Comprehensive Metabolite Profiling and Microbial Communities of Doenjang (Fermented Soy Paste) and Ganjang (Fermented Soy Sauce): A Comparative Study

Correlation between monosaccharide, oligosaccharide, and microbial community profile changes in traditional soybean brick (meju) fermentation

Meju is essential for making diverse traditional fermented soybean foods in Korea. To understand the changes in carbohydrates during fermentation, we aimed to identify autochthonous microorganisms from spontaneously fermented meju and compare the alterations in monosaccharides and oligosaccharides throughout the fermentation process. Microbial diversity was determined using a metabarcoding approach, and monosaccharide and oligosaccharide profiles were obtained by HPLC-Q-TOF MS and HPLC-MS/MS analyses, respectively. The dominant bacterial genera were Weissella, Lactobacillus, and Leuconostoc, while Mucor was highly abundant in the fungal community. The total monosaccharide content increased from Day 0 to Day 50, with the highest amount being 4.37 mg/g. Oligosaccharide profiling revealed the degradation of soybean dietary fiber during fermentation, and novel oligosaccharide structures were also discovered. Correlation analysis revealed that the fungus Mucor was positively related to pentose-containing oligosaccharides, galactose, and galacturonic acid, indicating that Mucor may degrade soybean dietary fibers such as xylogalacturonan, arabinogalactan, and rhamnogalacturonan. The negative relationships between the abundances of Weissella and oligo- and monosaccharides suggested that the bacteria may utilize saccharides for fermentation. These findings provide insights into the mechanisms underlying carbohydrate degradation and utilization; the key components involved in saccharide transformation that contribute to the characteristics of traditional meju were subsequently identified.

Taxonomic Variations of Bacterial and Fungal Communities depending on Fermentation Temperature in Traditional Korean Fermented Soybean Food, Doenjang

Meju, a fermented soybean brick, is a key component in soybean foods like doenjang and ganjang, harboring a variety of microorganisms, including bacteria and fungi. These microorganisms significantly contribute to the nutritional and sensory characteristics of doenjang and ganjang. Amplicon-based next-generation sequencing was applied to investigate how the microbial communities of meju fermented at low and high temperatures differ and how this variation affects the microbial communities of doenjang, a subsequently fermented soybean food. Our metagenomic data showed distinct patterns depending on the fermentation temperature. The microbial abundance in the bacterial community was increased under both temperatures during the fermentation of meju and doenjang. Weissella was the most abundant genus before the fermentation of meju, however, it was replaced by Bacillus at high temperature-fermented meju and lactic acid bacteria such as Weissella and Latilactobacillus at low temperature-fermented meju. Leuconostoc, Logiolactobacillus, and Tetragenococcus gradually took over the dominant role during the fermentation process of doenjang, replacing the previous dominant microorganisms. Mucor was dominant in the fungal community before and after meju fermentation, whereas Debaryomyces was dominant under both temperatures during doenjang fermentation. The dominant fungal genus of doenjang was not affected regardless of the fermentation temperature of meju. Strong correlations were shown for specific bacteria and fungi linked to specific fermentation temperatures. This study helps our understanding of meju fermentation process at different fermentation temperatures and highlights different bacteria and fungi associated with specific fermentation periods which may influence the nutritional and organoleptic properties of the final fermented soybean foods doenjang.

