Homo erectus developed the first stone tools to consume scavenged meat around two million years ago. Now scientists are developing tools to grow meat in the lab. But why is there a sudden interest in growing our own meat?

The Food and Agriculture Organization of the United Nations (FAO) has predicted that meat demand will increase by 73 % by 2050 [1]. With increasing concerns of environmental issues, food security, and animal welfare involved in cattle rearing, will scientists be the farmers of the future?

In vitro or “cultured” meat has been on the news menu since 2013, when Mark Post, a professor at Maastricht University, The Netherlands, presented a proof-of-concept by producing, cooking, and eating a hamburger made from cultured beef. Because of the novelty of the technologies involved, the burger cost 250,000 EUR to make and was funded by Google co-founder Sergey Brin. Post’s aim was to publicize cultured beef as a feasible alternative to animal agriculture [2].

1. The First Cultured Burger

What does it take to produce cultured meat? Scientists “farm” synthetic meat by using the same technology used in regenerative medicine: stem cell isolation and identification, ex vivo cell cultures, and tissue engineering [2].

1.1. Cells

Scientists first harvested muscle tissue from a living cow. To separate the muscle tissue from the fat cells, scientists cut the muscle cells into tiny pieces. Muscle tissue (pictured below) contains myosatellite cells, which have stem cell-like abilities.

Whereas stems cells can become any type of cell, satellites cells have a defined role in muscle repair and regeneration – they transform into adult muscle cells in case of injury. Myosatellites are a good choice for in vitro meat because, like stem cells, they are able to rapidly proliferate, but they are hard-wired to become muscle.

1.2 Cell Culturing

To culture the cells, scientists placed each myosatellite cell in a petri dish containing a suitable nutrient solution supplemented with fetal bovine serum (FBS – a controversial slaughterhouse byproduct). After three weeks, each myosatellite cell has produced several billion additional cells. Scientists then placed the cells in a nutrient-poor growth medium to starve the cells, forcing them to differentiate into fully developed muscle cells called myocytes. After enough time, the muscle cells will naturally align and link together to form myotubes – a developing muscle strand just 0.3 mm long.

1.3 Tissue Engineering

The muscle cells’ natural tendency to contract enables them to grow into a small strand of muscle tissue. Scientists placed several myotubes around a gel hub in a new petri dish. After a few more weeks, the myotubes merge together to form a long bundle of skeletal muscle fibers. The muscle tissue was then removed from its gel hub, sliced open and flattened to form a single straight strand. Around 10,000 individual muscle strips were eventually layered together to form the meat patty.

Finally, scientists added beetroot juice and saffron to mimic the color of beef. But a good burger is much more than just a mass of muscle – fat tissue is a crucial component of the taste. As a result, the team’s prototype mimicked the texture of beef but was labeled “a bit bland” during the taste testing.

2. Cultured Meat for the Masses?

Research in this field is not advancing as fast as it could be because not enough research exists to support grant applications; the field stands alone as a completely new medical research/food science hybrid [3]. Two organizations, New Harvest and The Good Food Institute, are working to advance “cellular agriculture” as a field in its own right by attracting funding, connecting the community, and educating the public [3,4]. A number of scientists are working on tissue engineering technologies that could be exploited for cultured meat. However, progress may be slow as these technologies are primarily directed at better-funded medical applications.

To maximize the combined efforts of researchers and attract funding, the first annual symposium on cultured meat was organized at Maastricht University in October 2015. At the symposium, Post announced the launch of his spin-off company founded at the university, called “MosaMeat” [5].

MosaMeat claims it has managed to reduce the cost of the burger dramatically and a commercial product is expected to be ready in five years [6]. In addition to finding a plant-based alternative to serum, the company is also investigating several research streams studying the protein content, fat tissue, and color of the meat [5]. To be considered as a widely acceptable alternative, the final product needs to be sufficiently similar to meat in taste, texture, and appearance.

Despite the media hype, cultured meat is still a relatively small field involving only a few private companies/organizations:

2.1 Memphis Meats: Pork

Memphis Meats, San Francisco, USA, is a collaboration between University of Minnesota Professor Uma Valeti, Research Director Nicholas Genovese, and former biochemical engineer and BBQ restaurant owner Will Clem. It is a relatively new venture aiming to create cultured pork [7]. Memphis Meats is growing animal muscle tissue in bioreactors seeded with muscle-specific cells and nutrients. Because the tissue lacks a capillary system to transport blood, cells are grown in extremely thin layers so it remains well-oxygenated. Like MosaMeat, the team is also using FBS but claim they are researching a plant-based substitute. They may have a pork product ready to bring to market within a year.

2.2. The Modern Agriculture Foundation: Chicken

The Modern Agriculture Foundation is a nonprofit organization founded in early 2014, focused exclusively on cultured chicken. The project is headed by an expert in Tissue Engineering, Professor Amit Gefen, Tel Aviv University, Israel. Constructing an entire chicken breast, however, poses challenges when it comes to developing the structure and architecture of the lab-grown tissues. Gefen is working to find a suitable scaffold to culture the cells together in a 3D structure [8].

