248 DIFCO MANUAL 



BACTO 



PRUNE AGAR (B56) 



DEHYDRATED 



Prunes, Infusion from 36 g. 



Bacto-Agar 15 g. 



Bacto-Prune Agar is recommended for the cultivation of phytopathological 

 and other fungi. In the preparation of this medium the infusion of prunes is 

 solidified by the addition of 1.5 per cent Bacto-Agar. The final reaction of the 

 medium is pH 5.6, well suited for the growth of a large number and variety of 

 fungi. 



To rehydrate the medium, suspend 24 grams of Bacto-Prune Agar in 1000 ml. 

 cold distilled water and heat to boiling to dissolve the medium completely. 

 Distribute in tubes or flasks and sterilize in the autoclave for 15 minutes at 15 

 pounds pressure (121°C.). Final reaction of the medium will be pH 5.6. 



One pound of Bacto-Prune Agar will make 18.9 liters of medium. 



BACTO 



W. L. NUTRIENT MEDIUM (B424) 



DEHYDRATED 



Bacto- Yeast Extract 4 g. 



Bacto-Casitone 5 g. 



Bacto-Dextrose 50 g. 



Monopotassium Phosphate 0.55 g. 



Potassium Chloride 0.425 g. 



Calciuni Chloride 0.125 g. 



Magnesium Sulfate 0.125 g. 



Ferric Chloride 0.0025 g. 



Manganese Sulfate 0.0025 g. 



Bacto-Agar 20 g. 



Bacto-Brom Cresol Green 0.022 g. 



Bacto-W. L. Nutrient Medium is recommended for use in the control of brew- 

 ing and industrial fermentation processes. It is prepared according to the formula 

 described by Green and Gray.^-- The nutrient medium permits the development 

 of the yeast. Also, in those instances in which the number of yeast cells is com- 

 paratively small, certain bacteria can be detected. A similar medium, Bacto-W. L. 

 Differential Medium, containing actidione as a selective agent inhibits the devel- 

 opment of yeast and molds but permits unrestricted growth of bacteria. Gray^ in 

 a discussion on the microbiological control for beer quality describes in detail 

 the value of these two media and the type of information they are able to give. 



The microbiological population of beers is an important factor in the scientific 

 control of brewing and other fermentation industries. Direct microscopic counts 

 do not give sufficient or specific information. In their study of various fermenta- 

 tion processes, Green and Gray pointed out the inadequacy of the microscopic 

 count in fermentation control procedures and made an exhaustive study of the 

 method of examination of worts, beers and liquid yeast and similar fermentation 

 products. The application of their method to other fermentation industries was 

 also shown by these authors. Two media were developed, one containing no 

 selective agent, and the other, a differential medium, containing, as a selective 

 agent, the antibiotic actidione, having the ability to inhibit the development of 

 yeasts without in any way interfering with the development of bacteria generally 

 encountered in beers. Experimental results indicated that yeasts grew as well on 



