Yeast and Mould Broth

Yeast and Mould Broth is used for the isolation and cultivation of yeasts and moulds.

Composition

Final pH (at 25°C): 6.8±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 20.0 grams in 1000 ml distilled water. Heat if necessary to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.

Principle And Interpretation

Yeast and Mould Broth is based on the formulation described by Wickerham (1,2). Yeast and mould broth is recommended for cultivation of yeast and moulds. Ammonium salts and yeast extract serve as organic and inorganic nitrogen source while dextrose serves as carbon and energy source to yeast and mould. Necessary growth factors are provided by yeast extract. Dibasic and monobasic salts of potassium act as buffering system for the medium. Sodium chloride helps to maintain osmotic balance of the cells. The complete medium is recommended for examination of the microbiological quality of beers in process, pitching yeasts and packaged beers.

Quality Control

Appearance: Cream to yellow homogeneous free flowing powder

Colour and Clarity of prepared medium: Light amber coloured clear to slightly opalescent solution

Reaction: Reaction of 2.0% w/v aqueous solution at 25°C. pH: 6.8±0.2

pH: 6.60-7.00

Cultural Response

Cultural characteristics observed after an incubation at 25-30°C for 40-72 hours.

Cultural Response

Key :*- Formerly known as Aspergillus niger

Storage and Shelf Life

Store below 30°C in tightly closed container and prepared medium at 2-8 °C. Use before expiry date on label.

Reference

1. Wickerham L.J. (1951) U.S. Dept. Agric. Tech. Bull. No 1029, 1-19.
2. Wickerham L.J. and Rettger L.F (1939) J. Tropical Med. Hyg. 42. 174-179.