Thermoacidurans Agar

Intended Use

Thermoacidurans Agar is used for isolating and cultivating Bacillus coagulans (Bacillus thermoacidurans) from foods.

Summary and Explanation

Stern et al.¹ described a medium for isolating B. coagulans (B. thermoacidurans), which causes “flat sour” spoilage in tomato juice and other canned foods. Bacterial growth results in a 0.3-0.5 drop in pH; the ends of the can remain flat. B. coagulans is a soil microorganism that can be found in canned tomato products and dairy products. Conditions favorable to multiplication of the organism can result in spoilage of the food product.²

Thermoacidurans Agar can also be used to isolate mesophilic spore-forming anaerobes (Clostridium spp.) from foods. These microorganisms tolerate high heat, grow in the absence of oxygen and grow over the range of temperatures used in canned and processed foods. They are of primary importance in spoilage of low-acid foods packed in hermetically sealed containers.²

Principles of the Procedure

Thermoacidurans Agar contains peptone to provide the carbon and nitrogen for general growth requirements. Yeast extract supplies B-complex vitamins which stimulate bacterial growth. Dextrose is the carbohydrate source. Agar is the solidifying agent.

User Quality Control

Identity Specifications
Thermoacidurans Agar
Dehydrated Appearance: Light tan, free-flowing, homogeneous.
Solution:                       3.9% solution, soluble in purified water upon
                                   boiling. Solution is light amber, opalescent.
Prepared Appearance:    Light amber, opalescent.
Reaction of 3.9%
Solution at 25°C:           pH 5.0 ± 0.2
Cultural Response

Thermoacidurans Agar
Prepare the medium per label directions. Inoculate and incubate at 55 ± 1°C for 18-48 hours.

Formula

Thermoacidurans Agar
Approximate Formula* Per Liter
Yeast Extract................................................................ 5.0 g
Proteose Peptone.......................................................... 5.0 g
Dextrose ..................................................................... 5.0 g
Dipotassium Phosphate.................................................. 4.0 g
Agar........................................................................... 20.0 g
*Adjusted and/or supplemented as required to meet performance criteria.

Directions for Preparation from Dehydrated Product

1. Suspend 39 g of the powder in 1 L of purified water. Mix thoroughly.
2. Heat with frequent agitation and boil for 1 minute to completely dissolve the powder.
3. Autoclave at 121°C for 15 minutes. Avoid overheating which could cause a softer medium.
4. Test samples of the finished product for performance using stable, typical control cultures.

Procedure

Consult appropriate references for recommended test procedures. ^1,2

Expected Results

Refer to appropriate references and procedures for results.

Limitations of the Procedure

Microorganisms other than B. coagulans may grow on this medium. Perform microscopic examination and biochemical tests to identify to genus and species if necessary.

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