Fermented Soybean Products Research Articles

Phenotypic and genomic analyses of bacteriocin-producing probiotic Enterococcus faecium EFEL8600 isolated from Korean soy-meju.

Enterococcus faecium is a prevalent species found in fermented soybean products, known for its contributions to flavor development and inhibition of pathogenic microorganisms during fermentation. This study aims to provide comprehensive phenotypic and genomic evidence supporting the probiotic characteristics of E. faecium EFEL8600, a bacteriocin-producing strain isolated from Korean soy-meju. Phenotypic analysis revealed that EFEL8600 produced a peptide with inhibitory activity against Listeria monocytogenes, estimated to be 4.6 kDa, corresponding to the size of enterocins P or Q. Furthermore, EFEL8600 exhibited probiotic traits, such as resilience in gastrointestinal conditions, antioxidant and anti-inflammatory activities, and protection of the intestinal barrier. Safety assessments demonstrated no hemolytic and bile salt deconjugation activities. Genomic analysis revealed the presence of several genes associated with probiotic characteristics and bacteriocin production, while few deleterious genes with a low likelihood of expression or transferring were detected. Overall, this study highlights E. faecium EFEL8600 as a potent anti-listeria probiotic strain suitable for use as a starter culture in soymilk fermentation, providing potential health benefits to consumers.

Production and characterization of bioactive peptides in fermented soybean meal produced using proteolytic Bacillus species isolated from kinema.

The study aims to enhance the functional properties of soybean meal (SBM) using potent proteolytic Bacillus strains isolated from kinema, a traditional fermented soybean product of Sikkim Himalaya. Selected Bacillus species; Bacillus licheniformis KN1G, B. amyloliquifaciens KN2G, B. subtilis KN36D, B. subtilis KN2B, and B. subtilis KN36D were employed for solid state fermentation (SSF) of SBM samples. The water and methanol extracts of SBM hydrolysates presented a significant increase in antioxidant activity. The water-soluble extracts of B. subtilis KN2B fermented SBM exhibited the best DPPH radical scavenging activity of 2.30mg/mL. In contrast, the methanol-soluble extract of B. licheniformis KN1G fermented SBM showed scavenging activity of 0.51mg/mL. Proteomic analysis of fermented soybean meal revealed several common and unique peptides produced by applying different starter cultures. Unique antioxidant peptides (HFDSEVVFF and VVDMNEGALFLPH) were identified from FSBM via LC/MS. B. subtilis KN36D showed the highest diversity of peptides produced during fermentation. The results indicate the importance of specific strains for fermentation to upgrade the nutritional value of raw fermented biomass.

Volatile profiles and aroma-active components of Northern Thai fermented soybean (thua nao) produced from controlled and uncontrolled fermentations

Thua nao is a fermented soybean product that is widely consumed, especially in the northern part of Thailand. Thua nao can be used as a condiment to enhance the aroma and flavor of foods. In general, commercial thua nao is traditionally made by indigenous microbial, especially Bacillus spp. fermentation under ambient conditions, leading to inconsistencies in product aroma quality. To solve this problem, inoculation of selected microorganisms can help control thua nao consistency. The objective of this research was to characterize and compare volatile aroma-active compounds in three samples, including thua nao made by commercial Bacillus subtilis inoculation fermented under controlled conditions (YSB) and two thua nao products made by indigenous fermentation in commercial production sites in Lumpoon (LPN) and Chiang-Mai (CMI) provinces, Thailand. It was found that 2-methyl butanoic acid, phenylethyl alcohol, benzaldehyde, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine and 2-methoxy phenol were dominant compounds in the YSB samples. These compounds contributed to fermented/sour, floral, almond-like and nutty aromas, which were related to positive attributes perceived by consumers. In contrast, several aldehydes and ketones related to off-aroma as oxidized, fatty, green, and earthy attributes derived from lipid oxidations were dominantly detected in samples from uncontrolled fermentations (LPN and CMI). From the study, it can be implied that inoculation of B. subtilis in thua nao fermentation could enhance aroma compounds with positive attributes and thus improve the organoleptic property of the product. These findings could benefit fermented soybean manufacturers to improve their aroma quality and to control products’ consistency by controlling fermentation conditions.

