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.

Since 15%-20% sucrose is usually added in a small baked bun, it is necessary to reduce the sucrose content and develop a non-sucrose small baked bun.Maltol, fructooligosaccharides, isomaltooligosaccharides, and galactooligosaccharides were used to replace sucrose to prepare sucrose-substituted small baked bun, and their effects on the quality of small baked bun were investigated, the reasons for the differences were discussed from the aspects of embryogenic properties and micro-state of starch and protein in small baked bun.Results showed that the effect of sucrose substitute on the color and taste of small baked buns was related to its properties and the influencing factors on taste are relatively complex.The hardness and specific volume of the small baked bun were 1 138.82 g and 1.81 mL/g, the hardness of fructooligosaccharides, isomaltooligosaccharides, and galactooligosaccharides group increased to 1 998.31, 1 956.79, and 1 426.21 g, respectively, and the specific volume decreased to 1.48, 1.49, and 1.29 mL/g.Further analysis showed that different sucrose substitutes had different abilities of hydrogen bond formation, which led to different distributions of water in embryogenesis, and then affected the rheological properties and formation difficulty of embryogenesis.The hardness of a small baked bun was positively correlated with the final viscosity of starch gelatinization and negatively correlated with the short-range ordering of starch, fructooligosaccharides, and isomaltooligosaccharides increased the final viscosity by 11.3% and 8.1%, respectively, and decreased the short-term order of starch by 17.3% and 12.1%.The specific volume of a small baked bun was negatively correlated with the gelatinization viscosity of starch and positively correlated with the thermodynamic termination temperature and the content of protein β-folding.The galactooligosaccharide group had higher gelatinization viscosity, lower termination temperature (72.90 ℃), and lower content of protein β-fold (38.36%), which resulted in slower gas expansion and earlier thermal solidification, the stability of the protein network was decreased and its specific volume was 1.29 mL/g.

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.

Curcumin is a natural polyphenolic substance extracted from ginger plant.Adding curcumin into foods can make them have unique color, produce special flavor, and provide people with certain health care functions.Moreover, curcumin has significant medicinal value, such as improving human immunity and accelerating body metabolism.Specifically, curcumin has many physiological functions, for example, it can act as an anti-inflammation agent, antibacterial agent, antioxidant, lipid-lowering agent, and gallbladder enhancer.Curcumin has been widely used in the fields of food, pharmacy, and animal production, but its poor water solubility and stability limited its application.In this paper, the physicochemical properties, extraction, functional properties, application, and solubilization technology of curcumin were reviewed, providing a reference for further research on curcumin.

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.

Enzymes of Daqu are one of the key factors affecting the quality of Daqu and Baijiu.Understanding the enzymes is of great significance for optimizing the Daqu-making technology and revealing the mechanism of Baijiu fermentation.In this study, advanced technologies for investigating the enzymes of Daqu were introduced, and their advantages and disadvantages were discussed.Additionally, known functional enzymes in typical Daqu were summarized.High-throughput sequencing and metaproteomics could be used to analyze the composition and function of enzymes in Daqu from the perspective of genome, transcriptome, and proteome.Currently, the key functional enzymes involved in the pathways of saccharification and ethanol fermentation in low-temperature Daqu, medium-temperature Daqu, and high-temperature Daqu have been identified by using the above technologies.However, because the above technologies have difficulties in detecting enzymes with lower content in Daqu, the functional enzymes involved in the pathways of flavor compound metabolism in Daqu cannot be fully identified at present.There is an urgent need to upgrade relevant technologies to promote the research on the enzymes in Daqu.

Triacetic acid lactone (TAL) is a promising platform polyketide with broad applications, especially it can be used as a precursor for the synthesis of various organic compounds.This study characterized the repeating sequences on the yeast genome to integrate the TAL biosynthesis pathway into these sites for enhanced gene expression and TAL production by Saccharomyces cerevisiae.Firstly, this study used the green fluorescent protein as the reporter to characterize multi-copy integration by the Delta1 site.It showed that truncating the promoter of a selection marker gene (for geneticin or hygromycin B) or increasing the antibiotic concentration, were effective in improving the integration efficiency and copy numbers.The highest copy number of multi-copy integration was obtained when truncating the antibiotic gene promoter to 15 bp, and using an antibiotic at 160 μg/mL.The optimization system was subsequently used to characterize the second multi-copy integration site, Delta2, with similar results.Then, the optimized multi-copy integration system was applied to introduce the TAL biosynthesis pathway into S.cerevisiae.The highest pathway copies using Delta1 and Delta2 sequences were 10 and 7, respectively, with Delta1 slightly better than Delta2.After 48 h fermentation in YTD medium, TAL titers of the Delta1-integration strain and the Delta2-integration strain were 1.50 mmol/L and 1.17 mmol/L, respectively, 460% and 337% higher than the single-copy integration strain.This study demonstrates that the multi-copy integration system is an efficient approach to introducing heterologous pathways into S.cerevisiae to improve biocatalytic efficiency.

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 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.

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。

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 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.

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 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.

