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How to brew milk (and more) with yeast

Sensemaking / How to brew milk (and more) with yeast

Biotech-modified microbes offer a sustainable alternative to livestock products, including milk proteins, gelatin and ivory.

By Naomi Kreitman / 24 Jul 2017

Recent advances in cellular agriculture have gained a lot of coverage for their potential to replace livestock in the meat industry, but they could also disrupt the traditional production of other animal products, such as milk, eggs and ivory.

We can now genetically modify microbes, like yeast and bacteria, to make a range of useful proteins. The end product is molecularly and chemically exactly the same as its livestock counterpart, but the mode of production is dramatically different, with a significantly lower environmental impact. Unlike cultured meat, equivalents to products such as milk, eggs, leather and gelatin do not require a biopsy of animal tissue to start the culturing process. Rather than multiply the whole animal cell, it is possible to create individual proteins unique to the product.

So how does it work?

The process involves producing individual proteins rather than entire cells. Essentially, microbes like yeast or bacteria are genetically modified to hold the DNA of these proteins, and then fermented in a nutritious medium to produce them. The use of one genetically modified yeast to produce a protein is not an entirely novel concept. Rennet, traditionally found in the stomach lining of calves, has been used for thousands years to make milk into cheese. Since the 90s, the majority of cheese we eat has been made using bioengineered rennet that has never seen the inside of a cow.

Let’s go through the process step by step. Want to make some milk without milking any cows? Here’s how:

Credit: New Harvest // Milk is usually made by mother cows kept in a lactating state in an industrial setting. Instead, we can make the exact same milk by brewing it, using a culture that consumes simple sugars to make milk proteins.

  1. Identify the proteins that make milk what it is. The most important one is casein.

  2. Insert the DNA carrying the casein blueprint into your yeast. This mix of yeast and DNA is your culture; you only have to do this once.

  3. Brew your milk proteins using some sugar to feed the yeast, using the age old process of fermentation which gives us beer, bread and pickles.

  4. Purify to separate out the yeast - and now you have your casein!

  5. Add some plant-based sugars and fats to get that milky mouthfeel.

  6. Add some plant-based vitamins and calcium to match (and even surpass) the nutritional benefits of conventional milk.

  7. Enjoy lactose-free, sustainable, animal free milk without any of the health risks of livestock farming.

One leader in the production of ‘cow-free’ milk is Perfect Day, whose product is scheduled to be on the market later this year.

What are the benefits?

Livestock account for 15% of global anthropogenic (human caused) greenhouse emissions, and 45% of methane emissions - methane is an especially harmful greenhouse gas; biotech would significantly decrease the energy required to produce animal products. With industrial farming there are also health risks such as antibiotic resistance and infection - when dairy and eggs are produced without cows and chickens there is no need for antibiotics and the contamination risk is significantly reduced.

For examples of what can be made, see Meat aside: other applications for cellular agriculture.  

When can we expect these products to be available?

‘Clean’ or cow-free milk appears to be first in the pipeline with plans to start selling their product later this year. Leather is expected to be ready for retail in 2018, and egg whites are also expected to be available in the next year or so. The technology for creating individual proteins is further ahead than the technology to create cell cultures, so we can expect to see cow-free milk on shelves before cow-free burgers.

Bioengineered yeast has the potential to revolutionize the mode of production for a huge range of proteins we consume and use everyday. Is a more sustainable future brewing?


What might the implications of this be? What related articles have you seen?

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