Using high-throughput sequencing technology and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), this study analyzed the microbial diversity and volatile flavor components of Xizang yak yogurt.On this basis, the correlation between microbial community structure and flavor substances, as well as related metabolic functions, was explored.The results showed that the dominant bacteria in Xizang yak yogurt were Lactobacillus, Streptococcus, Enterococcus, and Lactococcus, while the dominant fungi were Geotrichum, Kluyveromyces, and Pichia.In the analysis of volatile flavor components, a total of 37 volatile flavor compounds were detected in Xizang yak yogurt.The main flavor substances were ethyl hexanoate, ethyl L-lactate, ethyl octanoate, ethyl decanoate, isoamyl alcohol, 2,3-butanediol, phenylethyl alcohol, 2-methylhexanoic acid, and 2-nonanone.Correlation analysis indicated that Lactobacillus, Streptococcus, Geotrichum, and Pichia were the microorganisms most significantly associated with volatile flavor components. Lactobacillus and Streptococcus showed a positive correlation with most metabolic products.This study explored the correlation between volatile flavor substances in Xizang yak yogurt and microbial community structure, providing a theoretical basis for improving the quality and taste of Xizang yak yogurt。

Microorganisms from extreme environment are valuable sources for discovering new enzymes with unique properties, particularly highly stable enzymes with significant potential for industrial applications.In this study, a segment of predicted glutaminase gene from Thermomicrobium roseum DSM 5159 source was expressed by heterologous recombination and its enzymatic properties were investigated.The expression product was purified using nickel column affinity chromatography, the purification results were identified by matrix-assisted laser desorption/ ionization time of flight mass spectrometry (MALDI-TOF-MS), the catalytic function of the recombinant enzyme was analyzed, the expression conditions were optimized by orthogonal test, and the enzymatic properties of the recombinant enzyme were investigated.The results revealed that the secondary structure of the recombinant glutaminase consisted of 35.78% α-helix, 14.07% β-sheet, 16.06% β-turn, and 34.19% random coil.The thermal denaturation temperature (T_m) and enthalpy change (ΔH) were 94.38 ℃ and 1 672 kJ/mol, respectively.The optimal reaction temperature for using L-glutamine as the substrate was 70 ℃, and the optimal pH value was 9.0.The enzyme retained more than 50% of its activity after 12 hours at temperatures below 70 ℃, demonstrating excellent heat stamina.Kinetic studies indicated that the recombinant glutaminase had a higher affinity for L-glutamine than for D-glutamine.Additionally, Mn²⁺, Fe²⁺, Zn²⁺, Cu²⁺, and Co²⁺ significantly inhibited enzyme activity.The study of the structure and enzymatic properties of glutaminase from Thermophilic archaea provides a certain reference value for mining and developing enzymes with excellent thermal stability for industrial production.

The alluring aroma of jasmine is adored by people worldwide.Benzyl acetate, a key component of the scent of jasmine, is a valuable aromatic ester compound and extensively used as flavor and fragrance in food, cosmetics, and pharmaceutical industries.However, its current production heavily relies on chemical synthesis.In this study, a de novo synthesis pathway of benzyl acetate was established in Escherichia coli strains, and benzyl acetate was successfully synthesized by microbial fermentation.Firstly, to construct the synthesis pathway of benzyl acetate, nine functional enzymes were co-expressed in BL21 (DE3) using a modular strategy.The resulting strain BZ04 produced (85.55±10.85) mg/L benzyl acetate by two-phase in situ extractive fermentation.Subsequently, the production of benzyl acetate was enhanced through the optimal screening of key acyltransferase derived from various sources and optimization of various flask culture conditions including the screen of carbon sources, the addition of solubilizer, and the increase of oxygen supply.Under optimal fermentation conditions, the final strain of BZ05 produced (592.22±36.95) mg/L benzyl acetate from glycerol in shake flasks, which was seven times compared to original production of benzyl acetate.This study provides an eco-friendly and sustainable approach for benzyl acetate production.

