Engineered bacteria pave the way for vegan cheese and yogurt

Bacteria should transform the future of dairy products without dairy products. Scientists have successfully designed E. coli to produce key milk proteins essential to the production of cheese and yogurt, without using ingredients derived from animals. This opens the way to dairy alternatives based on plants that imitate traditional dairy products at a molecular level but are durable and without cruelty.

A recent study published in Biotechnology trends have reported two casein production methods (a milk protein) which are nutritionally and functionally similar to bovine casein.

Casein is a highly sought -after component in food and adult food regimes, because it is digestible, of high quality, and provides several essential amino acids that our body needs. The global casein market, worth 2.7 billion US dollars in 2023, has the price of cruelty to animals and high environmental impact. This increase in the demand for sustainable options and without dairy products led researchers to seek alternative methods of casein production.

Food and pharmaceutical industries have used microorganisms as cellular factories for large-scale production of biomolecules, food supplements and enzymes for a certain time. Scientists were curious to see if the same approach could be used for recombinant casein proteins, produced by genetic engineering in microbial cell factories. However, these techniques often fail to reproduce a key factor which gives casein its unique properties: phosphorylation, a biological process where a phosphate group is added to a protein.

The phosphorylation of serine residues (amino acid components) is essential for the capacity of casein to bind to calcium, which makes milk stable and offers it nutritional properties. The calcium link also guarantees the formation of protein structures on a nanometric scale called casein micelles, which act as delivery agents for calcium and bioavailable phosphate.

To overcome this question, the researchers adopted two main strategies. First of all, they designed bacteria to co-express three kinase proteins from Bacillus Subtilis, which are enzymes that catalyze the addition of protein phosphate groups. Secondly, they designed a phosphomimetic version of the αS1 casin, in which serine residues phosphorylated in the natural protein were replaced by aspartic acid to imitate the negative load and the functional effects of phosphorylation.

The team carried out a structural analysis, calcium link tests and simulated gastrointestinal digestion of the derived αs1 box. The results indicated that the phosphorylated and phosphomimetic boxes of bacterial origin had a high calcium binding capacity, and their digestibility and structure were comparable to those of the casein derived from cattle.

Researchers have stressed that, although phosphorylation mediated by kinase provides a path to closely imitate native casein, phosphomimetic casein provides a simpler path to produce functionally similar proteins. They also suggested that an additional quantitative analysis is necessary to fully unlock our ability to use microbial production of casins for durable dairy and food applications without cruelty.

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