Malt Extract Agar

Malt Extract Agar

EMD Cat. No. 1.05398.0100/0500

100 g, 500 g

For the detection, isolation and enumeration of fungi, particularly yeasts and molds, in various materials and for the cultivation of test strains for the microbiological vitamin assays.

Additives

Mode of Action	Preparation
Experimental Procedure and Evaluation	Quality Control
Typical Composition (g/liter)	Literature
Picture/Image

Mode of Action
If fungal counts are to be performed, the pH value of the culture medium should be adjusted to 3.5 to suppress the growth of the bacterial flora.
REISS (1972) recommends a modified malt extract agar for the selective cultivation of Aspergillus flavus. According to RAPP (1974), addition of certain indicator dyes to malt extract agar allows differentiation of yeast and bacterial colonies.

Malt Extract Broth:
Typical Composition (g/liter)
Malt extract 17.0.

Preparation
Suspend 17.0 g/liter, dispense into suitable containers, autoclave under mild conditions (10 min at 115 °C).
pH: 4.8 ± 0.2 at 25 °C.
The prepared broth is clear and yellow.

Experimental Procedure and Evaluation
Depend on the purpose for which the media are used.
Incubation: 7 days at 28 °C aerobically (yeasts: 3 days)

Quality control of Malt Extract Agar

Test strains	Growth
Geotrichum candidum	good
Penicillium spp.	good
Aspergillus niger	good
Trichophyton ajelloi	fair / good

Quality control of Malt Extract Agar (spiral plating method)

Test strains	Inoculum (cfu/ml)	Recovery rate
Candida albicans ATCC 10231	10³-10⁵	70 %
Saccharomyces cerevisiae ATCC 9763	10³-10⁵	70 %
Saccharomyces cerevisiae ATCC 9080	10³-10⁵	70 %
Rhodotorula mucilaginosa DSM 70403	10³-10⁵	70 %

Quality control of Malt Extract Broth

Test strains	Growth
Candida albicans ATCC 10231	good / very good
Saccharomyces cerevisiae ATCC 9763	good / very good
Saccharomyces cerevisiae ATCC 9080	fair / good
Geotrichum candidum DSM 1240	good / very good
Rhodotorula mucilaginosa DSM 70403	fair / very good
Penicillium spp.	good / very good
Aspergillus niger	good / very good
Trichophyton ajelloi	good / very good

Malt Extract Agar:
Typical Composition (g/liter)
Malt extract 30.0; peptone from soymeal 3.0; agar-agar 15.0:

Preparation
Suspend 48 g/liter, autoclave under mild conditions (10 min at 121 °C).
Do not overheat.
pH: 5.6 ± 0.2 at 25 °C.
The plates are clear and yellowish-brown.
If the pH has to be lowered, liquefy the sterile culture medium and adjust the pH with filter-sterilized 10 % lactic acid solution or 5 % tartaric acid solution. Avoid subsequent heating.

Literature

RAPP, M.: Indikatorzusätze zur Keimdifferenzierung auf Würze- und Malzextrakt-Agar. - Milchwiss., 29; 341-344 (1974)
REISS, J.: Ein selektives Kulturmedium für den Nachweis von Aspergillus flavus in verschimmeltem Brot. - Zbl. Bakt. Hyg. I. Abt. Orig. A 220; 564-566

Malt Extract Agar - Saccharomyces cerevisiae