• Journal of Food Hygiene and Safety
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• v.23 no.2
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• pp.108-112
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• 2008

A survey of total aflatoxin levels was conducted on 158 samples (nuts, fermented foods and their processed products) collected in local markets in Gyeonggi-do and Domestic Internet Site. The total aflatoxins were quantified by the immunoaffinity column clean-up method followed by high performance liquid chromatography (HPLC)-fluorescence detector (FLD). Aflatoxins were found in 45(28.5%) samples including 34 nuts and nut products, 7 soybean pastes, 1 meju, 1 bean product and 2 corn snacks with a range of $0.02{\sim}3.96\;{\mu}g/kg$. These results show that the contamination level of aflatoxin in foods consumed in Korea is low compared with the standard in Korea Food Code($10\;{\mu}g/kg$ as aflatoxin $B_1$). Aflatoxin $B_1$ content was increased in peanuts and com snacks during storage but it was decreased in doenjang (soybean paste).

• Korean Journal of Food Science and Technology
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• v.50 no.2
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• pp.152-164
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• 2018

Fermented seasoning pastes were prepared by Aspergillus oryzae and Bacillus subtilis using three edible insects, Tenebrio molitor larvae (TMP), Gryllus bimaculatus (GBP), and Bombyx mori pupa (SPP), with soybean (SBP) as a negative control. Volatile compounds were extracted by the headspace solid-phase microextraction (HS-SPME) method and confirmed by gas chromatograph-mass spectrometry (GC-MS). In total, 121 volatiles from four samples were identified and sub-grouped as 11 esters, 18 alcohols, 23 aldehydes, 5 acids, 10 pyrazines, 2 pyridines, 7 aromatic hydrocarbons, 10 ketones, 19 alkanes, 9 amides, 4 furans and 3 miscellaneous. TMP, GBP, SPP and SBP had 48, 54, 36, and 55 volatile compounds, respectively. Overall, 2,6-dimethylpyrazine and trimethylpyrazine were found by a high proportion in all samples. Tetramethylpyrazine, a main flavor of doenjang, a Korean fermented seasoning soybean paste, was identified as one of the major compounds in TMP, SPP, and SBP. SBP had benzaldehyde, hexanal, n-pentanal, and aldehydes and SPP with pyrazines.

• Journal of Life Science
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• v.26 no.10
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• pp.1113-1120
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• 2016

Two bacterial strains producing extracellular man nanase were isolated from doenjang, a traditionally fermented soybean paste in Korea. The isolates, WL-6 and WL-11, were identified as Bacillus subtiis on the basis of their 16S rRNA gene sequences, morphological, and biochemical properties. Two genes encoding the mannanase of both B. subtilis WL-6 and B. subtilis WL-11 were each cloned into Escherichia coli, and their nucleotide sequences were determined. Both mannanase genes consisted of 1,086 nucleotides, encoding polypeptides of 362 amino acid residues. The deduced amino acid sequences of the two WL-6 and WL-11 mannanases, designated Man6 and Man11, respectively, differed from each other by eight amino acid residues, and they were highly homologous to those of mannanases belonging to the glycosyl hydrolase family 26. The 26 amino acid stretch in the N-terminus of Man6 and Man11 was a predicted signal peptide. Both Man6 and Man11 were localized at the level of 94–95% in an intracellular fraction of recombinant E. coli cells. The enzymes hydrolyzed both locust bean gum and mannooligosaccharides, including mannotriose, mannotetraose, mannopentaose, and mannohexaose, forming mannobiose and mannotriose as predominant products. The optimal reaction conditions were 55°C and pH 6.0 for Man6, and 60°C and pH 5.5 for Man11. Man11 was more stable than Man6 at high temperatures.

• Korean Journal of Microbiology
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• v.54 no.4
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• pp.398-409
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• 2018

In the present study, biogenic amine-forming Bacillus spp. and bacteriocin-producing lactic acid bacteria (LAB) isolated from Doenjang were generally identified through 16S rRNA gene sequencing, and the physicochemical and microbiological characteristics of cheonggukjang prepared using the isolated strains were investigated. Biogenic amine-producing bacteria from the samples were identified as Bacillus licheniformis DB102, B. subtilis DB203, B. stearothermophilus DB206, B. pumilus DB209, B. subtilis DB310, B. coagulans DB311, B. cereus DB313, B. amyloliquefaciens DB714, B. amylolique-faciens DB915, B. licheniformis DB917, B. cereus DB1019, B. subtilis DB1020, B. megaterium DB1022. The bacteriocin-producing LAB showed antibacterial effect against biogenic amine-producing Bacillus spp. were identified as Lactobacillus plantarum DLA205, L. brevis DLA501, L. fermentum DLA509, L. acidophilus DLA703, and Enterococcus faecalis DLA804. The bacteriocin produced by the LAB significantly decreased the viable numbers and the amine production ability of the biogenic amine-forming Bacillus spp. in a concentration dependent manner. Therefore, the pH, ammonia nitrogen and biogenic amine content of cheonggukjang prepared by mixed culture of the LAB and Bacillus spp. were significantly decreased compared to the control group.

• Journal of Life Science
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• v.27 no.7
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• pp.805-811
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• 2017

In the previous paper, we isolated a bacterium that can hydrolyze various organic materials from soybean paste, including cellulose, lipids, starch, and protein. The activity and chemical properties of the crude enzymes produced by the isolate Bacillus subtilis CK-2 were further investigated. Cellulase showed the highest activity at pH 5.0 and $55^{\circ}C$. The stability of cellulase was maintained within the ranges of pH 5.0~10.0 and $20{\sim}50^{\circ}C$. Cellulolytic enzymes were activated by a $Co^{2+}$ ion, demonstrating the highest activity at a 0.45%(w/v) concentration of $Co^{2+}$. The optimal conditions for amylase were pH 5.0 and $50^{\circ}C$. The activity of amylase was stable within the ranges of pH 4.0~5.0 and $20{\sim}50^{\circ}C$. The $Co^{2+}$ ion was also necessary for amylase activity, which was the highest at a 0.2%(w/v) concentration of $Co^{2+}$. The optimal pH and temperature conditions of protease were pH 8.0 and $50^{\circ}C$. The activity of protease was stable within the ranges of pH 7.0~8.5 and $20{\sim}50^{\circ}C$. Protease activity was catalyzed by $Mn^{2+}$, which was the highest at a 0.125%(w/v) concentration of $Mn^{2+}$. The isolate B. subtilis CK-2 demonstrated a high activity of autolysin. Based on these results, we identified and suggested the optimal pH, temperature, and metal ion concentration in the use of the hydrolytic enzymes of B. subtilis CK-2 for industrial purposes.