Comparison of microbial diversity and metabolites on household and commercial doenjang

In this study, the microbial diversity, free amino acid (FAA), and biological activities of household doenjang (HDJ) from four different regions and commercial doenjang (CDJ) four manufacturers were analyzed. And volatile flavor compound (VFC) and isoflavone profiles were analyzed using gas chromatograph-mass spectrometer (GC-MS) and high performance liquid chromatography (HPLC), respectively. The major bacterial genus in 1HDJ and 2HDJ was Bacillus (97.5%), while in 3HDJ and 4HDJ, it was Enterobacter (47.5%) and Pseudomonas (80%), respectively. Tetragenococcus was the main bacterial genus of CDJ. The Zygosaccharomyces genus among yeast was comparatively high in all samples. In all samples, glutamic acid predominated among the FAAs, and the 3-methyl butanal, benzeneacetaldehyde, and diallyl disulphide were major VFCs. CDJ contained higher levels of isoflavone-glycoside and total phenolics. Except for 3HDJ and 4CDJ, the isoflavone-aglycone and total flavonoid contents were higher in HDJ. The correlation between bacterial genus and metabolited of doenjang showed that Tetragenococcus was closely related to glutamic acid, Bacillus was related to aglycones and ammonia, and Pseudomonas was highly related to isovaleric acid. While, correlation between yeast genus and metabolited of doenjang confirmed that Candida, Hanseniaspora, and Saccharomyces were related with furfural, benzeneacetaldehyde, and 3-methyl butanal, respectively. The results of this study can be utilized as basic data for the industrialization and development of doenjang.

Fermentation-promoting effect of three salt-tolerant Staphylococcus and their co-fermentation flavor characteristics with Zygosaccharomyces rouxii in soy sauce brewing

Staphylococcus is the dominant genus in the fermentation process of soy sauce, but its effect on the flavor of soy sauce has not been clearly established. In order to investigate the role of this genus in soy sauce fermentation, individual fermentation with Staphylococcus spp. screened from the moromi and their co-fermentation with an ester-producing yeast of Zygosaccharomyces rouxii were designed. Through the analysis of physicochemical properties, organic acid composition, volatile flavor compounds (VFCs) and sensory characteristics during fermentation, Staphylococcus was confirmed as a contributor to the acidity, ester aroma and alcohol aroma of soy sauce. In their co-fermentation with yeast, the ester aroma of soy sauce was further enhanced. Moreover, pathway enrichment analysis and network construction of key VFCs also revealed potential metabolic networks for formation of characteristic flavor compounds in co-fermentation. This work will help optimize the fermentation functional microbiota to obtain better soy sauce flavor.

Microbiome and metabolome in home-made fermented soybean foods of India revealed by metagenome-assembled genomes and metabolomics

Grep-chhurpi, peha, peron namsing and peruñyaan are lesser-known home-made fermented soybean foods prepared by the native people of Arunachal Pradesh in India. Present work aims to study the microbiome, their functional annotations, metabolites and recovery of metagenome-assembled genomes (MAGs) in these four fermented soybean foods. Metagenomes revealed the dominance of bacteria (97.80 %) with minor traces of viruses, eukaryotes and archaea. Bacillota is the most abundant phylum with Bacillus subtilis as the abundant species. Metagenome also revealed the abundance of lactic acid bacteria such as Enterococcus casseliflavus, Enterococcus faecium, Mammaliicoccus sciuri and Staphylococcus saprophyticus in all samples. B. subtilis was the major species found in all products. Predictive metabolic pathways showed the abundance of genes associated with metabolisms. Metabolomics analysis revealed both targeted and untargeted metabolites, which suggested their role in flavour development and therapeutic properties. High-quality MAGs, identified as B. subtilis, Enterococcus faecalis, Pediococcus acidilactici and B. velezensis, showed the presence of several biomarkers corresponding to various bio-functional properties. Gene clusters of secondary metabolites (antimicrobial peptides) and CRISPR-Cas systems were detected in all MAGs. This present work also provides key elements related to the cultivability of identified species of MAGs for future use as starter cultures in fermented soybean food product development. Additionally, comparison of microbiome and metabolites of grep-chhurpi, peron namsing and peruñyaan with that of other fermented soybean foods of Asia revealed a distinct difference.

