In this article we will discuss about the ideal choices of farming for the production of plant systems.
1. Leafy Crops:
Tobacco has been established as a model system for molecular farming and is the most ideal choice for the production of pharmaceutical products. The main advantages of tobacco includes to the clarity of technology for gene transfer in vitro regeneration efficacy and gene expression, besides, the high biomass yield i.e., more than 100,000 kg per hactare and the availability to large scale infrastructure for processing.
In most cases, nuclear transgenic plants have been used for production of the protein which has been extracted from leaf tissue. In tobacco, proteins are targetting to the secretary pathway result in their exudation from leaves or roots i.e., phyllosecretion and rhizosecretion. This strategy could minimise harvesting process.
The technology is under commercial development for the production of human secreted alkaline phosphate. Even larger molecules like monocloclonal antibody were secreted into hydroponic culture medium resulting in a yield of 11.7 kg antibody per gram of dry root per day. Alternatively, tobacco chlorplasts have been used for the production of many proteins.
Apart from tobacco, alfa alfa and soyabean have also been investigated for molecular farming due to their advantages of atmospheric nitrogen fixation. Both of the legumes have been used to process recombinant antibodies.
Efforts of Canadian biotechnology company, Medicago resulted in the production of increased number of biopharmaceutical proteins. Later potato is also being investigated for edible vaccine production and is in main pipeline in one series of clinical trials for a vaccine against the hepatitis B virus.
2. Cereals and Legume Seeds:
Expression of protein in seeds has several advantages over leafy crops due to their long storage, even at room temperature. For example, antibodies expressed in seeds remain stable for atleast three years at ordinary temperature.
Due to the lack of phenolics in cereal seeds, downstream processing becomes much convenient in the industries. Several crops have been investigated for seed based production including cereals (rice, wheat and maize) and legumes (pea and soyabean). Rice, wheat, pea and tobacco have been used to express the same single chain Fv antibody which is useful for the comparison of merits of each production system.
3. Fruits and Vegetable Crops:
Production of proteins in fruits and vegetable crops becomes an attractive approach. This is because the edible organs can be consumed as uncooked, unprocessed and making them ideal for the production of recombinant subunit vaccines, nutriceuticals and antibodies. Potatoes are the major system for vaccine production.
Tomatoes are more palatable than potatoes and high biomass yield. Tomatoes were first used for the production of a rabies vaccine and have also been used to produce antibodies. Bananas are attractive vehicles for edible vaccine distribution as they are widely grown in the countries in which vaccines are most needed.
4. Fibre and Oil Crops:
The main advantage of fibre and oil crops, such as flax, cotton and oil seed rape, is the potential for the cost reduction of recombinant protein production due to secondary revenues from alternative products. However, both fibre and oil can interfere with downstream processing.
The oleosin-fusion technology developed by SemBiosys Genetic however displayed good example of single downstream processing, for protein purification.