Improvement of decarboxylating agar medium for screening biogenic amine-producing bacteria in kimchi

A modification of decarboxylating agar medium as described by Niven was performed to improve the detection method of biogenic amine-producing bacteria and to eliminate the false-positive. A total of 120 bacterial strains isolated from kimchi were used to evaluate different decarboxylating agar media and for screening biogenic amines. Potential false-positives ranged from approximately 66 to 79% of the strains tested in the already well-known media. In our improved medium, none of the 120 strains showed the potential false-positives. There was a good agreement (81.7%-87.5%) between the results obtained by the improved medium and by HPLC analysis. Consequently, this medium was greatly improved in screening biogenic amine-producing bacteria and discarding false-positives. Of the 120 kimchi isolates, 14.2, 18.3, 37.5, and 0.8% were found by HPLC to be the producers of histamine, tyramine, putrescine las a form of spermine), and cadaverine, respectively. The proportion of biogenic amine producer during kimchi fermentation increased to a maximum at an immature period and decreased thereafter.