Cell Ag Glossary: Media

Another jargon-buster for people interested in cultivated meat. This is part 2 of a series of glossaries that make it easier to understand what's going on. Part 1 was on cells.

Cultivated meat?and?cellular agriculture?have a growing audience -?headlines are breaking?into the mainstream and the industry is growing in appeal for non-scientists who?want to work?in sustainability.

Many challenges need to be solved before foods made this way become widely available and easily affordable. Not least, making them taste fantastic with no trade-offs on health and nutrition. Whether technical, regulatory, financial or something else, the challenges typically relate in some way to the core elements that go into making cell-based meat:

• Cells
• A liquid which feeds the cells (called "medium", or "media" more generally)
• A container to hold the liquid and the cells (a "bioreactor")
• Typically, something to give the final product a meat-like texture (some kind of edible "scaffold", often plant-based)

In my last glossary, I covered terms used to describe cells. In this glossary, I cover terms used to describe cell culture media. These are important because cell culture media present multiple challenges for producing cultivated meat.

So, here is my...

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 specialized type to another, typically more specialized

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 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 a 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)

Final notes:

• If you found this useful, please share with others in the comments who you think might also benefit from it
• If you think there are terms missing or badly described, also let me know in the comments
• Here's a helpful guide to ingredients in culture media, created by the Good Food Institute