agar and 4-anisyltetrazolium-blue

A new technique for the detection of antimicrobial substances produced by lactic acid bacteria has been developed. In this technique, milk agar plates were supplemented with tetrazolium chloride or tetrazolium blue dyes. Comparisons of milk agar assays with M17 agar plates indicated that, out of 30 bacterial strains, 13 strains produced bacteriocins or inhibitory substances that were detectable on milk agar plates but not on M17 agar plates. Multiple-strain lactococcal cultures are used in milk fermentations. To identify suitable strains to combine for industrial use, component strains must be tested for compatibility. The procedure described allows optimization of compatibility. The assay of putative producer and sensitive indicator strains using milk agar plates (11% nonfat dry milk plus .8% agar and .02% tetrazolium chloride or tetrazolium blue) provides an important tool to prevent allopathic interactions in mixed cultures.

Topics: Agar; Animals; Bacteriocins; Culture Media; Fermentation; Lactococcus lactis; Milk; Tetrazolium Salts