Cell-Based Meat with a Side of Science

Sustainable nutrition outlook SOPHIE CASSON FOR NATURE FOR SOPHIE CASSON Cell-based meat with a side of science

Growing a burger in a laboratory is one challenge, growing an industry to do it at scale is quite another. By Elie Dolgin

hen Laura Domigan started her efforts on creating artificial corneas for eye in October 2020, a team led by Domigan won research group at the University surgery — a far cry from anything resembling a multi-million dollar grant from the New of Auckland, New Zealand, in 2015, a lab-grown steak. Zealand and Singaporean governments to she hoped to continue her work Still, she never gave up on her dream of stud- explore questions such as which cells are the developing protocols for growing ying in vitro meat. “I had to be super patient best starting material for cultured meat, and Wcell-based meat in the laboratory. But with and keep trying,” Domigan says. And although is the nutritional profile of meat grown in a lab funding for cultivated-meat research prac- it took several years, Domigan’s strategy even- equivalent to the real thing. “There is so much tically non-existent in academia at the time, tually paid off. research that needs to be done,” Domigan says. Domigan pivoted to working on biomedical Initially, she secured funding for a PhD And much of it is only beginning to happen, at materials for use in tissue engineering. A pro- student to begin developing formulations of least in any sort of transparent way. tein biochemist by training, she focused her nutrient media to grow cell-based meat. Then, Investors have poured hundreds of millions

