A chemically defined medium is entirely free of animal-derived components (including microbial derived components such as yeast extract) and represents the purest and most consistent cell culture environment. By definition chemically defined media cannot contain either fetal bovine serum, bovine serum albumin, or human serum albumin as these products are derived from bovine or human sources and contain complex mixes of albumins and lipids. The term 'chemically defined media' is often misused in the literature to refer to serum albumin-containing media. Il siero animale o l'albumina viene aggiunto di routine ai terreni di coltura come fonte di nutrienti e altri fattori non definiti, nonostante gli svantaggi tecnici della sua inclusione e il suo costo elevato. Gli svantaggi tecnici dell'uso del siero includono la natura indefinita del siero, la variabilità da lotto a lotto nella composizione e il rischio di contaminazione. Ci sono crescenti preoccupazioni per la sofferenza degli animali inflitta durante la raccolta del siero che aggiungono un imperativo etico per abbandonare l'uso del siero quando possibile. Chemically defined media differ from serum-free media in that bovine serum albumin or human serum albumin with either a chemically defined recombinant version (which lacks the albumin associated lipids) or synthetic chemical such as the polymer polyvinyl alcohol which can reproduce some of the functions of serums.

On the other hand undefined media has some complex ingredients, such as yeast extract or casein hydrolysate, which consist of a mixture of many, many chemical species in unknown proportions. Undefined media are sometimes chosen based on price and sometimes by necessity - some microorganisms have never been cultured on defined media.A defined medium (also known as chemically defined medium or synthetic medium) is a medium in which all the chemicals used are known, no yeast, animal, or plant tissue is present. A chemically defined medium is a growth medium suitable for the culture of microbes or animal cells (including human) of which all of the chemical components are known. Il termine medium chimicamente definito è stato definito da Jayme e Smith come una formulazione di base che può anche essere priva di proteine ed è composta esclusivamente da costituenti biochimicamente definiti a basso peso molecolare.

Fonte dell'immagine:- Google

L'immagine mostra :- media indefiniti

The following are the differences between synthetic media and complex media:-

1. In a synthetic media, the exact chemical composition is known while it may not be so clearly known in case of a complex media.
2. Synthetic media usually contains peptone water medium while complex media usually contains materials of biological origin such as blood or milk, peptone yeast extract and beef extract.
3. Due to its composition, complex media provides a full range of growth factors while synthetic media provides only limited growth factors.
4. Synthetic media are usually used for the cultivation of autotrophs while complex media is widely used for the cultivation of heterotrophic microorganisms.