To investigate the effect of high hydrostatic pressure on the enzymatic hydrolysis of high molecular weight hyaluronic acid (HMW-HA). This study adopted high hydrostatic pressure (0.1, 50, 100, 150 and 200 MPa) to assist bovine testicular hyaluronidase in hydrolyzing HMW-HA. Subsequently, the degree of hydrolysis and molecular weight of the hydrolysate were measured to investigate the effects of pressure, hydrolysis time, and enzyme concentration on the hydrolysis results, thereby determining optimal reaction conditions. Additionally, the chemical structure and thermal stability of the hydrolysis products were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). The results indicated that bovine testicular hyaluronidase at a concentration of 40000 U/g was suitable for the preparation of low molecular weight hyaluronic acid (LMW-HA) under pressure treatments ranging from 0.1, 50, 100, 150 and 200 MPa. Pressures of 50 MPa and 100 MPa effectively controlled the excessive hydrolysis of HMW-HA into HA oligosaccharides, increased the LMW-HA content. The 100 MPa treatment yielded the highest LMW-HA content at 65.5%, representing a 19.9% increase compared to atmospheric pressure. However, treatment with excessively high pressure (150, 200 MPa) inhibited bovine testicular hyaluronidase from hydrolyzing HMW-HA. FT-IR and NMR results indicated that high hydrostatic pressure treatment did not significantly disrupt the chemical structure of hydrolysates. However, XRD analysis revealed that high pressure markedly disrupted their crystalline structure, with crystallinity decreasing as pressure increases. Additionally, DSC results indicated that lower pressure treatments (50, 100 MPa) had a minor effect on the thermal stability of hydrolysate products, whereas higher pressure treatments (150, 200 MPa) significantly (P<0.05) altered their thermal stability. In summary, high hydrostatic pressure treatment at appropriate pressure can inhibit the hydrolysis of HMW-HA into oligosaccharides while minimally affecting its chemical structure, thereby increasing the yield of low molecular weight hyaluronic acid.

This study focused on the enzymatic properties of the protease produced by Brevibacillus borstelensis S8, and constructed an ultrasound assisted enzymatic system for yak meat tenderization. SDS-PAGE was used to verify the purification effect of protease. Single factor experiments were used to explore the enzymatic properties. Response surface experiments were used to optimize the yak meat tenderization process. Subsequently, the tenderization effect of yak meat was characterized by shear force, water holding capacity, myofibrillar fragmentation index, and texture characteristics. The results showed that the purified protease exhibited a single band with a molecular weight of approximately 47 kDa by SDS-PAGE electrophoresis. The investigation of enzymatic properties showed that the enzyme activity was optimal under pH7.0, 30~40 ℃, and with 20 mmol/L Mg²⁺ supplementation. The optimal process parameters for ultrasound assisted protease tenderization of yak meat obtained through response surface optimization experiments were as follows: Protease concentration 2.5%, ultrasonic temperature 34.6 ℃, and treatment duration 39.6 min. Under the above conditions, the shear force of yak meat decreased by 63.3%, steaming loss decreased by 33.7%, centrifugation loss decreased by 52.0%, myofibrillar fragmentation index increased by 47.3%, myofibrillar protein was degraded, and the texture characteristics were significantly improved. This study provides a reference for the development and utilization of protease from B. borstelensis S8, and also provides new protease resources and technical support for yak meat tenderization process.