This study aimed to investigate the impact of different solvent extraction methods on the quality of Antarctic krill oil.The extraction efficiency of total lipid, phosphatidylcholine (PC), lysophosphatidylcholine (LPC), as well as the levels of eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were selected as the investigation parameters.Furthermore, the molecular species composition of PC/LPC in the extracted Antarctic krill oil was examined and analyzed using hydrophilic interaction chromatography-tandem mass spectrometry technology.Consequently, the effects of various solvents, including 95% ethanol, n-hexane, isopropyl alcohol, ethyl acetate, isopropyl alcohol/n-hexane (1∶1, v∶v), ethyl acetate/n-hexane (1∶1, v∶v), and Folch solvent (trichloroethane/methanol, 2∶1, v∶v), on the quality of Antarctic krill oil were examined.Results showed that 95% ethanol and isopropyl alcohol/n-hexane exhibited higher extraction efficiency, as well as higher EPA and DHA contents (20.05% and 20.42%, respectively).Conversely, the extraction efficiency and EPA/DHA levels were lower when n-hexane and ethyl acetate were employed.In addition, 95% ethanol, ethyl acetate/n-hexane, and isopropyl alcohol/n-hexane demonstrated greater extraction efficiency for PC/LPC, while the efficiency of ethyl acetate, isopropyl alcohol, and n-hexane was comparatively lower.Furthermore, n-hexane, ethyl acetate/n-hexane, and isopropyl alcohol yielded higher proportions of PC 22∶6/22∶6, PC 20∶5/22∶6, and PC 20∶5/20∶5.Conversely, LPC extracted with isopropyl alcohol/n-hexane, Folch solvent, and 95% ethanol contained a higher proportion of PC 0∶0/20∶5 and PC 0∶0/22∶6.In conclusion, the results suggested that 95% ethanol and isopropyl alcohol/n-hexane exhibited notable enrichment effects on EPA/DHA and PC, making them the most suitable solvents for the extraction of Antarctic krill oil.

Postbiotics are inanimate microorganisms and/or their components that are beneficial to host health, and they are superior to probiotics in terms of safety and stability.This paper described the main active components of postbiotics such as short-chain fatty acids, extracellular polysaccharides, antimicrobial peptides, and cell-free supernatant, as well as their functional properties as antimicrobials, antioxidants, and anti-inflammatory agents.In addition to health benefits, postbiotics also have good application prospects in food quality improvement, food storage, food packaging, etc.Besides, the paper reviewed the effects of postbiotics on the microorganisms, physicochemical properties, and sensory quality of meat products and summarized the development directions of postbiotics in meat products, such as its effective dosage, processing and storage stability, and application in antimicrobial packaging.This paper provides a reference for the future application of postbiotics in improving the quality of meat products and developing functional meat products.

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.

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.

Menaquinone-7 (MK-7), as one of the vitamin K₂ subtypes, has the effects of treating osteoporosis and protecting cardiovascular health.Common MK-7 production is mainly fermented by food such as natto, but there are problems such as low yield and complex extraction.Bacillus subtilis, as a common production strain of MK-7, also faces the problems of long fermentation period and low titer.In this study, a strain of Escherichia coli introducing mevalonate pathway was modified.Firstly, four key enzymes were screened by DLKcat model, including heptaisopentadiene pyrophosphate synthase BtHepS\BtHepT, 1,4-dihydroxy-2-naphthoic acid heptaenyl transferase MnMenA, and menadione biosynthesis C-methyltransferase NtMenG.The expression optimization was carried out to construct the endogenous synthesis of MK-7 pathway in E. coli.Subsequently, the prenylated pyrophosphate isomerase EcIdi was integrated and expressed to enhance the precursor supply, and then the fed-batch fermentation conditions of the obtained strains were optimized, including delaying the induction time, increasing the dissolved oxygen to 60. The MK-7 production reached 929.58 mg/L, but there was 1 217.58 mg/L demethylmenaquinone-7 (DMK-7) accumulation.Then, different sources of MenG were further screened to reduce the accumulation of DMK-7, and it was found that MenG from B. subtilis 168 could reduce the accumulation of DMK-7.Finally, the production of MK-7 reached 1 090.45 mg/L and DMK-7 decreased to 231.14 mg/L in a 5 L fermenter.The results of this study have certain guiding significance for the application of E.coli to produce MK-7.

Heat-moisture treatment is a common method of physical modification of starch.Proper heat-moisture treatment can effectively change the granular structure and molecular structure of starch, thus affecting its solubility and swelling power, gelatinization, retrogradation and other physical and chemical properties, to improve food quality.Firstly, this article briefly introduced the principle and characteristics of heat-moisture treatment, then analyzed the influence of heat-moisture treatment on starch structure and physicochemical properties, and finally discussed the application of heat-moisture treatment in food processing such as noodles, bread, and biscuits to deepen the understanding of heat-moisture treatment, providing theoretical basis and scientific suggestions for promoting the application of heat-moisture treatment in modifying botanical starch and improving the safety and quality of starchy food.