Yeasts and moulds · Wild yeast detection
Lysine Medium – detection of wild yeasts in brewing
Lysine Medium is a selective medium for detecting wild yeasts in breweries, in pitching yeast and in yeast propagation. Culture yeasts of the genus Saccharomyces cannot use L-lysine as their only nitrogen source, while many wild yeasts such as Pichia, Candida and Brettanomyces can.
- Detects wild (non-Saccharomyces) yeasts
- Culture yeasts do not grow on lysine
- For breweries, wineries and yeast propagation
How Lysine Medium works
The medium contains glucose, vitamins and mineral salts, with L-lysine as the only source of nitrogen. Brewing and baking strains of Saccharomyces cannot assimilate lysine and do not form colonies, so colonies that appear after incubation show contamination with wild yeasts.
Typical colony appearance
| Organism | Colonies |
| Wild yeasts (e.g. Pichia, Candida) | Colonies |
| Saccharomyces cerevisiae (culture yeast) | No growth |
Applications and practical notes
Media for brewing, wine and fermentation microbiology are used to monitor culture yeasts and detect wild yeasts and contaminating bacteria. Typical applications include:
- Monitoring of culture yeasts in breweries and wineries
- Detection of wild yeasts and contaminating bacteria
- Bakery and fermentation starters
- Beverage quality control
Working with Lysine Medium: Wash the yeast sample in sterile water or saline before plating, because nitrogen carried over from wort or beer can let culture yeast form small colonies.
Good practice with dehydrated media: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About yeast and mould methods: in the food chain, yeasts and moulds are counted by spread plating on DRBC Agar for products with a water activity above 0.95 according to ISO 21527-1, and on DG18 Agar for drier products according to ISO 21527-2. The FDA BAM Chapter 18 describes similar plate count methods. In pharmaceutical microbiology, the total yeast and mould count (TYMC) and the test for Candida albicans use Sabouraud media according to EP 2.6.12 / 2.6.13 and USP <61> / <62>. COLO.Science offers counting media, identification media, supplements and reference strains for every step.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Lysine Medium is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Lysine Medium, please send us a request. With every delivery of Lysine Medium you receive the lot number and expiry date, and on request we send the available documentation for Lysine Medium.
Where Lysine Medium fits in yeast and mould testing
- Food and feed counts – DRBC Agar for aw > 0.95 (ISO 21527-1) and DG18 Agar for aw ≤ 0.95 (ISO 21527-2); alternatives: Rose Bengal Chloramphenicol, PDA with chloramphenicol, YGC for dairy products
- Pharmaceutical products – Sabouraud Dextrose Agar and Broth for TYMC and the Candida albicans test (EP 2.6.12 / 2.6.13, USP <61> / <62>)
- Cultivation and identification – PDA, Malt Extract and Czapek-Dox Agar for moulds; Corn Meal, chromogenic Candida and BIGGY Agar, Yeast Nitrogen Base for yeasts
- Fermentation and QC – WL Nutrient, Wort Agar and YPD for brewing and culture yeasts; C. albicans and A. brasiliensis reference strains for media testing
See the complete yeast and mould set in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Lysine Medium | PRO7533 | 500 g |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
Sales and technical support
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Quotations and technical support for culture media and microbiology products across our international sales territory. B2B prices are net, excluding VAT.
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Need the complete set for your method?
Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
