The Ultimate Cultivated Meat Glossary

The Ultimate Cultivated Meat Glossary

• Cultivated meat has a specific scientific language, which is crucial for operating within the area but may be challenging at first.
• Multus created the Cultivated Meat Glossary for anyone to accustom themselves to the terminology.
• This helps take down communication barriers to foster collaboration between the diverse skillsets we need to drive innovation and scale-up.
• This glossary covers key language around cells, media and media metrics. 

Cultivated meat has a growing audience - headlines are breaking into the mainstream, and the industry is beginning to attract non-scientists who want to work on food sustainability.

Like any field, cultivated meat has its language, which can be confusing at best, even alienating and restrictive at times, as it can hinder communication. For example, in a 2020 study from The Ohio State University, authors found that the existence of scientific jargon in text resulted in readers becoming discouraged. One reason was that reading language that was specialised made study participants feel like “they don’t belong”. However, having a common language within the industry is extremely important as it can foster collaboration between the players and drive major developments. 

To help newcomers to the cultivated meat industry who have yet to become familiar with the jargon, we decided to spare them the time on research, and we've gathered the key terms in one place. 

Glossary of terms used to describe cells in cultivated meat

(Cell) Type: normally (but not exclusively) used to inquire or distinguish between cells from different species or tissues, e.g. avian vs. bovine, or muscle vs. fat

Undifferentiated: cells that don't yet have a tissue type

Differentiated: cells that have a specific tissue type

Transdifferentiated: cells that have converted from one developed cell type to another

Lineage committed: a cell that has changed from undifferentiated to being on a developmental path towards a specific cell type

Primary: cells taken directly from living tissue (e.g. biopsy material) for growth in vitro

Pluripotent: cells able to develop ("differentiate") into many types (in terms of tissue, not species)

Multipotent: cells able to develop into more than one cell type, but not all (they're more limited than pluripotent cells); adult stem cells and cord blood stem cells are considered multipotent

Totipotent: cells able to develop into any embryonic and adult cell type

Stem: cells are able to develop into many types (i.e. stem cells are pluripotent)

Embryonic stem: cells taken from a blastocyst (the ball of cells that a fertilised egg cell grows into about a week after conception)

Adult stem: undifferentiated multipotent cells, found throughout different tissues in the body after development, that multiply and replenish dying cells and regenerate damaged tissues

Somatic stem: same as "adult stem"

MSC: Mesenchymal stem cells, multipotent cells that can develop many types, including osteoblasts (bone cells), myocytes (muscle cells) and adipocytes (fat cells)

Satellite: a population of muscle-resident stem cells that are essential for efficient tissue repair

Progenitor: descendants of stem cells that have started to differentiate, typically are multipotent rather than pluripotent, and are on the way to further differentiating into specialised cell types

Precursor: a more differentiated cell than a progenitor cell that is typically multipotent and has lost most (but not all) of its stem cell properties; often used to describe the intermediate cell before it becomes fully differentiated

Induced: typically used to describe "induced pluripotent stem cells" (iPSCs), where "induced" means the cells (typically adult stem cells) have been genetically reprogrammed into an embryonic stem (ES) cell-like state through the forced expression of genes needed to maintain the defining properties of ES cells

Immortalised: cells grown from a primary cell culture (which would normally not replicate through cell division indefinitely) which, due to either spontaneous or targeted mutation, can keep undergoing division

Line: typically (although not exclusively) used equivalently to "immortalised", i.e. a "cell line" is a culture of immortalised cells. Broadly, a cell line is a cell culture selected for uniformity from a cell population taken from a homogeneous tissue source.

Adherent: cells that need to be attached to a surface in order to grow (true of most cell types and primary cell cultures), so growth is constrained by available surface area

Suspension-adapted: cells that can grow without attachment to a surface, so growth is constrained by viable cell density

Myocyte: muscle cell

Myoblast: the precursor of a myocyte

Adipocyte: fat cell

Pre-adipocyte: the precursors of an adipocyte

Fibroblast: a cell that creates connective tissue

Bovine: from a cow

Porcine: from a pig

Ovine: from a sheep

Avian: from a bird (galline is specifically from a chicken, although avian is more commonly used)

Piscine: from a fish

Murine: from a mouse (often comes up because mouse cells have historically been used in cell culture research)

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Glossary of terms used to describe media for cultivated meat

Media: a liquid mixture of ingredients, providing cells with a nourishing environment to live in

Culture media: typically used to mean a complete media formulation that combines basal media and a formulation of signalling ingredients, such as serum

Complete media: same as "Culture media"

Growth media: generally the same as "Culture media", although can be specific to "Expansion media" or "Proliferation media"

Expansion media: media used to grow the number of cells, typically aiming for sustained fast growth over multiple cell divisions, with a high density of cells

Proliferation media: same as "Expansion media"

Differentiation media: media that promotes cells to change from one, typically less specialised type, to another, typically more specialised

Starvation media: media depleted in certain ingredients in order to control cell behaviour, often used as part of a differentiation protocol

Basal media: part of a complete growth media formulation, mainly providing the nutrients that cells need: carbohydrates, amino acids, fatty acids, salts and vitamins