Consumer Preference of Traditional Korean Soy Sauce (Ganjang) and Its Relationship with Sensory Attributes and Physicochemical Properties

This study aimed to investigate the physicochemical characteristics, sensory attributes, and consumer acceptance of the Certification of Quality of Traditional Food (CQT) ganjang samples produced in different provinces of Korea. Wide variations in physicochemical properties were found among the samples, especially in lipids, total nitrogen, acidity, and reducing sugar. Traditional fermented foods are known to be closely tied to regional features, but the composition and characteristics of CQT ganjangs might be influenced much more by individual ganjang producers than by region. Preference mapping was performed to understand consumer behavior towards ganjang, and most consumers tended to have similar preferences, implying shared a common sensory ideal. The results of the partial least squares regression revealed drivers of liking for ganjang among sensory attributes, free amino acids, and organic acids. Overall, sensory attributes such as sweetness and umami were positively associated with acceptability, while the terms related to fermentation were negatively associated. In addition, amino acids, such as threonine, serine, proline, glutamate, aspartate, and lysine, and organic acids, such as lactate and malate, were positively associated with consumer acceptance. The important implications of the findings of this study for the food industry can be utilized to develop and optimize traditional foods.

Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method

BACKGROUND

Soy sauce is widely used in a variety of Asian dishes to enhance flavor. Soybean and most soybean products, including soy sauces, are listed as prohibited foods in a low iodine diet. However, the iodine content in soy sauces is largely unknown. The aim of this study was to determine the iodine content in domestic soy sauces in Taiwan.

METHODS

Twenty-five different kinds of soy sauces were diluted with distilled water and with a dilution factor of fifty or above. Iodine concentrations of the diluted samples were measured colourimetrically based on the Sandell-Kolthoff reaction by a modified microplate method. All the measurements were repeated twelve times on three different days for determination of mean and standard deviation (SD), and coefficients of variance (CV). Serial dilution and recovery tests were also performed for validation. The results were confirmed by an inductively coupled plasma mass spectrometry (ICP-MS) method.

RESULTS

Among the twenty-five surveyed soy sauces, most of them (n=22) were iodine-free (<16 ug/L, and thus un-detectable). The iodine concentrations (mean ± SD) of the three iodine-containing soy sauces were 2.7 ± 0.1, 5.1 ± 0.2, and 10.8 ± 0.6 mg/L, respectively. The inter-assay, intra-assay and total CVs were all <5.3% for the modified microplate method. The results obtained by ICP-MS were consistent with those of the modified microplate method. The recovery rates in the serial dilution test and recovery test ranged from 94.7% to 118.6%. Two of the three iodine-containing soy sauces were supplemented with kelp extract, while the other one without kelp extract had the highest amount of salt among the three iodine-containing soy sauces. Therefore, we postulate that iodized salt instead of kelp extract is the source of higher iodine content in that sauce.

CONCLUSION

The results suggest that most soy sauces are iodine-free and may be allowed during low iodine diets.

Comprehensive Metabolite Profiling of Four Different Beans Fermented by Aspergillus oryzae

Fermented bean products are used worldwide; most of the products are made using only a few kinds of beans. However, the metabolite changes and contents in the beans generally used during fermentation are unrevealed. Therefore, we selected four different beans (soybean, Glycine max, GM; wild soybean, Glycine soja, GS; common bean, Phaseolus vulgaris, PV; and hyacinth bean, Lablab purpureus, LP) that are the most widely consumed and fermented with Aspergillus oryzae. Then, metabolome and multivariate statistical analysis were performed to figure out metabolite changes during fermentation. In the four beans, carbohydrates were decreased, but amino acids and fatty acids were increased in the four beans as they fermented. The relative amounts of amino acids were relatively abundant in fermented PV and LP as compared to other beans. In contrast, isoflavone aglycones (e.g., daidzein, glycitein, and genistein) and DDMP-conjugated soyasaponins (e.g., soyasaponins βa and γg) were increased in GM and GS during fermentation. Notably, these metabolite changes were more significant in GS than GM. In addition, the increase of antioxidant activity in fermented GS was significant compared to other beans. We expect our research provides a basis to extend choice for bean fermentation for consumers and food producers.

