Diamalt Agar

Composition**

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 17 grams in 100 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. The medium will be turbid but filtration is not necessary. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Fungi including yeasts and filamentous species or moulds are ubiquitously distributed in the environment. The association between fungal densities and organic loading suggests that fungi may be useful indicators of pollution. Fungi have also been found in potable water (1,2) and on the inner surface of distribution system pipes (3). Of the total number of fungal colonies obtained from polluted waters, as many as 50% may be yeast colonies.

Diamalt Agar is used for isolation and identification of yeast from water samples as recommended by APHA (4). Solid media such as Diamalt Agar is used for counting fungal colonies from various samples either directly by using pour plate method or spread plate method or following enrichment. Diamalt Agar is also useful in the purification of yeast isolates and for study of yeast species in various specified tests.

Diamalt provides an acidic environment with necessary nutrients for growth and metabolism of yeasts. Standard procedures for isolation of fungal and yeast cells should be followed (4).

Quality Control

Appearance

Cream to beige homogeneous free flowing powder

Gelling

Firm, comparable with 2.0% agar gel.

Colour and Clarity of prepared medium

Dark amber coloured, clear to slightly opalescent gel forms in Petri plates

Cultural Response

M438: Cultural characteristics observed after an incubation at 30°C for 24-48 hours.

Storage and Shelf Life

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

Reference

1. Nagy L. A. and Olson B. H., 1982, Can. J. Microbiol., 28:667
2. Nimi R. M., Kunth S. and Lundstrom K K., 1982, Appl. Environ. Microbiol., 43:378
3. Nagy L. A. and Olson B. H., 1985, Proc. American Water Works Assoc. Water Quality Technology Conf., pg. 213
4. Clesceri L. S., Greenberg A. E., Eaton A. D., (Eds.), Standard Methods for the Examination of Water and Wastewater, 20th Ed., 1998, Published by APHA-AWWA-WPCF, 9-136