The production of 1,6-hexanediamine as the synthetic monomer of nylon 66 is mainly monopolized by foreign countries, and the traditional chemical synthesis of hexanediamine contains highly toxic cyanide, high technical barriers, long production process, how to use the biological method to make innovative breakthroughs in the context of carbon neutrality has become a challenge.However, up to now, no natural hexanediamine synthesis pathway has been reported.In this study, 6-aminohexanoic acid, a widely available substrate, was used to construct a synthetic pathway for hexanediamine through component-adapted assembly, and fermentation enhancement was combined to increase the yield of hexanediamine in engineered strains.Finally, excellent carboxylic acid reductase MAB CAR L342E, single transaminase HATA, and double transaminase combination PatA/VFTA were obtained through screening, and the initial hexanediamine yields of the engineered strains after combination could reach 3.01 mg/L (DAH4) and 8.50 mg/L (DAH37), respectively.On this basis, the fermentation conditions were optimized, and the yields of 1,6-hexanediamine reached 64.33 mg/L and 153.93 mg/L, which were 20.37 times and 17.11 times higher than those before optimization, respectively.This study has successfully constructed a pathway for the synthesis of hexanediamine by biological method, which provides technical support for the breakthrough of domestic chemical products.

Deep eutectic solvent (DES), emerging as a novel generation of green solvents, due to their simple preparation process, minimal toxicity, biodegradability, and other advantageous characteristics, can overcome the limitations of traditional organic solvents.Consequently, DES serve as excellent alternatives to conventional organic reagents.This paper presents a comprehensive review of the most recent research findings in the field of DES, including the composition categorization, preparation techniques, performance parameters, and its advancements in natural product extraction, food testing and analysis, as well as catalytic reaction media.This review summarizes the concerned issues currently associated with DES, while also prognosticating potential future applications.This work offers a valuable reference for further exploration of the biochemical characteristics of green solvent systems and their practical applications.

Inhibiting the activity of acetylcholinesterase (AChE) is beneficial to the elevation of acetylcholine levels thereby alleviating cognitive impairment and memory decline in the elderly.In this study, the active ingredients in soymilk and fermented soymilk were extracted by ethanol solvent, and the AChE inhibitory activity of the two extracts was measured.Then, ultra-performance liquid chromatography quadrupole time of flight mass spectrometry was used to identify the extracts in the chemical components.The differential components with significant content changes before and after fermentation were screened by SIMCA software.After that, molecular docking technology was used to screen the active ingredients among the differential components, and their binding ability and interaction forces with AChE were explored.Results showed that lactic acid bacteria fermentation can significantly (P<0.05) improve the AChE inhibitory activity of soymilk, and its IC₅₀ value decreased from 3.24 mg/mL to 2.55 mg/mL.A total of 84 components were identified from soymilk and fermented soymilk extracts, of which 19 components had significant content changes before and after fermentation.The molecular docking results showed that 13 components were able to tightly bind with AChE.These active ingredients mainly interact with amino acid residues in AChE active sites through hydrogen bonding and hydrophobic interactions, thereby inhibiting AChE activity.

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。

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.

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.

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.

To enhance the stability of natural anthocyanins in the indicator membranes, grape-skin red (GSR) synthetic microcapsules were embedded with gelatin (GEL) and chitosan (CS) as wall materials and incorporated into potato starch (PS) and peanut shell cellulose (PSC) to prepare PS/PSC GEL/GSR/CS indicator films.The film properties were tested and analyzed, and the indicator films were applied in freshness monitoring of South American white shrimp.The results showed that when microencapsulation, peanut shell cellulose, and potato starch were used to prepare the composite film in the mass ratio of 2∶3∶50, the film was relative to the PS/PSC/GSR film, and the grapheme-red microencapsulation could increase the tensile strength of the indicator film from 11.95 MPa to 13.25 MPa, and the melting point was increased by 11 ℃, and the film could be stored at 4 ℃ (refrigerated), protected from light, and in 30% RH environment.It could be stored at 4 ℃ (refrigerated), protected from light and 30% RH for 15 days without obvious color difference and showed very high pH color response.The indicator film in the South American white shrimp freshness monitoring to verify the applicability of the color of the indicator film with the shrimp deterioration showed red-gray-yellow changes, the shrimp volatile saline nitrogen and other corruption index changes with the indicator film chromaticity value changes in the same trend, the color difference was visible, and would be extended for two days of color stability.Therefore, the freshness indicator film has high stability and has a promising application in the food field.

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.

The Chinese characteristic jujube honey was applied to develop functional goat milk yogurt, and the changes in product quality during refrigeration were evaluated.Jujube honey with different proportions of 4%, 8%, and 12% was added after the fermentation of goat milk, and the effects of the addition of jujube honey on the sensory quality, titratable acidity, pH, lactic acid bacteria amount, texture properties, water holding capacity, and antioxidant activity of goat milk yogurt during 28 days of refrigeration were investigated.Results showed that jujube honey could significantly improve and maintain the sensory quality of goat milk yogurt during shelf-life, and effectively reduce its acidification rate.The number of viable lactic acid bacteria decreased with the increase of jujube honey addition and continued to decline during refrigeration, while it was still significantly higher than the national standard limit at the end of refrigeration.The texture properties of goat milk yogurt added jujube honey reached maximum values after 14 days of refrigeration, with hardness, consistency, cohesiveness, and viscosity increasing by 19.50%-34.96%, 16.72%-23.16%, 26.86%-33.06% and 8.50%-12.01%, respectively, and their water-holding capacities were also maintained better than that of control yogurt.In addition, jujube honey endowed the product with stronger antioxidant activities, which increased further during refrigeration.Therefore, the jujube honey addition effectively enhances the quality and functional value of goat milk yogurt during its shelf-life, and it is an excellent choice for developing new functional goat milk products.

