23 May 2008

A kilogram of meat for a million dollars: activists get a discount!

Most likely, in recent days you have read at least once about a new PR campaign by one of the most extremist animal rights organizations - PETA (People for the Ethical Treatment of Animals – "People for the Ethical Treatment of Animals"). This time, instead of organizing another nudist show in defense of the rights of crustaceans to be cooked on a fast fire, Peta's management announced a prize of one million dollars for a group of scientists or a company that by June 30, 2012 will develop a method of making chicken meat "in vitro" (and so that the quality is like real!) and it will start selling it in at least ten US states (and not more expensive than usual!).

The absurdity of this idea is obvious to anyone who knows at least a little about cellular technologies. And instead of writing a new article, we suggest you read this one, also not too old. We especially recommend paying attention to such a fine detail as the composition of the medium necessary for growing animal cells. Maybe someday it will be possible to solve the problem of an artificial steak identical to a natural one. But there is no doubt that nothing fundamentally new will happen in this area by 2012.

A. Chubenko, "Science and Life" No. 6-2005

A person needs about 100 grams of protein daily, of which two-thirds should come from animal products, which is equivalent to 300 grams of meat or fish per day. For a quarter or even half of the world's population, this is an unthinkable luxury.

The successes of biotechnology suggest the possibility of at least partially feeding humanity with synthetic meat. Science fiction writers have been exploiting this idea for a long time, and in many science fiction novels, most of the inhabitants of the Galaxy eat synthetics, and only the rich can afford a natural product. And what are the real achievements?

Fillet for astronauts

In March 2002, biotechnologists from Touro College in New York organized a presentation of a project commissioned by NASA. They managed to make the muscle tissue of a goldfish (Carassius auratus) grow in a nutrient solution, doubling the weight in about a month. Fried in olive oil with garlic, lemon and pepper, the pieces looked and smelled exactly like fried fish, but none of those invited to the presentation dared to make sure that they tasted no different from fish. Whether the authors themselves have tried their product is unknown, but if they are real experimenters, they probably took a risk without waiting for FDA approval (Food and Drug Administration – the FDA in the USA).

Developers and customers are confident that the astronauts will not be picky, and continue to work. Pieces of chicken and beef fillet are already able to live in a nutrient solution, it remains only to achieve their growth, arrange another presentation and continue research. The article by M. A. Benjaminson and his colleagues can be found in the journal "Acta Astronautica" for December 2002. The research is undoubtedly valuable, but more for tissue engineering than for the food industry.

There are many reasons why even astronauts in the next hundred or two years will eat "test tube" steaks at best only on Cosmonautics Day, and then on Earth. First of all, the law of conservation of mass. For the synthesis of one gram of dry matter of muscle tissue, theoretically, at least ten grams of dry weight of reagents will be required. But in practice – many times more: water can be regenerated, and the nutrient medium, spoiled by the products of cell metabolism, will have to be sent to the converter along with unused reagents.

And the bioreactor itself, in which a pound of fillets would ripen once a week, looks something like in this picture. It's cheaper to stock up on frozen meat on the way to Mars and back. So while space technologies are being worked out on an overpopulated and malnourished Earth. But can Earthlings count on test-tube steaks?

In science fiction, there is a description of biofactories where muscle tissue is grown with an optimally balanced composition for human nutrition – guess what kind of living creatures?

If you don't want cutlets from the culture of human embryonic cells, you can divorce stem cells isolated from your own bone marrow. Don't like it either? Well, at least you have no prejudice against the muscle cells of cattle? Then get out your checkbook.

Perhaps, a nutrient medium based on the blood serum of calf embryos is best suited for growing space fillets: hormones, cytokines and other known and unknown substances contained in it stimulate cell growth. Cells are considered not kilograms, but millions of pieces, 20-30 microns in diameter each, but, having got confused in zeros, I got that only reagents for growing a kilogram of cells will cost 10 thousand dollars. Even if it is possible to grow a steak (rather minced meat) on less expensive serum from the blood of adult bulls and cows, it will still be many times more expensive than caviar. Animal cells do not grow on cheap serum-free media. A reduction in prices for sterilizers, bioreactors and nutrient media is not expected in the next hundred years. And we will also have to solve a lot of technical issues. In culture, cells stick to the bottom and to each other, stop growing and die. To prevent this, the medium is mixed. Attempts to grow in vitro not cell culture, but tissue create a lot of additional difficulties. The body has a system of tissue microcirculation, which delivers nutrients and oxygen to each cell and removes metabolic products. To provide something similar in a bioreactor, it is necessary to provide for the inclusion of capillaries and larger vessels in the system, connected instead of the heart to a flame motor. And if such solutions are found, they should be used not for the production of steaks, but for the cultivation of artificial organs for the purpose of transplantation – only in this case the price will pay off by its weight in gold.

