A bioreactor may refer to any manufactured or engineered device or system that supports a biologically active environment.[1] In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms. This process can either be aerobic or anaerobic. These bioreactors are commonly cylindrical, ranging in size from litres to cubic metres, and are often made of stainless steel. A bioreactor may also refer to a device or system meant to grow cells or tissues in the context of cell culture. These devices are being developed for use in tissue engineering or biochemical engineering. On the basis of mode of operation, a bioreactor may be classified as batch, fed batch or continuous (e.g. a continuous stirred-tank reactor model). An example of a continuous bioreactor is the chemostat. Organisms growing in bioreactors may be suspended or immobilized. Immobilization is a general term describing a wide variety of the cell or the particle attachment or entrapment.[2] It can be applied to basically all types of biocatalysts including enzymes, cellular organelles, animal and plant cells.[3] Large scale immobilized cell bioreactors are: Plants Bioreactors and Their Classification A Bioreactor is a device or vessel in which are designed to provide an effective environment for conversion of one material into some product by appropriate biochemical reactions and this conversion is carried out by the action of a biocatalysts like enzymes, microorganisms, cells of animals and plants, or subcellular structures such as chloroplasts and mitochondria. There are different bioreactors and they have different applications are including those for cell growth, enzyme production, biocatalysis, food production, milk processing, tissue engineering, algae production, protein synthesis, and anaerobic digestion. Bioreactors are classified depending on their operational conditions and the nature of the process. Bioreactors can be from different sources like animals, plants, microbes,etc. Plants as bioreactors- Plant cells are an attractive heterologous expression host for foreign protein production. These are unique biocatalysts that have characters different from microorganisms or animal cells. Plants have become economically important systems for producing heterologous proteins. Expressing heterologous proteins in plant material that is used in human food or animal feed allows proteins to be applied orally or topically without having to purify them from the plant material. Plants have a distinct advantage for these applications. Thus, the recombinant products have an advantage over traditional microbial or mammalian host systems and the other features of plant cells as a production host along with are the cost-effective biomanufacturing and the capacity for complex protein post-translational modifications. Heterologous proteins like therapeutics, antibodies, vaccines and enzymes are expressed in plant cell culture-based bioreactor systems including suspended dedifferentiated plant cells, moss, and hairy roots, etc. The in vitro liquid cultures of plant cells in a fully contained bioreactor have become very promising alternative to traditional microbial fermentation and mammalian cell cultures as a foreign protein expression platform. These plant bioreactors are mainly used to produce therapeutic proteins, edible vaccines and antibodies for immunotherapy. There are two basic processes that are used to produce recombinant proteins in plants one is generating the transgenic plants by stable integration of transgene into plant genome and the other is transient expression of the transgene using plant viruses as vectors. The other techniques used for direct gene transfer are electroporation, polythene glycol mediated gene uptake and particle bombardment. There are different plant bioreactors classified based on where the protein is produced- Plant suspension cultures- In this plant cells are grown under sterile conditions as suspension or callus cultures and given the appropriate hormonal supplements for growth and are used in expression of recombinant proteins, secondary metabolites and antibodies. Chloroplast bioreactor- The nuclear chromosomes of chloroplasts are inserted with the foreign genes that are responsible for required product. Insulin, interferons and other proteins can be prepared in chloroplast bioreactor. Hairy root system bioreactor- This has rhizosecretion caused due to infection of agro bacterium rhizogenes and is highly stable and suitable for different biopharmaceuticals. Seed based plant bioreactors- Seed is the most suitable bioreactor because of their large protein accumulation during its development. But specificity of expression and subcellular storage environment are the factors that will decide which seeds are used for producing desired products. There are two types of seed based plant bioreactors- Seed protein storage vacuole bioreactors- The protein storage vacuoles in seeds contain some dominant sub compartments like matrix, globoid and crystalloids which are best for storing recombinant protein. Matrix is suitable for soluble storage proteins, globoids for hydrolytic enzymes and crystalloids for some intrinsic protein sequences. Seed oil body bioreactors- This bioreactor can store a large amount of macromolecules. It has oleosin proteins which are ideal carriers of heterologous proteins encircling the seed oil body. This also provides recognition signal for lipase binding during oil mobilization in seedlings. Achieving the highest possible level of foreign protein production is transgenic plant is very important and this needs to have a strong promoter sequence that can enhance the expression of interest. These plant bioreactors with their unique features show not only advantages but also some disadvantages. Advantages- They are cost effective, faster than transgenic animals, can produce large biomass and the pathogens do not effect animals and humans. Disadvantages- The difference in codons of prokaryotes and plants can lead to inefficient expression, different polysaccharides may be attached to proteins and some plants may contain allergic compounds.
Posted on: Thu, 30 Jan 2014 11:33:11 +0000
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