Proteins and polyphenols can interact in reversible or irreversible ways, thus affect the sensory, texture and nutritional properties of foods.To investigate the types of non-covalent interactions between anthocyanins (centaurin-3-O-glucoside (C3G)) and bovine serum albumin (BSA) and their effects on BSA protein properties, multispectral techniques and molecular docking methods were used.The effects of C3G on the properties of BSA protein were also studied.First, Fourier infrared spectroscopy showed that the amide I and A bands were redshifted and their peak intensities weakened after C3G combined with BSA.The results of circular dichroism spectrum showed that the structure of BSA protein became loose and the secondary structure of BSA was changed in the presence of C3G.The α-helix content decreased from 31.8% to 31.1%, and the β-fold content increased from 18.1% to 18.5%.Next, the fluorescence spectra confirmed that the quenching of BSA by C3G is a static quenching caused by the formation of ground state complex.Thermodynamic and molecular docking results showed that the force between BSA and C3G is mainly contributed by electrostatic attraction and hydrogen bond, and C3G entered the BSA cavity structure.Finally, the study on the physical properties of BSA showed that the addition of C3G could expand the BSA domain and increase the particle size from 244.75 nm to 644.70 nm.Interestingly, C3G significantly enhanced the solubility, water holding capacity and oil holding capacity of BSA, as well as improved foam properties and emulsification properties.This study provides an important experimental and theoretical basis for understanding the effects of C3G on the conformation and protein properties of BSA, and provides a theoretical basis and reference for the application of protein-anthocyanin complexes.

The purpose of this study was to investigate the auxiliary protective effect of seabuckthorn oil on alcoholic liver injury in rats.In the experiment, 100 male SD rats were randomly divided into blank control group, model control group and low, medium and high dose groups of seabuckthorn oil.The animal model of acute liver injury was induced by 50% anhydrous ethanol.The effects of different doses of seabuckthorn oil on liver metabolic enzymes, liver and serum lipid levels, liver lipid accumulation and alcohol metabolic enzymes in rats were analyzed and compared.Results showed that there was no significant difference in body weight and weight gain, liver weight and liver index among the groups.After 30 days of administration of the test substance, compared with the model control group, the levels of reduced glutathione in the liver of each dose group were significantly increased, while the levels of triglyceride in the liver, serum total cholesterol and alanine aminotransferase were significantly decreased, the levels of malondialdehyde (MDA) in the liver of the low and medium dose groups were significantly decreased, and the serum levels of aspartate aminotransferase and low-density lipoprotein cholesterol were significantly reduced in the high dose group.After giving the test substance for 50 days, the MDA level and pathological score of the low dose group were significantly lower than those of the model control group, the level of reduced glutathione was significantly increased, and the MDA level of the middle and high dose groups was significantly decreased.There was no significant difference in the activity of acetaldehyde dehydrogenase and alcohol dehydrogenase in the liver of each dose group of 50 days.The results showed that seabuckthorn oil may reduce liver cell damage through antioxidant effects and regulation of lipid metabolism, thereby providing auxiliary protection against alcoholic liver injury.However, the effects of seabuckthorn oil on liver biochemical indicators and serum biochemical indicators exhibited a complex dose-dependent relationship.In practical applications, the appropriate dosage of seabuckthorn oil should be selected according to specific circumstances.This study provides a scientific basis for the application of seabuckthorn oil in food products, nutraceuticals, and related industries.

Litchi, as a popular summer fruit, is highly susceptible to peel browning and fruit rot after harvesting, which severely affects its storage life.Currently, most litchi freshness packaging on the market uses traditional packaging technologies such as foam boxes, cartons, and films, which can solve the aforementioned problems to some extent.However, in recent years, with the continuous development of packaging technology and the growing needs of people for a better life, higher standards have been set for the appearance, freshness, quality, and shelf life of litchis post-harvest.Therefore, this paper sequentially discusses the research and application of traditional freshness packaging, release-activated packaging, and intelligent packaging in the field of litchi freshness, comprehensively analyzes the current status, limitations, and challenges of litchi freshness technology, and aims to provide a direction for future research, with the expectation of supporting the high-quality development of the litchi industry.

