Bacteria as Machines: The Science of Acellular Agriculture

You may have heard of cellular agriculture, the emerging technology that promises to produce animal products such as beef, pork and chicken without the actual animal. But, what about animal derived products like milk, butter and eggs? They’re not that much better for the environment and they work themselves into so many other things — it’s hard to keep track!

Just one litre of milk, for instance,

takes 6 football fields worth of land, 1093 litres of drinking water, 1.3–6.2 megajoules of energy and 0.67–12.3 kg of CO2.

Similar trends follow for almost any other animal product around including eggs, gelatin and fatty acids — we’re putting so much more into the animal than we’re getting out of it.

And we’ve come to think of animals exactly like this — like a function, like a machine. And that shortsighted and inhumane mentality leads to situations like our current ones: factory farms where animals are treated beyond unethically.

So, what’s the fix? Not only are our current methods inhumane, but they are also resource inefficient and pollutive. Given our rapidly changing climate and expanding population, we can’t afford to allow the simple and necessary act of eating to literally destroy our planet.

Well, acellular agriculture might just be the trick.

Acellular agriculture has to do with using microflora and bacteria as mini factories to produce animal derived products (like milk, cheese, eggs and fats)

On average, using acellular agriculture takes

91% less land 98% less water, 65% less global warming potential, and 84% less greenhouse gasses than producing the same product conventionally.

What’s more, the controlled conditions in which these products are made can allow us to enhance them nutritionally and produce them free of antibiotics (hence, making them better for our health). And, it’s total unreliance on animals prevents them from being mistreated in the first place.

What are we trying to produce?

To understand how acellular agriculture works, we first need to understand what it is that we are trying to create.

The products created by “cellular agriculture” are things that involve cells, or once living tissue. The products created by “acellular agriculture” are the non living components that are produced by the living cells. These are things like lipids and proteins which specific animals are capable of producing. Cheese and milk for instance are mostly casein protein, eggs come from ovalbumin and fats come from gelatin and fatty acids.

How does it work?

Step 1: Getting Recombinant DNA

Proteins are coded for by genes — specific segments of an animal’s DNA. The first step is getting the genes responsible for the protein we want to synthesize. These genes are usually turned into a plasmid (a little closed double helical circle) and is called the recombinant DNA.

Step 2: Genetic Transformation

Now, we select a kind of bacteria or microflora that’s going to act as our “conversion machine”. Through a process called genetic transformation, we insert our recombinant DNA into the DNA of the bacteria.

To do this, we need our bacteria to be competent — able to intake foreign, extra cellular DNA. It also needs to be able to horizontally transfer genes — i.e. integrate the foreign genes into it’s own DNA.

Horizontal gene transfer is much more difficult in eukaryotic organisms than prokaryotic organisms. This is because eukaryotic organisms, have both a cell membrane and a nuclear membrane which the plasmid needs to get through. In prokaryotic organisms, the plasmid just has to penetrate the cell membrane.

So, let’s consider a non naturally competent prokaryotic cell like E. coli. In order to make it competent, we must

1. Expose it to a salt such as CaCl_2 which neutralizes the negative charges on the cell membrane’s phosphate heads as well as the negative charges on the plasmid. This prevents the two from repelling.
2. Heat shock it by incubating it in warm water for a few seconds. This opens up large pores on the surface of the cell which the plasmid can get into.

Step 3: Fermentation

Now, we need to use our conversion machine. By feeding our bacteria/microflora sugar, it’s cells will grow and divide, duplicating all of it’s DNA along with our recombinant DNA. Then the bacteria will express our DNA, meaning it will read off the genetic instructions and do what it says (in this case, produce the specific protein). This process is called fermentation.

Step 4: Purification.

In order to get rid of the residual bacteria, we can expose it to an antibody raised against the protein we’ve produced. In this way, everything that doesn’t contain our protein will die off.

We could also use something called a centrifuge. This basically spins a mixture around an axis with a lot of force in order to separate out solids from liquids.

Or, we could soak our solution in a well buffered ionic solution (like sodium chloride). This employs a principle called osmosis to suck all the water out of the bacteria, eventually killing them.

Who is working in the space?

A company called Perfect Day foods is using these techniques to generate casein which they use for dairy products including ice cream and milk. Another organization called JUST plans to bring egg and egg whites to consumers this way.

Acellular agriculture was also used to create the Impossible Burger — a completely vegan and plant based burger that looks, smells and tastes like meat. How? They generated a little known protein called heme.

The science can behind acellular agriculture can even be used to produce non animal products. Insulin used to be obtained from the ground up pancreas of pigs. In 1978, Arthur Riggs, Keichi Itakura and Herbert Boyer inserted genes for human insulin into bacteria and were able to produce it much more efficiently.

Vanillin — which is a principle ingredient in vanilla extract — is typically chemically synthesized or extracted from tropical forests. A company called Evolve is working on using yeast to produce it instead. Ginkgo bioworks is a company planning to similarly generate flower fragrances which can be integrated into perfumes.

So, there you go, a way to get any animal product in a vegan friendly way :)