2.3 Modern Meadow: Steak

Modern Meadow, Brooklyn, New York, USA, was co-founded by Professor Gabor Forgacs along with his son Andras; the pair previously founded a company developing bioprinted human tissue (Organovo Inc.). Instead of 3D printing, their new venture uses a similar culturing method to Post’s to create “steak chips” [9]. After separating the cells from the culture medium, the team adds pectin (a gelling agent derived from citrus or apples), along with flavors and spices. The flavored meat is then baked in a food dehydrator to make chips. Modern Meadow is also developing lab-grown leather from cultured cells to create an alternative biomaterial to traditional leather.

3. Challenges to the Perfect Recipe

3.1 Sustainability

Currently, the efficiency of cultured meat can only be predicted based on assumptions, but it is expected to reduce water, land, and energy expenditures significantly [10].

Controversially, all lab-grown meat uses FBS harvested from unborn cows to culture the muscle tissue. Blood is drawn from the fetus during the slaughter of the pregnant mother. The blood is put through a centrifuge to separate the blood cells from the serum, which is then filtered further. The final product (pictured on the right) is low in antibodies and high in growth factors, providing a Michelin-star meal for the muscle tissue at a high cost [11].

FBS provides the best results compared with serum-free media, but being a slaughterhouse byproduct, FBS is neither well accepted nor amenable to large-scale use. Scientists are therefore investigating cheaper, non-animal-derived feed sources. Blue-green algae are a potential substitute, but this is also expensive, and there is no current method to cheaply scale up production [11].

3.2. Scale-Up

Post’s method of cell culturing on 2D plates was suitable to produce one burger, but the process has to be scaled up to be commercially viable. Efficient large-scale production of stem cells involves culturing cells inside bioreactors and using microcarriers (beads to which cells can stick to and grow side-by-side) [12]. The formation of steak-like 3D structures will require a 3D framework or scaffold to ensure that every cell/fiber has a continuous and adequate supply of nutrients and oxygen [13]. 3D Printing may have a role to play in generating such channel structures [14]. The framework should also allow the subsequent release of the tissue from the support without damage. Furthermore, waste products also need to be continuously removed from the system.

Previous studies have involved other type of cells, so scientists will have to develop new optimized systems for satellite cells used for cultured beef [12]. The greater scale of cell and tissue culture required for food applications compared with medical applications means that existing technology will need to be revolutionized.

Despite a proof-of-concept, the technology to grow meat in vitro is still in its infancy. Examples of mass production of cultured organisms exist in the pharmaceutical industry (e.g., E. coli, yeast) and microbial biotechnology (e.g., for the beer and cheese industries). It is likely that some of the established technologies and methodologies can be adapted for the production of cultured meat. Clearly, this next step will require a great amount of funding. Aside from the many scientific challenges involved [15], there remains one crucial question: When it is finally possible to produce cultured meat on a large scale, will the consumer have an appetite for it?

References

[1] Food and Agriculture Organization of the United Nations (FAO), World Livestock 2011. Livestock in Food Security, 2011.

[2] M. J. Post, J. Sci. Food. Agric. 2014, 94, 1039–1041. DOI 10.1002/jsfa.6474

[3] New Harvest, http://www.new-harvest.org/ (accessed Apr 1, 2016).

[4] The Good Food Institute, http://www.gfi.org/ (accessed Apr 1, 2016).

[5] R. Wyers, Cultured Meat Researchers Form University Spin-Off Company, Set 5 Year Target for Commercial Applications,
Food Ingredients 1st 2015 (accessed Mar 29, 2016).

[6] P. Ghosh, Team wants to sell lab grown meat in five years, BBC News 2015 (accessed Mar 29, 2016).

[7] J. Bunge, Sizzling steaks may soon be lab-grown, The Wall Street Journal 2016 (accessed Mar 29, 2016)

[8] L. Manning, 4 Q&As with Dr. Amit Gefen on Developing a Bioengineered Chicken Breast, AgFunderNews 2015 (accessed Mar 29, 2016)

[9] The New Culture of Meat: Q+A with Modern Meadow CEO, Andras Forgacs, Climate Confidential 2015 (accessed Mar 29, 2016).

[10] H. L. Tuomisto and M. J. de Mattos, Environ. Sci. Technol. 2011, 45, 6117–6123. DOI: 10.1021/es200130u

[11] The Crux, Steak of the Art: The Fatal Flaws of In Vitro Meat, Discover Magazine 2012 (accessed Mar 30, 2016).

[12] M. S. M. Moritz et al., J. Integr. Agric. 2015, 14, 2, 208–216. DOI: 10.1016/S2095-3119(14)60889-3

[13] M. J. Post, Meat Sci. 2012, 92, 297–301. DOI: 10.1016/j.meatsci.2012.04.008

[14] M. J. Post et al., Regener. Med. 2013, 8, 759–770. DOI: 10.2217/rme.13.74

[15] I. T. Kadim et al., J. Integr. Agric. 2015, 14, 222–233. DOI: 10.1016/S2095-3119(14)60881-9

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Also of Interest

• Lab-Grown Meat,
  ChemistryViews.org 2015.
  Molecular biology increasingly contributes to the production and preparation of food.