Characterization and correlation of microbial communities and metabolite and volatile compounds in doenjang fermentation

Discovery of Doenjang aging marker and metabolites alteration during long-term aging period: Targeted and untargeted metabolomic study

The aging of Doenjang enhances its flavor and complexity, making it highly valued by consumers. However, most previous studies have focused on aging periods of two years or less. Additionally, many analyzed samples are produced in laboratories or restricted to specific regions, limiting our understanding of long-term metabolic changes. In this study, we analyzed 49 traditional Doenjang samples aged from 1 to 30 years using CE-TOF/MS with both untargeted and targeted metabolomics to identify aging markers and metabolite profiles. The aging process significantly influenced the metabolites, increasing lactate, 13 amino acids, and four biogenic amines (histamine, tyramine, putrescine, and 2-phyenylethylamine), while reducing concentrations of arginine and tryptophan. These metabolic changes effectively distinguished short-term-aged Doenjang (1-2 years) from long-term-aged Doenjang (7-30 years). This integrated targeted and untargeted metabolomics provides better understanding into metabolic changes occurring during Doenjanbg maturation with practical applications for optimizing its safety and quality.

Bacillus that produces TTMP enhances the total ester content in Baijiu through biofortification

TTMP is a key flavor compound in Baijiu and also has potential health benefits. Bacillus are vital producers of TTMP; however, the connection between Bacillus in strong-flavor Daqu and TTMP is restricted. In this study, morphological and molecular biological screening and identification of Bacillus strains in strong-flavor Daqu were carried out, and their TTMP production capabilities were evaluated. Additionally, the influence of the selected strains on Baijiu flavor was assessed through simulated fermentation experiments. The experimental results demonstrated that out of the 18 strains of Bacillus spores screened, 12 could produce TTMP, indicating a diverse population of Bacillus spores capable of generating pyrazine compounds in Daqu. Among these, Bacillus subtilis YR-5 yields the highest TTMP at 761.32 mg/L, followed by Bacillus velzensis YR-3 and Bacillus velzensis YR-12 with yields of 553.25 mg/L and 341.19 mg/L, respectively. Under simulated fermentation conditions, the TTMP content increased significantly from 0.19 mg/mL to 0.63 mg/mL, 0.92 mg/mL, and 0.53 mg/mL after adding YR-3, YR-5, and YR-12 respectively; meanwhile, ester content in fermentation system increased by 69.84%,79.35%, and 64.15% respectively. These findings imply that the functional microorganisms required in the search for Baijiu can be screened and identified in Daqu, and the selected strains can be utilized for biofortification to enhance the content of TTMP in Baijiu and improve the flavor of Baijiu.

The effect of lactic acid bacteria as a starter on the microbial community and flavors of the fermented beef-soybean paste

In order to confirm how Lactobacillus plantarum (Lp) and Pediococcus pentosaceus (Pp) regulate the flavor and microbial community in fermented soybean products. This study compared the microbial community structure, physicochemical properties, and flavor of four different beef-soybean pastes fermented with Lp, Pp, a mixed starter (Lp and Pp were mixed in a 1:1 volume ratio, Lp-Pp), and a control (non-inoculated lactic acid bacteria, CK) and analyzed the correlation between dominant microbial genera and critical volatile flavor compounds. The results showed that lactic acid bacteria inoculation fermentation (particularly in the Pp and Lp-Pp groupings) increased bacterial richness while reducing fungal abundance, and promoted the formation of critical flavor compounds. The benzaldehyde, furfural, and methional, were strongly (r > 0.731) positively correlated with dominant microbial genera Lactobacillus, Diutina, and Kodamaea. This confirmed our hypothesis that lactic acid bacteria inoculation promotes flavor development by altering the microbial community structure.

Investigation of Microbial Community of Korean Soy Sauce (Ganjang) Using Shotgun Metagenomic Sequencing and Its Relationship with Sensory Characteristics

