Gelrite

Gelrite is the brand name for a low-acyl form of gellan gum, an anionic polysaccharide used as a gelling agent in biology and horticulture. It is produced by fermentation of the bacterium Sphingomonas elodea (formerly Pseudomonas elodea) and is purified for laboratory use. Gelrite forms gels in the presence of cations, particularly divalent ions such as calcium or magnesium, and remains liquid without these ions. Compared with agar, Gelrite can produce clear, firm gels at lower concentrations, and its gel strength and transparency can be tuned by adjusting the polymer concentration and the ionic content of the medium.

In plant tissue culture, Gelrite is commonly used to solidify growth media, offering clear gels and consistent texture that can improve observation of explants and uniformity of culture conditions. Typical application ranges are around 0.4–0.7% (weight/volume), with calcium or other cations provided in the medium to promote gelation. Gelrite can also be used as an alternative gelling agent in some microbial culture systems, though gel properties such as diffusion and colony morphology may differ from those formed with agar.

Gelrite gels are generally stable across a wide pH range and standard culture temperatures. It is intended for laboratory use under appropriate biosafety and handling guidelines and is not meant for ingestion. Preparation involves dispersing Gelrite in water with stirring and heating to dissolve, followed by sterilization and cooling before use in plates or culture vessels, with ionic content adjusted to achieve the desired gel strength.