The Role of Enterococcus faecium as a Key Producer and Fermentation Condition as an Influencing Factor in Tyramine Accumulation in Cheonggukjang

Technological and Enzymatic Characterization of Autochthonous Lactic Acid Bacteria Isolated from Viili Natural Starters

Viili, a Finnish ropy fermented milk, is traditionally manufactured through spontaneous fermentation, by mesophilic lactic acid bacteria and yeast-like fungi, or back-slopping. This study evaluated four natural viili starters as sources of lactic acid bacteria for dairy production. Back-slopping activation of the studied viili samples was monitored through pH and titratable acidity measurements and enumeration of mesophilic lactic acid bacteria. Sixty lactic acid bacteria isolates were collected, molecularly identified, and assayed for acidification performance, enzymatic activities, production of exopolysaccharides (EPSs), presence of the histidine decarboxylase (hdcA) gene of Gram-positive bacteria, and production of bacteriocins. A neat predominance of Lactococcus lactis emerged among the isolates, followed by Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, Enterococcus lactis, and Lactococcus cremoris. Most isolates exhibited proteolytic activity, whereas only a few enterococci showed lipase activity. Five isolates identified as L. cremoris, L. lactis, and E. faecalis showed a good acidification performance. Most of the isolates tested positive for leucine arylamidase, whereas only one E. durans and two L. lactis isolates were positive for valine arylamidase. A few isolates also showed a positive reaction for beta-galactosidase and alpha- and beta-glucosidase. None of the isolates produced EPSs or bacteriocins. The hdcA gene was detected in five isolates identified as L. lactis and E. faecium. A few L. cremoris and L. lactis isolates for potential use as starter or adjunct cultures for dairy processing were finally identified.

Culture-dependent and -independent analyses of bacterial compositions and its contributions to formation of γ-aminobutyric acid and poly-γ-glutamic acid in Cheonggukjang

This study was performed to unveil bacterial compositions and their contributions to the formation of γ-aminobutyric acid (GABA) and poly-γ-glutamic acid (γ-PGA) in Cheonggukjang. To predict possible key factors contributing to the content of the bioactive compounds in Cheonggukjang, commercial products were analyzed for various parameters. The content of GABA and γ-PGA showed a negative (R2 = 0.61 - 0.73) and positive correlation (R2 = 0.53 - 0.96) with antioxidative activity. Consistently, GABA content showed a moderate negative correlation with γ-PGA content (R2 = 0.58). Among the physicochemical and microbial parameters, only salinity showed a moderate negative correlation with γ-PGA content (R2 = 0.75), which might be due to the inhibition of bacterial growth. It was also suggested that multiple factors (including bacterial species) were involved in the formation of GABA and γ-PGA in Cheonggukjang. To reveal dominant bacterial species and further presume their contributions to the bioactive compound formation in Cheonggukjang, both culture-independent (metagenomic) and -dependent (culturomic) methods were used. Culture-independent method showed that Bacillus piscis was dominant (23.37 - 94.89 %), followed by B. hisashii (0.00 - 62.45 %) and B. coagulans (0.00 - 13.82 %). Considering the quantitative speciation data on the bioactive compound content in Cheonggukjang (and bacterial production capability) together, it was further elucidated that B. piscis contributed primarily to the bioactive compound formation. Unlike this, culture-dependent analysis revealed that B. licheniformis and B. subtilis were dominant (30.0 - 47.6 and 17.5 - 39.5 %, respectively). Based on the quantitative speciation data on the bacterial production capability of GABA and γ-PGA, B. subtilis was the primarily contributing bacterial species to the bioactive compound formation. Consequently, it was observed that the bacterial compositions and their contributions to the bioactive compound formation determined by the two methods differed considerably, i.e., B. piscis and B. subtilis were identified to be prominent bacterial contributors, respectively, depending on the method used.

Biogenic amine reduction by food additives in Cheonggukjang, a Korean fermented soybean paste, fermented with tyramine-producing heterogeneous bacterial species