As for food, they can be obtained not just cheaper, but even cost-effective methods. And at the same time it will be possible to do without the culture of animal tissues.

Thirty years ago, when there were smelly tanks with food waste on every landing, such a project was put forward: to grow larvae of ordinary house flies on these and other wastes for livestock feed, and possibly for human nutrition. There are many original recipes in the cookbooks of the peoples of the world, from raw lice to baked missionaries. Maggots are really healthier in composition than beef, but for aesthetic reasons, I prefer a steak made of well-fried microorganisms to them.

Omnivorous yeast

The idea to use yeast for the production of food protein arose at the end of the XIX century. During the First World War, Germany produced up to 10 thousand tons of yeast per year for food ersatz, and in the thirties of the XX century, plants for processing waste from various industries into feed protein, from molasses and whey to sawdust and corn stalks hydrolyzed with sulfuric acid, started operating all over the world. At the same time, the Soviet science fiction writer Alexander Belyaev wrote the story "Eternal Bread". Its plot is similar to a fairy tale about a magic pot: a certain professor, wishing to benefit humanity, discovered yeast that fed on air and produced tasteless, but nutritious biomass. It almost ended in a global catastrophe: the freebie began to spread uncontrollably through the biosphere, doubling in volume every half hour. Fortunately, the professor managed to discover a virus that is deadly for "eternal bread" and harmless for everything else.

In the sixties of the twentieth century, on the wave raised by forecasts of an imminent ecological and demographic catastrophe, yeast strains capable of feeding on petroleum products were brought out (using old methods – there was no genetic engineering at that time). Plants for the conversion of oil to livestock feed have been built all over the world, from England to Japan. Ahead of the whole planet was the rich and great country of the USSR. Fortunately, the oil crisis broke out in the seventies, and by the mid-eighties the production of protein from oil had practically stopped. Fortunately, because petroleum protein and its production waste turned out to be so strong allergens that the incidence of bronchial asthma in the city of Kirishi, Leningrad region, located on the outskirts of the Kirishinefteorgsintez plant with the largest Soviet production of protein–vitamin concentrate (BVK), was ten times higher than the average.

Now BVK, also known as the protein of unicellular organisms (BOO), is obtained mainly from yeast grown on food industry waste, and is used as an additive to feed for farm animals. Once, out of curiosity, I chewed a granule of such a concentrate – to be honest, it was disgusting, but the chickens pecked enthusiastically. If such a concentrate is deodorized and flavored, it would not be distinguishable from soy in sausage.

But yeast has too many nucleic acids: the faster cells divide, the more DNA and RNA they contain. And purine bases in the human body turn into uric acid and in large quantities disrupt purine metabolism and cause diseases, primarily of the joints and kidneys. Two grams of nucleic acids per day in addition to the usual diet is the maximum recommended by the World Health Organization. Therefore, only biologically active additives from brewer's yeast are used in human nutrition – a source of B vitamins and other biologically active substances. Yeast and algae, including chlorella, which is popular among the heroes of science fiction novels, have another drawback - the cell wall is too strong, because of which the contents of the cells are poorly absorbed.

Animals eat food with the addition of BOO from yeast or chlorella with pleasure and health benefits. A thick cell wall in the digestive system of a cow or chicken is digested without problems, and purine bases are not terrible for cattle: uric acid in the body of animals turns into urea.

By the way, only primates do not have a gene encoding the uricase enzyme necessary for this. This deletion – the loss of a gene from a chromosome set – is considered one of the reasons that we primates are so smart. Uric acid in the structure of the molecule is similar to caffeine and may stimulate brain activity. In all animals, except primates, uric acid decomposes before it hits the head, but they have gout and kidney stones less often than we do.