To systematically analyze the quality characteristics of different types of Daqu and their fermentation efficiency under the same brewing process, and to elucidate the intrinsic correlation between Daqu quality parameters and baijiu flavour characteristics, this study systematically compared and analyzed the physicochemical indices, microbial community structures, and brewing effects of medium-, medium-high-, and high-temperature Daqu. Furthermore, the internal relationships among these three aspects were examined. The analysis of physicochemical indices revealed that medium-temperature Daqu exhibited the highest moisture content, saccharifying power, and liquefaction power, while high-temperature Daqu showed the highest acidity. In terms of microbial community structure, the main dominant genera in medium-temperature Daqu were Aspergillus (70.90% abundance), Thermomyces (10.74% abundance), Bacillus (32.54% abundance), and Staphylococcus (15.56% abundance). In medium-high-temperature Daqu, the dominant genera included Aspergillus (75.52% abundance), Saccharomycetales (14.97% abundance), and Weissella (16.65% abundance). High-temperature Daqu was primarily characterized by the presence of Aspergillus (33.84% abundance), Thermomyces (33.67% abundance), Virgibacillus (25.52% abundance), and Kroppentedtia (24.10% abundance). The analysis of the brewing effect showed nine different flavour substances in the three kinds of Daqu baijiu. The sensory experience of medium-temperature Daqu baijiu was sweet and harmonious. Medium-high-temperature Daqu baijiu had a pleasing grain aroma, and high-temperature Daqu baijiui had a rich aroma and pure aftertaste. The results of the correlation analysis indicated that acidity was positively correlated with the abundance of Thermoascus and Virgibacillus. Liquefaction power positively correlated with Wallemia, Staphylococcus, and Saccharopolyspora abundance. Additionally, saccharifying power was positively correlated with Pantoea, while fermentation power was positively correlated with Weissella abundance. The physicochemical properties of Daqu significantly influenced its microbial community composition. Aspergillus showed a negative correlation with the content of methanol and isobutanol. Bacillus, Staphylococcus, and Saccharopolyspora abundance were positively correlated with ethyl acetate and ethyl lactate, whereas Lactobacillus abundance was negatively correlated with ethyl acetate content. The various flavour types of Daqu differed significantly in the physicochemical and microbial compositions among the various flavour types of Daqu. Within the same process, the style of different flavour types of Daqu baijiu was primarily determined by the processing style. The physicochemical properties and microbial diversity of Daqu were closely linked to the quality of baijiu. This study demonstrated the influence of Daqu and processing methods on baijiu style, explored the relationship between Daqu's physicochemical and microbial aspects and baijiu flavour, and provided a theoretical foundation for enhancing the quality of different flavour baijiu and integrating various flavour types.

β-Glucosidase can hydrolyze aryl-glucoside and holds significant application value in the fields of food and biotransformation. To investigate the influence of substrate side-chain groups on the activity of β-glucosidase, the β-D-Glu from Aspergillus niger was cloned and expressed. Through in silico saturation mutagenesis followed by experimental validation, key amino acid was identified within 4 Å of the β-D-Glu binding pocket, molecular docking and molecular dynamics simulations were employed to analyze the structure-activity relationship between the enzyme and substrate. β-D-Glu exhibited significant differences in activity toward structurally similar monocyclic aryl-glycoside substrates with varying side chains. Specifically, the enzymatic activities toward salicin, arbutin, and pNPG were measured at 44.72, 103.97, and 839.02 IU/mL, respectively. Through in silico saturation mutagenesis followed by experimental validation, residue R98 was identified as a key amino acid within 4 Å of the β-D-Glu binding pocket. Mutation at this site exerted substrate-specific effects on catalytic activity towards different substrates. Compared to wild-type enzyme, R98F mutation increased the relative activity towards salicin to 266.08%, while R98I and R98Q mutations decreased the relative activities to 37.62% and 35.05%, respectively. All three mutants showed decreased relative activities towards arbutin, but the relative activities towards pNPG remained almost unchanged. Specifically, the R98F mutant exhibited significantly enhanced activity towards salicin, while its activity towards arbutin and pNPG decreased by 16.44% and 7.54%, respectively. Molecular docking and molecular dynamics simulations revealed that differences in the polarity and electron-donating capacity of the side-chain groups in monocyclic aryl-glucoside substrates lead to distinct binding modes with the enzyme. The R98F mutation modulates both the conformational flexibility at the binding pocket entrance and the binding affinity between catalytic key residues and substrates. It is speculated that the mutation specifically enhances the hydrolytic activity toward salicin by improving both glycosidic bond cleavage efficiency and reaction rate. The results of this study help to reveal the hydrolysis characteristics of β-glucosidase towards different aryl-glucoside substrates and provide a scientific basis for the design and modification of this enzyme.

