WL Differential HiVeg™ Broth

Principle and Interpretation

These media are prepared by using HiVeg hydrolysate instead of casein enzymic hydrolysate which makes the media free of BSE/TSE risks. WL (Wallerstein Laboratory) HiVeg Media are the modifications of WL (Wallerstein Laboratory) media which are formulated as described by Green and Gray for the examination of materials encountered in brewing and in industrial fermentations with mixed flora of yeasts and bacteria (1). At pH 5.5, viable baker's yeast can be enumerated and at pH 6.5 count of baker's yeast as well as distiller's yeast can be enumerated. Yeast extract, HiVeg hydrolysate, dextrose in the media provide growth requirements for microorganisms. Monopotassium phosphate buffers the media. Potassium chloride, calcium chloride and ferric chloride are essential ions that help to maintain the osmotic balance. Magnesium sulphate and manganese suplhate are the sources of divalent cations. Bromo cresol green is the pH indicator. Actidione (Cycloheximide) suppresses growth of yeast and moulds in brewing samples, permitting the detection and enumeration of bacteria that may be present in small numbers. While determining microbial counts using these media, temperature and time of incubation will vary depending on the nature of material under test. Temperatures of 25°C are employed for brewing materials while 30°C are employed for baker's yeast and alcohol fermentation mash analyses. WL Differential HiVeg Agar plates are incubated aerobically for the growth of acetic acid bacteria, Flavobacterium species, Proteus spceies and thermophilic bacteria while for the growth of lactic acid bacteria and Pediococcus species they should be incubated anaerobically.