Large Scale Cultures
Large scale or commercial applications of tissue culture necessitate scaling up of culture systems which can be done by increasing the number or size of culture vessels.
Agar Cultures : Agar gelled medium is most commonly used for experimental and commercial activities like micropropagation. Scaling up of agar cultures involves considerable labor since each vessel has to be handled individually during subculture, etc.
Suspension Cultures : it allows easy and extensive scaling up by employing bioreactors.
i) Batch Bioreactors
In such bioreactors, the medium and inoculum are loaded in the beginning, and the cells are allowed to grow. There is no addition/replacement of medium, and the entire cell mass is harvested at the end of incubation period.
ii) Continuous Bioreactors :
There is a continuous inflow of fresh medium and outflow of used medium (with or without cells) during the entire incubation period. A spin-filter bioreactor is a good example of continuous flow bioreactor. It is used to grow cells at a specified cell density in an active cell growth phase; such cultures may either provide inocula for further culture or may serve as a continuous source of biomass yields.
iii) Multistage Bioreactors :
Such culture systems use two or more bioreactor in a specified sequence each of which carries out a specific step of the total production process. In biochemicals like shikonin, both the reactors are batch type: the first bioreactor provides condition for rapid cell proliferation and favors biomass production, while the second bioreactor has conditions conductive for shikonin biosynthesis and accumulation. The cell biomass is then collected from first stage bioreactor and is used as inoculum for the second stage bioreactor.
iv) Immobilized Cell Bioreactors :
These are based on cells entrapped either in gels, such as agarose, agar, chitosan, gelatin, gellan, polyacrylamide and calcium alginate, to produce beads, or in a membrane or metal screen compartments or cylinder. Cell immobilization changes the physiology of cells as compared to that of cells in suspension. This technique is useful where the biochemical of interest is excreted by the cells into the medium. Product excretion may also be brought about by immobilization itself, or by certain treatments like altered pH, use of DMSO as a permealizing agent, changed ionic strength of medium, an elicitor.
The main topics which are considered in Plant Biotechnology are discussed in brief as follows:
- Large Scale Cultures
- Biochemical Production
- Enhancing Biomass Yields
- Improving Biochemical Production
- Virus Free Plants
- Somaclonal Variation
- Haploid Plants
- Embryo Rescue
- Somatic Hybrids And Cybrids
- Germplasm Conservation
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