The objectives of this study were to identify the histamine-forming bacteria and bacteriocin-producing lactic acid bacteria (LAB) isolated from Myeolchi-jeot according to sequence analysis of the 16S rRNA gene, to evaluate the inhibitory effects of the bacteriocin on the growth and histamine accumulation of histamine-forming bacteria, and to assess the physico-chemical properties of the bacteriocin. Based on 16S rRNA gene sequences, histamine-forming bacteria were identified as Bacillus licheniformis MCH01, Serratia marcescens MCH02, Staphylococcus xylosus MCH03, Aeromonas hydrophila MCH04, and Morganella morganii MCH05. The five LAB strains identified as Pediococcus acidilactici MCL11, Leuconostoc mesenteroides MCL12, Enterococcus faecium MCL13, Lactobacillus sakei MCL14, and Lactobacillus acidophilus MCL15 were found to produce an antibacterial compound with inhibitory activity against the tested histamine-producing bacteria. The inhibitory activity of these bacteriocins obtained from the five LAB remained stable after incubation at pH 4.0-8.0 and heating for 10 min at 80°C; however, the bacteriocin activity was destroyed after treatment with papain, pepsin, proteinase K, α-chymotrypsin, or trypsin. Meanwhile, these bacteriocins produced by the tested LAB strains also exhibited histamine-degradation ability. Therefore, these antimicrobial substances may play a role in inhibiting histamine formation in the fermented fish products and preventing seafood-related food-borne disease caused by bacterially generated histamine.

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This study evaluated the antibacterial activity of bacteriocin produced by Bacillus strains against biogenic amines (BA)-forming lactic acid bacteria (LAB), and the applicability of desirable strains as Bacillus starters for safety and quality improvement of fermented soybean products. The BA-forming ability of the tested LAB in amino acid decarboxylase broth was mostly strain specific rather that species specific. The bacteriocin produced by specific Bacillus strains: Bacillus sp. DB407, Bacillus licheniformis DB612, and Bacillus subtilis DB821 may play a contributory role in the inhibiting the growth of BA-forming strains. In fermented soybean products manufactured using different starter cultures, there was a significant reduction (p < 0.05) in the cell counts of LAB by application of a mixed culture containing B. subtilis DB821, which showed the highest antimicrobial activity. Specifically, B. subtilis DB821 was highly efficient in reducing accumulation of cadaverine, tryptamine, and tyramine produced by Enterococcus faecium D12 and Enterococcus faecalis D51 during soybean fermentation. In conclusion, the bacteriocin-producing Bacillus strains such as Bacillus sp. DB 407, B. licheniformis DB612, and B. subtilis DB821 can be used as a starter culture for the production of BA-controlled soybean products and for the enhancement of the quality and safety of fermented foods.

The purpose of this study was to determine the microbial contamination and the content of biogenic amines (BA) in over-ripened kimchi prepared with different kinds of salted and fermented seafoods during fermentation. The number of bacterial cells in the overall kimchi samples reached a maximum after 3-6 months of fermentation and then gradually decreased thereafter. Yeasts were detected from the overall kimchi samples after 3 months of fermentation, however the amounts of yeast cells were significantly lower than lactic acid bacteria (LAB) cells throughout the fermentation periods. As the fermentation progresses, pH levels and salinity of all kimchi samples gradually decreased, whereas titratable acidity values and amino-type nitrogen and volatile base nitrogen contents sharply increased. There were significant differences (p<0.05) in the microbiological and physicochemical properties observed in freshly-made kimchi and over-ripened kimchi prepared by using different kinds of salted and fermented seafoods. Immediately after preparation, BA-producing LAB were isolated from kimchi samples with salted and fermented seafoods, and the strain numbers of the bacteria in over-ripened kimchi were significantly higher than in freshly-made kimchi. In contrast, the reduction of histamine and putrescine contents in some over-ripened fermented kimchi samples prepared with 'Kanari-aekjeot' and 'Myeolchi-aekjeot' was observed during the late stage of fermentation, which may be the effect of microorganisms with antibacterial activity against BA-producing bacteria or BA-degrading bacteria. Key words：biogenic amine, lactic acid bacteria, over-ripened kimchi, salted and fermented seafood

The objective of this study was to evaluate biogenic amine (BA) formation and degradation abilities of Bacillus strain and lactic acid bacteria (LAB) isolated from meju and doenjang and to determine the microbiological and physicochemical qualities of Cheonggukjang prepared by mixed culture of these strains. Accumulation of cadaverine (421.7 ± 11.0 mg/L) and histamine (628.7 ± 24.1 mg/L) was assessed in the culture media of Bacillus subtilis MJ226 that displayed lysine and histidine decarboxylase activities. No ability to form cadaverine, histamine, putrescine, tryptamine, and tyramine by Lactobacillus acidophilus D11, L. acidophilus D38, Lactobacillus sakei D44, Lactobacillus plantarum D70, which exhibited high BA degradation ability. The amino nitrogen and free amino acid contents were significantly (p<0.05) increased in Cheonggukjang prepared by the mixed culture of LAB (L. sakei D44, L. plantarum D70, or L. pentosus D74) and B. subtilis MJ226, whereas the ammonia nitrogen and BA (cadaverine and histamine) contents were significantly (p<0.05) decreased. Consequently, it was confirmed that BA formation in Cheonggukjang prepared by starter culture of B. subtilis was effectively inhibited by the certain strains of LAB having BA-degrading ability. Key words：Bacillus, biogenic amine, Cheonggukjang, lactic acid bacteria