Shikimic acid is a natural aromatic compound with antioxidant, anti-inflammatory, and antibacterial effects, and it has important application value in the medical field.This study aimed to enhance the biosynthesis of shikimic acid through metabolic engineering and optimization of culture medium in Escherichia coli.The metabolic pathway was modified at the genomic level from wild-type Escherichia coli W3110, and a strain that could efficiently produce shikimic acid was successfully constructed by knocking out the shikimic acid consumption pathway, strengthening the shikimic acid synthesis pathway, and improving the supply of precursors.Based on this, the medium was optimized.The factors affecting the production of shikimic acid in the fermentation medium were firstly evaluated by using the single factor experiments and the Plackett-Burman test, and 3 factors including yeast extract, peptone, MgSO₄·7H₂O were screened out with significant effects.Box-Behnken was applied for the three-factor three-level design and response surface model construction and analysis to obtain the optimal fermentation medium formulation, which was initially glucose 10 g/L, yeast extract 2.06 g/L, peptone 1.52 g/L, K₂HPO₄ 3 g/L, KH₂PO₄ 3.5 g/L, (NH4)₂SO₄ 3 g/L, MgSO₄·7H₂O 0.20 mmol/L, betaine phosphate 0.22 g/L, CaCl₂·2H₂O 15 mg/L, vitamin B1 0.5 mg/L, trace element mixture 1 mL/L, and pH 7.0-7.2.Under this condition, the yield of shikimic acid reached 2.66 g/L in the shake flask, which was twice as much as that before optimization.This study lays the foundation for scientific research and industrial fermentation production on shikimic acid biosynthesis by Escherichia coli.

Indole-3-carbaldehyde (IAld), a derivative of tryptophan, is a unique metabolic product of microorganisms that has been proven in in vitro studies to have certain anti-inflammatory and anti-tumor activities.However, it is still unclear whether gut microbiota exerts related effects in vivo through the production of IAld.This study is centered on investigating the potential protective effects of a probiotic strain of Bifidobacterium animalis SHXXA4M1, which produces a high level of IAld, in a colitis-associated colorectal mouse model.The findings indicated that compared with the model group, mice in the SHXXA4M1 intervention group exhibited enhancements in several markers, including body weight, survival rate, colon length, and spleen index.Following the probiotic intervention, the relative abundance of Bifidobacterium significantly increased (P<0.05), IAld content in the colon also significantly increased (P<0.05), along with decreased levels of pro-inflammatory factors IL-1β, IL-17A, and IFN-γ, and increased levels of the anti-inflammatory factor IL-10.Additionally, there was a notable increase in the relative expression level of mRNA associated with intestinal barrier function, as well as observed apoptosis of tumor cells in the colon.The aforementioned findings suggest that supplementation of high-yield IAld Bifidobacterium animalis may mitigate inflammation in colitis-associated colorectal tumor mice through modulation of immune response and enhancement of intestinal barrier function.

To improve the extraction rate of soluble dietary fiber (SDF) from moso bamboo leaves, the extraction rates, structural and functional characteristics of soluble dietary fiber from bamboo leaves extracted by hot water extraction method, steam explosion method, sodium hexametaphosphate extraction method, and steam explosion-assisted sodium hexametaphosphate extraction method were compared and analyzed.Results showed that the extraction efficiency of the steam explosion-assisted sodium hexametaphosphate extraction method was the highest (51.15%), followed by the sodium hexametaphosphate method, steam explosion method, and hot water extraction method.The structure and composition of SDF were different between the steam explosion and the sodium hexametaphosphate explosion.The SDF with the combined method had the most complex structure, the smallest particle size and the highest absolute value of zeta-potential, which were 434.90 nm and -20.37 mV, respectively.The SDF extracted by the combined method had better functional properties and glucose adsorption capacity, cholesterol adsorption capacity, and ·OH radical scavenging capacity were the best, which were (52.04±0.19)%, (57.14±0.73)% (pH=2), (62.53±5.31)% (pH=7), and (95.50±1.46)%, respectively.The results provide a theoretical basis and data support for the extraction and application of soluble dietary fiber from moso bamboo leaves.

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.

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.

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.

This study investigated microbial diversity, flavor compound changes, and the contribution of dominant microbial genera to key metabolic pathways during highland barley wine fermentation.The macro-genome sequencing technology and solid-phase microextraction gas chromatography were utilized to analyze the process.The main dominant bacteria identified were Lactobacillus, Rhizopus, Wickerhamomyces, and Pichia.A total of 37 flavor substances, including 13 esters, 15 alcohols, 4 aldehydes, 2 ketones, 2 phenols, and 1 pyrazine, were detected.Metagenomic sequencing yielded 8 230 72 genes, and 5 microbial species for KEGG gene function were annotated.Notably, global and overview maps revealed high relative abundance in carbohydrate metabolism, signal transduction, energy metabolism, and amino acid metabolism.Furthermore, the distribution of different microorganisms in substrate metabolism networks and flavor formation varied.Lactobacillus, Pediococcus, Rhizopus, Saccharomyces, and Pichia were predicted to play significant roles in flavor formation.This study sheds light on the metabolic effects of diverse microorganisms during highland barley wine fermentation.

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.

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.