Physicochemical Properties and Bacterial Community Profiling of Optimal Mahewu (A Fermented Food Product) Prepared Using White and Yellow Maize with Different Inocula

Mahewu is a fermented food product from maize, commonly consumed in Southern Africa. This study investigated the effect of optimizing fermentation (time and temperature) and boiling time of white maize (WM) and yellow maize (YM) mahewu, with the use of the Box–Behnken-response surface methodology (RSM). Fermentation time and temperature as well as boiling time were optimized and pH, total titratable acidity (TTA) and total soluble solids (TSS) determined. Results obtained showed that the processing conditions significantly (p ≤ 0.05) influenced the physicochemical properties. pH values of the mahewu samples ranged between 3.48–5.28 and 3.50–4.20 for YM mahewu and WM mahewu samples, respectively. Reduction in pH values after fermentation coincided with an increase in TTA as well as changes in the TSS values. Using the numerical multi-response optimisation of three investigated responses the optimal fermentation conditions were observed to be 25 °C for 54 h and a boiling time of 19 min for white maize mahewu and 29 °C for 72 h and a boiling time of 13 min for yellow maize mahewu. Thereafter white and yellow maize mahewu were prepared with the optimized conditions using different inocula (sorghum malt flour, wheat flour, millet malt flour or maize malt flour) and the pH, TTA and TSS of the derived mahewu samples determined. Additionally, amplicon sequencing of the 16S rRNA gene was used to characterise the relative abundance of bacterial genera in optimized mahewu samples, malted grains as well as flour samples. Major bacterial genera observed in the mahewu samples included Paenibacillus, Stenotrophomonas, Weissella, Pseudomonas, Lactococcus, Enterococcus, Lactobacillus, Bacillus, Massilia, Clostridium sensu stricto 1, Streptococcus, Staphylococcus, Sanguibacter, Roseococcus, Leuconostoc, Cutibacterium, Brevibacterium, Blastococcus, Sphingomonas and Pediococcus, with variations noted for YM mahewu and WM mahewu. As a result, the variations in physicochemical properties are due to differences in maize type and modification in processing conditions. This study also discovered the existence of variety of bacterial that can be isolated for controlled fermentation of mahewu.

Fermented soybean foods: A review of their functional components, mechanism of action and factors influencing their health benefits

After thousands of years of evolution and development, traditional fermented soybean foods, with their unique charm, have gained a stable place in the global market. With the explosive development of modern biological technologies, some traditional fermented soybean foods that possess health-promoting benefits are gradually appearing. Physiologically active substances in fermented soybean foods have received extensive attention in recent decades. This review addresses the potential health benefits of several representative fermented soybean foods, as well as the action mechanism and influencing factors of their functional components. Phenolic compounds, low-molecular-weight peptides, melanoidins, furanones and 3-hydroxyanthranilic acid are the antioxidative components predominantly found in fermented soybean foods. Angiotensin I-converting enzyme inhibitory peptides and γ-aminobutyric acid isolated from fermented soy foods provide potential selectivity for hypertension therapy. The potential anti-inflammatory bioactive components in fermented soybean foods include γ-linolenic acid, butyric acid, soy sauce polysaccharides, 2S albumin and isoflavone glycones. Deoxynojirimycin, genistein, and betaine possess high activity against α-glucosidase. Additionally, fermented soybean foods contain neuroprotective constituents, including indole alkaloids, nattokinase, arbutin, and isoflavone vitamin B12. The anticancer activities of fermented soybean foods are associated with surfactin, isolavone, furanones, trypsin inhibitors, and 3-hydroxyanthranilic acid. Nattokinase is highly correlated with antioxidant activity. And a high level of menaquinones-7 is linked to protection against neurodegenerative diseases. Sufficiently recognizing and exploiting the health benefits and functional components of traditional fermented soybean foods could provide a new strategy in the development of the food fermentation industry.

