Getting your meat done, in vitro way

Experts assure that further developments in biotechnology will improve the quality of meat produced and cut down the cost, writes M S S Murthy.

More than six decades ago, cell biologists laid the foundations for “cultured meat” by growing mammalian cells in the laboratory for clinical research. With the discovery of embryonic stem cells, tissue engineers have been able to apply cell culture techniques to grow human organs such as bladder, for transplant.

Now, food technologists have used the same techniques to demonstrate the feasibility of growing meat in vitro, that is, in the laboratory. In fact, NASA scientists have succeeded in culturing turkey muscle cells and goldfish cells as a potential way to feed astronomers on long space missions.

From the lab to the table

If our skin is cut, it will grow back in a few days; when we donate blood, the blood cells are regenerated. These are possible due to the presence of stem cells in these tissues.

Generally, these cells remain in a quiescent state, but turn into an active mode when the need arises. Meat consists of skeletal muscle. Skeletal muscle fibres also harbour other types of special cells known as myoblasts and satellite cells. Both are quiescent cells, but are ready to develop into muscle cells on demand.

Hence, production of cultured meat begins by taking a few of the above cells from a farm animal and placing them in what is known as a bioreactor. The bioreactor contains a liquid medium made up of all the nutrients like amino acids, vitamins, minerals at an optimum temperature and pH and provided with an adequate supply of carbon dioxide and oxygen. In this environment, the cells grow and multiply into billions of muscle cells.

Any amount of muscle cells can be grown by renewing the liquid nutrient medium in the bioreactor.

However, meat is not just an aggregate of muscle cells. Depending upon the animal and the organ from which it is derived, meat will have its own colour, taste and structure. To provide these attributes to the cultured muscle, two types of scaffolds, made out of edible material such as collagen, are provided in the bioreactor to which the cells attach themselves during growth. One of the scaffolds is in the form of a grooved bio-film and the other in the form of porous microspheres. The cells attached to the bio-film fuse into myotubes which differentiate into muscle fibres.

The process of differentiation to muscle cells is further stimulated by stretching the scaffold just by ten per cent at a time and by changing the temperature or pH of the growth medium. Stretching helps in giving a structure to the cultured muscle fibre as in a well-exercised animal. While myofibers grown on sheet scaffolds can be laid over one another to a substantial thickness for use, say in hamburgers, those grown on micro spheres can be processed to make sausages.

Prof Mark Post of the University of Netherlands, who is in the forefront of research on in vitro meat production, recently exhibited a hamburger made with pieces of cow muscle – about 2 cm long, 1 cm wide and 1 cm thick – grown in his laboratory. In theory, cells taken out from a handful of animals without sacrificing them could produce the world’s meat supply.

However, the technology is not yet ready to place a piece of steak on the dinner plate. While hamburgers and sausages are processed meat, the greater challenge is to produce highly structured meat like steak, chicken breast etc. One of the approaches would be to seed the bioreactor with small tissue explants, like growing crystals in a Physics laboratory, to grow thick, structured muscle chunks.

Explants have the advantage that they contain all types of cells that make up the muscle in right proportion.

However, the biggest problem is in insuring constant supply of nutrients to the growing cell mass, without which the cells will die. While it is accomplished in live animals by blood circulating through fine capillaries, scientists are yet to figure out a suitable scaffold structure that can take nutrients to all cells.

But that does not mean that in vitro meat is just some peoples’ fantasy. The organisation known as People for Ethical Treatment of Animals (PETA) has announced prize of US$ one million for anyone who can develop a commercially viable procedure for in vitro meat production.

“In-vitro Meat Consortium” – a group formed by international researchers interested in this technology held their first international conference in Norway in April 2009 to discuss commercial possibilities of producing in vitro meat at affordable cost. More than 30 laboratories around the world are engaged in in- vitro meat research.

Experts assure that further developments in biotechnology will improve the quality of meat produced and cut down the cost. Scientists at New Harvest, an organisation actively engaged in promoting cultured meat envisages a counter top device, like a bread machine, which could produce the meat we need in our own kitchens.