What is Solidifying Agent and Its Use in Tissue Culture?
15 Dec 2021

What is Solidifying Agent and Its Use in Tissue Culture?

Anjali Singh, MS

As a content and community manager, I leverage my expertise in plant biotechnology, passion for tissue culture, and writing skills to create compelling articles, simplifying intricate scientific concepts, and address your inquiries. As a dedicated science communicator, I strive to spark curiosity and foster a love for science in my audience.

Anjali Singh, MS
Table of Contents

Overview of Solidifying Agent

Growing plants in laboratory conditions require a suitable medium, which can provide all essential minerals and nutrients for the growth and development of plants. Several culture medium are available based on different requirements of different species of plants, including MS (Murashige and Skoog) medium, Linsmaier and Skoog (LS) medium, Gamborg (B5) medium, Nitsch and Nitsch (NN) medium, and White’s Medium.

But, medium alone can’t provide a firm ground for the plants to grow. And, in this case, solidifying agents play the role. They provide a semi-solid surface for the plants to grow and develop. So, solidifying agents can be defined as substances that solidify and provide a ground for organisms to breathe and grow.

In plant tissue culture, this role is played by agar and gellan gum. The type of solidifying agent can influence the growth of tissues in the culture based on their purity and properties. Even the cost of the solidifying agents is an essential factor to look to when it comes to research or production operations.

In this article, we will cover everything on what agar and gellan gum are and how they are added to the media. Further, it will also cover how the concentration of these agents is an essential factor in media preparation, fine differences between agar and gellan gum, and which one is more favorable.

Get 15% off gellan gum by making your purchase from the PCT store. Check out all its other offers here!

What is Agar?

It’s a jelly-like substance obtained from the cell wall of some species of red algae (Rhodophytes), specifically Gracilaria and Gelidium. Chemically, It consists of two components: agarose, a linear polysaccharide (make 70% of the compound); and agaropectin, a mixture of smaller molecules.

Agar solidifies at about 32–40 °C (305–313 K, 90–104 °F) but melting at 85 °C (358 K, 185 °F). Further, it should also be noted that the solidification of agar is pH-dependent. It solidifies in the pH range of 5.4-5.7. And, for this purpose, 0.1M potassium hydroxide is used to increase and the pH to its optimal level.

Agar is usually added to media at a concentration of 6-8 g/L (0.5%-10%). It is stable for an extended period and does not bind excessively with media components. Agar has several applications in and out of the labs. Some of which are:

  • The research-grade agar is used in labs to support the growth and development of organisms. In microbiology, it’s also used to measure the movement of microbes.
  • The food-grade agar is used to prepare certain food items including dessert, vegetable aspics, or cake.
  • It’s used as an impression in dentistry.
  • It acts as a medium to embed tissue specimens for histopathology (it’s the study/microscopic examination of tissues to understand the manifestation of diseases) processing/studies.
  • For electrochemistry, it is used as salt bridges or gel plugs.

Get 15% off gellan gum by making your purchase from the PCT store. Check out all its other offers here!

What is Gellan Gum?

Gellan gum is a jelly-like substance and chemically it’s a naturally derived, water-soluble, anionic polysaccharide, obtained from the bacterium Sphingomonas elodea. From a structural standpoint, it is a polymer of a tetrasaccharide consisting of two residues of D-glucose and one residue of each of L-rhamnose and D-glucuronic acid.


Gellan gum is of two types based on the number of acetate groups attached to the polymer: low acyl and high acyl. Gellan gums with low acyls form firm, non-elastic, brittle gels, whereas those with high acyls form soft, elastic gels.

Gellan gums are used as an alternative to agar in microbiology and plant biology labs. It is added to the media in a concentration range of 2-4 g/L. Its transparency allows researchers to observe root growth, perform microscopic analysis of tissue or cells, and identify contamination at an early stage.

Furthermore, in many countries, it’s used in the preparation of food, non-food, cosmetic, and pharmaceutical products. It’s used to manufacture vegan varieties of gum candies, as well as in ice cream and sorbet recipes.

Get 15% off gellan gum by making your purchase from the PCT store. Check out all its other offers here!

How Agar and Gellan Gum Are Different?

Some differences in agar and gellan gum are:

  • Gellan gum is clearer than agar.
  • Gellan gum is only required in half the quantity of agar to give the same strength as provided by agar.
  • Gellan gum is more rigid and brittle than agar when compared to preparing a mixture of the same concentration.
  • Gellan gum does not contain any impurities that hinder the growth of tissues, compared to agar.
  • In contrast to agar, gellan gum can withstand 120°C, which makes it suitable to culture thermophilic microorganisms.
  • Compared to agar, gellan gum takes more preparation time.
  • In MS media, adding 0.2% gellan gum can substantially alter elements like Na (sodium), Al (aluminium), Sr (strontium), Ti (titanium), Cu (copper), and V (vanadium). Alternatively, agar merely disturbs the composition of sulfur and silica in the media.

Get 15% off gellan gum by making your purchase from the PCT store. Check out all its other offers here!

How Plant Cell Technology Can Help You to Procure Best Quality Lab-grade Solidifying Agent?

Plant Cell Technology is helping tissue culturists procure all their requirements from one place at a reasonable price. Its one-stop store contains everything from culture media to lab-grade agar and gellan gum. It also provides the most efficient solution for contamination prevention, that is plant preservative mixture (PPM), its trademark product.

Currently, you can purchase gellan gum at 15% off. Check out here now!

The company also provides the world’s most simplified temporary immersion bioreactor–Biocoupler(™). It has consultation services as well to help you with all the stages of your culturing process.

Want to learn more about PCT and its products, visit its store to explore more! And, contact us for any of your concerns.

Happy Culturing!

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