Low Acyl Gellan Gum is a bacterial polysaccharide produced by Sphingomonas elodea. It dissolves in hot water and forms transparent, firm, and brittle gels upon cooling in the presence of cations. The low acyl (deacylated) form is optimized for rigidity and optical clarity — qualities that make it a preferred gelling agent in plant tissue culture, microbiology and laboratory research.
Key technical notes
Forms firm gels at low concentrations (typically 0.2–0.5% w/v depending on ions and target firmness).
Requires divalent cations (e.g., Ca²⁺, Mg²⁺) to achieve maximal gel strength.
High transparency and thermal stability after autoclaving — suitable for observation of roots and small organs in vitro.
Chemical overview
Structure
Repeating tetrasaccharide units (glucose, glucuronic acid, rhamnose).
Solubility
Soluble in hot water; gelling on cooling with cations.
Typical use concentration
0.2–0.5% (w/v) for plant tissue culture gels — species and protocol dependent.
Practical advantages
Excellent optical clarity for observation.
Consistent batch-to-batch reproducibility when high-purity grades are used.
Lower impurities and reduced microbial load vs some agar grades.
Chemical Properties & Gel Formation
Gelation is a cation-mediated process. Ion type and concentration, polymer concentration, and thermal history determine final gel strength and texture.
Controlling factors
Gellan concentration: increasing concentration raises gel strength and decreases brittleness.
Divalent cations: Ca²⁺ and Mg²⁺ increase gel network crosslinking; monovalent cations (e.g., K⁺, Na⁺) have weaker effects.
pH: generally compatible with neutral pH; extremes can alter gel properties.
Temperature profile: dissolve in near-boiling water and cool steadily; avoid sudden cooling that traps bubbles.
Media example (basic)
Basic plant tissue culture gel (example)
- Distilled water: 1 L
- MS basal salts (or medium of choice): as per protocol
- Sucrose: 20 g
- Low Acyl Gellan Gum (E418): 2.5 g (0.25% w/v) — adjust 1.5–5 g depending on firmness needed
- Calcium source: 50–100 mg/L CaCl2 (adjust according to protocol)
Method:
1. Dissolve salts and sucrose in distilled water.
2. Slowly add gellan gum with vigorous stirring to avoid clumps.
3. Adjust pH if required (typically pH 5.6–5.8).
4. Distribute into vessels and autoclave (121°C, 15–20 min).
5. Pour plates/tubes when the medium is 45–60°C to avoid condensation.
Applications in Plant Tissue Culture
Low Acyl Gellan Gum is used for solid media supporting micropropagation, callus culture, root/shoot assays, and germination tests. Common advantages include:
Superior transparency for observation of root systems and embryogenesis.
Uniform texture giving reproducible mechanical support for explants.
Lower contamination risk associated with high-purity laboratory grades.
Typical use cases
Orchid seed germination and symbiotic culture
Micropropagation of ornamental plants and woody species
Research assays where optical clarity and reproducibility are essential
Laboratory Best Practices
Laboratory checklist
Use analytical balances and distilled/deionized water for media prep.
Pre-dissolve salts before adding gellan to avoid clumping.
Autoclave media using validated cycles; avoid excessive sterilization time.
Control cation levels precisely when reproducing gel strength across batches.
Pour plates at recommended temperatures and allow to set on level surfaces to avoid uneven gels and condensation.
Storage & handling
Store dry powder in a cool, dry place in sealed containers.
Prepared gels can be stored at 4°C for short periods; monitor for contamination.
Label lots and record supplier/lot numbers for traceability.
FAQ
Can Low Acyl Gellan Gum fully replace agar?
In most protocols, yes — provided the gellan concentration and ion composition are adjusted to match the mechanical and diffusion properties originally supplied by agar.
Are Gelrite® and Phytagel® chemically different?
No. Both are Low Acyl Gellan Gum. Differences usually come from purity, QC testing, and supplier documentation.
Which cations are used to control gel strength?
Calcium (Ca²⁺) and magnesium (Mg²⁺) are commonly used; potassium (K⁺) and sodium (Na⁺) have weaker effects. Use careful titration when altering recipes.
Any tips to avoid weak gels after autoclaving?
Ensure correct polymer concentration and avoid over-dilution; verify autoclave cycles and avoid overheating or extended sterilization beyond recommended cycles.