Determination of γ-aminobutyric acid in fermented soybean products by HPLC coupled with pre-column derivatization

This study reports a pre-column derivatization HPLC stragety to determine the content of GABA in fermented soybean products. 9-Fluorenylmethyloxycarbonyl chloride (Fmoc-Cl) is employed as the derivative reagent with chromophore linked to GABA, which lacks of chromophore for UV/DAD analysis in its pristine structure. After the detection wavelength was confirmed, the derivatization and analysis conditions were also optimized, including pH and amount of boric acid buffer, amount of derivative reagent, the mobile phases and their gradient. Methodological investigation showed that the derivatized GABA (Fmoc-GABA) has good linearity in the range of 1–100 µg/mL, low limit of quantification (LOQ, at 1 µg/mL) and limit of detection (LOD, at 0.3 µg/mL), and good recoveries of three spiked levels (between 83.8% and 100.8% with RSDs less than 5%). Furthermore, thirty-two commercial fermented soy products in four matrices (soy sauce, soy paste, bean curd, lobster sauce) were analyzed by the proposed method for validation. As a consequence, the concentrations of GABA in these soy products were in the range of 48.4–381 mg/kg.

Nutritional aspects and amino acid profiles of tempe from local, imported, and black soybean relating to the functional properties

Soybean (Glycine max L) is a legume rich in protein, fat, vitamins, minerals and fibre. The nutritional value of soybeans and the amino acid profiles of the processed fermented soybean (Tempe) products need to be studied. Soybean and Tempe flour from black soybean, local soybean (Anjasmoro variety) and imported soybean (USA soybean) were analyzed proximately, including carbohydrates (spectrophotometric method), protein (Kjeldahl method), fat (Soxletation method), fiber (gravimetric method), and water content (gravimetric method). The amino acid profile of Tempe flour was measured by UPLC and LC/MS/MS methods. Local soybeans had the highest protein content (45.19%), followed by black and imported soybeans (36.87% and 35.95%, respectively). The protein content of local soybean Tempe flour was the highest (45.83%) compared to other soybean Tempe flour. The fiber content of local and black soybean Tempe flour (14.79% and 13.81%, respectively) was higher than that of imported Tempe. Amino acid profiles test of black soybean Tempe flour, local soybean, and imported soybean showed that the amino acids L-Glutamic Acid, L-Arginine, L-Leucine, and L-Aspartic Acid had the highest amounts compared to other amino acids, ranging from 30-75 thousand ppm. This shows that various soybeans affect the amino acid composition of the soybean protein. The amino acid content of Tempe from local soybeans is higher than the amino acid content of tempe from black and imported soybeans. This may influence the amino acids or peptides’ functional properties, such as antihypertensive and antimicrobial properties. Continuous research in vitro and in vivo should be conducted to explore the functional properties of Tempe flour from local soybean.

Distribution of vitamin K_2 content in Chinese traditional fermented soybean products

To determine the content of vitamin K_2 in different types of fermented bean products and analyze the difference of vitamin K_(2 )content. A total of 98 kinds of typical fermented bean products were included in Chinese traditional fermented bean products(Douchi, Sufu, soybean paste). Process, region, sales volume, raw materials and flavor were considered, and the content of vitamin K_2 in fermented bean products was determined by high performance liquid chromatography. Chinese bean fermented foods generally contained vitamin K_2, and the subtype menaquinone-7(MK-7)was the main one. The content of vitamin K_2 in Douchi was the highest(437.55 μg/100 g), the content of vitamin K_2 in Sufu and Soybean paste were lower(7.48 μg/100 g and 2.47 μg/100 g). The content of vitamin K_2 in bacterial Douchi was higher than that in Mucor type and Aspergillus oryzae type which were 403.94, 232.98 and 81.00 μg/100 g(P<0.05). Soybean type Douchi was higher than that in black bean type of Douchi which were 610.41, 178.08 μg/100 g(P<0.05), and the content of vitamin K_2 in dry Douchi was higher than the content of vitamin K_2 in water Douchi which were 1 517.45 μg/100 g, 297.58 μg/100 g(P<0.05). However, there were no significant difference in the content of vitamin K_2 in Soybean paste and Sufu in different types and regions(P > 0.05). Vitamin K_2 is widely contained in Chinese fermented bean products, and its content is mainly affected by fermentation microorganisms and processing technology.

Evaluation of Sufu Fermented Using Mucor racemosus M2: Biochemical, Textural, Structural and Microbiological Properties.