Microbial succession and its effect on key aroma components during light-aroma-type Xiaoqu Baijiu brewing process

Light-aroma-type Baijiu is a Chinese distilled alcoholic beverage produced from fermented sorghum. Microbial composition and dynamics during Baijiu production have a great influence on the flavor and quality of Chinese Baijiu. However, the microbial changes that occur during brewing of Xiaoqu Baijiu are poorly understood. In this study, the microbial composition of light-aroma-type Xiaoqu Baijiu at the saccharification and fermentation stages was investigated to explore microbial dynamics and their effects on aroma components using high-throughput sequencing and gas chromatography-flame ionization detection (GC-FID). Rhizopus, Pichia, Wickerhamomyces, Saccharomyces, Acinetobacter, Lactobacillus, and Weissella constituted the core microbes for Xiaoqu Baijiu production. Microbial succession during brewing could be divided into two phases: at the saccharification and early fermentation stages (F-0d to F-4d), Rhizopus and Acinetobacter were identified as the predominant microbes, accounting for 78.2-90.8% and 53.9-89.5% of the fungal and bacterial communities, respectively, whereas at the middle and late stages of fermentation (F-5d to F-14d), the abundance of Pichia, Wickerhamomyces, Saccharomyces, and Lactobacillus increased. Redundancy analysis (RDA) and Mantel tests indicated that the water, amino acid nitrogen, acid, and reducing sugar contents were significantly correlated with the fungal and bacterial communities in grains (p < 0.05). Pichia, Rhizopus, Saccharomyces, and Wickerhamomyces, especially Saccharomyces, were closely related to the contents of major alcohols, esters and aldehydes, and these microbes had an important functional role in the formation of Xiaoqu Baijiu flavor. This work provides insights into the microbial succession that occurs during brewing of light-aroma-type Xiaoqu Baijiu and the microbial contribution to flavor, which have potential for optimizing production and enhancing the flavor of Baijiu.

Alleviation of Metabolic Disturbance by Substituting Kanjang High in Bacillus for Salt through Modulation of Gut Microbiota in Estrogen-Deficient Rats

A high salt intake may exacerbate menopausal symptoms and substituting for different types of traditionally made kanjang (TMK; soy sauce) may prevent it. This study examined whether substituting salt with lyophilized TMK containing low and high Bacillus and biogenic amines in a high-fat diet might modulate the menopausal symptoms and the energy, glucose, and lipid metabolism in ovariectomized (OVX) rats. They were categorized into salt (Control), TMK with high Bacillus and low biogenic amines (HBLB), TMK with high Bacillus and high biogenic amines (HBHB), TMK with low Bacillus and low biogenic amines (LBLB), and TMK with low Bacillus and high biogenic amines (LBHB). Sham-operated rats consumed the same diet as the Control. HBLB, HBHB, and LBHB prevented increased tail skin temperature compared to the Control. HBHB and HBLB partially inhibited the increased weight gain and abdominal fat mass by reducing the food efficiency without changing the serum 17β-estradiol concentrations. Serum glucose and insulin concentrations and the insulin resistance index by the homeostatic model assessment for insulin resistance showed a positive association for weight gain. HBLB and HBHB decreased the serum malondialdehyde and tumor-necrosis factor-α levels. Hepatic triglyceride storage was lower in all TMK groups than in the Control, while hepatic glycogen accumulation was higher in the HBLB, HBHB, and LBHB groups than in the Control and LBLB groups. Accordingly, the mRNA expression of peroxisome proliferator-activated receptors-γ(PPAR-γ) was higher in the HBLB and HBHB groups compared to the Control, and that of fatty acid synthase was opposite to PPAR-γ expression. However, HBLB and HBHB improved dyslipidemia and insulin resistance compared to the Control, but their improvement did not reach that of the Normal-control. The acetic acid concentrations in the portal vein were lower in the LBLB than in the Control, while the butyric acid contents were higher in the LBHB and HBLB groups than in the Control. HBHB, HBLB, and LBHB elevated Akkermansia and Lactobacillus, and HBLB and LBLB increased Bacteroides and Ruminococcus compared to the Control. Polycyclic aromatic hydrocarbon degradation, bile acid synthesis, and unsaturated fatty acid biosynthesis were significantly higher in the HBLB group than in the Control group. In conclusion, substituting salts to TMK with a high Bacillus content regardless of the bioamine contents partially improved the menopausal symptoms and metabolic disturbance in estrogen-deficient animals.