This study aimed to screen lactic acid bacteria (LAB) with uric acid-regulating potential from the gut microbiota of Trachemys scripta elegans and systematically evaluate their functional characteristics. The selective culture medium with uric acid as the sole carbon and nitrogen source was established for primary screening, combined with in vitro uric acid (UA) degradation activity test and xanthine oxidase (XOD) inhibition experiment for secondary screening. Finally, two dominant strains were identified by 16S rDNA sequencing, and their functional characteristics were characterized. Results demonstrated that strains Enterococcus hirae YL-3 and Enterococcus durans YL-8 exhibited UA degradation rates of 83.83% and 85.48%, respectively, along with XOD inhibition rates of 71.72% and 65.79%, indicating significant hypouricemic potential. Additionally, strain YL-3 exhibited excellent fermentation and probiotic characteristics. In media with 6% NaCl, it achieved an OD₆₀₀ of 0.76, outperforming the blank group's 0.55 (P<0.05). It also showed a survival rate of 75.46% under pH3.0 conditions and 99.53% in the presence of 0.3% bile salts; Its autoaggregation rate was 89.38%. Strain YL-8 demonstrated strong antioxidant activity, with its fermentation supernatant achieving DPPH·, ABTS⁺·, and ·OH scavenging rates of 60.22%, 93.66%, and 99.25%, respectively. In this study, LAB with high uric acid degradation ability and xanthine oxidase activity were isolated from the intestine of Trachemys scripta elegans for the first time, which provided theoretical basis for developing probiotic preparation to alleviate hyperuricemia.

To investigate the changes in bioactive compounds and the hypoglycemic action mechanisms of chickpea milk fermented by probiotics, Lacticaseibacillus rhamnosus FMBL L23004 CNN that capable of enhancing the α-amylase and α-glucosidase inhibitory activities was selected in this study. The changes of flavor profiles and functional components were characterized in basis of optimizing the fermentation process of chickpea milk fermented by L. rhamnosus FMBL L23004 CNN, and untargeted metabolomics, network pharmacology and molecular docking techniques were combined to explore the potential hypoglycemic components and their mechanisms in fermented chickpea milk. The results showed that the optimal process for the fermentation of chickpea milk were involved following parameters: 3% of the inoculation amount of L. rhamnosus FMBL L23004 CNN, fermentation temperature of 36.5 ℃, and fermentation duration of 17 h. L. rhamnosus FMBL L23004 CNN not only significantly enhanced the α-amylase and α-glucosidase inhibitory activity (30.96%), antioxidant capacity (ABTS⁺ radical scavenging activity: 72.39%, DPPH radical scavenging activity: 83.55%) and the contents of total phenols (30.46 mg/100 mL) and flavonoids (54.69 mg/100 mL) in chickpea milk through fermentation, but also improved the flavor by decomposing beany flavor substances such as 2-pentylfuran, octenal, and hexanal. Untargeted metabolomics revealed that the fermented chickpea milk was mainly composed of amino acids, peptides and analogues, fatty acids and conjugates, carbohydrate derivatives, terpenoids, and flavonoids. Fermentation of chickpea milk with L. rhamnosus FMBL L23004 CNN contributed to a significant increase in 73 pre-existing compounds and the formation of 775 novel compounds. The potential hypoglycemic effects of 10 key compounds were analyzed using network pharmacology and molecular docking. The results indicated that bioactive constituents, such as Diosgenin, Lepidium terpenoid, and Inulobiose, may synergistically exert hypoglycemic effects through the involvement of the PI3K-Akt signaling pathway, the lipid metabolism and atherosclerosis pathways, as well as the Ras signaling pathway. Notably, Diosgenin exhibited high docking stability with target proteins through hydrogen bonding interactions: STAT3 (−8.9 kcal/mol), AKT1 (−8.3 kcal/mol), α-amylase (−9.7 kcal/mol), and α-glucosidase (−8.8 kcal/mol). This findings provided valuable technical insights into chickpea resource utilization, while also establishing a theoretical foundation for the application of L. rhamnosus FMBL L23004 CNN in food and medicine.