The quality and safety of sufu fermented using Mucor racemosa M2 was studied and compared with naturally fermented sufu. After 90 days post-fermentation, both naturally fermented and inoculated fermented sufu reached the maturity standard of sufu, and the degree of protein hydrolysis of natural sufu (WP/TP: 34% ± 1%; AAN/TN: 33% ± 1%) was slightly higher than that of the inoculated sufu (WP/TP: 28.2% ± 0.4%; AAN/TN: 27% ± 1%). The hardness and adhesiveness of inoculated sufu (Hadness: 1063 g ± 211 g; Adhesiveness: -80 g ± 47 g) were significantly greater than those of natural sufu (Hadness: 790 g ± 57 g; Adhesiveness: -23 g ± 28 g), and the internal structure of natural sufu was denser and more uniform than that of inoculated sufu. A total of 50 aroma compounds were detected in natural and inoculated sufu. The total number of bacterial colonies in naturally fermented sufu was significantly higher than that in inoculated sufu, and the pathogenic bacteria in both types of fermented sufu were lower than the limit of pathogenic bacteria required in fermented soybean products. The content of biogenic amines in sufu was determined by high performance liquid chromatography (HPLC), and the results showed that the content of biogenic amines (Putrescine, Cadaverine, Histamine, Tyramine, etc.) in naturally fermented sufu was significantly higher than that in inoculated fermented sufu. Especially the histamine content, after 90 days of fermentation, was found to be 64.95 ± 4.55 for inoculated fertilization and 44.24 ± 0.71 for natural fertilization. Overall, the quality of inoculated sufu was somewhat better than that of natural sufu, and the M2 strain can be used to ferment sufu.

Comparison of the Biotin Contents of Traditionally and Commercially Fermented Soybean Products

Comparison of the Biotin Contents of Traditionally and Commercially Fermented Soybean Products

Whole-Cell Biocatalytic Production of Acetoin with an aldC-Overexpressing Lactococcus lactis Using Soybean as Substrate

Douchi is a traditional Chinese fermented soybean product, in which acetoin is a key flavor substance. Here, the α-acetolactate decarboxylase gene aldC was cloned from Lactiplantibacillus (L.) plantarum and overexpressed in Lactococcus (L.) lactis NZ9000 by nisin induction. The ALDC crude enzyme solution produced an enzyme activity of 35.16 mU. Next, whole cells of the recombinant strain NZ9000/pNZ8048-aldC were employed as the catalyst to produce acetoin in GM17 medium. An optimization experiment showed that an initial OD600 of 0.6, initial pH of 7.5, nisin concentration of 20 ng/mL, induction temperature of 37 °C and static induction for 8 h were the optimal induction conditions, generating the maximum acetoin production (106.93 mg/L). Finally, after incubation under the optimal induction conditions, NZ9000/pNZ8048-aldC was used for whole-cell biocatalytic acetoin production, using soybean as the substrate. The maximum acetoin yield was 79.43 mg/L. To our knowledge, this is the first study in which the aldC gene is overexpressed in L. lactis and whole cells of the recombinant L. lactis are used as a biocatalyst to produce acetoin in soybean. Thus, our study provides a theoretical basis for the preparation of fermented foods containing high levels of acetoin and the biosynthesis of acetoin in food materials.

Glucoregulatory Properties of Fermented Soybean Products

Type 2 diabetes mellitus is a chronic metabolic disease, characterized by persistent hyperglycemia, the prevalence of which is on the rise worldwide. Fermented soybean products (FSP) are rich in diverse functional ingredients which have been shown to exhibit therapeutic properties in alleviating hyperglycemia. This review summarizes the hypoglycemic actions of FSP from the perspective of different target-related molecular signaling mechanisms in vitro, in vivo and clinical trials. FSP can ameliorate glucose metabolism disorder by functioning as carbohydrate digestive enzyme inhibitors, facilitating glucose transporter 4 translocation, accelerating muscular glucose utilization, inhibiting hepatic gluconeogenesis, ameliorating pancreatic dysfunction, relieving adipose tissue inflammation, and improving gut microbiota disorder. Sufficiently recognizing and exploiting the hypoglycemic activity of traditional fermented soybean foods could provide a new strategy in the development of the food fermentation industry.

Bacterial Communities in Lanna Fermented Soybeans from Three Different Ethnolinguistic Groups in Northern Thailand.