of dollars into cultured-meat research in the Technical University of Munich in Germany, for in the subject grows and grant applications past few years, bringing hype and breathless example, is accepting applications for a profes- increase, governments have begun to inject news coverage about an agricultural revolution sorship in cellular agriculture. And, as evidenced more cash into the field. Several large grants that could bypass the environmental and ani- by Domigan’s funding success, governments too have been issued in the past few months alone. mal-welfare issues of conventional meat pro- are heeding the call for financial support. In November, for example, the government duction. One estimate by the consulting firm The field of cellular agriculture is beginning agency Flanders Innovation and Entrepre- Kearney in Chicago, Illinois, suggests that 35% to take on some of its biggest scientific and neurship began funding a €2.1-million, 4-year of all meat consumed globally by 2040 will be engineering challenges, and scientists from project called CUSTOMEAT, run by scientists cultured — a change that is projected to reduce a range of backgrounds are entering the fray. at Ghent University and KU Leuven, both in greenhouse-gas emissions and antibiotic use. “This cellular-agriculture research is Belgium. In the United States, the National Sci- And thanks to the COVID-19 pandemic, which the stuff that gets me up in the morning,” ence Foundation (NSF) awarded around $3.5 revealed crucial weaknesses in global food-sup- says Glenn Gaudette, a biomedical engi- million in September to back a cultivated-meat ply chains, some people now expect the transi- neer at Worcester Polytechnic Institute in consortium at the University of California, tion to cell-based meat to happen even faster. Massachusetts. For almost 20 years he has Davis, for the next five years. Earlier this month, a US start-up called Eat studied scaffold technologies for heart-re- “Our hope is that we can provide basic Just announced that its chicken bites — which generation therapies; now he is applying his knowledge and build a trained workforce,” are 70% cultured chicken cells, with plant pro- expertise to the problem of how to grow meat. says chemical engineer David Block, who is tein added for structure and flavour — had won “Does it pay the bills? No, not yet — hopefully, leading the Davis effort. “Those are the kinds regulatory approval for sale to consumers in one day — but it’s really exciting.” of things that you need to grow an industry.” Singapore, a global first for the cultivated-meat Experts say that many cultivated-meat industry. The fight for funding companies will probably over-promise and Scientists worry that the commercial push In the early 2000s, the US space agency NASA under-deliver. But academic science can help to bring palatable products to market means briefly supported efforts to grow goldfish “keep credibility alive,” says Johannes le Cou- that fundamental studies are either not hap- muscle in the lab as a potential source of pro- tre, who led a research group at the Swiss food pening or remain cloaked in trade secrecy. tein for astronauts on long missions. A few giant Nestlé before joining the University of Start-ups have made splashy demonstrations years later, the Dutch government sponsored New South Wales in Sydney, Australia, in 2019 of their lab-grown chicken nuggets, pork sau- a €2-million ($2.3-million) project to cultivate to run a lab dedicated to cellular agriculture. sages, steak strips and seafood dumplings. But Amy Rowat, a biophysicist at the Univer- these show only that companies “can do this “This cellular-agriculture sity of California, Los Angeles, notes that aca- on a small level”, says Abhi Kumar, a venture demia also offers the intellectual freedom for partner at Lever VC, a New York-based venture research is the stuff that gets researchers to work on exploratory projects, capital fund that focuses on alternative-pro- me up in the morning.” using expertise in basic science to come up with tein start-ups. The challenge now, he says, is innovative ways of thinking, or to tackle ques- making it work at scale. tions not directly related to product develop- Improvements in cell source material and pork meat from stem cells — research that, ment but still significant to the overall domain. the nutrient media required to fuel cell growth with an extra €250,000 infusion from Google And according to David Kaplan, a bioengineer at are needed, as are scaffolds to support 3D tis- co-founder Sergey Brin, eventually led to the Tufts University in Medford, Massachusetts, the sue structures. Next-generation bioreactor field’s highest-profile moment so far, when next generation of scientists entering the field platforms that can grow huge numbers of vascular biologist Mark Post at Maastricht are “totally motivated to make a difference”. cells at high densities are also a must. These University in the Netherlands, unveiled the “I have never seen such driven, passionate are costly undertakings — so much so that world’s first cultured burger, in 2013. students in all my decades of doing this,” he many in the field are dubious that private But aside from intermittent funding oppor- says. Andrew Stout is a case in point. A PhD financing can support them, and still yield an tunities to explore the social ramifications student in Kaplan’s lab, Stout is rethinking the affordable product. of producing meat from cell cultures, there entire process of cellular agriculture, start- That’s why leading thinkers in cellular agri- have been few other public grants for culti- ing with the most basic ingredient: the muscle culture, such as Erin Rees Clayton at the Good vated-meat research. Government bodies cells themselves. Food Institute (GFI), argue in favour of more stayed away from the field in large part, says Most companies growing lab meat either open science and public investment. “There’s a Kate Krueger, former research director at the use cells taken directly from animal biopsies need for public-sector research in these areas,” non-profit organization New Harvest in Cam- or cell lines that have spontaneously become says Rees Clayton, who is associate director of bridge, Massachusetts, because the science immortal through natural mutations that science and technology at the GFI, a non-profit was unproven and crossed disciplines in ways allow indefinite proliferation in the lab. Few think tank in Washington DC. “There’s a lot of that defied the conventional dividing lines of firms will consider genetically manipulating room in the pre-competitive space for more funding-agency bureaucracy. the cells for optimal performance because of work to be done in an open way, so we can all “Cellular agriculture falls into this funding a fear of consumer backlash. But Stout real- benefit from it and move forward more quickly.” no-man’s land between biomedical research ized that genetic engineering offered a path To fill the funding gap, the GFI created a and agricultural research,” says Krueger, who to achieving the nutritional promise of cul- research-grant programme that has given out now runs a consulting firm, also in Cambridge, tivated meat. close to US$3 million over the past 2 years to centred around cellular agriculture. 16 research teams working on cultivated-meat Money from the GFI and New Harvest has Starting material projects. Academic institutions are beginning plugged the funding gap to some extent. But He inserted three genes into cow muscle to hire with the nascent discipline in mind — the the situation is changing. As scientific interest cells1. Each encoded an enzyme involved in

Sustainable nutrition outlook

in vitro culture media, creating the slaugh- ter-free products that the industry demands. But this serum-free media is too expensive for cultivated meat to be affordable on the supermarket shelves. “It’s difficult to find a cost-efficient option,” says Ka Yi Ling, chief scientific officer at Shiok Meats, a cell-based seafood company in Singapore.

Media matters According to an analysis by the GFI4, growth media currently make up the bulk of total production costs for cultivated meat, and proteins known as growth factors are the most expensive ingredient. Costs are com- ing down, as start-ups dedicated to serving the cellular-agriculture industry devise ways to manufacture these products. But as Matt Anderson-Baron, co-founder and chief scientific officer at one such company, Future Fields in Edmonton, Canada, concedes, “There’s still so much to be done on the opti- mization and discovery front.”