To develop a method for the preparation of selenium exopolysaccharide (Se-EPS) with high yield, the heat-resistant Weizmannia coagulans P-L1 was selected to produce Se-EPS through fermentation, with the addition of sodium selenite at a concentration of 20 mg/L, using anion exchange resins. In addition, Se-EPS was characterized using infrared spectroscopy, and in vitro hypoglycemic activity of Se-EPS was investigated. The results showed that the initial bacterial concentration, the employment of anion exchange resins and the fermentation time all had a significant effect on the yield of Se-EPS. With an initial bacterial concentration of 1×10⁶ CFU/mL, the yield of Se-EPS achieved up to 19.1 g/L after 8 days of fermentation, which was increased by 5.4-fold as compared to the yield of Se-EPS obtained with an initial bacterial concentration of 1×10⁵ CFU/mL, and was increased by 19.5-fold as compared to the yield of exopolysaccharide (EPS) obtained by conventional fermentation (without using anion-exchange resin). The selenium content of the Se-EPS reached up to 213 μg/g. Infrared spectroscopy analysis revealed that selenium was probably incorporated into the EPS via Se-O and Se=O bonds. Both EPS and Se-EPS derived from Weizmannia coagulans P-L1 exhibited good in vitro hypoglycemic activity, with Se-EPS showing significantly higher activity than EPS. At a concentration of 1 mg/mL, the inhibition of Se-EPS against α-glucosidase and α-amylase were 28% and 16% higher than those of EPS, respectively. The study provides theoretical support and technical references for the development and application of Se-EPS products derived from Weizmannia coagulans.

This study aimed to treat grape pomace-derived soluble dietary fiber (SDF) using two modification methods, optimize the modification parameters, compare the physicochemical properties of SDF before and after modification, and investigate its hypolipidemic effects in hyperlipidemic mice, thereby providing a theoretical basis for in-depth research on grape pomace SDF and food development. Using grape pomace SDF as the raw material, it was subjected to modification by microwave-acid (M-A) and cellulase-ultrasound wave (C-UW) methods. Based on single-factor experiments, response surface methodology was employed to optimize the experimental conditions and determine the optimal parameter combinations for modification. The physicochemical properties (including functional characteristics, cholesterol adsorption capacity, and cation exchange capacity) of unmodified SDF and the two modified SDF were compared. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses were also conducted. Additionally, a hyperlipidemic mouse model was established to explore the hypolipidemic effects of SDF before and after modification. Measurements and analyses were conducted on mouse body weight, four lipid profile indicators, serum ALT and AST activities, liver indices, and histological staining of liver sections. Results showed that the optimal parameter combination for M-A method modified SDF was a solid-to-liquid ratio of 1:24.97, microwave power of 220.56 W, microwave time of 60.24 s, and the yield of SDF was 22.17%. For validation, the process parameters were slightly adjusted to citric acid mass fraction 6%, solid-to-liquid ratio 1:25, and microwave power 240 W, resulting in an average SDF yield of 21.74%, with only a minor deviation of 0.41% from the theoretical yield. For the C-UW-modified SDF, the optimal parameters were: cellulase addition 0.38%, enzymatic hydrolysis temperature 54.04℃, and enzymatic hydrolysis time 28.61 min, resulting in an SDF yield of 28.8%. For validation, the process parameters were slightly adjusted to cellulase addition 0.4%, enzymatic hydrolysis temperature 55 ℃, and enzymatic hydrolysis time 30 min, resulting in an average SDF yield of 28.29%, with only a minor deviation of 0.51% from the theoretical yield. In terms of physicochemical properties, C-UW-modified SDF exhibited significant superiority over unmodified SDF and M-A-modified SDF. SEM results showed that C-UW-modified SDF formed a denser, rod-like structure, while FTIR analysis indicated that the main components and overall chemical structure of the three SDFs remained relatively stable without significant changes. These findings confirmed that C-UW-modified SDF demonstrated better modification effects compared to unmodified SDF and M-A-modified SDF. In the mouse experiments, compared to the model group, C-UW SDF significantly reduced TC, TG, and LDL-C, while significantly increasing HDL-C. Compared to other treatment groups (unmodified SDF, M-A SDF), C-UW SDF showed more pronounced effects in improving the four lipid profile indicators, particularly in reducing LDL-C and increasing HDL-C. Additionally, C-UW SDF exhibited a reducing effect on serum ALT and AST activities, an inhibitory effect on weight gain, and alleviated liver damage, protecting the integrity of hepatocytes. These results confirmed that C-UW SDF was more effective in reducing blood lipid levels in hyperlipidemic mice, laying a foundation for subsequent research on grape pomace SDF and food development.

