Biotransformation; Production of useful compounds through cell-culture
Biotransformation:- It is the conversion of simple, readily available, and inexpensive molecules into expensive and valuable final products by using plant cell cultures (biological systems).
Techniques of Biotransformation:-
1. Immobilized cells:- It has been reported that immobilized plant cells might have a higher production rate under some situations compared to free cells in the suspensions. In this technique, cells are immobilized using a gel of calcium alginate, polyvinyl alcohol resin on fixed support of foam, fabric, or hollow fibers for the accumulation of secondary metabolites.
Examples of biotransformation by immobilized plant-cells
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2. Hairy root culture:- It’s one of the most widely used techniques to obtain secondary metabolites. This is because plants’ roots are a rich source of propane alkaloids, Catharanthus alkaloids, atropine, and hyoscyamine. In this method, hairy roots are sub-cultured on a solid medium and then placed on a rotary shaker at 1000 rpm at 250°C in the dark in a liquid medium.
Examples of biotransformation using root cultures
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3. Free cells:- The biotransformation in free cells is taken by many reactions including methylation, oxidation, hydroxylation, and acylation. The cells for this purpose are grown mainly using two techniques:
a. Callus Culture:- Callus is an undifferentiated mass of cells. In tissue culture, it occurs when explants are cultured on a medium and the cells undergo differentiation and redifferentiation to develop into a whole plant.
b. Suspension Culture:- In this method, cells are suspended in a liquid medium. This is done by transferring a cell mass into a liquid medium and continuous agitation into an Erlenmeyer flask. The type of suspension cultures include:
i. Batch suspension cultures
ii. Semi-continuous culture
iii. Continuous culture
Examples of biotransformation by plant-cell culture
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Elicitation:- Elicitors are compounds of biological origin involved in plant microbe interaction. Elicitors are considered as mediator compounds which induce secondary metabolites formation in cells cultures. Varieties of elicitors have been used for production of secondary metabolites. Elicitation improves the efficiency of Sec. Product accumulation in plant cell culture by:
i. Minimizing up on time
ii. Avoiding change of media
iii. Induction of enzymes involved in biosynthetic pathway
iv. Inducing excretion of metabolites into the medium
Some of the biotic elicitor- induced products
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Precursor feeding:- Under in vitro circumstances, often the precursors of metabolite die and can’t carry out the reaction. This can be overcome by supplying enough precursors to cells, which can be done by two methods:
a. Add precussors:- By adding precursors in the medium so that their availability is not limited.
b. Prevent resistant precursor analogs:- By preventing resistant precursor analogs and increasing the intracellular levels of precursors for the metabolite production. Eg.-
i. Production of shikonin increased three-fold after the addition of L-Phenylalanine to the medium in Lithospermum species.
ii. Datura sp. cell suspension cultures are supplemented with hydroquinone, in traces, the arbutin synthesis increase considerably.
Production of useful compounds through cell-culture:- Biotransformation is used to production of secondary metabolites. The genetic information required for the manufacture of sec.
1. Biotransformations of Steroids:-
> Digitoxin and Digitoxigenin can be extracted from the leaves of Digitalis lanata.
> In the process of biotransformation of Digitoxin many compounds are produced:
Methyl digitoxin →→→→ Purpurea glycoside A + Deacetyl lanotoside C + Lanatoside C
> Purpurea glycoside A is major product, while Deacetyl lanotoside C and Lanatoside C are minor products.
2. Biotransformation of Alkaloids:-
> A variety of alkaloids have been used, as pharmaceuticals & most of them are plant metabolites.
> Research of production of useful alkaloids by plant cell cultures has been carried out for more than 25 years.
> Industrial production has not yet succeeded because of low producing ability of the cultured of the cultured cells.
> Plant used for their studies are mainly, Atropa belladonna, Hysocyamus niger, Datura metalloids.
> Some of the examples of the compounds in these groups include:
a. Morphine alkaloids
b. Berberine
c. Tropane alkaloids
d. Vincristine
a. Morphine alkaloids:-
- Papaver somniferum is a traditional commercial source of Codeine & Morphine. This Morphine can be converted to codeine.
- Codeine is an analgesic and cough-suppressing drug.
- Mature capsule of Papaver bracteatum accumulates up to 3.5 % of the baine, which also can be converted to codeine.
b. Berberine:-
- Berberine is an isoquinoline alkaloid, which is distributed in roots of Coptis japonica, &
cortex of Philodendra anurans.
- Addition of a polyamine, sperm dine, was found to stimulate the production of berberine by Thalictrum minus cell suspension cultures.
c. Tropane alkaloids:-
- Scopolamine & Hyosyamine are tropane alkaloids.
- The conc. of scopolamine & hyoscyamine in cultured cells are generally very low.
d. Vincristine:-
- It is reported biotransformation of a Hydrovincritin to Vindolin by a cell extract of Catharanthus-roseus cell suspension culture.
Hydrovincritin →→→→ Vindolin
- Catharanthus roseus plants produce two highly valuable drugs that are used for the treatment of cancer:-
i. Vinblastin
ii. Vincristine