The microbial community of a soy sauce is one of the most important factors in determining the sensory characteristics of that soy sauce. In this study, the microbial communities and sensory characteristics of twenty samples of Korean soy sauce (ganjang) were investigated using shotgun metagenome sequencing and descriptive sensory analysis, and their correlations were explored by partial least square (PLS) regression analysis. The metagenome analysis identified 1332 species of bacteria, yeasts, molds, and viruses across 278 genera, of which Tetragenococcus, Bacillus, and Enterococcus accounted for more than 80% of the total community. In the fungal community, Zygosaccharomyces rouxii, Candida versatilis, Rhodotorula taiwanensis, Debaryomyces hansenii, and Aspergillus oryzae were dominant, while the viral community consisted entirely of bacteriophages, with Bacillus phages SIOphi accounting for 93%. According to the results of the PLS analysis, desirable sensory characteristics, such as umami, sweet, and roasted soybean, as well as preference, were associated with Tetragenococcus, Lysinibacillus, Enterococcus, Staphylococcus, Lactobacillus, Pediococcus, and Weissella. The musty flavor, which is a typical property of traditional fermented foods, was related to Halomonas and Psychrobacte, while the bitter, acrid taste and sour smell were closely associated with Chromohalobacter. The results of this study provide comprehensive information on the microbial community of ganjang and may be used to select starter cultures for soy sauces.

Characterization of the microbial communities and their correlations with volatile flavor compounds and physicochemical factors in Bashang suancai, a traditional Chinese pickle

Bashang suancai is one of the most wellknown traditional fermented vegetables in North China. The study examined the variations in bacterial diversity, physicochemical properties, and volatile flavor compounds (VFCs) of Bashang suancai over a 7-day fermentation period, utilizing Illumina NovaSeq sequencing and headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The leading bacterial phyla were Firmicutes, Proteobacteria, and Cyanobacteria, while the predominant bacterial species included Vibrio, Lactiplantibacillus, Cyanobacteriales, Weissella, and Latilactobacillus. The bacterial community diversity decreased significantly following 7 days of fermentation. The microbial profiles were markedly affected by pH, reducing sugar content (RSC), and salt content (SC). A total of 187 VFCs were identified from the specimens. Following 5 days of fermentation, the taste compounds achieved equilibrium, with isothiocyanates, alcohols, and esters predominating among the volatile molecules. Spearman correlation analysis revealed that a strong link between Latilactobacillus, Levilactobacillus, Lactiplantibacillus, Weissella, and Vibrio with the flavor of pickles. This study established a significant foundation for identifying strains that enhance taste development and improve the nutritional and sensory quality of Bashang suancai.

Unraveling the correlations between microbial communities and metabolic profiles of strong-flavor Jinhui Daqu with different storage periods

Daqu is a saccharification agent required for fermenting Baijiu, a popular Chinese liquor. Our objective was to investigate the relationships between physicochemical indices, microbial community diversity, and metabolite profiles of strong-flavor Jinhui Daqu during different storage periods. During different storage periods of Jinhui Daqu, we combined Illumina MiSeq sequencing and non-target sequencing techniques to analyze dynamic changes of the microbial community and metabolite composition, established a symbiotic network and explored the correlation between dominant microorganisms and differential metabolites in Daqu. Fungal community diversity in 8d_Daqu was higher than that in 45d_Daqu and 90d_Daqu, whereas bacterial community diversity was higher in 90d_Daqu. Twelve bacterial and four fungal genera were dominant during storage of Daqu. Bacillus, Leuconostoc, Kroppenstedtia, Lactococcus, Thermomyces and Wickerhamomyces decreased as the storage period increased. Differences of microbiota structure led to various metabolic pathways, and 993 differential metabolites were found in all Daqu samples. Differential microorganisms were significantly related to key metabolites. Major metabolic pathways involved in the formation of amino acids and lipids, such as l-arogenate and hydroxyproline, were identified. Interactions between moisture, acidity, and microbes may drive the succession of the microbial community, which further affects the formation of metabolites.

Effect of fermentation containers on the taste characteristics and microbiota succession of soy sauce

Modernization of the traditional fermentation industry has been a major trend recently, such as the upgrading of fermentation containers. This study investigated the taste differences and their material basis of soy sauce fermented in tank and pond (SSFT and SSFP), and further explore the key influencing factors of taste. The intensities of umami, kokumi and sour taste in SSFT were weaker than SSFP, which were associated with 9 basic taste-active compounds, including acetic acid, lactic acid, propanedioic acid, citric acid, glutamic acid, alanine, tyrosine, d-galactose and erythritol. Moreover, 270 peptides and amino acid derivatives were potential compounds for taste difference, of which 78 % were more abundant in SSFP. Five bacterial genera (Kocuria, Tetragenococcus, Pediococcus, Staphylococcus, Weissella) and 4 fungal genera (Wickerhamiella, Millerozyma, Candida, Zygosaccharomyces) may be the functional core microbe for flavor differences in SSFT and SSFP. This study will provide theoretical value for quality improvement in the modern large-scale production of soy sauce.