Assuming researchers find the right cell line IMAGES/ALAMY PARRY/PA DAVID Producing products such as the lab-grown meat burger at scale is still a long way from reality. and growth medium combination, they then have to grow those cells on a scaffold — ideally the synthesis of an antioxidant that mitigates executive director of Clean Research, a non- one that is edible so that it doesn’t have to be diseases associated with consuming red and profit organization in New York, now wants removed from the final product. For ground- processed meats, such as colon cancer. The to make it the go-to species for basic-research meat products, such as burgers and sausages, enzymes might also help with the manufac- projects in cellular agriculture as well. “There’s small beads known as microcarriers can pro- ture of cultured meat, because the unstable a lot of fundamental understanding that’s not vide the surface properties needed by most molecules that antioxidants attack reduce there yet,” he says. “We need the participation muscle and fat cells for growth. But for any- the proliferation of some lab-grown cells. If of a lot of people to just think freely through thing with a more complex meat structure — a consumers are willing to accept these types the science together.” steak or an Iberian ham, for example — a more of DNA enhancement, “genetic and metabolic And, as Rostain and his colleagues have sophisticated tissue-engineering approach engineering can offer a lot of impact and ben- described3, researchers can benefit from the is required. efit to cultured meat”, Stout says, “and could extensive molecular toolkit already estab- One option comes from a team at Harvard even allow us to create novel foods that we lished for zebrafish. Plus, as a lean fish with University in Cambridge, Massachusetts. Bio- couldn’t get any other way”. little fat content in the muscle, zebrafish fillets engineer Kevin Kit Parker and his colleagues Other researchers are reconsidering should be easier to produce than compara- have developed a spinning technique that whether the cells that go into cultivated-meat ble lab-grown cuts of fat-laced salmon, tuna, works like a candy-floss machine to extrude products need to come from species that are long, thin fibres from gelatin5. The researchers already commonly consumed in Western cul- “I have never seen such put the gelatin, a protein product derived from tures. For example, Natalie Rubio, another collagen, into their machine and produced tiny Tufts graduate student, has explored grow- driven, passionate threads — narrower than the width of a hair — ing meat from insect cells to create products students in all my that closely matched the architecture of fibres that can be designed to taste like crab, prawns decades of doing this.” found in muscle tissue. and other seafood. Using muscle cells from Last year, Parker and his colleagues showed fruit flies (Drosophila melanogaster)2 and that rabbit and cow muscle cells grown on the the caterpillar of the moth Manduca sexta, beef or pork. Cultivated zebrafish will proba- fibrous gelatin line up with the proper ori- Rubio showed that insect cells are easier and bly taste similar to white fish, such as cod or entation6. The cells were still not as densely cheaper to grow than cells from conventional haddock, Rostain says, and discoveries made packed as real muscle, but Parker, together livestock species, and might also have nutri- with zebrafish should translate to any other with three of his postdocs and students, has tional advantages. edible species. since created a company called Boston Meats Meanwhile, other scientists hope to rally Regardless of the starting material, all cells to improve the technology further. “Now, with the research community around the idea of will require an optimized growth medium our scaffolds,” he says, “you can move from cell-based zebrafish fillets, at least as a vehi- — the rich broth of chemicals and proteins hamburger to fillet.” cle for accelerating advances in the field. The needed to support proliferation and differ- Elsewhere, researchers have made scaffolds zebrafish (Danio rerio) is an established model entiation. Companies have already devised out of foods such as textured soya protein and organism for studying the genetic, neuronal ways to eliminate the nutrient-rich fetal various vegetables stripped of their cellular and behavioural basis of disease. Alain Rostain, bovine blood that is the cornerstone of most material so that only supporting structural