This study was conducted to mitigate the food safety risks related to biogenic amine (BA) by reducing the BA content in Cheonggukjang using applicable food additives. In in-vitro experiments, of the additives tested, tartaric acid (TA), potassium sorbate (PS), and sodium benzoate (SB) considerably inhibited tyramine production of strains of Bacillus spp. and Enterococcus faecium while less affecting their growth. In addition to these three additives, two additives, glycine (GL) and nicotinic acid (NA), reported to have significant inhibitory effects in previous studies, were applied to the Cheonggukjang fermentation with prolific tyramine-producing strains of B. subtilis and E. faecium. The content of tyramine in the Cheonggukjang samples treated with TA, PS, SB, GL, and NA was significantly reduced by 27.5%, 50.7%, 51.4%, 76.1%, and 100.0%, respectively, compared to the control sample. Additionally, the content of polyamines (putrescine, cadaverine, spermidine, and spermine) in the GL-treated sample was reduced by 42.6%-62.4%. The mode of action could be attributed to inhibiting the bacterial decarboxylase activity and/or growth. Consequently, excluding NA that interfered with Cheonggukjang fermentation, GL was the most outstanding additive with an inhibitory effect on tyramine formation in food, followed by SB and PS, all of which showed a more than 50% reduction. Therefore, the use of appropriate additives could be one of the promising strategies to avoid the food safety issues implicated in BAs in Cheonggukjang.

Monitoring and risk assessment of biogenic amines in Korean commercial fermented seasonings

Fermented seasonings are widely used in Korean cuisine; however, some contain high levels of biogenic amines (BAs). In this study, in order to estimate the potential BA risk from fermented seasoning, the BA contents in 50 commercial brands (n = 292) of five seasonings (soy sauce, Gochujang, Doenjang, Ssamjang, and Cheonggukjang) and their changes due to different cooking methods were evaluated by high-performance liquid chromatography. The risk assessment for consumer exposure was evaluated by computing the estimated daily intake (EDI), histamine (HIS) intake, and tyramine (TYR) intake. Maximum contents of HIS detected in Cheonggukjang, soy sauce, Doenjang, and Ssamjang were 318.46, 148.15, 123.65, and 114.07 mg/kg, respectively. However, even in the worst-case scenario, the EDI value and HIS intake results demonstrated that the seasonings had a limited impact on the risk of HIS poisoning due to their low consumption. Cheonggukjang exhibited the highest TYR content (312.89 mg/kg), and the TYR exposure results implied that those taking classical antidepressant monoamine oxidase inhibitors should pay attention to Cheonggukjang. After stir-frying, the total BA retentions in soy sauce and Gochujang were only 51.45% and 57.08%, respectively, which may be caused by high temperature. Based on the results of this study, the five seasonings contained various BAs, which can be influenced by the cooking process, and all five seasonings are safe for the general population in terms of the risk of BAs.

First report on metagenomics and their predictive functional analysis of fermented bamboo shoot food of Tripura, North East India

Moiya pansung, mileye amileye, moiya koshak, and midukeye are naturally fermented bamboo shoot foods of Tripura. The present study aimed to reveal the whole microbial community structure of naturally fermented moiya pangsung, mileye amileye, moiya koshak, and midukeye along with the prediction of microbial functional profiles by shotgun metagenomic sequence analysis. The metataxonomic profile of moiya pangsung, mileye amileye, moiya koshak, and midukeye samples showed different domains, viz., bacteria (97.70%) followed by the virus (0.76%), unclassified (0.09%), eukaryotes (1.46%) and archaea (0.05%). Overall, 49 phyla, 409 families, 841 genera, and 1,799 species were found in all the fermented bamboo shoot samples collected from different places of Tripura. Firmicutes was the most abundant phylum (89.28%) followed by Proteobacteria (5.13%), Bacteroidetes (4.38%), Actinobacteria (1.02%), and Fusobacteria (0.17%). Lactiplantibacillus plantarum was the most abundant species in moiya pangsung, mileye amileye, moiya koshak, and midukeye followed by Lactococcus lactis, Levilactobacillus brevis, Leuconostoc mesenteroides, Weissella paramesenteroides, Leuconostoc kimchii, Pediococcus pentosaceus, Leuconostoc gasicomitatum, and Lacticaseibacillus casei. A few phyla of fungus were found, viz., Ascomycota, Basidiomycota, and Glomeromycota, where Ascomycota was present in high abundance. Functional analysis of moiya pangsung, mileye amileye, moiya koshak, and midukeye metagenome revealed the genes for the synthesis and metabolism of a wide range of bioactive compounds including, various essential amino acids, and conjugated amino acids. The abundance profile and predictive analysis of fermented bamboo shoots revealed a huge plethora of essential microorganisms and KEGG analysis revealed genes for amino acid metabolism, pectin degradation, lipid metabolism, and many other essential pathways that can be essential for the improvement of nutritional and sensory qualities of the fermented bamboo shoot products.