Unpretentious spirulina

A promising object for obtaining food protein is filamentous unicellular cyanobacteria (blue–green algae) of the genus Spirulina. Unlike bacteria and fungi, spirulina is able to absorb atmospheric nitrogen. In nature – far away on Lake Chad, in shallow coastal bays and ponds with alkaline water - the biomass of spirulina doubles in three to four days. Tangled spiral threads several millimeters long with gas-filled vacuoles float to the surface, and wind and surf throw them ashore. In places, the shores of the romantic Lake Chad are covered with a thick, thick layer of S. platensis biomass. Probably, the very first locals guessed to taste it. Independently of them, on the other side of the Atlantic, residents of the vicinity of Mexican lakes began to collect biomass of a related species of spirulina.

Spirulina has a thin cell wall, and it digests easier than chlorella or yeast. It contains two times less nucleic acids than yeast, a lot of vitamins, trace elements, polyunsaturated fatty acids and 65-70% of the dry weight of an almost ideal protein composition.

Description of a phytotron for growing spirulina, even on a space station, even on a polar station (there would be heat, water, mineral salts and light) I read back in the eighties.

But until now, spirulina is used as a food product only by poor Mexicans and Africans, who have it lying under their feet.

To everyone else, it is sold not in pound cakes, but in tablets at the price of a dietary supplement, although all that is needed for its cultivation is a lot of sun and an alkaline environment in the reservoir.

In tropical countries, tortillas have been prepared for thousands of years from carbohydrate raw materials fermented under the influence of various mold fungi, thereby compensating for the lack of proteins and vitamins. And the technology of industrial production of such tortillas has been worked out for a long time, but has not become popular even in the tropics, although wheat flour turns out to be a useful and, according to descriptions, delicious product enriched with vitamins and containing six to seven times more protein (up to 70%), besides better nutritional properties than protein cereals. In my opinion, the main reason that such tortillas (for example, tempeh from soy fermented with Rhizopus oligosporous fungus) are bought only by vegetarians is the conservatism of consumers.

In the seventies of the twentieth century, the British Ministry of Agriculture, after careful tests of nutritional value and harmlessness, gave permission for the sale of mycoprotein – an artificially grown mycelium (simply put, mold fibers) of a mutant strain of a well–known phytopathogen, the fungus Fusarium graminearum. In appearance and structure, the pressed mycelium resembled crab sticks (they are known to be made from fillets of cheap fish and broth from canned crab), in taste – something identical to natural, and in nutritional value in all respects was better than meat. Meat in terms of dry weight contains about 60% protein and 40% fat; mycoprotein contains 50% protein, 15% fat (more useful than beef fat), 10% carbohydrates and 25% healthy dietary fiber. Semi–finished dishes based on mushroom protein in England and the USA can be bought if desired, but their manufacturers advertise mainly the absence of meat in the product and hint that all mushrooms, including truffles, are relatives.

From the point of view of the efficiency of protein synthesis, no agricultural animal is a match for microorganisms. For ease of comparison, we will tabulate only two indicators: the total biomass (without horns and hooves, but with bones and cartilage, which microbes do not have) and the yield of pure protein per kilogram of feed.

Please note: fusarium synthesizes more than a kilogram of biomass from a kilogram of carbohydrates in the nutrient mixture! The law of conservation of matter is not violated. This is not a dry weight, but a total one – both mold and cow are mostly water.

But in terms of pure protein per kilogram of feed, the fungus overtakes animals at times. As an additional source of nitrogen for the synthesis of amino acids, ammonia gas is passed through the nutrient medium or urea and other nitrogen-containing substances are added.

If you have forgotten the school chemistry course and the word "urea" causes you unpleasant associations, listen carefully to the advertisement of chewing gum with xylitol and carbamide. Carbamide – "carbonic acid" – in a foreign manner and in accordance with the international chemical nomenclature is called a substance isolated from animal urine with the non-nomenclature Russian name "urea". As a fertilizer for plants, it is sold under this name to peasants and summer residents accustomed to manure and compost. For humans, urea in the quantities in which it is contained in chewing gum is safe, and for microbes (in large quantities) can serve as a full-fledged raw material for protein synthesis.

Will microbes feed the world?

It is more profitable to grow proteins in a bioreactor than in a stall, and for many other reasons besides the efficiency of feed use. The most precocious broiler doubles its biomass in about a month and grows from a fifty-gram chicken to a kilogram chicken carcass in six months. Microorganisms, under favorable conditions, double the biomass in a few hours, or even faster, that is, microbes are hundreds of times more efficient than animals in terms of the rate of protein production.

