Deciphering dynamic interactions between spermatozoa and the ovarian microenvironment through integrated multi-omics approaches in viviparous Sebastes schlegelii.

The ovarian microenvironment plays a crucial role in ensuring the reproductive success of viviparous teleosts. However, the molecular mechanism underlying the interaction between spermatozoa and the ovarian microenvironment has remained elusive. This study aimed to contribute to a better understanding of this process in black rockfish (Sebastes schlegelii) using integrated multi-omics approaches. The results demonstrated significant upregulation of ovarian complement-related proteins and pattern recognition receptors, along with remodeling of glycans on the surface of spermatozoa at the early spermatozoa-storage stage (1 month after mating). As spermatozoa were stored over time, ovarian complement proteins were progressively repressed by tryptophan and hippurate, indicating a remarkable adaptation of spermatozoa to the ovarian microenvironment. Before fertilization, a notable upregulation of cellular junction proteins was observed. The study revealed that spermatozoa bind to ZPB2a protein through GSTM3 and that ZPB2a promotes spermatozoa survival and movement in a GSTM3-dependent manner. These findings shed light on a key mechanism that influences the dynamics of spermatozoa in the female reproductive tract, providing valuable insights into the molecular networks regulating spermatozoa adaptation and survival in species with internal fertilization.

Stretchable, antifatigue, and intelligent nanocellulose hydrogel colorimetric film for real-time visual detection of beef freshness.

The use of biopolymers as matrices and anthocyanins as pH-sensing indicators has generated increasing interest in freshness detection. Nevertheless, the weak mechanical properties and color stability of biopolymer-based smart packaging systems restrict their practicality. In this study, a nanocellulose hydrogel colorimetric film with enhanced stretchability, antifatigue properties, and color stability was prepared using soy hull nanocellulose (SHNC), polyvinyl alcohol (PVA), sodium alginate (SA), and anthocyanin (Anth) as raw materials. This hydrogel colorimetric film was used to detect beef freshness. The structure and properties (e.g., mechanical, thermal stability and hydrophobicity) of these hydrogel colorimetric films were characterized using different techniques. Fourier-transform infrared spectroscopy revealed the presence of hydrogen and ester bonds in the hydrogel colorimetric films, whereas scanning electron microscopy revealed the fish scale-like and honeycomb network structure of the hydrogel colorimetric films. Mechanical testing demonstrated that the SHNC/PVA/SA/Anth-2 hydrogel colorimetric film exhibited excellent tensile properties (elongation = 261 %), viscoelasticity (storage modulus of 11.25 kPa), and mechanical strength (tensile strength = 154 kPa), and the hydrogel colorimetric film exhibited excellent mechanical properties after repeated tensile tests. Moreover, the hydrogel colorimetric film had high transparency, excellent anti-UV linearity, thermal stability and hydrophobicity, and had displayed visually discernible color response to pH buffer solution and volatile NH3 by naked eyes, which was highly correlated with the TVB-N and pH values. Notably, the release of anthocyanin in distilled water decreased from 81.23 % to 19.87 %. The designed SHNC/PVA/SA/Anth hydrogel colorimetric films exhibited potential application as smart packaging film or gas-sensing labels in monitoring the freshness of meat products.

Analysis of roasted peanuts based on GC-MS combined with GC-IMS.

The present study used gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) to separate and identify the characteristic volatile flavor substances in 30 roasted peanut samples. GC-MS identified 59 volatile compounds, and GC-IMS detected 61 volatile flavor substances. The 30 peanut varieties were then divided into four groups on the basis of their volatile flavor substances using principal component analysis (PCA), and a fingerprint profile of the varieties' volatile characteristics was established from information peaks identified in the spectra. Descriptive sensory analysis (DSA) was performed to distinguish differences in flavor attributes between roasted peanut varieties. Partial least squares regression (PLSR) was performed with the volatile flavor content of roasted peanuts as the independent variable and the flavor attribute score as the dependent variable. These findings provide a basis for predicting the appeal of roasted peanuts based on their composition and demonstrate a potential avenue for improving food flavor quality.

The decreased interface tension increased the transmembrane transport of soy hull polysaccharide-derived SCFAs in the Caco-2 cells.

