Chymosin & Recombinant Chymosin for cheese-making - wiki

CHYMOSIN COMPLEX WITH THE INHIBITOR CP-113972 (Photo credit: Wikipedia)

Chymosin /ˈkaɪməsᵻn/ or rennin /ˈrɛnᵻn/ is a protease found in rennet. It is an aspartic endopeptidase belongs to MEROPS A1 family. It is produced by newborn ruminant animals in the lining of the fourth stomach to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. It is widely used in the production of cheese. Bovine chymosin is now produced recombinantly in E. coli, Aspergillus niger var awamori, and K. lactis as alternative resource.

Recombinant Chymosin

Because of the imperfections and scarcity of microbial and animal rennets, producers sought replacements. With the development of genetic engineering, it became possible to extract rennet-producing genes from animal stomach and insert them into certainbacteria, fungi or yeasts to make them produce chymosin during fermentation. The genetically modified microorganism is killed after fermentation and chymosin is isolated from the fermentation broth, so that the fermentation-produced chymosin (FPC) used by cheese producers does not contain any GM component or ingredient. FPC contains the identical chymosin as the animal source, but produced in a more efficient way. FPC products have been on the market since 1990 and have been considered in the last 20 years the ideal milk-clotting enzyme.

FPC was the first artificially produced enzyme to be registered and allowed by the US Food and Drug Administration. In 1999, about 60% of US hard cheese was made with FPC and it has up to 80% of the global market share for rennet.

By 2008, approximately 80% to 90% of commercially made cheeses in the US and Britain were made using FPC. Today, the most widely used fermentation-produced chymosin is produced either by the fungus Aspergillus niger and commercialized under the trademark CHY-MAX® by the Danish company Chr. Hansen, or produced by Kluyveromyces lactis and commercialized under the trademark MAXIREN® by the Dutch company DSM.

FPC contains only chymosin B, achieving a high degree of purity compared with animal rennet. FPC can deliver several benefits to the cheese producer compared with animal or microbial rennet, such as higher production yield, better curd texture and reduced bitterness.

A protease (also called a peptidase orproteinase) is any enzyme that performs proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in a polypeptide chain.

"Ostkaka" ("cheese cake"), traditional Swedish dish made of milk and cheese rennet. (Photo credit: Wikipedia)

Rennet /ˈrɛnᵻt/ is a complex of enzymes produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease enzyme that curdles the casein in milk. This helps young mammals digest their mothers' milk. Rennet can also be used to separate milk into solid curds for cheesemaking and liquid whey. In addition to chymosin, rennet contains other important enzymes such as pepsin and a lipase.

Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specializedstomach prior to digestion, principally through microbial actions. The process typically requires the fermented ingesta (known as cud) to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word "ruminant" comes from the Latin ruminare, which means "to chew over again".

Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) to bring together genetic material from multiple sources, creatingsequences that would not otherwise be found in the genome. Recombinant DNA is possible because DNA molecules from all organisms share the same chemical structure. They differ only in the nucleotide sequence within that identical overall structure.

Escherichia coli (/ˌɛʃᵻˈrɪkiə ˈkoʊlaɪ/;also known as E. coli) is a Gram-negative, facultatively anaerobic, rod-shaped bacterium of the genusEscherichia that is commonly found in the lower intestine of warm-bloodedorganisms (endotherms).

Aspergillus niger or A. niger is afungus and one of the most common species of the genus Aspergillus.

Kluyveromyces lactis is a Kluyveromyces yeast commonly used for genetic studies and industrial applications. Its name comes from the ability to assimilate lactose and convert it intolactic acid.

Further reading

The three‐dimensional structure ofrecombinant bovine chymosin at 2.3 Å resolution

GL Gilliland, EL Winborne, J Nachman, A Wlodawer - Proteins: Structure, Function, …, 1990

Cited by 124

Cheddar cheesemaking with recombinantcalf chymosin synthesized in Escherichia coli

ML Green - Journal of dairy research, 1985

Cited by 47

Comparison of Cheddar cheese made with arecombinant calf chymosin and with standard calf rennet

VE Bines, P Young, BA Law - Journal of dairy research, 1989

Cited by 46

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