Transgenic rennet. A history of cheese and rennet

Transgenic rennet. A history of cheese and rennet

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Among the debates that arise all the time around GMOs, an argument emerged that argued that if GMOs were banned in a country, it would be unable to eat cheese, because now it is made with GMO rennet. In this article we share with you some information collected on the subject.

Eleven thousand years before Christ, when the gatherers and hunters became sedentary, they began pastoral practices, they had learned the value of livestock and domesticated some bovines called Uros. He milked and stored his milk in leather wineskins - bags made from the stomachs of ruminants - and wooden containers.

Then they realized that milk could solidify, change flavor and be preserved. The origin of cheese dates back to these times. Since then, different types of rennet have been used over the stomach of ruminants, including for example certain plants, the juice of the green fig, etc.

The most widely held opinion is that it was in the Middle East that cheese was first produced. The first types of sour milk were discovered almost simultaneously with the domestication of animals that could be milked. According to a legend that a curious or hungry nomadic shepherd from the Middle East once tasted the uniform paste into which the milk was often transformed by the action of natural enzymes that remained in the bags, after being stored in those containers made of leather. And he didn't find it bad at all. He discarded the whey - the clear liquid that curdled milk exudes - and studied how to systematically produce the paste. Cheese was born.

It is quite possible that nomadic tribes in Central Asia have found it useful to transport the milk in sacks made of animal skin. The fermentation of the sugars in the milk would cause it to curdle, which gave them an important source of animal protein.

Some archaeologists have found cheese made from cow and goat milk and stored in ceramic containers dating back to 6,000 years before Christ. Murals in 4,000-year-old Egyptian tombs showed milk stored and suspended in leather sacks, revealing the knowledge of dairy preservation methods.

Along with the production of cheese, the obtaining of liquid milk ferments also emerged, such as yoghurt, koumiss and kefir.

Cheese was a common food in biblical times and about 1900 years ago the writer Pliny the Elder, author of "Naturalis Historia", who had a great influence on European scientific and medical evolution, praised its delicious taste, explaining that in Rome the preferences they turned to blue cheeses, predecessors of the current Roquefort.

Homer, around 1184 BC refers to the making of cheese in the mountain caves of Greece from goat and sheep milk. Feta cheese today is believed to be a descendant of the so-called "Cynthos" cheese.

Aristotle (384 - 322 BC) commented on cheese made from the milk of mares and donkeys - the Russian "koumiss" which is derived from mare's milk and is fermented to provide an alcoholic content above 3%.

By AD 300, there was a regular export of cheese along the Mediterranean. And the Romans expanded cheese throughout their empire, first to landowners, but then many of the soldiers who married local women, stayed in their towns and taught local populations how to make cheese, which popularized the use of the cheese.

With the fall of the Roman Empire around 410 AD, cheese-making spread throughout the Mediterranean, Aegean, Adriatic, and Southern and Central Europe, and then spread across rivers to mountainous areas, where cheese making was adapted to local conditions. In Eastern Europe, cheese making was held back by constant wars and was restricted to very remote mountainous areas.

In the European monasteries of the Middle Ages, where some varieties of cheeses were born. For example, Munster cheese was born in the abbeys located on the slopes of the Vosges, while the Trappiste de Citeaux was a creation of the congregation of the same name that lived in the Burgundy area.


Rennet is the common name for products that coagulate milk. They are differentiated by the adjective natural, microbial, genetic or plant.

To make cheese, rennet must be added to milk, which is extracted from the stomach walls of animals (calves, adult cows and pigs), but especially from lactating calves.
Chymosin or renin is the active enzyme of rennet, a substance present in the abomasum of ruminant mammals. This is the essential enzyme for the digestion of milk and therefore the ideal enzyme for milk coagulation. It coagulates milk because it acts on a protein that milk has, called casein.

Chymosin is used in the manufacture of cheeses whose function is to separate casein (approximately 80% of the total proteins) from its liquid phase (water, whey proteins and carbohydrates), called whey.

The action of the enzyme on casein and calcium dissolved in milk to form calcium paracaseinate or rennet. Rennet has been known since ancient times, but its active and pure component, chymosin, has only been known for a few decades.

The most common way to make rennet is from the stomach of lactating calves.

To do this, part of the stomach is immersed in brine, and after letting it rest until the renin diffuses into the brine, part of that liquid is used in the milk to curdle.

There is also a chemical rennet, pure chymosin, and it is used in more industrial cheese production, so it is easier to standardize curdling times. As for pure rennet, there are natural rennet: chymosin chemically extracted from the stomach of calves, and synthetic rennet, discovered a decade ago and presented in pills: it is chymosin obtained from chemical synthesis procedures without using the stomach of calves as raw material.

According to historical tradition, rennet was first discovered approximately 4000 to 5000 years ago in Egypt. Guts and, above all, dry stomachs were used to store liquids in them. Probably, the practice of transporting milk in bags made with the stomachs of animals, led to the more or less accidental production of the first cheeses.