Polysaccharides impact intestinal fermentation and regulate interfacial properties which affect absorption and transportation. Short-chain fatty acids (SCFAs), the main metabolites of soy hull polysaccharide lysate, are readily absorbed by the body and perform various physiological functions. We analysed the interfacial properties and transport of soy hull polysaccharide-derived SCFAs in the Caco-2 cell model to clarify the transmembrane transport mechanism. The results showed that the interfacial properties of the co-culture system were influenced by both transit time and concentration of SCFAs, the uptake and transit rates of SCFAs at 1-3 h increased significantly with time (P < 0.05). With increasing transit time and concentration, the transit rates of SCFAs on the apical side (AP) â†’ basolateral side (BL) and BL â†’ AP sides increased and then stabilised, the transit rate of the AP â†’ BL side was higher than that of the BL â†’ AP side. Proteomic analysis showed that soy hull polysaccharide-derived SCFAs resulted in the differential expression of 285 upregulated and 501 downregulated after translocation across Caco-2 cells. The differentially expressed proteins were mainly enriched in ribosomes, oxidative phosphorylation, nuclear transport, and SNARE vesicular transport. This study lays the theoretical foundation for understanding the structure-activity relationship of soy hull polysaccharides in the intestine.

Virtual screening, activity evaluation, and stability of pancreatic lipase inhibitors in the gastrointestinal degradation of nattokinase.

Nattokinase is an alkaline serine protease secreted by natto during fermentation. Despite its good thrombolytic effect, it is intolerant to gastrointestinal conditions and is easily digested and degraded into polypeptides, oligopeptides, and amino acids. However, whether these peptides inhibit fat-digesting enzymes and other biological activities remains unknown. To explore the bioactivity of peptides produced through nattokinase degradation, nattokinase was subjected to simulated digestion in the gastrointestinal tract, and 41 small peptides were obtained through the enzymolysis of gastric enzymes, pancreases, and chymotrypsin. Four pancreatic lipase (PL) inhibitory peptides (SW, ASF, GAY, and PGGTY) were selected based on their activity scores, water solubility, and toxicity predictions. The molecular docking results revealed that hydrogen bonds and electrostatic interactions were the main forces for inhibiting PL activity. The results of enzyme activity verification revealed that all four peptides inhibited PL activity. Among them, GAY exhibited the strongest inhibitory effect, with an inhibitory rate of 10.93 % at a concentration of 1 mg/mL. Molecular dynamics simulations confirmed that the GAY-1ETH complex demonstrated good stability. Natto foods containing nattokinase own the activity of inhibiting fat-digesting enzymes and show antiobesity potentials.

Ultrasound-assisted fermentation for antioxidant peptides preparation from okara: Optimization, stability, and functional analyses.

This study investigated the effects of ultrasound-assisted fermentation (UAF) on the preparation of antioxidant peptides (UAFP) from okara and examined their content, chemical structures, and antioxidant activity. After the optimal ultrasonic processing (time, 20 min; frequency, 45 KHz; power, 120 W/L), the peptide content yield reached the maximum of 12.36 ± 0.02 mg/mL, and their DPPH free radical scavenging rate was 65.15 ± 0.32 %. UAF increased the number of globular aggregates with deeper gullies, a looser structure, and higher porosity. The experiments conducted using the oxidative stress injury model of HepG2 cells showed that okara UAFP promoted cell growth and exerted a protective effect. Moreover, ultrasonic treatment remarkably improved the environmental stability (NaCl, glucose, sodium benzoate, temperature, pH, metal ions) and antioxidant activity of UAFP. Concisely, optimal ultrasonic processing can aid the fermentation of agroindustrial by-products to prepare antioxidant peptides, such as natural food antioxidant peptides from soybean waste.

Na+/K+ enhanced the stability of the air/water interface of soy hull polysaccharide and intestinal mucus.

The stable energy barrier of mucin and soy hull polysaccharide (SHP) is established at the air/water interface in the intestinal fluid and is conducive to the absorption and transportation of nutrients. This study aimed to investigate the effect of different concentrations (0.5 % and 1.5 %) of Na+ and K+ on the energy barrier through the digestive system model in vitro. The interaction between ions and microwave-assisted ammonium oxalate-extracted SP (MASP)/mucus was characterized by particle size, zeta potential, interfacial tension, surface hydrophobicity, Fourier transform infrared spectroscopy, endogenous fluorescence spectroscopy, microstructure, and shear rheology. The results showed that the interactions between ions and MASP/mucus included electrostatic interaction, hydrophobic interaction, and hydrogen bond. The MASP/mucus miscible system was destabilized after 12 h, and the ions could improve the system stability to some extent. MASP aggregated continuously with the increase in the ion concentration, and large MASP aggregates were trapped above the mucus layer. Furthermore, the adsorption of MASP/mucus at the interface increased and then decreased. These findings provided a theoretical basis for an in-depth understanding of the mechanism of action of MASP in the intestine.

