Comparative Metabolomic Analysis of Moromi Fermented Using Different Aspergillus oryzae Strains.

Aspergillus oryzae (A. oryzae) is an important starter in the fermentation of koji and moromi. However, the effect of different A. oryzae strains on the quality of moromi has rarely been studied. For this reason, this study analyzed the physicochemical properties, enzyme activity, sensory quality, and metabolite profiles of moromi samples fermented using two strains (A. oryzae KCCM12012P (moromi-1) and KCCM12804P (moromi-2)), which were newly isolated from fermented soy foods, and compared them to those of a commercialized A. oryzae strain (control). Amino-type nitrogen contents of moromi-1 and moromi-2 samples were higher than that of control moromi, and their amylase and protease activities were also higher. Moreover, metabolite profiles of moromi were significantly altered according to strains. In particular, the levels of many amino acids, peptides, nucleotides, and acidic compounds were altered, which resulted in changes in the sensory quality of moromi. Although volatile compounds were not investigated, the results suggested that the quality of moromi was significantly different for newly isolated strains, especially A. oryzae KCCM12804P, and they were superior to the commercial strain in terms of taste-related substances. Therefore, these strains could be used as good starters to produce moromi and soy sauce with good sensory quality.

Shotgun metagenomics of Cheonggukjang, a fermented soybean food of Korea: Community structure, predictive functionalities and amino acids profile.

Cheonggukjang is a naturally fermented soybean food of Korea. The present study was aimed to reveal the whole microbial community structure of naturally fermented cheonggukjang along with the prediction of microbial functional profiles by shotgun metagenomic sequence analysis. Metataxonomic profile of cheonggukjang samples showed different domains viz. bacteria (95.83%), virus (2.26%), unclassified (1.84%), eukaryotes (0.05%) and archaea (0.005%). Overall, 44 phyla, 286 families, 722 genera and 1437 species were identified. Firmicutes was the most abundant phylum (98.04%) followed by Proteobacteria (1.49%), Deinococcus-Thermus (0.14%). Bacillus thermoamylovorans was the most abundant species in cheonggukjang followed by Bacillus licheniformis, Bacillus glycinifermentans, Bacillus subtilis, Bacillus paralicheniformis, Bacillus amyloliquifaciens, Brevibacillus borstelensis, Brevibacillus sonorensis Brevibacillus, Acinetobacter, Carnobacterium, Paenibacillus, Cronobacter Enterococcus, Enterobacter, Terriglobus, Psychrobacter and Virgibacillus. A colossal diversity of the genus Bacillus was detected with 150 species. Functional analysis of cheonggukjang metagenome revealed the genes for the synthesis and metabolism of wide range of bioactive compounds including, various essential amino acids, conjugated amino acids, different vitamins, flavonoids, and enzymes. Amino acid profiles obtained from KEGG annotation in cheonggukjang were validated with experimental result of amino acid profiles.

Significance of LED lights in enhancing the production of vinegar using Acetobacter pasteurianus AP01.

Vinegar is a common food additive produced by acetic acid bacteria (AAB) during fermentation process. Low yield and long incubation time in conventional vinegar fermentation processes has inspired research in developing efficient fermentation techniques by the activation of AAB for acetic acid production. The present study intends to enhance vinegar production using acetic acid bacteria and light emitting diode (LED). A total of eight acetic acid bacteria were isolated from Korean traditional vinegar and assessed for vinegar production. Isolate AP01 exhibited maximum vinegar production and was identified as Acetobacter pasteurianus based on the 16S rRNA sequences. The optimum fermentation conditions for the isolate AP01 was incubation under static condition at 30 °C for 10 days with 6% initial ethanol concentration. Fermentation under red LED light exhibited maximum vinegar production (3.6%) compared to green (3.5%), blue (3.2%), white (2.2%), and non-LED lights (3.0%). Vinegar produced using red LED showed less toxicity to mouse macrophage cell line (RAW 264.7) and high inhibitory effects on nitric oxide and IL-6 production. The results confirmed that red LED light could be used to increase the yield and decrease incubation time in vinegar fermentation process.

