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Cultured meat from stem cells: challenges and prospects (Meat Science, 2012)

This publication by Mark Post was summarized by Barnaby Dawson, with edits by Francis Runge. The original paper can be accessed here.

Overview

The author (Mark Post) was the scientist behind the first in-vitro meat burger. He reviews the why, how and what next of in-vitro meat. Motivations are laid out, challenges are analysed and prospects discussed. The paper is a essentially a review article setting out the state of play in the field and the full text is well worth a read.

Motivations

The motivations behind the in-vitro project are many and varied.

  • Economically, the supply of meat is likely to be outstripped by demand and this will further worsen the already very unequal global distribution of food. In vitro meat, though not currently economic, shows great potential to be a more economic source of meat.
  • Environmentally, livestock breading and management increases greenhouse gasses and demands more land, water and energy than other food sources and in particular more than estimates of the environmental impacts of in vitro meat.
  • In terms of animal welfare the author just notes the clear benefits of in vitro meat and observes that the public are increasingly expecting higher standards in our treatment of animals.
  • In terms of public health he not only highlights the risks from food-borne pathogens but also the breading ground that intensive farming provides for influenza strains such as swine and bird flu.

Finally, he discusses the requirements of a meat alternative in the market (visual appearance, smell, texture and taste) and observes that existing meat alternatives have difficulty fully replicating the texture of meat.

Challenges

The author lays out the key technological challenges to the development of economic in vitro meat as scalability, quality control of mammalian cell/tissues cultures, the sterility of culture and the maintenance of cell donor animals. A key biological challenge is producing large three-dimensional blocks of muscle tissue when the cells require nutrients and oxygen to grow. He speculates that three-dimensional printing technologies could be used to produce scaffolding for the muscle blocks. Another challenge is the isolation and identification of suitable animal stem cells. He anticipates that this is just a matter of looking long and hard enough. A further challenge is the optimization of culture media with thousands of variables that need to be considered. Other issues include the need for mechanical or electrical stimulation to be applied to encourage muscle tissues to take on the desired texture.

Prospects

The author discusses the prerequisite technologies that are making in vitro meat a real possibility now as opposed to 30 years ago. These are the growing sophistication of stem cell isolation and identification, the development of ex-vivo cell culture and the development of tissue engineering techniques. He observes that artificial muscles have been grown for 15 years. He concludes with a restatement of the challenges, expressing a cautious optimism with the prospects for in vitro meat.

Points of interest

The author discusses the prospects for combined cultures of photosynthetic organisms (one assumes he means single celled ones such as algae or cynobacteria) and animal cells, the former providing nutrition for the latter. He describes cell culture as a two stage process. Proliferation of the stem cells and then differentiation of the stem cells into, primarily, muscle cells. He also discusses the possibility of sourcing meat from insects and the economic advantages of this.

Key Points

  • Three reasons to pursue alternatives to conventionally produced meat: 1) increase in meat demand, 2) environmental impact of livestock breeding/management, 3) animal and human health.
  • Two requisites for alternatives to be accepted and industrialized: 1) indistinguishability and 2) efficiency.
  • Existing meat alternatives are currently based on soy, milk proteins, wheat proteins, or mycoprotein.
  • In vitro meat has been made a possible alternative based on stem cell isolation/identification, ex vivo cell culture, and tissue engineering. Challenges will include identifying the best cell type, determining the cell culture conditions for both proliferation and differentiation, and scaling up.

Notable Statistics

  • Worldwide meat consumption will double in the next 40 years (FAO 2006).
  • The Earth’s meat production capacity is near maximum (FAO 2011).
  • The CO2, methane, NO, contribution to all greenhouse gases from livestock is 9, 39, 65% respectively (FAO 2006).
  • Overconsumption of meat is responsible for ¼ of all ischemic heart disease, >1.8M deaths annually. (Larsson et al. 2006, Song et al. 2004)
  • Total sales US 2010 frozen meat substitutes: $267M vs $74B in beef sales. (Salvage 2012).