Effects of Salinity on Physicochemical Properties, Flavor Compounds, and Bacterial Communities in Broad Bean Paste-Meju Fermentation

Broad bean paste (BBP) is a traditional fermented soy food, and its high salt content not only prolongs the fermentation time but also threatens human health. In this study, three BBP-meju with different salt concentrations were prepared, and the effects of varying salinity on fermentation were comprehensively compared. The results showed that salt-reduced fermentation contributed to the accumulation of amino acid nitrogen, reducing sugars, free amino acids, and organic acids. Alcohols, esters, aldehydes, and acids were the main volatile flavor compounds in BBP-meju, and the highest total volatile flavor compounds were found in medium-salt meju. Bacillus, Staphylococcus, Aspergillus, and Mortierella were the dominant microbial communities during fermentation, and there were also three opportunistic pathogens, Enterobacter, Pantoea, and Brevundimonas, respectively. According to Spearman correlation analysis, Wickerhamomyces, Bacillus, Staphylococcus, and Mortierella all showed highly significant positive correlations with ≥3 key flavor compounds, which may be the core functional flora. Furthermore, the dominant microbial genera worked synergistically to promote the formation of high-quality flavor compounds and inhibit the production of off-flavors during salt-reduced fermentation. This study provides a theoretical reference for the quality and safety control of low-salt fermented soy foods.

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.

Unraveling the carbohydrate metabolic characteristics of Leuconostoc mesenteroides J18 through metabolite and transcriptome analyses

The metabolic characteristics of Leuconostoc mesenteroides subsp. mesenteroides J18, which is mainly responsible for kimchi fermentation, on various carbon sources were investigated through carbon utilization, metabolite, and transcriptome analyses at different culture conditions (10 and 30 °C with/without 2.5% NaCl). The metabolic features of strain J18 were relatively similar across the four culture conditions. However, the metabolic characteristics of strain J18 showed significant variations depending on the carbon source. These distinct metabolic traits of strain J18 on various carbon sources were validated through transcriptomic analyses and the reconstruction of metabolic pathways. The transcriptional expression of the metabolic pathways in response to each carbon source consistently correlated with the production profiles of metabolites, including ethanol, acetoin, diacetyl, and riboflavin, in each carbon source. Our findings suggests that the abundance of Leu. mesenteroides during fermentation and the taste and flavor of fermented food products can be controlled by altering the carbon sources.

Flavor Characterization of Traditional Fermented Soybean Pastes from Northeast China and Korea

This study compares the physicochemical properties, taste, and volatile compounds of Northeastern Chinese dajiang (C) and Korean doenjang (K) and distinguishes the discriminant volatile metabolites between them. The result revealed that compared to group C, group K exhibited more similar physicochemical properties and had lower pH, moisture, and amino acid nitrogen content, while demonstrating higher titratable acidity, salt content, and reduced sugar content. The electronic tongue analysis showed that the saltiness and umami of soybean pastes had high response values, enabling clear differentiation of the overall taste between the two types of soybean pastes. A total of 71 volatile substances from the soybean pastes were identified through solid-phase microextraction gas chromatography-mass spectrometry. Furthermore, orthogonal partial least squares discriminant analysis revealed 19 volatile compounds as differentially flavored metabolites. Our study provides a basis for explaining the differences in flavor difference of Northeastern Chinese dajiang and Korean doenjang from the perspective of volatile metabolites.

Comparison of microbial communities and volatile profiles of wines made from mulberry and grape

In this study, three kinds of wines separately made from mulberry (MW), grape (GW), or mulberry/grape (MGW) were developed and their enological parameters, sensory scores, volatile components, and microbiota were investigated and compared. Contrary to the order of residual sugar and acidity of the three kinds of wines, the order of alcohol content from high to low is GW, MW, and MGW. A total of 60 volatile components (VCs), including esters (17), alcohols (12), acids (6), aldehydes (7), ketones (3), alkenes (3), amines (3), alkanes (4), pyrazines (2), benzene (1), sulfide (1), and thiazole (1), were identified by gas chromatography-ion mobility spectrometer (GC-IMS). The fingerprint of VCs and principal component analysis revealed that the volatile profiles of MGW and GW were more similar in comparison to that of MW and were significantly correlated with the mass ratio of mulberry to grape. Lactobacillus, Weissella, Pantoea, Leuconostoc, Lactococcus, Paenibacillus, Pediococcus, and Saccharomyces were identified as the main microflora at the genus level shared by the MW, MGW, and GW, suggesting that the heterolactic bacteria may contribute more to the high content of volatile acids in MW and MGW. The heatmap of core microbiota and main VCs of MW, MGW, and GW suggested the complicated and significant correlation between them. The above data implied that the volatile profiles were more closely related to the raw materials of winemaking and markedly affected by the fermentation microorganisms. This study provides references for evaluation and characterization of MGW and MW and improvement of MGW and MW winemaking process. KEY POINTS: • Fruit wine enological parameters, volatile profile, and microbiota were compared. • Sixty volatile compounds were identified by GC-IMS in three types of fruit wines. • Winemaking materials and microbiota affect volatile profiles of the fruit wines.