Serum: the fluid component of blood, commonly used in traditional cell culture media - as a supplement to basal media - because it contains a complex (undefined) mix of additional nutrients and critically, biologically active molecules that support cell growth

FBS (alternatively FCS): fetal bovine (or calf) serum, the most common type of serum used, sourced from cow fetuses slaughtered with the pregnant mother

Platelet lysate: an alternative to serum as a source of the biologically active molecules that support cell growth; historically sourced mainly from human blood, now being sourced increasingly from cows

Serum-free media: used to describe either a serum-free replacement for FBS or a complete media formulation that doesn't contain any serum

Chemically defined media: a formulation in which all the ingredients are known, often used to indicate that the formulation is serum-free

Animal-component free (ACF) media: a formulation with no animal-sourced ingredients (including sourced from humans) directly included or used in the production process of any included ingredients

Xeno-free: "xeno" means "other" (cf. "xenophobia"), and in media terms, it specifically means free of non-human animal ingredients, so, for example, human platelet lysate is a xeno-free alternative to serum

Media exchange: media in bioreactors typically needs to be exchanged for a fresh formulation because nutrients are depleted while metabolites that limit growth, like lactate and ammonia, accumulate

Conditioned media: media that has had cells growing in it which have released biologically active components that affect the behaviour (e.g. differentiation) of other cells subsequently cultured in the media

Spent media: the residual media after cultured cells have grown or differentiated in it, often analysed during media development for insights into improving the initial formulation (e.g. identifying which nutrients could be added in greater quantity to accelerate cell growth)

Recycled media: media that is re-used, having been removed from cell culture and treated in some way to replenish its nutritional or biological capacity (in order to reduce the total cost and quantity of ingredients for a given amount of biomass produced)

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Glossary of terms used to describe media metrics for cultivated meat

Yield coefficient: the ratio of cell biomass produced to the mass of substrate (media ingredient, e.g. glucose) consumed. This is a common metric in chemistry and biology.

Feed conversion ratio: inverse of yield coefficient (i.e. the ratio of ingredient consumed to biomass produced). This is a common metric in agriculture and is sometimes used to compare cultivated meat with livestock farming.

Mass balance: conversion ratio of inputs to outputs, e.g. media glucose to cell mass, media amino acids to cellular protein, or overall media nutrients to cellular "dry matter". This is used in some cultivated meat life cycle analyses to quantify nutrients required per kg of biomass produced.

Depletion rate: rate at which a particular ingredient is consumed in a media formulation. This is important in media optimisation as metabolism varies between different cell types, so ideal formulations will likely also be different.

Media cost per L:

• Cost of all nutrients (carbohydrates, amino acids, lipids, vitamins, salts), maybe buffers and biologically active components (e.g. proteins) and other ingredients that promote productive cell behaviour (e.g. growth or functionality)
• Conventionally, broken out into the cost per L of basal media and cost per L of supplement (e.g. a serum-free supplement like Multus Proliferum M)
• Cultivated meat companies typically aim for under USD 1 as a target for this, once the supply chain and production systems are at industrial scale; currently, low double-digit USD per L is a good benchmark
• However, cost per L is only half the picture without a metric on L required per kg biomass...

Powder cost per kg: for basal media sourced as powder, cost per kg becomes important as it's the feedstock that's procured for larger scale production processes.

Media cost per kg biomass: ultimately metric this is most important as it fits into the unit economics of meat production.

Media L per kg biomass:

• This metric combines with cost per L to provide the media cost per kg
• The volume of media to produce a quantity of meat depends on several factors including the growth rate and density of cells and the media replacement protocols used in bioreactors
• Typically, cultivated meat producers are aiming for 10-50 L per kg, (noting that based on typical mass balance ratios, the commonly used DMEM/F12 medium would require over 200 L for a kg of biomass...)

Biomass g per media L: the inverse of L / kg, this metric measures the yield per liter and so typically, cultivated meat producers are aiming for 20-100 gm per L of media.

Media L per bioreactor L:

• To maintain optimum levels of components in a media formulation (including low levels of waste products like lactate and ammonia), media is refreshed in the course of a bioreactor batch (or if the bioreactor is continuous flow, the media is constantly refreshed)
• Hence for any given bioreactor size, the volume of media used is a multiple of the bioreactor capacity
• Media exchange protocols can be optimised by working on cells to adjust metabolism, media formulation to influence cell metabolism and protein components to increase stability and reduce the need to refresh for biological activity

Media L per bioreactor L per [day/week/month]): ultimately, process turnover combined with input costs will drive the profile of spend on media. Together with the productivity of the process in terms of biomass per L of bioreactor capacity, this metric becomes important in the financial plan of a cultivated meat production process.

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About Multus:

Having precise, common terminology for cellular agriculture is a crucial part of scaling cultivated meat effectively, affordably and collaboratively.

Media costs block cultivated meat companies from scaling up, and media development is slow and expensive. ​We make it faster and cheaper to get media that scales, so companies can go from lab to market.

Click here to learn more about the challenges for scaling cultivated meat and how they can be solved.

Or here if you think we missed an essential term or you have other ideas for improving our glossary.

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