Bacteria or mycelium of fungi, unlike algae, have to be grown not in ponds, but in fermenters. But microbes are much less demanding of the conditions of detention than animal cells and especially their tissues. It is much cheaper to feed microbes than pigs or chickens. At any plant for processing agricultural products, waste containing a lot of carbohydrates, vitamins and trace elements will be given to a subsidiary or adjacent production of the BOO for free, and they will also say "thank you" for not having to bother with their neutralization. True, complex equipment is needed to grow microbes, but one qualified operator can replace ten tractor drivers, shepherds and butchers.

The microbiological plant, which occupies the area of several suburban areas, can produce dozens of tons of tasty, useful and nutritious biomass from the waste of traditional industries every day. The same amount of protein can be obtained if you slaughter a herd of cows or other smaller brothers every day. And, unlike animals, microbes do not need pastures and fields, which means that each biomass plant frees up an area for gardens and meadows. And the waste products of some microorganisms can be processed into biogas and fertilizers in a neighboring bioreactor with the help of other microorganisms. There are much more problems with manure.

The production of products from microbial biomass may well be cost–effective - it is also profitable to make livestock feed from it. Environmental, demographic and economic reasons will not force humanity to switch to fantastic food products for several decades. And what will happen in twenty years if the current rates of population growth and agricultural productivity continue? One thing is certain: if the world becomes more well-fed and healthy in a few decades, it will only be thanks to the increasingly widespread introduction of biotechnology achievements.

The most realistic source of increasing agricultural productivity is transgenic plants, primarily resistant to diseases and pests, salinization, drought, heat, cold, etc. Secondly, with a modified composition of nutrients and increased yield. In 2004, 81 million hectares, more than 6% of the world's arable land, were sown with transgenic plants. Basically, these are plants resistant to insect pests (the total number of insects on "transgenic" fields is greater than on ordinary ones etched with insecticides) and to herbicides (as a result, the total amount of "chemistry" on the field is also reduced). Cultures with improved consumer properties are waiting for permission to be introduced. In 2003, Indian biotechnologists completed work on a potato variety with almost twice the protein content (as much as 3.5%). An additional amount of vegetable protein would allow the population of poor countries to suffer less from malnutrition, but the introduction of protato (protein + potato), rice with carotene (hypovitaminosis A is a big problem in countries where a handful of rice forms the basis of the diet) and many other transgenic plant varieties is being postponed. The struggle of politicians, irreconcilable "greens", producers of pesticides, etc. against GMOs, despite the proven and over–proven safety of varieties approved for use by competent government organizations, is a separate and sad story. Now there are so many things growing in experienced nurseries that one enumeration of the names and properties of these plants would take up more space than this article. The victory of the second "green revolution" is inevitable, no matter what arguments the opponents of transgenic plants put forward.

Transgenic animals are about to leave the vivariums for the fields and stalls. Perhaps, at first, animals producing proteins in milk for medical needs will find practical application, and genetically modified meat herds will appear later. They will be more resistant to diseases, grow faster, etc., then their consumer qualities will change. For example, in the spring of 2004, scientists from Harvard University created a line of mice in whose genome a gene borrowed from the nematode Caenorhabditis elegans, a millimeter-long worm, was introduced. The protein encoded by this gene converts omega-6 fatty acids, which are synthesized by mammalian cells, into omega-3 fatty acids, which lower blood pressure, reduce the likelihood of cardiovascular diseases and have long been known as "vitamin F" (from the English fat - fat). The continuation of these studies will allow us to breed domestic animals whose meat, milk and eggs will be as good for the heart as fish.

It is also possible to list the names and properties of promising transgenic breeds of domestic animals for a very long time. The question is not whether they will be allowed to be used or not, but whether it will happen in five years or twenty and how difficult it will be to convince consumers of the safety of genetically modified meat.

Microorganisms as a source of food raw materials, unlike transgenic plants and animals, cause consumers much less concern. Bread, cheese, wine, beer have been made with the help of microbes since time immemorial, and this does not frighten anyone. The production of microbial protein from carbohydrate raw materials does not present technical difficulties, including in Russia. The most difficult thing is to generate demand for an unusual product.

Portal "Eternal youth" www.vechnayamolodost.ru 30.04.2008

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