Lee's Multi-differential Agar (LMDA) Medium

The main types of wort and beer spoilage bacteria include: Flavobacterium, Enterobacter, Escherichia, Lactobacillus, Pediococcus, Acetobacter, Acetomonas, and Zymomonas . Wild yeast strains come in two groups: Saccharomyces and Non-Saccharomyces. Both bacteria and wild yeast can cause turbidity, haze, slime formation, over-attenuation, souring, and off flavours in the product. LMDA Medium is used for bacteria and yeast detection / enumeration. Colonies of acid producing bacteria will be easily identified by the development of a clear zone around them because of their ability to dissolve calcium carbonate present in LMDA medium. Furthermore, colonies identification will be facilitated by the characteristic color reactions. Bromocresol green turns yellow to indicate acid production.n Both ingredients work together to differentiate between true acid producers and slight acid producers. LMDA plates can be used aerobically or anaerobically depending on which bacteria the brewer wants to detect. Incubation is done under anaerobic conditions, except when acetic acid bacteria are of major interest, then aerobic incubation is used. An antifungal such cycloheximide can be added to suppress culture yeast growth, therefore making this media selective to bacteria. LMDA Medium mg/l Glucose 14,850.8 Agar 15,000.0 Bromocresol green 22.0 Calcium carbonate 5,000.0 Calcium pantothenate 2,000.0 Citric Acid 1,100.0 Dipotassium phosphate, K2HPO4 742.5 Ferrous sulfate 10.0 Magnesium sulfate anhydrous 144.3 Manganese sulfate 10.0 Monopotassium phosphate, KH2PO4 742.5 Tryptone 20,000.0 Sodium chloride 10.0 Tomato powder 9,701.7 Tween 80 500.0 Yeast extract 14,850.8 84,684.7  ,