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Mardi, 15 Novembre 2011 20:45

Lab-Grown Meats Face Long Road to Supermarket

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Lab-Grown Meats Face Long Road to Supermarket

By John Timmer, Ars Technica

On Friday, Reuters ran a story about a Dutch scientist who is attempting to make the first synthetic animal meat, starting with nothing more than stem cells. In it, the reporter focused on some of the grim numbers that make our current trajectory of livestock-based agriculture unsustainable, and suggested that the economics of meat from a tissue culture dish would eventually cause it to win out. But that eventually might be a long way away, as the first burger-sized samples of artificial meat are estimated to cost about a quarter of a million euros.

Can artificial meat’s price eventually come down? Absolutely. But there are a lot of technical hurdles that will need to be cleared out of the way first, and some of them might not be all that easy to clear.

Reuters’ story doesn’t spend much time on the current costs, but goes on at length about a somewhat related issue: the taste. Right now, the artificial meat consists of little more than muscle tissue grown from stem cells. An actual piece of meat is substantially more complex, as the muscle fibers have integrated into a coherent tissue and built up through use. Associated tissues, like blood and fat, also contribute to taste, appearance, and texture.

It might be possible to overcome these hurdles. Stem cells for blood and fat have been identified, and culturing them and getting them to differentiate into mature tissues is probably not much more complex than getting muscle fibers to grow in a dish. But this comes back to cost: getting any cells to grow into mature tissues is ferociously expensive, and adding additional cell types will increase the complexity and cost.

Show me the money

Our bodies expend lots of energy creating an environment in which a variety of cell types can flourish. Tissues are bathed in appropriate combinations of fuel, salts, minerals, hormones, and signaling molecules. They’re in contact with neighbors and various beds of proteins that the neighboring cells create. Without all of this extensive support, most cells get very sick very quickly.

Recreating this sort of environment is really difficult. Some things, like reasonable concentrations of salts, are easy. Others, like the right mix of growth factors, is phenomenally challenging — so challenging, in fact, that the first work with stem cells didn’t even bother. The first stem cells were cultivated on a layer of feeder cells that provided them the right kind of surface to grow on. Instead of trying to get the right mixture of proteins in the growth medium, researchers turned to a natural source: the serum of blood obtained during the slaughter of livestock.

Let that sink in: initial efforts at creating artificial meat would have had to rely on the agricultural system it was intended to replace.

Even then, the serum wasn’t enough for stem cells, and the medium had to be spiked with a cocktail of growth factors purified from other sources. Many of those growth factors are purified form vertebrate cells, probably ones grown in medium that uses (you guessed it) serum.

Over time, experience and experimentation has gotten rid of a lot of these requirements. Feeder cells are a thing of the past and we’ve got a much clearer sense of which growth factors help keep which cell types growing happily. However, the need for serum has been a difficult one to shake. A paper from last year managed to get one type of cell growing without serum, but called the result “unique.” Just this year, however, we’ve managed the same trick with adipose stem cells, which are a bit closer to what we’d need to incorporate into meat.

That doesn’t mean things are cheap, however. The serum-free medium that helps these stem cells grow costs about $250 for a half-liter; the company that sells it estimates you’ll need nine liters to expand out a stem cell population to the point where it’s possible to do something with it. And that still doesn’t get into the cost of the various growth factors that are necessary for most cell types to grow in culture.

Can we overcome more of these hurdles and bring the cost down so that it’s competitive with current agriculture? Maybe, but it’s not a sure thing.

A greener meat?

And that may end up being unfortunate because, as the Reuters article notes, our current agricultural trends are on an unsustainable trajectory. As more of the world’s economies are getting wealthier, the demand for meat has gone up considerably. And, by most calculations, it takes a lot of plant material to make an equivalent amount of meat (the Reuters article cites a figure where each pound of meat requires almost 7 pounds of plant matter). Associated with that are high expenditures of energy, water, and land. Ultimately, there probably isn’t room enough on the planet for all 7 billion of us to eat a meat-rich western diet, certainly not one dominated by beef.

Artificial beef might provide a way to satisfy more of the demand, according to a study mentioned by Reuters. In it, the authors calculate various impacts of different forms of livestock. Pigs and poultry come out looking good, but nowhere near as good as artificial meat, which uses very little land and water, and about the same amount of energy as your equivalent pulled-pork sandwich.

But are those numbers realistic? The paper makes its estimates based on supplying the cells with nutrients and proteins obtained by growing photosynthetic cyanobacteria in tanks. Anything, like growth factors, that don’t come from that extract will be supplied using genetically engineered E. coli. Right now, we’re not at the point where we can make those things happen. It’s not clear we ever will be, either, since it may end up being impossible to get bacteria to produce some of the hormones and growth factors we end up needing to support stem cells.

Will this change the energy requirements for growing artificial meat? Quite possibly not, but it does provide an indication that the calculations that suggest artificial meat is an inevitability involved some significant simplifications.

Image: Aurich Lawson/Ars Technica

Source: Ars Technica

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