BG11 Broth

BG11 Broth

Chemically Defined Medium for Axenic Cultivation of Freshwater Cyanobacteria

Catalog Number: AS-1137

Overview

BG11 Broth is a chemically defined liquid culture medium universally accepted for the axenic cultivation of freshwater cyanobacteria and selected unicellular green algae. Originally formulated by Stanier and colleagues and subsequently standardised in international methods, BG11 remains the gold-standard reference medium in phycology, biotechnology, and aquatic ecology.

The medium is optimised for photoautotrophic growth, using nitrate as the sole nitrogen source, no combined organic carbon, and carefully balanced trace metals. It is widely used for cultivation of genera such as Synechococcus, Anabaena, Nostoc, Microcystis, and Spirulina, as well as for cyanobacterial genomics, physiology, and toxicity testing.

Key Features & Benefits

• Chemically defined formulation for reproducible results

• Nitrate as sole nitrogen source (ideal for non-N₂-fixing strains)

• No organic carbon; strictly photoautotrophic growth

• Optimised trace metals for cyanobacterial metabolism

• Transparent medium for photosynthesis and light-response studies

Typical Applications

Phycology & Algal Research

• Axenic culture of freshwater cyanobacteria

• Growth of reference strains such as Synechococcus elongatus PCC 7942 and Anabaena PCC 7120

Biotechnology & Applied Research

• Production of cyanobacterial biomass

• Pigment and bioactive compound studies

Environmental & Ecotoxicology Studies

• Toxicity testing using cyanobacteria (e.g. OECD 201)

• Ecophysiology and nutrient-limitation experiments

Genomics & Physiology

• Reference medium for cyanobacterial genetics and metabolism

Principle of the Medium

BG11 Broth provides all essential inorganic nutrients required for cyanobacterial growth while excluding organic carbon sources. Growth is driven by photosynthesis, with nitrate supplying nitrogen and a low-phosphate background minimising precipitation and metabolic interference. A defined trace-metal system (A5) supports enzymatic and photosynthetic processes while maintaining clarity for optical measurements.

Composition (Typical – per litre)

Macronutrients

• Sodium nitrate (NaNO₃): 1.5 g

• Dipotassium phosphate trihydrate (K₂HPO₄·3H₂O): 0.04 g

• Magnesium sulfate heptahydrate (MgSO₄·7H₂O): 0.075 g

• Calcium chloride dihydrate (CaCl₂·2H₂O): 0.036 g

• Sodium carbonate (Na₂CO₃): 0.02 g

Chelators & Iron

• Citric acid: 0.006 g

• Ammonium ferric citrate (green): 0.006 g

• EDTA disodium salt: 0.001 g

Trace Metal Mix A5

• Added at 1.0 mL per litre

Final pH after sterilisation: 7.4–7.6

Trace Metal Mix A5 (Typical Composition – per litre of mix)

• Boric acid (H₃BO₃): 2.86 g

• Manganese chloride tetrahydrate (MnCl₂·4H₂O): 1.81 g

• Zinc sulfate heptahydrate (ZnSO₄·7H₂O): 0.222 g

• Sodium molybdate dihydrate (Na₂MoO₄·2H₂O): 0.39 g

• Copper sulfate pentahydrate (CuSO₄·5H₂O): 0.079 g

• Cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O): 0.0494 g

Preparation (Typical)

• Dissolve macronutrients and sodium carbonate in approximately 900 mL distilled water

• Add 1 mL of trace metal mix A5

• Adjust volume to 1 L and pH to 7.5

• Dispense into suitable culture vessels

• Sterilise by autoclaving at 121 °C for 15 minutes
  (Filter sterilisation may be used for heat-sensitive strains)

Variants & Modifications

• BG11-N (Nitrogen-free): Omit NaNO₃ for N₂-fixing strains

• High-density cultures: Supplement with 2–5 mM NaHCO₃

Incubation Conditions

• Temperature: 25–30 °C

• Illumination: 20–100 µmol photons m⁻² s⁻¹, continuous light

• Agitation: Gentle shaking or aeration with air or air/CO₂

Storage & Stability

Prepared medium

• Store at 2–8 °C, protected from light

• Use within 3 months under recommended conditions

Intended Use

For laboratory research and environmental studies only.

Not for diagnostic, therapeutic, food, or agricultural use.

Quality & References

• Reference medium described by Stanier et al. and Rippka et al.

• Widely cited in ISO 10712, OECD 201, and phycology literature

• Manufactured under controlled conditions for batch consistency

• Certificate of Analysis (COA) available

• Safety Data Sheet (SDS) available upon request