Tamiya medium

A5 + Co trace element solution

per 100 mL of solution · usage rate 1 mL per 1 L of medium (sufficient for 100 L) · storage at 4 °C in dark glass, 12 months

Dissolve KNO₃ → MgSO₄·7H₂O → KH₂PO₄ → FeSO₄·7H₂O (from a freshly prepared acidified solution at 3 g/L, take 1 mL) → 1 mL of A5 → make up to 1000 mL → pH 6.0–6.8.

• The medium is designed for cultivation with sparging of air enriched with 1–5 % CO₂. Without a CO₂ supply the high nitrogen dose (49.5 mM) cannot be used and simply remains in the medium.
• The half-strength version ("½ Tamiya") is used for maintaining cultures in tubes — the full formulation is excessive and causes osmotic stress at small volumes.
• Calcium is absent from the formulation: for prolonged subculturing add CaCl₂·2H₂O at 0.025 g/L.
• Dissolve the salts one at a time, in the order given; H₃BO₃ dissolves slowly — warming to 40 °C is permissible. Cobalt is added from a primary stock solution: a weighed amount of 4.94 mg cannot be measured on an ordinary balance. Primary Co stock solution: 494 mg Co(NO₃)₂·6H₂O in 100 mL of water, take 1 mL. Without cobalt the solution is simply called "A5". The appearance of a precipitate or turbidity indicates that the solution is no longer usable.