Metagenomic-Metabolomic Mining of Kinema, a Naturally Fermented Soybean Food of the Eastern Himalayas

Kinema is a popular sticky fermented soybean food of the Eastern Himalayan regions of North East India, east Nepal, and south Bhutan. We hypothesized that some dominant bacteria in kinema may contribute to the formation of targeted and non-targeted metabolites for health benefits; hence, we studied the microbiome-metabolite mining of kinema. A total of 1,394,094,912 bp with an average of 464,698,304 ± 120,720,392 bp was generated from kinema metagenome, which resulted in the identification of 47 phyla, 331 families, 709 genera, and 1,560 species. Bacteria (97.78%) were the most abundant domain with the remaining domains of viruses, eukaryote, and archaea. Firmicutes (93.36%) was the most abundant phylum with 280 species of Bacillus, among which Bacillus subtilis was the most dominant species in kinema followed by B. glycinifermentans, B. cereus, B. licheniformis, B. thermoamylovorans, B. coagulans, B. circulans, B. paralicheniformis, and Brevibacillus borstelensis. Predictive metabolic pathways revealed the abundance of genes associated with metabolism (60.66%), resulting in 216 sub-pathways. A total of 361 metabolites were identified by metabolomic analysis (liquid chromatography-mass spectrophotometry, LC-MS). The presence of metabolites, such as chrysin, swainsonine, and 3-hydroxy-L-kynurenine (anticancer activity) and benzimidazole (antimicrobial, anticancer, and anti-HIV activities), and compounds with immunomodulatory effects in kinema supports its therapeutic potential. The correlation between the abundant species of Bacillus and primary and secondary metabolites was constructed with a bivariate result. This study proves that Bacillus spp. contribute to the formation of many targeted and untargeted metabolites in kinema for health-promoting benefits.

Microbial Composition of Fermented Korean Soy Paste (Doenjang) Prepared by Adding Different Herbs during Fermentation

The microbiota involved in Korean soy paste (doenjang) fermentation are the key factors determining its quality aspects. In this study, doenjang was prepared by adding three different herbs (Peppermint, Korean mint, and Coriander), and their effect on the microbiota composition was evaluated by 16S rRNA metagenomic analyses. The β-diversity statistics indicated clear distinctions in the doenjang microbiota after the addition of herbs. A microbial composition analysis revealed that Tetragenococcus was among the dominant genera in the four doenjang groups, with a relatively higher abundance in the Korean mint group. In the Peppermint and Korean mint doenjang groups, the levels of undesirable microbes, such as opportunistic pathogens belonging to the genera Sphingobacterium and Pantoea, were significantly reduced. Additionally, other desirable microbes that are known to exhibit beneficial properties and produce bioactive compounds, such as Saccharopolyspora and Buttiauxella, were present at significantly higher levels. Significant negative correlations between members of the Bacillaceae and Halomonadaceae, Lactobacillaceae and Tissierellaceae, and the Lacobacillaceae and Erwiniaceae families were observed, indicating possible antagonistic relationships. Taken together, our results demonstrated that the incorporation of herbs, particularly Peppermint and Korean mint, during doenjang fermentation resulted in significant shifts in the microbial composition and could be utilized for beneficial effect on its fermentation.