Northern Thailand, the main part of the Lanna region, is home to a diverse range of ethnic groups, each with their own food and cultural heritage. The bacterial compositions in fermented soybean (FSB) products indigenous to three Lanna ethnolinguistic groups, including Karen, Lawa, and Shan, were investigated in this study. Bacterial DNA was extracted from the FSB samples and subjected to 16S rRNA gene sequencing using the Illumina sequencing platform. Metagenomic data showed that the predominant bacteria in all FSBs were members of the genus Bacillus (49.5-86.8%), and the Lawa FSB had the greatest bacterial diversity. The presence of genera Ignatzschineria, Yaniella, Atopostipes in the Karen and Lawa FSBs and Proteus in the Shan FSB might be indicators of food hygiene problems during processing. The network analysis predicted antagonistic effects of Bacillus against some indicator and pathogenic bacteria. The functional prediction revealed some potential functional properties of these FSBs. The presence of Bacillus in all FSBs and Vagococcus in the Shan FSB suggests that these FSBs could potentially be good sources of beneficial bacteria, and they should be conserved and promoted for health and food security reasons. However, food processing hygiene measures should be introduced and monitored to warrant their properties as health foods.

Effects of selected Bacillus strains on the biogenic amines, bioactive ingredients and antioxidant capacity of shuidouchi

The control of biogenic amines (BAs) is crucial to guarantee the safety of fermented soybean products. In this study, the BAs composition of eleven shuidouchi samples was analyzed, and the BAs degradation strains were selected from shuidouchi samples with a low BAs content. Then the influences of screened BAs degradation strains on BAs, total phenolics (TP), total flavonoids (TF), isoflavones and the antioxidant ability of fermented shuidouchi were evaluated. Results showed that the total BAs content of all shuidouchi samples was within the safe range, while the GZXQ, GZQY and GZMX samples had higher levels of tyramine. Meanwhile, 109 strains were isolated from the YNLJ, GZLG, GZMZ, GZDY, and YNHY sample. Bacillus tropicus A11, Bacillus siamensis D11, Bacillus subtilis T2, and B. subtilis U2 with higher BAs degradation capacity and lower BAs production ability were selected to ferment shuidouchi. These four Bacillus strains could effectively control the BAs concentration of fermented shuidouchi, especially B. tropicus A11 and B. siamensis D11. Furthermore, compared to naturally fermented shuidouchi, higher levels of antioxidant ability, TP, TF, daidzein, glyciein, and genistein were found in the shuidouchi fermented with selected strains. These findings demonstrated that these screened strains could be applied as potential candidates for the production of high quality shuidouchi.

Determination of Γ-Aminobutyric Acid in Fermented Soybean Products by Hplc Coupled with Pre-Column Derivatization

Determination of Γ-Aminobutyric Acid in Fermented Soybean Products by Hplc Coupled with Pre-Column Derivatization

건강한 장(腸) 마이크로바이옴 환경조성에 도움을 주는 장(醬) 마이크로바이옴

‘마이크로바이옴"(microbiome)은 미생물군집(microbiota)과 유전체(genome)를 합한 말로, 인체에 존재하는 미생물 군집과 유전적 정보를 종합적으로 연구하는 기술로 정의된다. 최근에는 인체뿐만 아니고 식물, 토양, 식품 등 분야에서도 마이크로바이옴 기술을 접목한 연구가 식품의 품질향상과 안전성 확보를 위한 대안으로 주목을 받고 있다. 우리나라 대표적인 전통발효식품인 장류는 다양한 미생물의 분해작용에 의해 영양기능성이 우수한 기호식품이기는 하지만, 원하지 않는 미생물에 의한 아플라톡신, 바이오제닉아민 등 위해물질의 생성으로 안전성 논란의 중심에 있기도 하다. 따라서 장류식품에 포함된 다양한 미생물 군집의 실태를 파악하고 이들이 인체에 어떤 긍정적인 영향을 주는지 조사 연구하는 것은 매우 중요하다. 많은 연구자들에 의해 보도된 바와 같이 장류식품에는 품목에 상관없이 대체적으로 세균에서는 Bacillus 속이 진균에서는 Aspergillus, Zygosaccharomyces 속이 우점하고 있다. 일부 간장, 된장 등 높은 염도환경에서는 호염성균인 Tetragenococcus, Staphylococcus, 그리고 Candida속이 검출되기도 한다. 비배양식 방법인 metagenome 분석 기술을 접목하여 조금 더 다양한 미생물균총을 확인할 수 있게 되었지만, 아직까지도 16S rRNA, ITS 등 단편적인 유전자 염기서열 분석의 한계로 인해 명명이 명확하지 않고, 분석장비 종류, blast 데이터베이스 업로드 주기 등에 따른 편차도 있을 수 있다. 그럼에도 불구하고 단일 또는 복합종균 처리에 따른 장류 마이크로바이옴 변화를 모니터링하고 주요 대사산물과 핵심미생물 간 상관성 연구에도 활용되고 있다. 최근에는 장류 속 마이크로바이오타(jang microbiota) 비율을 달리하여 섭취하였을 때 동물 또는 인체적용시험 수준에서 장내 마이크로바이옴(gut microbiome)에 좋은 영향을 미친다는 것을 밝혀 오랫동안 섭취해온 우리나라 고유의 장류식품의 우수성을 밝히는데도 노력을 기울이고 있다. 앞으로 마이크로바이옴 데이터의 공유를 통한 다양한 분야에서 적용하기 위해서는 기본적인 데이터 수집, 저장, 및 공유에 이르기까지 전주기적 단계에서 DB화가 필요하며, 향후에는 다학제적 연구를 통해 개인맞춤형 마이크로바이옴 연구를 위해 활용될 것으로 기대된다. ‘Microbiome’ is a combination of microbiota and genome, and it is defined as a technology that comprehensively studies the microbial community and genetic information present in host such as human, plants, animals, and foods. It is very important to understand the microbial communities in the Jang (fermented soybean products) environment in order to consist healthy microbiome. Recently, it is applied to monitor the changes in gut microbiome with single or complex starters treatment and to research the correlation between core metabolites and microorganisms by analyzing metagenome There have been reports that different proportions of Jang microbiota had a positive effect on the gut microbiome at animal or human trial studies. In the future, it is expected to develop personalized microbiome and to utilize microbiome data in various fields.

