For detection of Penicillin-G in milk using Bacillus stearothermophilus. Dissolve 26.5gms in 1000 ml of distilled water. Gently heat to boiling with gentle swirling and dissolve the medium completely. Sterilize by autoclaving at 15 psi (121ºC) for 15 minutes. Cool to 45 - 50°C and mix well before pouring into sterile Petri plates. Appearance: Cream to yellow color, homogeneous, free flowing powder, pH (at 25°C): 6.6 ± 0.2
ANTIBIOTIC ASSAY MEDIUM NO. 4 (VEG.) is prepared by incorporating vegetable peptones in place of animal peptones. This medium is suitable for the detection of antibiotics like penicillin in milk. These medium is formulated in accordance to the specifications detailed by the Food and Drug Administration. For indicator organism like Bacillus stearothermophilus, Micrococcus luteus, Hi Veg. peptone, Hi Veg. extract, yeast extract acts as a source of amino acid, vitamin, and minerals. Dextrose serves as the carbon and energy source. Freshly prepared plates should be used for antibiotic assays. The use of this medium assures well defined zones of the test organism.