Effects of Salt Treatment Time on the Metabolites, Microbial Composition, and Quality Characteristics of the Soy Sauce Moromi Extract.

Salt is one of the most important factors for fermented foods, but the effect of salt treatment time on the quality of fermented foods has rarely been studied. In this study, the effect of different salt treatment times (0, 48, and 96 h) after the start of fermentation on the quality of the soy sauce moromi extract (SSME) was investigated. As the salt treatment time was delayed, the population of Aspergillus oryzae, Lactobacillaceae, and Enterococcaecea in SSME increased, whereas the population of Staphylococcaceae and Bacillaceae decreased, leading to changes in the enzymatic activity and metabolite profiles. In particular, the contents of amino acids, peptides, volatile compounds, acidic compounds, sugars, and secondary metabolites were significantly affected by the salt treatment time, resulting in changes in the sensory quality and appearance of SSME. The correlation data showed that metabolites, bacterial population, and sensory parameters had strong positive or negative correlations with each other. Moreover, based on metabolomics analysis, the salt treatment-time-related SSME metabolomic pathway was proposed. Although further studies are needed to elucidate the salt treatment mechanism in fermented foods, our data can be useful to better understand the effect of salt treatment time on the quality of fermented foods.

Supplementation with Aspergillus oryzae-fermented kochujang lowers serum cholesterol in subjects with hyperlipidemia.

BACKGROUND & AIMS: Kochujang, a traditional fermented red pepper paste, is known for its hypocholesterolemic effect; however, these studies used non-commercial preparations of kochujang. In this study, we examined whether commercially-made kochujang in which Aspergillus oryzae (also known as koji) was used as a microorganism for fermentation has the same cholesterol-lowering effects. METHODS: Hyperlipidemic subjects (based upon criteria of 110 ∼ 190 mg/dL LDL cholesterol or 200 ∼ 260 mg/dL total cholesterol) who had not been diagnosed with any disease and met the inclusion criteria were recruited for this study. The 30 subjects were randomly divided into either the kochujang (n = 15) or placebo (n = 15) group. All subjects ingested either the kochujang pill (34.5 g/d) or a placebo three times daily during meals for 12 weeks. Outcomes included measurements of efficacy (total cholesterol, LDL-cholesterol, HDL-cholesterol, and triglyceride) and safety (adverse events, laboratory tests, electrocardiogram, and vital signs). RESULTS: In the kochujang-supplemented group, subjects' total cholesterol level significantly decreased (from 215.5 ± 16.1 mg/dL to 194.5 ± 25.4 mg/dL, p = 0.001). LDL-C cholesterol levels were also decreased by kochujang supplementation (from 133.6 ± 14.8 mg/dL to 113.5 ± 23.1 mg/dL); however no significant difference was seen between groups (p = 0.074). There were no statistically significant differences in HDL-cholesterol and triglyceride levels between the supplemented and non-supplemented groups. None of the subjects complained of any adverse effects. CONCLUSIONS: These results indicate that A. oryzae-fermented kochujang elicits a significant hypocholesterolemic effect and might be useful for improving blood cholesterol levels in subjects at high risk for cardiovascular disease. CLINICAL TRIAL REGISTRATION: NCT01865370.

Bacillus licheniformis isolated from Korean traditional food sources enhances the resistance of Caenorhabditis elegans to infection by Staphylococcus aureus.

We investigated whether Bacillus spp., newly isolated from Korean traditional food resources, influence the resistance of hosts to foodborne pathogens, by using Caenorhabditis elegans as a surrogate host model. Initially, we selected 20 Bacillus spp. that possess antimicrobial activity against various foodborne pathogens, including Staphylococcus aureus. Among the selected strains, six strains of Bacillus spp. used in preconditioning significantly prolonged the survival of nematodes exposed to S. aureus. Based on 16S rRNA gene sequencing, all six strains were identified as B. licheniformis. Our findings suggest that preconditioning with B. licheniformis may modulate the host defense response against S. aureus.