Effects of Different Cooking Methods on Phenol Content and Antioxidant Activity in Sprouted Peanut.

Peanut sprout is a high-quality healthy food, which not only has beneficial effects, but also a higher phenol content than peanut seed. In this study, peanut sprout was treated with five cooking methods, namely boiling, steaming, microwave heating, roasting, and deep-frying, and the phenol content, monomeric phenol composition, and antioxidant activity were determined. The results showed that, compared with unripened peanut sprout, the total phenol content (TPC) and total flavonoid content (TFC) decreased significantly after the five ripening processes, and the highest retention of phenols and flavonoids was associated with microwave heating (82.05% for TPC; 85.35% for TFC). Compared with unripened peanut sprout, the monomeric phenol composition in germinated peanut was variable after heat processing. After microwave heating, except for a significant increase in the cinnamic acid content, no changes in the contents of resveratrol, ferulic acid, sinapic acid, and epicatechin were observed. Furthermore, there was a significant positive correlation of TPC and TFC with 2,2-diphenyl-1-picrylhydrazyl scavenging capacity, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) scavenging capacity, and ferric ion reducing antioxidant power in germinated peanut, but not with hydroxyl free radical scavenging capacity, in which the main monomer phenolic compounds were resveratrol, catechin, and quercetin. The research results indicate that microwave heating can effectively retain the phenolic substances and antioxidant activity in germinated peanuts, making it a more suitable ripening and processing method for germinated peanuts.

The ancient CgPEPCK-1, not CgPECK-2, evolved into a multifunctional molecule as an intracellular enzyme and extracellular PRR.

Phosphoenolpyruvate carboxykinase (PEPCK) is a well-known lyase involved in gluconeogenesis, while their evolution and function differentiation have not been fully understood. In this study, by constructing a phylogenetic tree to examine PEPCKs throughout the evolution from poriferans to vertebrates, Mollusk was highlighted as the only phylum to exhibit two distinct lineages, Mollusca_PEPCK-1 and Mollusca_PEPCK-2. Further study of two representative members from Crassostrea gigas (CgPEPCK-1 and CgPEPCK-2) showed that they both shared conserved sequences and structural characteristics of the catalytic enzyme, while CgPEPCK-2 displayed a higher expression level than CgPEPCK-1 in all tested tissues, and CgPEPCK-1 was specifically implicated in the immune defense against LPS stimulation and Vibrio splendidus infection. Functional analysis revealed that CgPEPCK-2 had stronger enzymatic activity than CgPEPCK-1, while CgPEPCK-1 exhibited stronger binding activity with various PAMPs, and only the protein of CgPEPCK-1 increased significantly in hemolymph during immune stimulation. All results supported that distinct sequence and function differentiations of the PEPCK gene family should have occurred since Mollusk. The more advanced evolutionary branch Mollusca_PEPCK-2 should preserve its essential function as a catalytic enzyme to be more specialized and efficient, while the ancient branch Mollusca_PEPCK-1 probably contained some members, such as CgPEPCK-1, that should be integrated into the immune system as an extracellular immune recognition receptor.

Effect of Ultrasonic Induction on the Main Physiological and Biochemical Indicators and γ-Aminobutyric Acid Content of Maize during Germination.

Research on the nutrient content of cereal grains during germination is becoming a hot topic; however, studies on germinated maize are still scarce. This study aimed to provide a technical reference and theoretical basis for the development of functional maize health foods and to expand the application of ultrasonic technology in the production of germinated grains. In this study, the germination rate of maize was used as the evaluation index, and the ultrasonic frequency, ultrasonic temperature, and induction time were selected as the influencing factors in orthogonal experiments to determine the optimal process parameters for ultrasonic induction of maize germination (ultrasonic frequency of 45 kHz, ultrasonic temperature of 30 °C, and ultrasonic induction time of 30 min). Based on this process, the effects of ultrasonic induction on the main physiological, biochemical, and γ-aminobutyric acid contents of maize during germination were investigated. The results showed that the respiration of the ultrasonic treated maize was significantly enhanced during germination, resulting in a 27% increase in sprout length, as well as a 4.03% higher dry matter consumption rate, and a 2.11% higher starch consumption rate. Furthermore, the reducing sugar content of germinated maize increased by 22.83%, soluble protein content increased by 22.52%, and γ-aminobutyric acid content increased by 30.55% after ultrasonic induction treatment. Throughout the germination process, the glutamate acid decarboxylase activity of the ultrasonically treated maize was higher than that of the control group, indicating that ultrasonication can promote maize germination, accelerate the germination process, and shorten the enrichment time of γ-aminobutyric acid in germinated maize. The results of this study can be applied to the production of γ-aminobutyric acid enrichment in germinated maize.

