Abstract: Samples containing enramycin were determinated by the double disk method with Bacillus subtilis as test microorganism and antibiotics standardization medium Ⅱ.The determination conditions were optimized through the investigations of extraction solution composition, extraction time and the concentrations of Bacillus subtilis. The linearity of the dose-response relationship was analysised upon it, and the accuracy of the method was checked. The results showed that the optimum deternmination conditions were acidic acetone solution B and 80 min for extraction. The calibration curve was linear within the range from 0.56 to 35.79 U/mL between the logarithm of concentration and the diameter of inhibition zone with the 10⁶ spores /mL of test microorganism constration,the correlation coefficient was 0.9960.The proposed method has been applied to the determination of samples containing enramycin. The recoveries was 95.90%,relative standard deviation (RSD) was 1.95%. This method applies to the detection of enramycin sample.

Key words: enramycin; extraction; potency determination; microbiological assay