TOS Propionate Agar – Selective Medium for Bifidobacteria Enumeration in Milk Powder

The TOS Propionate Agar (also known as TOS MUP Medium Base) is a specialized selective medium designed for the enumeration of Bifidobacteria in milk powder and dairy products. The formulation includes sodium propionate and galactooligosaccharide (TOS), which enhance the selective growth of bifidobacteria while inhibiting unwanted flora.

When supplemented with mupirocin lithium salt, the medium becomes TOS MUP Agar, which further improves selectivity by suppressing non-target bacteria. This makes it an excellent tool for use in food microbiology, probiotic quality control, and dairy research laboratories.

Product Information:

• Name: TOS Propionate Agar (TOS MUP Medium Base)

• Form: Dehydrated culture medium (powder)

• Pack Size: 250g per bottle

• Storage: Store at room temperature

• Shelf Life: 3 years

Formula per Liter:

• Trypticase Peptone: 10.0 g

• Yeast Extract: 1.0 g

• KH₂PO₄: 3.0 g

• K₂HPO₄: 4.8 g

• (NH₄)₂SO₄: 3.0 g

• MgSO₄·7H₂O: 0.2 g

• L-cysteine HCl·H₂O: 0.5 g

• Sodium Propionate: 15.0 g

• Galactooligosaccharide (TOS): 10.0 g

• Agar: 15.0 g

• pH: 6.7 ± 0.2 (25℃)

Preparation Instructions:

1. Suspend 62.5 g of medium in 1L distilled or deionized water.

2. Heat to boiling until completely dissolved.

3. Dispense into appropriate containers.

4. Sterilize at 121℃ for 15 minutes or 115℃ for 30 minutes.

5. Shake gently after sterilization to prevent agar sedimentation.

6. For TOS MUP Agar: After cooling to 50–55℃, add 1 vial of mupirocin lithium salt (5mg) per 100ml medium, mix gently, pour plates, allow to solidify.

⚠️ Note: May contain slight insoluble particles, which do not affect performance.