To address the fishy odor of large yellow croaker (Larimichthys crocea), this study investigated deodorization via yeast fermentation using high-activity dry yeast as the fermentation strain. Single-factor experiments were conducted to evaluate the effects of fermentation temperature, fermentation time, and yeast dosage on sensory scores and product freshness. Subsequently, the fermentation parameters were optimized using response surface methodology, with sensory scores used as the response variable. Under the optimized conditions, differences in color, pH, water-holding capacity (WHC), cooking loss, textural properties (hardness, springiness, chewiness, and gumminess), free amino acid (FAA) composition, and volatile compounds in large yellow croaker before and after fermentation were further analyzed. The optimal fermentation conditions were determined to be a temperature of 28 ℃, duration of 55 min, and yeast addition level of 1.75%. Under these conditions, fermentation enhanced textural characteristics and color attributes, with WHC increasing by 4.14% and cooking loss decreasing by 3.11%. FAA analysis showed that the total free amino acid content decreased by 154.07 mg/100 g after fermentation, with the umami, sweet, and bitter amino acid contents decreasing by 9.9, 61.33, and 74.62 mg/100 g, respectively, and the proportions of umami and sweet amino acids increasing by 4% and 0.52%, respectively. SPME/GC–MS analysis demonstrated a significant reduction in fishy aldehydes (nonanal, heptanal, pentanal, and hexanal) and a substantial increase in pleasant fermented aroma compounds (alcohols, ketones, and esters). In summary, yeast fermentation effectively improved the flavor profile and product quality of large yellow croaker. This study provides a theoretical basis for the application of fermentation-based deodorization technology in large yellow croaker processing.

To investigate the preparation of freeze-dried Pediococcus pentosaceus sourdough and its effects on the quality of multigrain steamed bread, this study utilized skim milk powder as a cryoprotectant to prepare freeze-dried P. pentosaceus sourdough. The cryoprotective effects of different skim milk powder concentrations were evaluated, and the ability of the freeze-dried sourdough to improve the textural quality of sorghum steamed bread was further explored. Results indicated that the survival rate of P. pentosaceus in freeze-dried sourdough with 10% skim milk powder was 28.5%, significantly lower than those with 15% and 20% skim milk powder. However, this group exhibited the highest dough fermentation capacity, a specific volume of steamed bread (2.58 mL/g), and sensory scores. An in-depth analysis of macromolecular structures revealed that sourdough fermented with 10% skim milk powder showed a significant decrease in β-sheet content and an increase in α-helix content in gluten protein secondary structures, alongside a notable rise in starch gelatinization temperature and a reduction in enthalpy. Applying the 10% skim milk powder freeze-dried P. pentosaceus sourdough in sorghum steamed bread preparation significantly improved the dough's textural properties. It enhanced the overall sensory score of the steamed bread. This study provides insights into the commercial production of freeze-dried P. pentosaceus sourdough and its application in multigrain steamed bread.