The milk that was stored in this way was casually curdled thanks to the curdling enzyme, also achieving that the product was better preserved. In this way, the art of making cheese developed over the centuries. The natural rennet is therefore related to the production of cheese since time immemorial.

The Romans were the first to describe the production process in detail, and the Roman legions helped spread the art of making cheese throughout Europe. In Roman times, a preparation rich in enzymes extracted from the stomachs of goats, lambs and even hares was mixed with goat or sheep milk (cow's milk did not begin to be produced on a large scale until the 13th century) . The curd separated from the whey was salted and stored for later consumption.

The preparation of rennet cheeses, which required a certain technique, began much later; precisely Serma cites the contribution of the Roman invaders to the empirical technique of the Celts and contemporary peoples, since it is known, without a doubt, that the Greeks and Romans coagulated milk with vegetable rennet (the common aceradilla or agrilla, the Alpine aceradilla, artichoke, rennet figi), and also used the curdled milk from the stomach of young ruminants.

In the 19th century, some farmers sold extracts of cow rennet in small quantities to meet the needs of making homemade cheese. In 1874, a Danish chemist founded a laboratory in Copenhagen and started the industrial production of calf rennet, extracted from the stomachs of calves slaughtered for meat, and in which chymosin is the most abundant enzyme.

Today there are two main sources of coagulating chymosins for milk: those of animal origin and those obtained from various types of fungi. To these have been added the chymosins obtained from genetically modified (transgenic) fungi. In the latter case, copies of the gene responsible for the production of chymosin are isolated in the stomach cells of calves and introduced into the genetic material of the cells of micro-organisms, which can be cultivated in industrial quantities, and then isolate the chymosin containing.

Transgenic rennet

With the development of genetic engineering came the possibility of using calf genes that synthesize rennet enzymes (chymosin) to genetically modify some bacteria, fungi, or yeasts and produce recombinant chymosin.

Chymosin produced by genetically modified enzymes was the first artificial enzyme registered and allowed by the US FDA (Food and Drug Administration).

The most used way to make genetic rennet is through the Aspergillus niger fungus, a common soil fungus, to which the genes that synthesize the enzyme chymosin, used in the manufacture of cheese and originally obtained from the stomach, are inserted into micro-organisms. of calves. These transgenic micro-organisms are allowed to grow in large fermenters to produce the recombinant chymosin enzyme.

Another micro-organism used in the production of transgenic fluke is the yeast Kluyveromyces lactis. In this case, the genes that synthesize the protein chymosin are inserted and the transgenic yeast grown in a fermentor. After fermentation, the yeast is killed with benzoic acid and the chymosin is isolated by filtration.

In 1999 about 60% hard made in the United States is made from genetically engineered chymosin, especially from the Chymogen® type which is a type of transgenic rennet developed by Genencor International and marketed by Chr. Hansen’s.

Another type of GMO rennet is Chymax, developed by Pfizer. Ironically, cheeses made from this transgenic rennet are promoted as suitable for vegetarians, since it does not come from natural animal sources, although it does come from animal genes inserted into micro-organisms.

Another transgenic rennet is Maxiren.
The industrial production of enzymes is a business that at the beginning of the 21st century moves around 1,600 million dollars a year, of which 70% is due to products of the Bacillus genus. The enzyme chymosin generates profits of 60 million dollars a year for the transnational companies that produce it.

Other GM cheeses

A New Zealand dairy company, Fonterra, applied for permission to transform microorganisms (bacteria and yeasts commonly used in the dairy industry), to which apple, kiwi, blueberry and Arabidopsis genes would be added, to synthesize enzymes that produce new flavors in dairy products. These flavors could be different from those that characterize the plants from which the genes come.
Also in New Zealand, a group of scientists have created cloned genetically modified cows, to produce milk rich in a protein useful for the cheese industry. These cows produce 20% more of the enzyme beta-casein, and twice as much kappa-casein than natural milk. Casein accounts for about 77% to 82% of milk proteins.

According to the scientists, this will allow to produce more cheese without increasing the volume of the milk. This is an innovation that will basically benefit the large New Zealand cheese industry.

This team created a number of transgenic cell lines, each with 39 additional copies of the genes that synthesize the enzyme casein. These cells were fused with the reproductive cells of the cow (with the egg or zygote), a cloned embryo was obtained, which was implanted in cows.

Although it is only in its experimental stage, the New Zealand public is very concerned about these experiments and is unwilling to consume a cheese made from a cloned, transgenic cow.

C. L. HICKS, J. O'LEARY, and J. BUCY. Use of Recombinant Chymosin in the Manufacture of Cheddar and Colby Cheese.
BIO - Biotechnology Industry Organization. 2008. Agricultural Biotech Products on the Market.
WIPO. (WO / 2004/065593) Recombinant Bovine Pepsin And Pepsinogen Produced In Prokaryotic And Eukaryotic Cells
The history of cheese.


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