title: Improved microbiological procedure for determining bacitracin in premixes and mixed feeds.
abstract: An improved microbiological procedure is presented for determining bacitracin in premixes and mixed feeds. Premixes are extracted with acidic 50% aqueous methanol, and mixed feeds are extracted with 50% dimethylformamide after washing with acetone to remove fats and pigments. Extracts are diluted with pH 6.0 phosphate buffer and assayed by using a 2-point assay system with Micrococcus flavus as the test organism. The simpler extraction coupled with the 2-point assay system measured bacitracin levels as low as 10 g/ton. Accuracy and repeatability of the 2-point system were at least equivalent to those for official AOAC methods.
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D001414:Bacitracin / Q000032:analysis*; D001681:Biological Assay; D008826:Microbial Sensitivity Tests; D012997:Solvents
chemical_list: D012997:Solvents; D001414:Bacitracin