본 연구에서는 청국장 및 볏짚에서 분리한 미생물중 decarboxylase 배지에서 탈탄산효소 활성이 낮은 균주로 $B.$ $subtilis$ HH12, $B.$ $subtilis$ HR254, $P.$ $barcinonensis$ KR97을 선발하였다. 이들 선발 미생물들의 histidine decarboxylase($hdc$) gene 과 tyrosine decarboxylase($tdc$) gene을 조사한 결과, $hdc$ gene은 HH12, HR254, KR97 균주에서는 검출되지 않았으나, $tdc$ gene은 HH12, HR254, KR110 균주에서 검출되었다. 또한 HPLC를 통해 선발 균주들의 배양상등액 중 amines 생성량을 분석한 결과, HH12, HR254, KR110 균주는 histamine이 검출되지 않았고 tyramine은 HH12, HR254, KR110 균주는 각각 6.09, 3.68, 6.30 mg/L로 검출되었다. 선발한 biogenic amines 저감화 균주들의 BAs 생성량을 decarboxylase 고생산 미생물로 사료되는 $B.$ $subtilis$ MC138 균주와 비교해보면 현저히 낮은 수준으로 나타났다.
Microorganisms, having the lower decarboxylase activity, among the isolated strains from $cheonggukjang$ and rice-straw in this study were selected by using biogenic amine (BA) media. The selected strains were identified as $Bacillus$ $subtilis$ HH12, $B.$ $subtilis$ HR254, and $Paenibacillus$ $barcinonensis$ KR97, by using 16S rRNA analysis. PCR analysis showed that the histidine decarboxylase ($hdc$) gene was absent in the HH12, HR254, and KR97 strains. However, PCR analysis showed that the tyrosine decarboxylase ($tdc$) gene was present in the HH12, HR254, and KR97 strains. Quantitative analysis of the selected strains by using high-performance liquid chromatography showed that histamine was absent in the HH12, HR254, and KR97 strains. However, these 3 strains showed tyramine concentrations of 6.09, 3.68, and 6.30 mg/L, respectively. These strains produced lower concentrations of amines (approximately 7.9, 0, and 9.3% amines in the HH12, HR254, and KR97 strains, respectively) than the $B.$ $subtilis$ MC138 strain, which showed the higher protease activity.