Analysis of Oligosaccharides in Korean Fermented Soybean Products by the Combination of Mass Spectrometry and Gas Chromatography

Doenjang (fermented soybean paste) and ganjang (soy sauce) are traditional fermented foods that are widely consumed in Korea. The oligosaccharides found in soybean and its fermented foods have great potential to improve the quality of foods; however, their structural details have not been well studied. In this study, we used advanced mass spectrometry and gas chromatography to analyze oligosaccharides and their monomeric composition in two fermented soybean products. In both foods, oligosaccharides with a degree of polymerization ranging from 3 to 7 were found. Their constituent monosaccharides were characterized; galactose, xylose, arabinose, and rhamnose were the predominant constituents of the oligosaccharides, and fucose, fructose, mannose, glucose, and N-acetylglucosamine were also found. The great structural diversity of the oligosaccharides found suggests that soybean carbohydrates are hydrolyzed and/or transformed during fermentation and may yield novel oligosaccharides.

Substitution of Tempeh Flour with Beetroot Flour (Beta vulgaris L) in Cookies as Alternative High Protein Snack

Background: Tempeh is a fermented soybean product which high in protein, that beetroot also contains protein and antioxidant compounds. The substitution of tempeh flour and beetroot flour for the cookies can increase the protein nutritional value in cookies. Objectives: This research was to determine the nutrition value of the selected formulation cookies (F1) based on the result of acceptability test of cookies substitution with of tempeh flour and beetroot flour which compared with the SNI standard for supplementary feeding (MP-ASI biscuits). Methods: This is an experimental research with completely randomized design (CRD) with 2 treatment for cookies F1 (substitution of 0.09% tempeh flour and 10% beetroot flour) and cookies F0 (without substitution tempeh flour and beetroot flour). Parameter observed were the nutritional value of cookies are protein, carbohydrate, fat, fiber, water value, and ash value with 3 repetitions. The result of the analysis will be compared the SNI standard for MP-ASI biscuits. Results: From the results of the analysis of the nutrition value of the F1 cookies, that the protein value 12.19%, carbohydrate value 69.19%, fat value 22.73%, fiber value 11.15%, water value 2.96%, and the ash value 2.25% according to SNI requirements for MP-ASI biscuits with protein value of not less than 6 grams per 100 grams. There is a significant difference in protein nutrition value between F0 cookies and F1 cookies. Conclusions: Cookies F1 has protein value, water value, ash value according to SNI standard while charbohydrate and fat value exceeds SNI standard. One serving (2 pieces of cookies equivalent to 20 grams) can meet 9 - 16% of protein needs in toddler 1 - 5 years.