Complete Genome Sequence of Bacillus sp. Strain KICET-1, Isolated from Soybean Paste (Doenjang)

Bacillus sp. strain KICET-1, a bacterium isolated from traditional Korean soybean paste (Doenjang) at Osong, has one 4,099,652-bp DNA chromosome. The G+C content is 46.1%, and KICET-1 shares 99.64% similarity with Bacillus velezensis CR-502T (AY603658), according to phylogenetic classification based on 16S rRNA gene sequences.

Comparisons of Physicochemical Properties, Bacterial Diversities, Isoflavone Profiles and Antioxidant Activities on Household and Commercial doenjang

In this study, the physicochemical properties (pH, acidity, salinity, and soluble protein), bacterial diversities, isoflavone contents, and antioxidant activities of doenjang (fermented soy paste), household doenjang (HDJ), and commercial doenjang (CDJ), were assessed and compared. The values of pH 5.14-5.94 and acidity 1.36-3.03%, indicated a similar level in all doenjang. The salinity was high in CDJ at 12.8-14.6%, and the protein contents (25.69-37.54 mg/g) were generally high in HDJ. Forty-three species were identified from the HDJ and CDJ. The main species were verified to be Bacillus amyloliquefaciens (B. amyloliquefaciens), B. amyloliquefaciens subsp. plantarum, Bacillus licheniformis, Bacillus sp. and Bacillus subtilis. Comparing the ratios of isoflavone types, the HDJ has an aglycone ratio of >80%, and 3HDJ indicates a ratio of isoflavone to aglycone of 100%. In the CDJ, except 4CDJ, glycosides account for a high proportion of more than 50%. The results of antioxidant activities and DNA protection effects were variedly confirmed regardless of HDJs and CDJs. Through these results, it is judged that HDJs have a variety of bacterial species compared to CDJs, and these are biologically active and converted from glycoside to aglycone. Bacterial distribution and isoflavone contents could be used as basic data.

Succession and Diversity of Microbial Flora during the Fermentation of Douchi and Their Effects on the Formation of Characteristic Aroma

This study aims to understand the development and succession of the microbial community during the production of traditional Aspergillus-type Douchi as well as their effects on the formation and variation of characteristic aroma compounds. High-throughput sequencing technology, solid-phase microextraction, gas chromatography-mass spectrometry, and Spearman correlation analysis were conducted to study the changes in the microbial community and characteristic flavor during the fermentation process. Aspergillus spp. was dominant in the early stage of fermentation, whereas Staphylococcus spp., Bacillus spp., and Millerozyma spp. became dominant later. At the early stage, the main flavor compounds were characteristic soy-derived alcohols and aldehydes, mainly 1-hexanol, 1-octen-3-ol, and nonanal. In the later stage, phenol, 2-methoxy-, and 3-octanone were formed. Correlation analysis showed that six bacterial genera and nine fungal genera were significantly correlated with the main volatile components, with higher correlation coefficients, occurring on fungi rather than bacteria. Alcohols and aldehydes were highly correlated with the relative abundance of bacteria, while that of yeast species such as Millerozyma spp., Kodamaea spp., and Candida spp. was positively correlated with decanal, 3-octanol, 2-methoxy-phenol, 4-ethyl-phenol, 3-octanone, and phenol. The novelty of this work lies in the molds that were dominant in the pre-fermentation stage, whereas the yeasts increased rapidly in the post-fermentation stage. This change was also an important reason for the formation of the special flavor of Douchi. Correlation analysis of fungi and flavor substances was more relevant than that of bacteria. As a foundation of our future focus, this work will potentially lead to improved quality of Douchi and shortening the production cycle by enriching the abundance of key microbes.

