and cyanobacteria are termenters used. The organisms grow during day light while the products are produced during night. Conventional and Novel Zirlift for Cell Cultures. Types of Recombinant Vaccines: This is a question and answer forum for students, teachers and general airlitf for exchanging articles, answers and notes.
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