Meat Science 92 (2012) 297–301 Contents lists available at SciVerse ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci Review Cultured meat from stem cells: Challenges and prospects Mark J. Post ⁎ Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands article info abstract Article history: As one of the alternatives for livestock meat production, in vitro culturing of meat is currently studied. The Received 20 January 2012 generation of bio-artificial muscles from satellite cells has been ongoing for about 15 years, but has never Received in revised form 2 April 2012 been used for generation of meat, while it already is a great source of animal protein. Accepted 3 April 2012 In order to serve as a credible alternative to livestock meat, lab or factory grown meat should be efficiently produced and should mimic meat in all of its physical sensations, such as visual appearance, smell, texture Keywords: and of course, taste. This is a formidable challenge even though all the technologies to create skeletal muscle Cell culture fi Tissue engineering and fat tissue have been developed and tested. The ef cient culture of meat will primarily depend on culture Meat substitutes conditions such as the source of medium and its composition. Protein synthesis by cultured skeletal muscle cells should further be maximized by finding the optimal combination of biochemical and physical conditions for the cells. Many of these variables are known, but their interactions are numerous and need to be mapped. This involves a systematic, if not systems, approach. Given the urgency of the problems that the meat indus- try is facing, this endeavor is worth undertaking. As an additional benefit, culturing meat may provide oppor- tunities for production of novel and healthier products. © 2012 Elsevier Ltd. All rights reserved. Contents 1. Introduction .............................................................. 297 2. Why do we need meat alternatives? .................................................. 297 3. Requirements for a meat alternative .................................................. 298 4. Meat alternatives ........................................................... 298 5. Cultured meat ............................................................. 299 5.1. Stem cells ........................................................... 299 5.2. Cell culture ........................................................... 299 5.3. Tissue engineering ....................................................... 300 6. What after in vitro meat can be grown effectively? ............................................ 300 Acknowledgment .............................................................. 300 References ................................................................. 300 1. Introduction other hand a predicted rapid increase in global meat consumption (FAO, 2006). In recent years the notion has been growing that alternatives may In this review the state of the art of meat alternatives is discussed, be needed for conventional meat production through livestock. This is with a particular emphasis on cultured meat. The urgency of the generally based on concerns about sustainability, environmental bur- problem is apparent. The focus will be on tissue-engineering methods den and animal welfare. These concerns have grown due to further rather than bio-printing or expanding existing pieces of tissue intensification of livestock herding and slaughtering, and on the through culturing. 2. Why do we need meat alternatives? ⁎ Department of Physiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, The Netherlands. Tel.: +31 43 3881200, +31 6 46705558(M); fax: +31 43 388 3884166. There are at least three motivations to intensify the exploration of E-mail address: [email protected]. production alternatives to livestock meat production. First, with the 0309-1740/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2012.04.008 298 M.J. Post / Meat Science 92 (2012) 297–301 predicted substantial increase in meat demand, we will quickly run From an epidemiological point of view it is evident that these pathogens out of production capacity as already a large portion of arable land and emerging diseases, such as avian and swine influenza, are associat- is dedicated to livestock feeding and management. Second, there is ed with the intensity of livestock farming and other anthropogenic de- growing concern about the environmental impact of livestock breed- velopments in the bio-industry (Greger, 2007; Slingenbergh, Gilbert, de ing and management. Last, high volume herding and slaughtering has Balogh, & Wint, 2004). sparked societal concerns about animal welfare and public health. In summary, there are numerous and pressing reasons to explore Due to an expanding world population and to increasing meat alternatives to relieve the burden and pressure of livestock meat consumption in developing economies, it is predicted that meat con- production. sumption will double in the coming forty years (FAO, 2006). Although these predictions are associated with considerable uncertainty, the 3. Requirements for a meat alternative sheer magnitude of this alleged increase supports the assumption that demand will increase appreciably. At the same time it appears Mimicry and efficiency are the two key requisites for a meat alter- – also with margins of error – that the capacity of conventional native to be accepted and industrialized. For a new meat substitute to meat production is close to its maximum (FAO, 2011). As a result, be widely adopted, it needs to exactly mimic or even better, recreate meat will become scarce, therefore more expensive and eventually a conventional meat in all of its physical sensations, such as visual luxury food. This may then serve to aggravate the already unequal appearance, smell, texture and of course, taste (Bredahl, Grunert, & global distribution of food. Alternatively, many other techniques are Fertin, 1998; Verbeke et al., 2010). If such a product can be created, being investigated to improve the efficiency of the entire supply it will deserve the name “meat”, without any pejorative adjectives. chain of foods, such as decreasing post-harvest losses (wasting of Of these challenges, taste is arguably the most difficult, especially food). In addition to these, efficient production of food and meat in since the more than 1000 water soluble and fat derived components particular will have a great impact. may make up the species and perhaps strain specific taste of meat Livestock meat production accounts for a considerable portion of (Claeys, De Smet, Balcaen, Raes, & Demeyer, 2004; Mottram, 1998). greenhouse gas (GHG) emission, land usage, water and energy con- A high efficiency, bioconversion rate, is the basis for a sustainable sumption. Of the three major greenhouse gases specifically carbon di- product that will be able to improve on the carbon footprint of live- oxide, methane and nitrous oxide, the contribution of livestock to stock meat production and as a consequence will require less water, their total emission is 9%, 39% and 65% respectively (FAO, 2006). It land and energy input per kg of meat. The low bioconversion rate of has been noted that these numbers vary greatly per country and con- pigs and cattle of approximately 15% (Egbert & Borders, 2006; tinent, depending on many factors, including the presence or absence Pimentel & Pimentel, 2003) offers a wide margin for improvement. of collateral damage by deforestation (Capper, 2011; Cederberg, Nevertheless, the challenge to design an in vitro production process Persson, Neovius, Molander, & Clift, 2011; FAO, 2006; Peters et al., that is much more efficient will be formidable. 2010; Steinfeld, Mooney, & Schneider, 2010). It is clear however, Opportunities on the other hand are also numerous. In the pro- that major improvements can be made in the environmental impact duction phase, recycling mechanisms and combining culture with nu- of meat production, either through conventional (Capper, 2011)or trient supplying systems through for instance photo-synthesis would other technologies. In a preliminary life cycle analysis Tuomisto and create substantial benefit and value (Tuomisto & de Mattos, 2011). In de Mattos (2011), calculated for instance that in vitro production of vitro culturing of meat would also facilitate the design and produc- meat when using for instance cyanobacteria-produced biomass as a tion of novel products. For instance, stem cells from probably every nutrient source might reduce energy consumption and land usage mammalian source or blends of cell sources can be used as a basis by 99%, water usage by 90% and energy consumption by 40%. If real- for hitherto unimaginable meats. In addition, the biochemical compo- ized, these reductions lead to a large reduction in GHG emission. sition of meat might be changed to make it a healthier or specialized Another motivation for livestock alternatives is the concern about diet product, for instance by increasing the content of poly- animal welfare. Public debate on animal welfare surfaces on a regular unsaturated fatty acids through changes in culture conditions. basis. As shown by Tonsor and Olynk (2011), non-vegetarians decrease consumption of meat proportional with exposure to aware- 4. Meat alternatives ness campaigns of animal welfare through public