Fermented Foods of Korea and Their Functionalities

Fermented foods are loved and enjoyed worldwide and are part of a tradition in several regions of the world. Koreans have traditionally had a healthy diet since people in this region have followed a fermented-foods diet for at least 5000 years. Fermented-product footprints are evolving beyond boundaries and taking the lead in the world of food. Fermented foods, such as jang (fermented soybean products), kimchi (fermented vegetables), jeotgal (fermented fish), and vinegar (liquor with grain and fruit fermentation), are prominent fermented foods in the Korean culture. These four major fermented foods have been passed down through the generations and define Korean cuisine. However, scientific advancements in the fermentation process have increased productivity rates and facilitated global exports. Recently, Korean kimchi and jang have garnered significant attention due to their nutritional and health-beneficial properties. The health benefits of various Korean fermented foods have been consistently supported by both preclinical and clinical research. Korean fermented foods effectively reduce the risk of cardiovascular and chronic metabolic diseases, such as immune regulation, memory improvement, obesity, diabetes, and high blood pressure. Additionally, kimchi is known to prevent and improve multiple metabolic diseases, including irritable bowel syndrome (IBS), and improve beneficial intestinal bacteria. These functional health benefits may reflect the synergistic effect between raw materials and various physiologically active substances produced during fermentation. Thus, fermented foods all over the world not only enrich our dining table with taste, aroma, and nutrition, but also the microorganisms involved in fermentation and metabolites of various fermentations have a profound effect on human health. This article describes the production and physiological functions of Korean fermented foods, which are anticipated to play a significant role in the wellness of the world’s population in the coming decades.

Characterization of Bacillus subtilis bacteriophage BasuTN3 isolated from Thua Nao, a thai fermented soybean food product.

The infection of bacteriophage is of great concern in food industry as this can result in complete fermentation failure. In this study, a virulent bacteriophage, named BasuTN3, was isolated from Thua Nao, a Thai fermented soybean. The stability of BasuTN3 was evaluated under various ranges of temperature, pH, chloroform, UV, and disinfectants. The results showed that the isolated BasuTN3 appeared to be specific to its bacterial host, which was identified as Bacillus subtilis strain TN3 based on the 16S rRNA gene sequence analysis. Under TEM, the BasuTN3 belonged to the family Myoviridae. The isolated BasuTN3 could withstand wide temperature ranges (4-45°C) and pH conditions (5-11). The BasuTN3 was susceptible to chloroform, UV, and commonly used disinfectants. The results obtained expand the knowledge of the Bacillus bacteriophage diversity in the fermented soybean products and provide useful information for the bacteriophage and its bacterial starter cultures.

Improving the quality of fermented soybean products using low-frequency airborne ultrasonicated Koji

The aim of this study was to compare three fermented soybean products (soybean paste, red pepper paste, and soy sauce) prepared with non-treated (NK) and ultrasonicated Koji (UK, at 30 kHz). The physicochemical properties and ABTS radical scavenging activity were investigated during fermentation. The pH values of soybean products containing UK were found to be slightly more acidic compared to the NK-containing products after fermentation, whereas the titratable acidity gradually increased during the fermentation period. Hunter L-values of all soy sauce samples (UK and NK) decreased rapidly after fermentation, but the application of UK did not affect the color quality of the final product. All soybean products prepared with UK showed higher amino-type nitrogen contents than products prepared with NK owing to the high enzymatic activities of UK. The ABTS radical scavenging activity of soybean paste prepared with UK was significantly higher compared to the NK-containing sample at day 50. In conclusion, the application of UK showed significant potential to enhance the physicochemical qualities and antioxidant activity of fermented soybean products, suggesting its promising use as an ingredient in fermented soybean products.

Solid-state fermentation with Rhizopus oligosporus RT-3 enhanced the nutritional properties of soybeans.

Fermented soybean products are favorite foods worldwide because of their nutritional value and health effects. In this study, solid-state fermentation (SSF) of soybeans with Rhizopus oligosporus RT-3 was performed to investigate its nutraceutical potential. A rich enzyme system was released during SSF. Proteins were effectively transformed into small peptides and amino acids. The small peptide content increased by 13.64 times after SSF for 60 h. The antioxidant activity of soybeans was enhanced due to the release of phenolic compounds. The soluble phenolic content increased from 2.55 to 9.28 gallic acid equivalent (GAE) mg/g after SSF for 60 h and exhibited high correlations with microbial enzyme activities during SSF. The potential metabolic pathways being triggered during SSF indicated that the improved nutritional composition of soybean attributed to the biochemical reactions catalyzed by microbial enzymes. These findings demonstrated that SSF could evidently improve the nutritional value and prebiotic potential of soybeans.