Transcriptome and proteome analysis of ultrasound pretreated peanut sprouts.

Combined transcriptomic and proteome analyses were carried out to investigate the influence of ultrasound pretreatment on peanut sprouts. In total, 1104 differentially expressed genes (upregulated:538, downregulated:521) and 399 differentially accumulated proteins (upregulated: 197, downregulated: 202) were identified between ultrasound pretreated and nontreated peanut sprouts. These genes and proteins were related to a series of crucial biomolecular processes, including the metabolism of carbohydrates, terpenoids, and polyketides. The most enriched pathways were further analyzed in each category. Importantly, ultrasound upregulated three key genes namely the arahy. Tifrunner. gnm1.ann1.DXZI51, arahy.Tifrunner.gnm1.ann1.VGN2GE, and arahy.Tifrunner.gnm1.ann1.Y23DM6 that could have increased the content of resveratrol via phenylpropanoid biosynthesis. Furthermore, this study shows that B3, MYB transcription factor-like families play a significant role in response to ultrasound treatment. Overall, this study provides useful transcriptomics and proteomics information highlighting the molecular mechanisms that influence nutritional differences in peanut sprouts.

Hypoglycemic and hypolipidemic effects of polysaccharide isolated from Sphacelotheca sorghi in diet-streptozotocin-induced T2D mice.

Edible fungus has attracted great interest with many health benefits, and polysaccharides from them have shown great potentials. In this study, polysaccharides were extracted from Sphacelotheca sorghi (Link) Clint. Monosaccharide composition of S. sorghi polysaccharides (SSP) was detected by high-performance anion exchange chromatography (HPAEC) and mainly consists of glucose (70.5%), galactose (15.6%), mannose (7.2%), arabinose (5.8%), and rhamnose (0.9%). Type 2 diabetes (T2D) was induced by a high-fat, high-sugar diet-fed (HFSD) diet with streptozotocin (STZ) injection in mice, and hypoglycemic and hypolipidemic regulations of SSP were evaluated. After oral treatment of high dose of SSP (200 mg/kg/day), the fasting blood glucose (FBG) was reduced by 39.3%, the insulin resistance of T2D mice was relieved, the lipids metabolism disorder caused by diabetes was improved, and the levels of liver glycogen was increased by 34.1%, compared with the model control. Histopathological examination showed that SSP relieved liver damage. Furthermore, SSP regulated glucose and lipid metabolism by activating phosphoinositide 3-kinase/Akt signaling pathway. Overall, SPP is promising to be used as a functional food for the improvement of metabolic disorders. PRACTICAL APPLICATION: For enhancing the utilization rate and economic value of an edible fungi Sphacelotheca sorghi (Link) Clint., the total polysaccharides were isolated and used to investigate the effect of fungi in terms of balancing the levels of blood glucose and lipids. The S. sorghi polysaccharide treatment resolved the symptoms and insulin resistance in mice with diabetes, signifying its potential application in producing different functional foods for preventing or controlling diabetes.

Effects of pulsed light on germination and gamma-aminobutyric acid synthesis in brown rice.

This study observed the effects of pulsed light (PL) on the germination and gamma-aminobutyric acid (GABA) production of brown rice and analyzed the correlations among glutamic acid (Glu) content, glutamate decarboxylase (GAD) activity, and GABA content in germinating brown rice. Both germination and GABA content were increased by exposure to PL, and this effect was evident when brown rice was exposed to PL immediately after being soaked. The PL group had significantly higher Glu and GABA content than the control check (CK) group which was unexposed to PL during the germination of brown rice. Glu content peaked at 18 h and GABA peaked at 24h in the PL group, which were 12 h and 6 h earlier than the CK group, respectively. GAD activity of the PL group peaked 12 h after germination, 6 h earlier than the CK group. PL exposure also increased the free amino acid content in the earliest stage of brown-rice germination. During brown-rice germination, the production of GABA is regulated by GAD activity and is significantly positively correlated with Glu content. PL treatment had a significant effect on GAD activity and Glu content during the germination process of brown rice and helped to increase its GABA content. PRACTICAL APPLICATION: This study has shown that pulsed light exposure is an efficient and stable processing method for producing brown rice with high GABA. This will provide a new direction for developing novel germination grain foods.

