Universal Beer Agar (UBA Medium)

Universal Beer Agar (UBA Medium)

Cat. No. 1.00445.0500
(500 g)

Agar for the detection of beer spoilage microorganisms.

Universal Beer Agar is based on the formulation developed by KOZULIS and PHAGE (1968).


Typical Composition (g/liter)	Quality Control
Preparation	Picture/Image
Experimental Procedure and Evaluation	Literature

Mode of Action
The basal medium is a non-selective agar rich in nutrients that supports the growth and recovery of microorganisms. From a brewer's point of view, only those bacteria and yeasts, which are capable of growing under brewing conditions, are of real significance. The incorporation of beer in the medium adds hop constituents and alcohol which eliminate many airborne contaminants not originating from pitching yeasts, wort or beer, thus minimizing false positive results. Also it stimulates the growth of beer spoilage organisms, such as lactobacilli, pediococci, Acetobacter, Zymomonas spp. and wild yeast strains, which may be found infecting the pitching yeasts, the cooled wort or during fermentation or storage of the finished beer.
For the detection of bacterial contaminants in pitching yeasts, cycloheximide (1 mg/l) may be added.

Typical Composition (g/liter)
Peptonized milk 15.0; yeast extract 10.0; D(+)-glucose 10.0; tomato juice 7.0; dipotassium hydrogen phosphate 0.5; potassium dihydrogen phosphate 0.5; sodium chloride 0.01; iron(II) sulfate 0.01; manganese(II) sulfate 0.01; magnesium sulfate 0.01; agar-agar 12.0
pH 6.3 ± 0.2 at 25°C.

Preparation
Suspend 55 g in 750 ml purified water and heat to boiling until completely dissolved. Add 250 ml beer without degassing to the still hot medium, mix gently. Autoclave at 121°C for 10 min.
The color of the prepared basal medium (w/o beer) is clear and slightly brown.
Store in the refrigerator and protect from daylight. The shelf-life of prepared plates is approx. 1 week and 2 months for the medium dispensed into bottles when stored at +2 to +8°C.

Experimental Procedure
Either direct plating method is used or pour plate method (with serial dilutions) or the membrane filtration technique can be used.

The plates are incubated at 28-30°C for 3 days and examined daily, aerobically to detect Acinetobacter and anaerobically to detect microaerophilic lactobacilli, pediococci, and Zymomonas spp.

Interpretation of Results
Examine plates for growth and select identical and typical colonies, e.g. via Gram staining and catalase test. Gram-negative and catalase-positive reactions are commonly identified as non-beer-spoilage microorganisms.

Quality control

Test strains	Recovery (%)
Lactobacillus brevis ATCC 8287	>70
Lactobacillus lindneri DSMZ 20690	>70
Pediococcus damnosus DSMZ 20291	>70
Saccharomyces cerevisiae ATCC 9763	>70
Acetobacter pasteurianus ATCC 12879	>70
Enterobacter aerogenes ATCC 13048	>70

Additives

EMD Cat. No.	Product	Pack Size
1.11351.0001	Bactident^® Catalase	1 x 30 ml
65092-93	Gram Stain Set	4 x 500ml
13677	Anaerocult^® A	1 x 10

Literature

KOZULIS, J.A. AND PAGE, H.E. A new universal beer agar medium for the enumeration of wort and beer microorganisms. Proc. Am. Brew. Chem 52-58, (1968).

Universal Beer Agar - Lactobacillus fermentum