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KMID : 1134820170460121561
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Journal of the Korean Society of Food Science and Nutrition
2017 Volume.46 No. 12 p.1561 ~ p.1567
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Potential for Application as a Starter Culture of Tyramine-Reducing Strain
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Kang Hyang-Rin
Lee Yae-Lim
Hwang Han-Joon
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Abstract
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The aim of this study was to investigate tyramine-reducing strains in traditional fermented soybean pastes and finally select a suitable starter candidate for the manufacture of tyramine controlled Cheonggukjang. Prior to selection of reducing strains, biogenic amine contents of soybean paste samples, Cheonggukjang and Doenjang, collected from various food outlets in Korea were detected by using HPLC, and the microflora of samples were characterized and identified by denaturing gradient gel electrophoresis analysis at the genus level. As a result of the identification, the genera Bacillus, Enterococcus, Aneurinibacillus, Enterobacter, Aeribacillus, Lactobacillus, Lentibacillus were detected in the samples. Afterward, tyramine-reducing strains were morphologically isolated on Tryptic Soy Agar medium. The strains as starter candidates were selected based on their pigmentation, shape, size, and overall appearance of bacterial colonies on agar medium, and they were observed by phase contrast inverted microscopy. Tyramine-reducing activities of the selected strains were detected by using HPLC analysis. Finally, three selected starter candidates showed tyramine-reducing activities above 30% (approximately 39.50, 30.75, and 35.07% in the batch manufactured by isolate D31-21, O2-2, and H3 strains, respectively). The candidates were identified as Bacillus amyloliquefaciens D31-21, B. amyloliquefaciens O2-2, and B. subtilis H3, respectively, by 16S rRNA analysis. Genetic analysis using PCR revealed that the three selected starter candidates did not contain genes for B. cereus toxins, and the candidates were applied to Cheonggukjang manufacturing. In addition, potential for reduction of tyramine during the manufacturing of Cheonggukjang was investigated in situ test. Tyramine contents in Cheonggukjang samples inoculated with KCTC 3014, isolate D31-21, O2-2, and H3 were 339.44, 161.14, 206.45, and 116.21 mg/kg, respectively. These results indicated that B. subtilis H3 could be useful as a starter culture for the manufacturing of tyramine controlled soybean pastes.
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KEYWORD
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fermented soybean pastes, biogenic amine, tyramine, tyramine-reducing strain
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