Development of a screening method for biogenic amine producing Bacillus spp.

Most of the currently available screening methods for biogenic amine (BA)-producing microorganisms are based on differential media containing a pH indicator; BA production is detected as an increase in pH. However, such acid-alkaline detection methods cannot be adapted directly for use with alkaline bacteria such as Bacillus species. Here we describe an easy, rapid and reliable method for detecting BA-producing Bacillus strains using plate and broth methods. Positive selection using the plate method was achieved within 24 h. The broth method proved more precise and enabled quantitation of the BA production, and correlated well with the plate method. False-negatives were diminished using the broth method, and false-positives could be screened out by an additional test for glycerol metabolism. Of the 12 strains examined using new method, five (B. licheniformis cy2, B. polyfermenticus CJ9, B. licheniformis KCTC1918, B. subtilis KCTC1028, and B. subtilis KCTC1022) were BA-positive with the broth method, among which KCTC1022 was determined to be a false-positive using the glycerol metabolism examination. The suitability and accuracy of the broth method was confirmed by high-performance liquid chromatography detection of BA formation.

► New screening method to detect biogenic amine-producing Bacillus spp. ► Easy, quick, and reliable method using plate and broth method. ► Glycerol-amended decarboxylase medium based acid-alkaline detection method. ► Determination of BA-producing Bacillus without false positives and negatives. ► The developed broth medium allows for quantitative determination.