Improving the function of pickle insoluble dietary fiber by coupling enzymatic hydrolysis with HHP treatment

In order to improve the function of insoluble dietary fiber (IDF) extracted from pickle, the coupled enzymatic hydrolysis and high hydrostatic pressure treatment method (EHHP) was used to modify its structure. Compared with the unmodified IDF (U-IDF), analysis of the particle size dispersion, bulk density, surface structure monosaccharide composition, microstructure, thermodynamic properties showed that the modified IDF (EHHP-IDF) has a looser and more porous structure, reduced particle size, bulk density, crystal strength and thermal stability, and increased xylose and galactose content. Due to the special looser microstructure, EHHP-IDF has showed the notable capacity of absorption of oil, glucose, nitrite, cholesterol as well as Pb2+. Collectively, these results show that EHHP has good potential use as an ideal modification method to improve the function of IDF, and a novel functional ingredient of EHHP-IDF which could be used in future food processing was obtained in this study.

Relationship between the Dynamics of Gross Composition, Free Fatty Acids and Biogenic Amines, and Microbial Shifts during the Ripening of Raw Ewe Milk-Derived Idiazabal Cheese

This study reports for the first time the relationship between bacterial succession, characterized by high-throughput sequencing (sequencing of V3-V4 16S rRNA regions), and the evolution of gross composition, free fatty acids (FFAs) and biogenic amines (BAs) during cheese ripening. Specifically, Idiazabal PDO cheese, a raw ewe milk-derived semi-hard o hard cheese, was analysed. Altogether, 8 gross parameters were monitored (pH, dry matter, protein, fat, Ca, Mg, P and NaCl) and 21 FFAs and 8 BAs were detected. The ripening time influenced the concentration of most physico-chemical parameters, whereas the producer mainly affected the gross composition and FFAs. Through an O2PLS approach, the non-starter lactic acid bacteria Lactobacillus, Enterococcus and Streptococcus were reported as positively related to the evolution of gross composition and FFAs release, while only Lactobacillus was positively related to BAs production. Several environmental or non-desirable bacteria showed negative correlations, which could indicate the negative impact of gross composition on their growth, the antimicrobial effect of FFAs and/or the metabolic use of FFAs by these genera, and their ability to degrade BAs. Nonetheless, Obesumbacterium and Chromohalobacter were positively associated with the synthesis of FFAs and BAs, respectively. This research work provides novel information that may contribute to the understanding of possible functional relationships between bacterial communities and the evolution of several cheese quality and safety parameters.

Dynamics and correlation of microbial communities and metabolic compounds in doenjang-meju, a Korean traditional soybean brick

To investigate the general fermentation characteristics of doenjang-meju (a Korean traditional soybean brick), they were periodically collected from eight different manufacturers during all fermentation stages, and their microbial communities and metabolic compounds (metabolites and volatile compounds) were analyzed. Bacillus and/or lactic acid bacteria (LAB, mainly Enterococcus) and Aspergillus were abundant during fermentation. Fructose and glucose; glycerol; acetate and lactate; and cadaverine, putrescine, tyramine, and histamine were identified as the major sugars, carbon compound, organic acids, and biogenic amines, respectively. Tetramethylpyrazine, butyric acid, butyl butyrate, butanol, acetic acid, 2-methylbutyrate, acetoin, 2,3-butandiol, and nonadecane were the major volatile compounds. However, the profiles of microbial communities, metabolites, and volatile compounds during fermentation varied significanlty among samples. Principal component analysis revealed that doenjang-meju had two differentiated fermentation features, Bacillus-dominated fermentation and LAB (mainly Enterococcus)-dominated fermentation, each having different metabolite and volatile compound profiles. Particularly, fewer volatile compounds were detected in LAB-dominated doenjang-meju samples. Correlation analysis showed a strong negative correlation between Bacillus and LAB, and bacteria and fungi were less correlated with each other. Enterococcus, LAB, and Bacillus were positively correlated with lactate, flavonoid aglycones, and putrescine, respectively, suggesting that they might be mainly responsible for producing the compounds during fermentation. This study provides insights into the general fermentation characteristics of doenjang-meju.

Microbial Communities and Flavor Compounds during the Fermentation of Traditional Hong Qu Glutinous Rice Wine

As a traditional Chinese rice wine, Hong Qu glutinous rice wine (HQW) is popular among consumers due to its unique flavor. However, its quality changes during fermentation, and the potential relationships between flavor and microbes have not been systematically researched. In this work, physicochemical properties (pH, total sugar, alcohol, amino acid nitrogen), flavor compounds (organic acids, free amino acids, and volatile compounds), and microbial communities were investigated. The results revealed that Pantoea, Lactiplantibacillus, Lactobacillus, Leuconostoc, and Weissella predominated the bacterial genera, and Monascus was the predominant fungal genus. Organic acids, free amino acids, and key volatile compounds (esters and alcohols) significantly increased during fermentation. The correlations analysis showed that Lactiplantibacillus was closely associated with flavor compounds formation. This study deepens our understanding of the roles of microorganisms in flavor formation on traditional HQW fermentation.

