CALDO PA GRANULADO (PRESENCE ABSENCE BROTH) SEG US-EPA MERCK
RENDIMENTO 91,5G/L P/ PRESENÇA/AUSENCIA
Embalagem 500g.


The culture medium conforms with the recommendations of standard methods (US-EPA) for the examination of water.

Mode of Action
Peptones and meat extract give the nutrients and trace elements required for growth whereas the phosphate buffer and sodium chloride provide a good buffering capacity and the osmotic equilibrium.
Lactose-fermenting organisms form acid which is identified by the pH indicator bromocresol purple as a colour change from purple to yellow.
The selective component of the culture medium is sodium lauryl sulphate which largely inhibits the undesired accompanying flora - with the exception of the coliforms.

Typical Composition (g/litre): (single strength)
Meat extract 3.0;
peptones 5.0;
lactose 7.46;
tryptose 9.83;
dipotassium hydrogenphosphate 1.35;
potassium dihydrogenphosphate 1.35;
sodium chloride 2.46;
sodium lauryl sulphate 0.05;
bromocresol purple 0.0085.

Preparation
For the preparation of the triple strength concentrated broth, completely dissolve 91.5 g in 1 litre of demin water. Fill 50 ml quantities in 250 ml milk dilution bottles with screw caps and autoclave for 12 min. at 121 °C. Allow broth to cool to room temperature.
The pH of the single-strength broth: 6.8 ± 0.2 at 25 °C.
The prepared medium is clear to slightly opalescent and purplered.