Melanoidins present in traditional fermented foods and beverages

Traditional fermented foods and beverages (TFFB) are an important dietary component consumed in large quantities worldwide. Currently, much attention has been focused on the health benefits of TFFB. Melanoidins, a class of bioactive substance produced in the final stage of the Maillard reaction, not only have a significant impact on sensory properties of TFFB but also contribute to the health effects. Melanoidins formed in the fermentation system with a long reaction time at low temperature could be different from those obtained from high-temperature, short-duration roasted systems due to the multiple formative stages and involvement of microorganisms and enzymes. In this paper, the current state of knowledge regarding the formation, distribution, extraction and purification, physicochemical properties, structure characteristics, and biological activities of TFFB melanoidins are comprehensively reviewed, with predominant focus on TFFB that are typically brown like douchi, miso, cheonggukjang, soy sauce, huangjiu (Chinese rice wine), beer, vinegar, and sweet wine. The current challenges and prospective recommendations for the research of melanoidins in fermented systems are also presented. In future, people should pay more attention to the basic research on TFFB melanoidins, especially purification methods and formation mechanisms, further substantiation of health properties of TFFB melanoidins in vivo, and development of specific melanoidins to fulfill technological, productive, or health needs of consumers.

The Microbiota and It’s Correlation With Metabolites in the Gut of Mice With Nonalcoholic Fatty Liver Disease

In recent years, nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease in the world. As an important model animal, the characteristics of gut microbiota alteration in mice with NAFLD have been studied but the changes in metabolite abundance in NAFLD mice and how the gut microbiota affects these intestinal metabolites remain unclear. In this experiment, a mouse model for NAFLD was established by a high-fat diet. The use of 16S rDNA technology showed that while there were no significant changes in the alpha diversity in the cecum of NAFLD mice, the beta diversity changed significantly. The abundance of Blautia, Unidentified-Lachnospiraceae, Romboutsia, Faecalibaculum, and Ileibacterium increased significantly in NAFLD mice, while Allobaculum and Enterorhabdus decreased significantly. Amino acids, lipids, bile acids and nucleotide metabolites were among the 167 significantly different metabolites selected. The metabolic pathways of amino acids, SFAs, and bile acids were significantly enhanced, while the metabolic pathways of PUFAs, vitamins, and nucleotides were significantly inhibited. Through correlation and MIMOSA2 analysis, it is suggested that gut microbiota does not affect the changes of lipids and bile acids but can reduce thiamine, pyridoxine, and promote L-phenylalanine and tyramine production. The findings of this study will help us to better understand the relationship between gut microbiota and metabolites in NAFLD.

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.

Biofilm-associated heat resistance of Bacillus cereus spores in vitro and in a food model, Cheonggukjang jjigae

Bacillus cereus, a foodborne pathogen, is capable of forming spores and biofilms as methods to withstand environmental stresses. These bacterial structures are an issue for food safety as they aid the bacteria survive heat sterilisation processes of foods and food contact surfaces. This study was conducted to investigate the role of the biofilm structure in providing an extra layer of protection to spores against heat treatments. For this, heat resistance of B. cereus spores in intact biofilms was compared to that of planktonic spores in vitro and in a Cheonggukjang jjigae food model. Using methods developed in this study to measure the wet and dry heat resistance of spores in intact biofilms, it was found that B. cereus spores have significantly higher heat resistances when present in biofilms rather than as planktonic spores, and that dry heat is less effective than wet heat at killing spores in biofilms. In further detail, for wet heat treatments, spores in biofilms of the strain isolated from Cheonggukjang (Korean fermented whole soybean), B. cereus CH3, had generally higher wet heat resistances than the reference strain, B. cereus ATCC 10987, both in vitro and in the Cheonggukjang jjigae food model. However, the spores in biofilms of the two strains showed similar heat resistance to dry heat, with some exceptions, when biofilms were formed in vitro or in Cheonggukjang jjigae broth. Meanwhile, B. cereus ATCC 10987 spores in biofilms had higher or similar wet heat resistances in vitro compared to in Cheonggukjang jjigae broth. Wet heat resistances of B. cereus CH3 spores in biofilms were all statistically similar regardless of biofilm formation media (brain heart infusion and Cheonggukjang jjigae broths). For dry heat, spores in biofilms of both B. cereus strains were more heat resistant when biofilms were formed in the Cheonggukjang jjigae food model rather than in vitro. Altogether, heat resistances of spores in biofilms formed in vitro and in the food environment were found to be different depending on the tested B. cereus strain, but higher than planktonic spores in any case. This is the first study examining the heat resistance of B. cereus spores in intact biofilms matrices attached to the surface, both in vitro and in a food model. Therefore, this research is valuable to understand the protective effects of biofilms formed in food environments and to reduce the food safety risks associated with B. cereus.

