Initially protoplast (in Greek: proton = first and platho = mould) referred to the first organized body of a species this meaning is similar to the non-biological definition, the first from from which all subsequent forms are derived.

Subsequently it has several biological definitions:

• A protoplast is a plant, bacterial or fungal cell that has had its cell wall completely or partially removed using either mechanical or enzymatic means. Generally this is accomplished with cell wall degrading enzymes.In this case there are two types genereally recognized:
  • Protoplasts - Have their cell wall entirely removed
  • Sphaeroplasts - Have their cell wall only partially removed

• More generally a protoplast refers to that unit of biology which is composed of a cells nucleus and the surrounding protoplasmic materials.

Enzymes for the preparation of protoplasts

Cell wall are made from a varietly of polysaccharides, protoplasts can be made by degrading cell walls with a mixture of the appropriate polysaccharide degrading enzymes.

Following the digestion of the cell wall the protoplast is very sensitive to osmotic stress, and must be stored in an isotonic solution to prevent rupture.

Uses for protoplasts

Protoplast can be used to study membrane biology, including the uptake or macromolecules and viruses.

Protoplasts are widely used in for DNA transformation for making genetically modified organisms or for studying temporal gene expression. Protoplasts may also be used in plant tissue culture to regenerate whole plants.

Protoplasts may also be used for plant breeding, using a technique called protoplast fusion. Protoplasts from different species are forced to fuse in an electric field or in a solution of polyethylene glycol. This technique may be used to generate hybrids in tissue culture.