The raw materials and degree of fermentation affect the growth and metabolism of fermented Pu-erh tea microbiota, which ultimately affects the quality of fermentation.This study used 16S rRNA and ITS amplicon sequencing to study the effect of the raw materials and degree of fermentation on the fermented Pu-erh tea's microbiota differences and quality.Results showed that the abundance and diversity of the prokaryotic microbiota of high-fermented Pu-erh tea were significantly higher, but the abundance of eukaryotic flora decreased significantly.Compared to light-fermented teas, the high degree of fermentation was more conducive to increasing the content of soluble polysaccharides, lignin, total flavonoids, proteins, and theabrownin in Pu-erh tea.The fermentation of tea stems significantly increased Pseudomonas (86.78%) abundance and decreased protein content.Adding honey significantly increased Aspergillus (87.47%) abundance and increased the content of theabrownin.Fermentation of yellow tea-leaf comprehensively increased the abundance of Aspergillus (31.90%), Thermomyces (41.91%), Rhizomucor (20.09%), Pseudomonas (40.46%), and Bacillus (21.44%), and increased the content of soluble polysaccharides.The predictions of PICRUSt2 function revealed that the degree of fermentation had a greater effect on the microbiota of fermented Pu-erh tea than the fermented raw material.Redundancy analysis revealed that free amino acids, lignin, cellulose, and theabrownin were significantly associated with eukaryotic microbiota, while proteins and soluble polysaccharides were significantly associated with prokaryotic microbiota.This study provides a theoretical basis for the strain improvement of the fermentation process of Pu-erh tea.

Traditional fermented sufu is a daily condiment and appetizer, acting as a good source of plant-derived protein and bioactive peptides.To explore the angiotensin converting enzyme (ACE) inhibitory tetrapeptide and investigate the structure-activity relationships, the peptides of oil sufu were isolated using ultrafiltration and solid-phase extraction, and identified using Nano-LC-MS/MS.The potential ACE inhibitory peptides were preliminarily screened by online database, and then the peptides with high ACE inhibitory activity potential were further screened and analyzed using molecular docking, quantum chemical calculation, and quantitative structure activity relationship modeling.Their binding modes, distribution of the frontier molecular orbital, active sites, and inhibitory activities were analyzed.The results showed that peptides with molecular weight <3 kDa had the highest inhibitory activity [IC₅₀=(489.6±26.69) μg/mL], and a total of seven high-potential ACE-inhibitory tetrapeptides were screened after sequences identification.The molecular docking results showed that all seven peptides bound tightly to the receptor through hydrogen bonding, hydrophobic, electrostatic, and metal bonding interactions to exert their inhibitory effects.Quantum chemical results showed that the highest occupied molecular orbitals of the tetrapeptide were mainly distributed on the two-terminal proline (P), and they had a high electronegativity and was easy to become an active site;FALP, GWPT and EGWP had lower energy gap and higher molecular reactivity.The results of quantitative structure activity relationship modeling showed that the parametric characteristics of the amino acid residues at two-terminal of the tetrapeptide had a more significant effect on the IC₅₀ value;the smaller hydrophobicity and stereotropism of the amino acid, and larger electrical properties, the stronger the activity of the peptides.In conclusion, computer-assisted screening of ACE inhibitory peptides in furu was feasible, and the electrical properties of the two-terminal and proline were important to its inhibitory activity, which will provide a reference for the subsequent rapid screening of ACE inhibitory peptides and the study of structure-activity relationship.

Selenium polysaccharide (Se-polysaccharide) is a combination of selenium and polysaccharide, which is more easily absorbed and utilized by the body than inorganic selenium.It possesses a variety of biological activities, including antioxidant, anti-tumor, antiviral, immune enhancement and other aspects.Scientific studies suggest that Se-polysaccharide has the potential for future development in the fields of drug research and nutraceutical development.Through combining the relevant studies on selenium polysaccharide domestic and foreign, this article summarizes the synthetic methods and pharmacological activities of Se-polysaccharide, and hope to provide a valuable reference for the in-depth research of selenium polysaccharide.

