• Food Science and Preservation
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• v.22 no.5
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• pp.727-734
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• 2015

In this study, three GRAS (generally recognized as safety) strain was isolated from Doenjang and Cheonggukjang and identified as a protease-producing microorganism, following the appearance of a clear zone around its colony when cultured on a medium containing skim milk. Based on an analysis of the nucleotide sequence of 16S ribosomal RNA, the strains wereas identified as Bacillus amyloliquefaciens and wereas therefore named Bacillus amyloliquefaciens CDD5, Bacillus amyloliquefaciens CPD4, and Bacillus amyloliquefaciens CGD3. Here, we analyzed the protease and ${\alpha}$-glucosidase inhibitory activities of the three B. amyloliquefaciens strains. Among the isolated strains, B. amyloliquefaciens CGD3 exhibited the highest protease activity (9.21 U/mL, 24 hr). The protease activities of B. amyloliquefaciens CDD5 and B. amyloliquefaciens CPD4 reached 1.14 U/mL and 8.02 U/mL, respectively, at 48 hr. The proteases from the three B. amyloliquefaciens strains showed the highest activities within a pH range of 8.0-9.0 at $50^{\circ}C$, and casein was found to be the preferred substrate on evaluating enzyme activity in the substrate specificity assay. The B. amyloliquefaciens strains exhibited maximal growth when the nutrient broth medium had an initial pH within the range of 5.0-10.0, 6-9% sodium chloride (NaCl), and 5% glucose. B. amyloliquefaciens CDD5 exhibited a low ${\alpha}$-glucosidase inhibition rate (5.32%), whereas B. amyloliquefaciens CPD4 and B. amyloliquefaciens CGD3 exhibited relatively higher inhibition rates of 96.89% and 97.55%, respectively.

• Food Science and Preservation
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• v.23 no.4
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• pp.568-575
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• 2016

Bacillus amyloliquefaciens CGD3 was used as a starter for fermentation of amaranth and cultural characteristics and biological activities of amaranth were investigated. The viable cells in fermented amaranth was 4.54~8.01 log CFU/mL during 96 hr of fermentation period. Protease activities of amaranth showed the highest by 36.7 unit/mL after 72 hr of fermentation. The total phenolic and flavonoid contents of amaranth increased with fermentation time while its total sugar content decreased. The total protein content was the highest in amaranth fermented for 96 hr (0.25 mg/g). The DPPH scavenging activities, FRAP (ferric reducing antioxidant power), and reducing power of amaranth were highest in amaranth fermented for 72 hr, showing 84.46%, $551.91{\mu}M$, and 2.74, respectively. ACE (angiotensin converting enzyme) and ${\alpha}$-Glucosidase inhibition rates increased with fermentation time and showed the highest after 72 hr.