Characterization of the physicochemical properties, antioxidant activity, and antiproliferative activity of natural melanin from S. reiliana.

This study aimed to characterize the physicochemical properties and stability of L-25 melanin extracted from Sporisorium reilianum (S. reiliana). The results showed that the maximum absorption wavelength of melanin was 215 nm. Reducing agents, heat, light, microwaving, oxidants, and common food additives did not affect the melanin. Additionally, it has a good metal stability except Mn2+. The IR spectra revealed the presence of O-H, N-H, C=O, and C=C bonds as well as carboxyl, alcohol hydroxyl, and phenolic hydroxyl groups and a pyran ring. L-25 melanin could be defined as DL-hydroxy phenylalanine (DOPA)-melanin. The antioxidant and antiproliferative were also measured. The melanin has a specific stability and high antioxidant activity, including a strong DPPH free radical scavenging ability, and protected damaged HepG2 cells by reducing reactive oxygen species, malondialdehyde, and lactate dehydrogenase content. In conclusion, S. reilianum represents a novel source of melanin, that could be applied to health food or food additives. Our results show that melanin from S. reilianum is a natural pigment with good stability that has a great prospect of development and application, providing a theoretical basis and methods for its further processing and development as a functional food.

Effect of ultrasonic pre-treatment on Ara h 1 in peanut sprouts.

Ara h 1 is the most abundant sensitizing protein in peanuts; it has high thermal stability and is difficult to degrade. The peanut sprout is a high-quality, natural food that has various beneficial effects and lower allergenicity than peanut seeds. In this study, ultrasonication (US) of peanut sprouts was used to alter their Ara h 1 content. We determined that the optimal parameters for the US process were 35 °C temperature, 30 min duration, 240 W power, and 100 kHz frequency. After 5 days of germination, the protease activity of the control (blank) group increased to 262.39 ± 0.10 U, whereas that of the US group increased to 290.1 ± 0.25 U. We also investigated the effects of US on Ara h 1 protein composition, structure, and related gene expression during germination. ELISA results showed that after 5 days of germination, Ara h 1 content in the blank group decreased from 20.63 ± 0.31 ppm to 3.35 ± 0.42 ppm, whereas in the US group, they decreased to below the detection limit. SDS-PAGE bands between 50 and 70 kDa from peanut sprout extracts gradually became lighter in both groups. The band almost disappeared at day 5 of germination in the US group, indicating that US reduced the Ara h 1 content of peanut sprouts, consistent with the ELISA results. The expression of the Ara h 1 gene in peanut seeds was 173.92 ± 26.37. In the BK control group, it decreased to 0.49 ± 0.17 on the fourth day and increased slightly to 0.75 ± 0.09 on the fifth day. In the US group, it decreased to 1.37 ± 0.28 on the first day, dropped sharply to 0.00 on the third day, and increased slightly to 0.04 ± 0.01 on the fourth and fifth days. Protein structure results showed that the α-helix structure of Ara h 1 decreased after US, whereas the content of ß-fold structures increased. The surface hydrophobicity decreased, and the secondary and tertiary structures of Ara h 1 were loose.

Characterization and comparison of metaproteomes in traditional and commercial dajiang, a fermented soybean paste in northeast China.

Dajiang is a popular Chinese fermented soybean condiment. Here, a comparative metaproteomic analysis of traditional and commercial dajiang was performed during fermentation. A total of 4250 and 1421 peptide sequences were obtained from 3493 and 1987 proteins in traditional and commercial dajiang, respectively. 4299 differentially expressed microbial proteins show a high metabolic heterogeneity between the two types of dajiang. The KEGG annotation indicated that there were some pathways related to human diseases, which suggest that some microbes in traditional dajiang fermentation may have greater food safety hazards. In combination with qualitative metabolomic analysis, we further traced metabolic intermediates and key enzymes in several main fermentation pathways of dajiang to be mainly affiliated with Penicillium, Tetracoccus and Bacillus in traditional samples, as well as Aspergilus in commercial samples. These results could provide information for the selection of strains that are more suitable to produce high quality dajiang and other fermented products.