Constipation is a common gastrointestinal disease, and its incidence has obvious gender differences, in which women being more susceptible to constipation.Previous studies have found that the application of estrogen receptor β (ERβ) inhibitor (tamoxifen citrate) can successfully construct an animal model adapted to female constipation.Meanwhile, Bifidobacterium longum CCFM1240 has the effect of relieving female constipation, but the mechanism to exert its effect is still unknown.Based on that, this study intends to analyze the possible approaches of relieving female constipation from the perspective of repairing intestinal nerves and intestinal barriers.Results showed that compared with the model group, the intervention of B. longum CCFM1240 could significantly regulate the structure of intestinal microbiota (upregulate the relative abundance of Pediococcus, downregulate the relative abundance of Parabacterioids, Oscillibacter, Ruminococcus UGG-010, and Ruminiclostridium 9), increasing the content of six short chain fatty acids (especially acetic acid, butyric acid, and valeric acid), helping to restore the intestinal barriers and intestinal nervous system (promote the secretion of ACh by intestinal neurons, reduce the pro-inflammatory factor IL-6 and increase the proportion of Treg), and improving intestinal inflammatory response.This study demonstrates that B. longum CCFM1240 can balance the intestinal environment, repairing damaged intestinal barriers and intestinal nerves, thereby alleviate constipation in female rats induced by estrogen receptor beta inhibitors, and provide a new method to treat female constipation.

Streptococcus salivarius subsp. thermophilus is widely used in industrial fermentation due to its excellent fermentation and aroma production characteristics.Although there are unique and diverse resources of Streptococcus thermophilus in China, few studies have been conducted on the growth and fermentation characteristics of strains isolated from Chinese traditionally fermented dairy products.This study analyzed the growth and fermentation characteristics of four Streptococcus salivarius subsp. thermophilus strains isolated from China which are located in different branches of the evolutionary tree.It was found that only CCFM1095 and CCFM1308 could metabolize and utilize galactose in carbon source utilization.There were significant differences among different strains in terms of nitrogen source utilization, only CCFM1015 could utilize casein and CCFM1095 with 8 amino acid nutritional deficiencies.The composition of nitrogen sources in the milk system limited the growth and fermentation of all strains except CCFM1015.Therefore, strain CCFM1015 had the potential as a starter culture, CCFM1095 had fast lactose utilization ability and CCFM1038 was efficient in utilization of amino acids, which could provide a basis for the improvement of fermentation conditions and application of subsequent strains.

The aim of this study was to investigate the effects of steam explosion (SE) on the structural, physicochemical and functional properties of soluble dietary fiber (SDF) in pomegranate peel.Taken the extraction rate of SDF as index, the optimal technology of SE modification was as follows:the particle size of pomegranate peel residue was 60 mesh, the pressure was 0.60 MPa, and the maintenance pressure time was 140 s.Under these conditions, the extraction rate of SDF was (13.42±0.12)%, which was (5.91±0.04)% higher than that before modification.The analysis of Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy showed that more chemical groups were exposed, the intermolecular hydrogen bonding was strengthened, and the crystallinity was decreased after SE.The structure of SDF was also changed, and the surface was poriferous, rough and collapsed.The water-holding capacity, oil-holding capacity and swelling capacity of modified SDF were increased to (1.19±0.09) times, (1.60±0.16) times and (1.95±0.03) times of those before SE, respectively.In addition, SE improved the glucose adsorption capacity, alpha-amylase inhibition ability, cholesterol adsorption capacity and antioxidant ability of SDF in pomegranate peel residue.In conclusion, SE technology can effectively improve the physicochemical and functional properties of SDF from pomegranate peel residue, which provides a theoretical basis for the extraction and application of SDF from pomegranate peel residue.

