Presentation Information
[P152]Evaluation of Antibacterial Activity of Koji mold (Aspergillus oryzae) as an Alternative Protein Source
*SUHYUN JEON1, Daisuke Hagiwara 2, Yutaka Kitamura3, Mito Kokawa3 (1. Univ. of Tsukuba, Agro-bio sci and tech., 2. Koji Labo Co., Ltd, 3. Univ. of Tsukuba, Life and env.)
Keywords:
Aspergillus oryzae,Alternative protein,Antibacterial activity,Pasteurization,Disk diffusion test
【Purpose】 Koji (Aspergillus oryzae) has been gaining attention as a promising source of alternative protein. To use this source as a key ingredient for alternative meat products, it is essential to understand the storage characteristics of koji mycelium. Therefore, this study investigates how the heat treatment effects the preservation of koji mycelium, focusing on its resistance to the bacterial contamination during different storage periods.
【Methods】 Koij mycelium was cultivated in YG broth for 3 days in the shaker and collected. The collected mycelium was either heat-treated through pasteurization in the boiling water or was left unpasteurized. Both pasteurized and unpasteurized koji samples were inoculated with two typical foodborne bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) at a concentration of 5 x 103 CFU/g. Inoculated samples were stored at 20 ℃ for 0 to 4 days, and the bacterial viability was assessed by counting colony forming units (CFU). For the disk diffusion test, extracts from heat-treated and unheated koji that were stored for 5 and 7 days were prepared, and the diameter of an inhibition zone against E. coli and S. aureus were measured over time.
【Results】 In unpasteurized koji samples, the bacterial growth of both E. coli and S. aureus only slightly increased or even declined over time. In contrast, pasteurized koji samples exhibited a significant increase in both bacterial growths. The disk diffusion test supported the above results, by showing a wider inhibition zone against S. aureus over time, particularity with the unheated koji extract. These results suggest that koji mycelium contains heat-sensitive antibacterial compounds.
【Methods】 Koij mycelium was cultivated in YG broth for 3 days in the shaker and collected. The collected mycelium was either heat-treated through pasteurization in the boiling water or was left unpasteurized. Both pasteurized and unpasteurized koji samples were inoculated with two typical foodborne bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) at a concentration of 5 x 103 CFU/g. Inoculated samples were stored at 20 ℃ for 0 to 4 days, and the bacterial viability was assessed by counting colony forming units (CFU). For the disk diffusion test, extracts from heat-treated and unheated koji that were stored for 5 and 7 days were prepared, and the diameter of an inhibition zone against E. coli and S. aureus were measured over time.
【Results】 In unpasteurized koji samples, the bacterial growth of both E. coli and S. aureus only slightly increased or even declined over time. In contrast, pasteurized koji samples exhibited a significant increase in both bacterial growths. The disk diffusion test supported the above results, by showing a wider inhibition zone against S. aureus over time, particularity with the unheated koji extract. These results suggest that koji mycelium contains heat-sensitive antibacterial compounds.
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