Fortified Fermented Rice-Acid Can Regulate the Gut Microbiota in Mice and Improve the Antioxidant Capacity

The study aimed to explore the effects of fortified fermented rice-acid on the antioxidant capacity of mouse serum and the gut microbiota. Hair characteristics, body mass index, intestinal villus height, intestinal crypt depth, serum antioxidant capacity, and gut microbiota of mice were first measured and the correlation between the antioxidant capacity of mouse serum and the gut microbiota was then explored. The mice in the lactic acid bacteria group (L-group), the mixed bacteria group (LY-group), and the rice soup group (R-group) kept their weight well and had better digestion. The mice in the L-group had the better hair quality (dense), but the hair quality in the R-group and the yeast group (Y-group) was relatively poor (sparse). In addition, the inoculation of Lactobacillus paracasei H4-11 (L. paracasei H4-11) and Kluyveromyces marxianus L1-1 (K. marxianus L1-1) increased the villus height/crypt depth of the mice (3.043 ± 0.406) compared to the non-inoculation group (R-group) (2.258 ± 0.248). The inoculation of L. paracasei H4-11 and K. marxianus L1-1 in fermented rice-acid enhanced the blood antioxidant capacity of mouse serum (glutathione 29.503 ± 6.604 umol/L, malonaldehyde 0.687 ± 0.125 mmol/L, catalase 15.644 ± 4.618 U/mL, superoxide dismutase 2.292 ± 0.201 U/mL). In the gut microbiota of L-group and LY-group, beneficial microorganisms (Lactobacillus and Blautia) increased, but harmful microorganisms (Candidatus Arthromitus and Erysipelotrichales) decreased. L. paracasei H4-11 and K. marxianus L1-1 might have a certain synergistic effect on the improvement in antibacterial function since they reduced harmful microorganisms in the gut microbiota of mice. The study provides the basis for the development of fortified fermented rice-acid products for regulating the gut microbiota and improving the antioxidant capacity.

Bacterial Community and Anti-Cerebrovascular Disease-Related Bacillus Species Isolated from Traditionally Made Kochujang from Different Provinces of Korea

Traditionally made Kochujang (TMK) is a long-term fermented soybean and rice mixture with red pepper and salts. The ambient bacteria in rice straw and nutrient components of Kochujang influence the bacteria community. We aimed to investigate the bacterial composition and quality of TMK from different provinces of Korea: Chungcheung (CC), Jeolla (JL), Kyungsang (KS), and GeongGee plus Kangwon (GK) provinces, and Jeju island (JJ). Furthermore, Bacillus spp. isolated from TMK were studied to have anti-cerebrovascular disease activity and probiotic properties. Seventy-three TMK samples from different regions were collected to assess the biogenic amine contents, bacteria composition using next-generation methods, and bacterial functions using Picrust2. Bacillus spp. was isolated from the collected TMK, and their antioxidant, fibrinolytic, and angiotensin I conversion enzyme (ACE) inhibitory activities and probiotic properties were examined. KS TMK had lower sodium contents than the other TMK. There were no significant differences in histamine and tyramine contents among the TMK samples in different provinces. The predominant bacteria in TMK was Bacillus spp., but KS included much less Bacillus spp. and higher Enterococcus and Staphylococcus than the other TMK. Gene expression related to lipopolysaccharide biosynthesis was higher in KS TMK than the other TMK in Picrust2. The predominant Bacillus spp. isolated from TMK was B. subtilis and B. velezensis. B. subtilis SRCM117233, SRCM117245, and SRCM117253 had antioxidant activity, whereas B. subtilis had higher fibrinolytic activity than other Bacillus spp. Only B. velezensis SRCM117254, SRCM117311, SRCM117314, and SRCM117318 had over 10% ACE inhibitory activity. In conclusion, KS had less Bacillus related to lower sodium contents than the other TMK. The specific strains of B. subtilis and B. velezensis had antioxidant, fibrinolytic, and ACE inhibitory activity, and they can be used as a starter culture to produce better quality controlled Kochujang with anti-cerebrovascular disease activities.