Starch Agar was formulated by Vedder (1) in 1915, for the cultivation of Neisseria. Since then, other media have been developed that are superior to Starch Agar for the isolation of Neisseria species, including enriched GC Medium Base. Starch Agar (M107) is recommended for the detection of starch hydrolyzing microorganisms from foods (2) and clinical samples (3). Although the medium was originally formulated to perform the test for the identification of Bacillus cereus, it can be applied to any kind of microorganism where starch hydrolysis activity is required to be analyzed.
Peptic digest of animal tissue, yeast extract and beef extract provide nitrogenous compounds, carbon, sulphur, trace elements etc. to the microorganisms. Sodium chloride maintains osmotic equilibrium. Flood the surface of 48 hours old culture on Starch Agar with Grams Iodine (S013). Starch hydrolysis is seen as a colourless zone surrounding the colonies. A blue or purple zone indicates that starch is not hydrolyzed. Size of the clear zone is directly proportional to the starch hydrolyzing activity of the strain under study.
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.
References:
1. Vedder E. B., 1915, J. Infect. Dis., 16:385.
2. Harrigan W. and McCance M., 1976, Laboratory Methods in Food and Dairy Microbiology, Academic Press Inc. (London) Ltd.>br /> 3. Murray P. R., Baron J. H., Pfaller M. A., Jorgensen J. H. and Yolken R. H., (Eds.), 2003, Manual of Clinical Microbiology, 8th Ed., American Society for Microbiology, Washington, D.C.