Structural Transformation and Creativity Induced by Biological Agents during Fermentation of Edible Nuts from Terminalia catappa

Terminalia catappa L. (tropical almond) is a nutritious fruit found mainly in the tropics. This study is aimed to establish the naturally biotransformed molecules and identify the probiotic agents facilitating the fermentation. The aqueous extracts from both the unfermented and fermented T. catappa nuts were subjected to gas chromatography/mass spectrometry (GC/MS) analysis. Syringol (6.03%), glutamine (1.71%), methyl laurate (1.79%), methyl palmitate (1.53%), palmitic acid (5.20%), palmitoleic acid (2.80%), and methyl oleate (2.97%) were detected in the unfermented nuts of the T. catappa. Additionally, two of these natural compounds (palmitic acid (4.19%) and palmitoleic acid (1.48%)) survived the fermentation process to emerge in the fermented seeds. The other natural compounds were biotransformed into 2,3-butanediol (1.81%), butyric acid (16.20%), propane-1,3-diol (19.66%), neoheptanol (2.89%), 2-piperidinone (6.63%), palmitoleic acid (1.18%), formamide, n-(p-hydroxyphenethyl)- (2.80%), and cis-vaccenic acid (1.69%) that newly emerged in the fermented seeds. The phytochemical compounds are likely carbon sources for the organisms facilitating the biotransformed molecules and product production. Four (4) potential probiotic bacteria strains, namely, Probt B1a, Probt B2a, Probt B4a, and Probt B4b, were isolated from the fermented nut. Enterococcus faecum, and Enterococcus faecalis were the organisms identified as driving the fermentation of the seeds. All strains were gram-positive, catalase-negative, and non-hemolytic, which suggests their harmless nature. N-(p-hydroxyphenethyl)-) was associated with fermentation for the first time, and neoheptanol was discovered as the main alcoholic molecule formed during the fermentation of the seeds. This fermentation is a handy tool for bio-transforming compounds in raw food sources into compounds with nutritious and therapeutic potentials.

Current Perspectives on the Physiological Activities of Fermented Soybean-Derived Cheonggukjang

Cheonggukjang (CGJ, fermented soybean paste), a traditional Korean fermented dish, has recently emerged as a functional food that improves blood circulation and intestinal regulation. Considering that excessive consumption of refined salt is associated with increased incidence of gastric cancer, high blood pressure, and stroke in Koreans, consuming CGJ may be desirable, as it can be made without salt, unlike other pastes. Soybeans in CGJ are fermented by Bacillus strains (B. subtilis or B. licheniformis), Lactobacillus spp., Leuconostoc spp., and Enterococcus faecium, which weaken the activity of putrefactive bacteria in the intestines, act as antibacterial agents against pathogens, and facilitate the excretion of harmful substances. Studies on CGJ have either focused on improving product quality or evaluating the bioactive substances contained in CGJ. The fermentation process of CGJ results in the production of enzymes and various physiologically active substances that are not found in raw soybeans, including dietary fiber, phospholipids, isoflavones (e.g., genistein and daidzein), phenolic acids, saponins, trypsin inhibitors, and phytic acids. These components prevent atherosclerosis, oxidative stress-mediated heart disease and inflammation, obesity, diabetes, senile dementia, cancer (e.g., breast and lung), and osteoporosis. They have also been shown to have thrombolytic, blood pressure-lowering, lipid-lowering, antimutagenic, immunostimulatory, anti-allergic, antibacterial, anti-atopic dermatitis, anti-androgenetic alopecia, and anti-asthmatic activities, as well as skin improvement properties. In this review, we examined the physiological activities of CGJ and confirmed its potential as a functional food.

Tyrosinase Inhibitory Activity of Soybeans Fermented with Bacillus subtilis Capable of Producing a Phenolic Glycoside, Arbutin

The production of arbutin, an effective tyrosinase inhibitor as well as an outstanding antioxidant, by 691 Bacillus strains isolated from soybean-based foods was tested to enhance the tyrosinase inhibitory activity of soybeans via fermentation with the strains. Among the strains tested, the 5 strains capable of significantly producing arbutin were identified as B. subtilis via 16S rRNA sequencing. When soybeans were fermented with each of the selected strains, the arbutin content was highest on day 1 of fermentation and decreased thereafter. However, the tyrosinase inhibitory activity of the fermented soybeans continuously increased as fermentation progressed, whereas the activity of non-inoculated soybeans was consistently low. The results indicate that arbutin enhances the tyrosinase inhibitory activity of soybeans in the early period of fermentation, while other substances besides arbutin contribute to the activity in the later period. Consequently, soybeans fermented with arbutin-producing B. subtilis strains could be considered as a natural source of cosmeceuticals and nutricosmetics used in skin lightening and may be of interest in the food industry because they contain well-known and powerful antioxidants such as arbutin and other substances.