The perfect recipe for a petri-dish burger
“Do you think if I scraped these cells off this petri-dish and cooked them, they’d be like a teeny tiny burger?”
I looked up from the microscope, saw the horrified expression on my colleague’s face and realised maybe I’d been staring at my cells for a little too long.
“I mean, these are just mouse muscle cells – right?” I continued, “They should taste like whatever mouse meat tastes like…”
After some musing, we decided that yes, maybe it would, but we were definitely sure we wouldn’t be eating mouse meatballs. We’d stick to studying them.
But what if those weren’t mouse cells in my petri-dish but cow or pig or chicken?
Welcome to cellular agriculture.
Also known as artificial or cultured meat, there have been many promises of meat grown entirely in vitro since Mark Post famously ate the first “petri-dish burger” in 2013. For good reason too, there are many moral and environmental reasons to cut down on animal products. Who better to put it starkly than David Attenborough who said “We must change our diet. The planet can’t support billions of meat-eaters.”
And we are changing.
Last year up to 500,000 people joined the approximately 7.2 million adults already eating meat-free diets in the UK (1) and in a survey of adults in England, just over half were open to trying cultured meat (2). But as there seems to be a need and a market for kill-free meat, why is it taking so long to get to our supermarket shelves?
It’s not for lack of trying: there are many projects and start-ups working hard to produce affordable cultured animal products, but there are still some challenges to be faced. So, what will be the recipe for a perfect petri-dish burger?
Meat, being animal muscle tissue, is mainly composed of muscle cells, fat and collagen. To create our recipe, we’ll look at how muscle and fat cells can be produced for consumption and the issues with growing cells at scale.
Just one look at Dwayne “The Rock” Johnson is a reminder that muscle has an innate ability for growth in adults. When muscles need to grow or repair, stem-cell like satellite cells explode onto the scene and become myoblasts which after some replications mature into myocytes, forming new muscle fibres. For our purposes, satellite cells can be collected from live adult animals via small muscle biopsies then amplified and matured into muscle in vitro. However, satellite and myoblast cells have limited amplification capacity, so further work is needed to hold cells in the satellite cell stage and achieve optimum growth before maturation into muscle tissue (3).
For a lot of us over the 2020 lockdowns, just one look at ourselves was a reminder that fat, too, has the potential for growth. However, this is mostly due to the increase in size of individual fat cells (adipocytes) rather than replication. There are two ways we could produce new fat cells from an animal fat sample. We can capture a type of stem cell (mesenchymal stem cells), replicate these, and then differentiate them towards becoming fat cells. Or we can turn mature fat cells into a precursor type cell which can then replicate before differentiation back into fat cells. Again, these methods are limited by how many times the cells can replicate (4).
Alternatively, there are cell types that can replicate unlimitedly and wouldn’t require regularly bothering animals with sharp pointy things. Stem cell lines collected from embryos or created from adult cells can produce mature muscle and fat cells, though this requires reasonably complex protocols many of which are currently not efficient enough to be commercially sustainable (4). Immortalised cell lines are another possibility, these are mature cells that have a mutation so that they can replicate indefinitely. An issue with both of these methods is that the cell lines required can be very difficult to make for some species, and many cell lines which would be useful for cellular agriculture are currently only from mice or humans (3)– not appropriate species for eating!
The seasoning of our burgers is more high “steaks” (sorry) than some mere salt and pepper. Some of the chemicals standardly used to control the cell-type differentiation required for our burgers are toxic or could have unacceptable side-effects if eaten, as they can affect our own cells the same way (4). Additionally, many cell-types can currently only be grown using animal serum – which slightly defeats the purpose of producing animal-free meat, even though fewer animals would be used overall. So, standard protocols need to be adapted to avoid these problem ingredients.
Lastly, to produce our commercial scale “petri-dish” burgers, we’ll need to throw out the petri-dish. To optimise cell growth, most current methods first grow replicating cells floating around in large, stirred tanks then mature those cells into the finished tissue in specialised containers – for example giving them a collagen scaffold to grow around to produce a meat-like texture (3). There is a lot of work needed to cut down on costs at this step- both for the food companies as well as for our planet. An Oxford university group recently calculated that switching our diets from traditional to cultured meat will lead to less global warming for some but not all predicted future methods of cellular agriculture (5). We need to get the most efficient growth from cells from the minimum amount of resources – both energy-wise and the raw ingredients to feed our cells with.
So, (skipping over the hefty hurdles of regulatory and cultural acceptance) imagine we finally get our supermarket “petri-dish” burger. Freshly sizzling from the grill, this might be the kill-free, (hopefully) more sustainable future of our food.
Sounds like a tastier option than my mouse meatballs.
- UK diet trends 2021 | Finder UK [Internet]. [cited 2021 Jun 29]. Available from: https://www.finder.com/uk/uk-diet-trends
- Siegrist M, Hartmann C. Perceived naturalness, disgust, trust and food neophobia as predictors of cultured meat acceptance in ten countries. Appetite. 2020 Dec 1;155:104814.
- Post MJ, Levenberg S, Kaplan DL, Genovese N, Fu J, Bryant CJ, et al. Scientific, sustainability and regulatory challenges of cultured meat. Vol. 1, Nature Food. Springer Nature; 2020. p. 403–15.
- Fish KD, Rubio NR, Stout AJ, Yuen JSK, Kaplan DL. Prospects and challenges for cell-cultured fat as a novel food ingredient. Vol. 98, Trends in Food Science and Technology. Elsevier Ltd; 2020. p. 53–67.
- Lynch J, Pierrehumbert R. Climate Impacts of Cultured Meat and Beef Cattle. Front Sustain Food Syst. 2019 Feb 19;3.
About The Author: Martha McLaughlin is in her final year of the 4-Year PhD in Clinical Neuroscience programme at UCL Queen Square Institute of Neurology, funded by Brain Research UK. She works across Prof. Pietro Fratta’s and Prof. Linda Greensmith’s research groups on the RNA biology of ALS disease. She spends her time outside the PhD working on science public engagement projects, particularly with sustainability collaborative “PPL PWR”.