Ready-to-use media
WL Nutrient Modified Agar
Solid culture medium for the selective enumeration of bacterial contaminants in yeast-fermenting industrial processing.
- Cat. No.
- LC-4666
- Category
- Ready-to-use media
- Format
- 10 x 100 mL flasks
- Storage
- 8 to 25 °C
- Minimum guaranteed shelf life
- 6 months
- Minimum order
- 10 packs
The formulation of this medium corresponds to WL Nutrient Agar with the addition of cycloheximide, which inhibits the growth of yeasts and thus facilitates the growth of contaminating bacteria in fermentation processes.
Key features
Applications
Detection, growth and selective enumeration of microorganisms of the brewing industry.
Industry
Alcoholic beverages.
Presentation
10 prepared bottles, 125 mL, with 100 ± 3 mL.
Packaging
1 box with 10 bottles 125 mL. Metal non-injectable cap.
Description and technique
Description
For the differentiation of brewer's yeasts (wild type), it is better to use the medium with the pH adjusted to 6.5, which makes it possible to differentiate them both by colonial morphology and by the different shades of color they acquire.
Technique
Melt the medium contained in the bottles in a water bath (100 °C) or in a microwave oven, avoiding overheating, before pouring into Petri dishes (90 mm ø) when cooled to room temperature.
Once solidified on a flat surface, spread the plates by streaking methodology or by spiral method.
Plates prepared with both media are generally incubated at 25 °C if brewing materials are being studied, and at 30 °C for bakers' yeast and alcohol mash samples. Incubation may be continued for 4-7 days or ten days to two weeks, depending upon the microbiota present. Counts can be made at intervals during the incubation period.
Presentation
| Presentation | 10 prepared bottles, 125 mL |
|---|---|
| Filling | 100 ± 3 mL |
| Packaging | 1 box with 10 bottles 125 mL. Metal non-injectable cap. |
Composition
| Ingredient | g/L |
|---|---|
| Yeast extract | 4.0000 |
| Tryptone | 5.0000 |
| Dextrose | 50.0000 |
| Monopotassium phosphate | 0.5500 |
| Magnesium sulfate | 0.1250 |
| Calcium chloride | 0.1250 |
| Potassium chloride | 0.4250 |
| Iron(III) chloride | 0.0025 |
| Manganese sulfate | 0.0025 |
| Bromocresol green | 0.0220 |
| Cycloheximide | 0.0040 |
| Agar | 15.0000 |
Quality control
Physical/chemical control
| Color | Slightly green |
|---|---|
| pH | 6.5 ± 0.2 at 25 °C |
Microbiological control
Melt medium - pour plates - inoculation: practical range 100 ± 20 CFU; min. 50 CFU (productivity) / 10⁴-10⁶ (selectivity).
Aerobiosis. Incubation at 20-25 °C. Reading at 2-3 days up to 5 days.
| Microorganism | Growth |
|---|---|
| S. cerevisiaeATCC 9763, WDCM 00058 | Inhibited |
| Escherichia coliATCC 25922, WDCM 00013 | Good - green colonies |
Sterility control
Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.
Check at 7 days after incubation in same conditions.
Bibliography
- ATLAS, R.M., L.C. PARKS (1993) Handbook of Microbiological Media. CRC Press, Inc. London.
- GRAY, P.P. (1951) Some Advances in Microbiological control for beer quality. Wallerstein Lab. Com. 14:169.
- GREEN, S.R. & GRAY, P.P. (1950) Procedure for bacteriological investigation in brewing. Paper read at Am. Soc. of Brewing Chemists Meeting. Wallerstein Lab. Com. 12:43.
- GREEN, S.R. & GRAY, P.P. (1950) A differential procedure applicable to bacteriological investigation in brewing. Wallerstein Lab. Comm. 13:357.
- GREEN, S.R. & GRAY, P.P. (1951) A differential procedure for bacteriological studies useful in the fermentation industries. Wallerstein Lab. Com. 14:289.
- HALL, J.F. (1971) J. Inst. Brewing 77. 513-516.
- ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
- MBAA (2002) The Practical Brewer. 3rd ed. Master Brewers Association of Americas. St. Paul. Minnesota.
What you receive
The product
Shipped under controlled temperature when the product requires it.
Lot certificate
Every lot comes with its certificate.
Tracked shipment
Follow your shipment live, from our warehouse to your lab.
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Frequently asked questions
Can I ask for formats other than those listed?
Yes: custom formats and OEM packs are available on request. Tell us the quantities you need.
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