sugar molecules and proteins remain. At the University of Ottawa in Canada, for example, biophysicist Andrew Pelling and his students have taken decellularized stalks of celery and shown that the grooves created by its natural structure help to promote the patterning and alignment of muscle cells7. And at Worcester Polytechnic, Gaudette’s team has grown fat and muscle cells on cell-free spinach leaves — the plant’s branching network of delicate veins provide ideal conduits for the nutrient medium to reach every cultivated meat cell. Because muscle and fat cells require different growth media, however, researchers typically culture the two cell types separately, each on its own scaffold in a different nutrient bath. Some researchers, including Rowat, have devised strategies to then interlace the muscle and fat to achieve the flavour of a well-marbled steak. “The cells actually fuse together with the other partnering scaffold type on the time scale of hours to form these composite structures,” Rowat explains. In unpublished work, she has created miniature marbled steaks out Ka Yi Ling and Sandhya Sriram are co-founders of Shiok Meats in Singapore. of mouse and rabbit cells, and has begun to work with cells from pigs and cows, as well. annually, something that is not possible with cells at scale. “You have these two competing But even with the latest scaffolding strate- the types of batch bioprocessing techniques interests,” says Kahan. To support nutrient gies, some muscle biologists worry that key currently used in mammalian-cell-based and gas exchange, “you’re trying to keep aspects of tissue physiology are still being dis- manufacturing. Global capacity could fulfil things well mixed while at same time trying to counted. “This incredible focus that we have as about one-billionth of that requirement. “It’s subject the cells to very little mechanical fluid an industry on cell division ignores fusion and a massive limiting factor,” says Connon, who stress”. With input from industry partners, the maturation,” says James Ryall, chief scientific has developed a type of continuous cell-bio- consortium plans to build more complexity officer at Vow, a start-up in Sydney working reactor platform that he plans to commer- into its models to inform the design of biore- on cell-based meat from animals such as kan- cialize through a spin-off company called actors in the real world. garoo and alpaca. Block’s group, with its large NSF grant, To form muscle tissue, thousands of individ- “This incredible focus that isn’t even attempting to work on bioreactor ual precursor cells must first fuse together to designs; there is plenty to keep his team busy become long myotubes. These cells require we have as an industry on tackling the issues of cell lines, media and scaf- physical stimuli to mature into myofibres. cell division ignores fusion folds, as well as conducting feasibility assess- Only then will muscle grown in the laboratory and maturation.” ments of the cell-based meat industry. “To me,” have the texture and nutritional properties of says Block, “it’s not clear yet that this is going real meat, says Lieven Thorrez, a muscle-tissue to be a viable alternative” — whether from a engineer at the Kortrijk campus of KU Leuven. CellulaREvolution. technical, economic or sustainable stand- “And that is a process that takes time. You can- Meanwhile, computer scientist Simon point. But with each new grant or research not just differentiate cells over a period of a few Kahan, president of life-sciences software team entering the field, the goal of a perfectly days and say the myofibres will be the same as company Biocellion SPC in Seattle, is lead- grilled, medium-rare steak grown from cells those found in an adult animal,” he says. “That ing a team called the Cultivated Meat Mod- gets a little closer to becoming a reality. is largely overlooked.” eling Consortium that formed in 2019 with the aim of optimizing bioprocessing tech- Elie Dolgin is a science journalist in Scaling up niques through modelling techniques. With Somerville, Massachusetts. With so many scientific issues to resolve, cell- funding from the German technology com- based meat research, whether in academic pany Merck, the consortium has developed 1. Stout, A. J., Mirliani, A. B., Soule-Albridge, E. L., Cohen, J. M. & Kaplan, D. L. Metab. Eng. 62, 126–137 (2020). or private labs, remains at the experimental a proof-of-concept model of a stirred-tank 2. Rubio, N. R., Fish, K. D., Trimmer, B. A. & Kaplan, D. L. ACS stage. For commercial viability, the industry bioreactor, involving little more than a spin- Biomater. Sci. Eng. 5, 1071–1082 (2019). will need to find ways to produce tissue at a ning rotor and free-floating minute beads for 3. Potter, G. et al. One Earth 3, 54–64 (2020). massive, and unprecedented, scale. growing muscle cells. 4. Specht, L. An Analysis of Culture Medium Costs and Production Volumes for Cultivated Meat (The Good Food Tissue engineer Che Connon at Newcas- The bioreactor might be fairly rudimentary, Institute, 2020). tle University, UK, estimates that feeding but the consortium’s computer modelling is 5. Reza Badrossamay, M., McIlwee, H. A., Goss, J. A. & the world’s population with lab-grown meat anything but. The simulations of fluid dynam- Parker, K. K. Nano Lett. 10, 2257–2261 (2010). 6. MacQueen, L. A. et al. npj Sci. Food 3, 20 (2019). would necessitate building systems for grow- ics and cellular biomechanics have revealed 7. Campuzano, S., Mogilever, N. B. & Pelling, A. E. Preprint at ing on the order of a septillion (1024) cells a central challenge to growing muscle or fat bioRxiv https://doi.org/10.1101/2020.02.23.958686 (2020).