Meta-omics reveal microbial assortments and key enzymes in bean sauce mash, a traditional fermented soybean product.

BACKGROUND: Dajiang is fermented based on the metabolism of microbial communities in bean sauce mash, a traditional fermented soybean product in China. The current study first investigated the metaproteome of bean sauce mash. This was followed by an analysis of its biological functions and its microbial community to reveal information about strains and about the expressed proteins to better understand the roles of the microbiota in bean sauce mash. RESULTS: The metaproteomic results demonstrated that a total of 1415 microbial protein clusters were expressed mainly by members of the Penicillium and Rhizopus genera and were classified into 100 cellular components, 238 biological processes, and 220 molecular function categories by gene ontology (GO) annotation. Enzymes associated with glycolysis metabolic pathways were also identified. These can provide the energy required for microbial fermentation. Illumina MiSeq sequencing technology results showed that the microorganism communities of bean sauce mash exhibited a high level of diversity. Microbiological analysis demonstrated that the Penicillium, Mucor, Fusarium, Aspergillus, and Rhizopus fungi, and Lactobacillus, Enterococcus, Fructobacillus, Staphylococcus, Carnobacterium genera were predominant 22 samples. CONCLUSION: The profiles and insights in the current study are important for research on bean sauce mash and related products in terms of their food microbial ecology. The information obtained from this study will help the development of stable sufu starter cultures with unique sensory qualities. © 2019 Society of Chemical Industry.

An integrated metagenomic/metaproteomic investigation of microbiota in dajiang-meju, a traditional fermented soybean product in Northeast China.

Dajiang-meju have been used as major ingredients for the preparation of traditional spontaneously fermented soybean paste in Northeast China. In this work, we sequenced and analyzed the metagenome of 12 dajiang-meju samples. To complement the metagenome analysis, we analyzed the taxonomic and functional diversity of the microbiota by metaproteomics (LC-MS/MS). The analysis of metagenomic data revealed that the communities were primarily dominated by Enterobacter, Enterococcus, Leuconostoc, Lactobacillus, Citrobacter and Leclercia. Moreover, changes in the functional levels were monitored, and metaproteomic analysis revealed that most of the proteins were mainly expressed by members of Rhizopus, Penicillium and Geotrichum. The number of sequences allocated to fungi in the fermentation process decreased, whereas the number of sequences assigned to bacteria increased with time of fermentation. In addition, functional metagenomic profiling indicated that a series of sequences related to carbohydrates and amino acids metabolism were enriched. Additionally, enzymes associated with glycolysis metabolic pathways were presumed to contribute to the generation of flavor in dajiang-meju. Proteins from different dajiang-meju samples involved in global and overview maps, carbohydrate metabolism, nucleic acid metabolism and energy metabolism were differentially expressed. This information improves the understanding of microbial metabolic patterns with respect to the metaproteomes of dajiang-meju and provides a powerful tool for studying the fermentation process of soybean products.

Metaproteomics of Microbiota in Naturally Fermented Soybean Paste, Da-jiang.

Da-jiang is a typical traditional fermented soybean product in China. At present, the proteins in da-jiang are needed to be explored. The composition and species of microbial proteins in traditional fermented da-jiang were analyzed by metaproteomics based on sodium dodecyl sulfonate-polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). The results showed that the number and variety of microbial proteins in the traditional fermented da-jiang from different regions were different. The production site influences the fermentation in da-jiang. Then we analyzed the functions of the microbial proteins identified in da-jiang, and found that they were mainly involved in the process of protein synthesis, glycometabolism and nucleic acid synthesis. In addtion, we compared the proteins composition in different da-jiang. There are 51 common proteins of naturally fermented da-jiang, and 25 common microbial sources. The main commonly microbial sources of fungal proteins are Saccharomyces cerevisiae and Schizosaccharomyces; the main commonly microbial sources of bacterial proteins are Enterococcus faecalis, Leuconostoc mesenteroides, Acinetobacter baumannii, and Bacillus subtilis. These common microbes play the predominant role in da-jiang fermentation. The present results help us to understand the fermentation of da-jiang and improve the quality and safety of final products in the future. PRACTICAL APPLICATION: The study illustrated metaproteome of microbiota in traditional fermented soybean paste, da-jiang, by sodium dodecyl sulfonate-polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). A method of extracting metaproteome from microbiota in da-jiang was attempted. The findings help to understand the fermentation of da-jiang and improve the quality and safety of da-jiang in fermented industry.