As a green biodegradable material, plant-derived edible film can not only realize the function of preservative and freshness preservation, but also has many advantages such as safety and non-toxicity, isolation and protection, and as a carrier of active substances as well as edible raw materials.In view of the fact that plant-derived edible film has become a hot research topic in the field of food packaging and freshness preservation.This paper introduces an overview of three current plant-derived edible membranes of polysaccharides, proteins, and composites, elucidates the mechanisms and modes of action, and summarizes their applications in the field of food processing.Finally, the future development direction of edible films is prospected.The purpose of this review is to provide reference for further research on plant-derived edible packaging materials in the field of food preservation.

Lycopene is a natural antioxidant used in food and pharmaceuticals.The traditional methods of plant extraction and chemical synthesis of lycopene have the disadvantages of large environmental pollution, complicated steps and high production costs.Microbial synthesis of lycopene has attracted international attention because it can effectively avoid the above problems.In this study, the lycopene synthesis pathway was constructed and optimized in food-safe strain Bacillus subtilis.Firstly, the lycopene synthesis gene cluster was heterogeneously expressed in B.subtilis to achieve de novo synthesis of lycopene.By optimizing the ribosome binding sites (RBS) of each gene in the lycopene synthesis gene cluster, the titer of lycopene was increased to 0.57 mg/L.In addition, error-prone PCR was used to randomly mutate the RBS-optimized lycopene synthesis gene cluster, and a mutant with lycopene titer increased to 6.4 mg/L was obtained.Secondly, by screening the expression host of the lycopene synthesis gene cluster, the titer of lycopene was further increased to 15.5 mg/L.On this basis, the titer of lycopene reached 77.4 mg/L by strengthening the synthetic pathway and knocking out the competitive pathway.Finally, after fine-tuning fermentation conditions, the lycopene titer in shake flasks increased to 91.0 mg/L.This study laid a foundation for the synthesis of lycopene by microbial method.

In this study, commercial lactoferrin, bovine lactoferrin, human lactoferrin, and camel lactoferrin were studied.The digestibility of lactoferrin from different milk sources was determined by SDS-PAGE, molecular weight of polypeptide, hydrolysis degree, and free amino acid.The iron saturation of the four lactoferrins was 16.03%, 13.55%, 7.49%, and 20.19%, respectively.Results showed that lactoferrin was digested slowly in the stomach and quickly after entering the intestinal stage.Bovine lactoferrin was easier to digest than commercially available bovine lactoferrin.Camel lactoferrin was digested in the gut more slowly than other species of lactoferrin, but it released more free amino acids.Human lactoferrin showed high digestive resistance in both the stomach and intestine and tended to delay the digestion of other lactoferrin in the early stage of intestinal digestion.This study provides a reference for infant nutrition product formulation optimization, extraction, and application of lactoferrin supplementation.

This study investigates the probiotic properties and cholesterol-lowering abilities of fermentation bacteria, by isolating and purifying four strains of lactic acid bacteria from traditional fermented mare’s milk.The morphological, physiological, and biochemical characteristics of these strains were assessed, along with their growth curves, tolerance to bile salts and artificial gastric fluid, and susceptibility to antibiotics.Additionally, qualitative assays were conducted for bile salt hydrolase activity and cholesterol oxidase to evaluate their cholesterol scavenging potential.The strains were ultimately identified using 16S rRNA gene sequencing.The findings reveal that the isolated strains exhibited strong tolerance to high concentrations of bile salts (3.0 g/L) and artificial gastric fluid (pH 2.0) while remaining sensitive to the majority of the eight antibiotics tested.Distinct white precipitation zones around the filter paper disks of each strain indicated the presence of bile salt hydrolase activity.The cholesterol scavenging rates for single and composite strains in the culture medium ranged from (76.46±1.26)% to (87.96±0.43)%, with the composite strain demonstrating superior capacity for cholesterol compared to individual strains.These strains had been identified as Lactiplantibacillus plantarum.This study suggests that the four isolated strains possess fundamental probiotic attributes and a high safety profile, along with notable cholesterol-lowering capabilities in vitro, which warrant further explored in vivo.