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.

6-α-glucosyltransferase has catalytic activities of exo-hydrolysis towards α-1,4-glucan and transglycosylation, and can produce the α-glucan which links α-1,6 glycosidic bonds on the nonreducing end through transglycosylation activity.Therefore, it can be used to produce cyclic alternating sugars and their branched derivatives, as well as cycloisomaltooligosaccharide, which can be used as new functional sugar.To expand the application of 6-α-glucosyltransferase in the food industry, the 6-α-glucosyltransferase from Bacillus globisporus N75 was expressed heterologously in the food safety strain Bacillus subtilis, and the expression level of recombinant protein increased by selecting the host strain and optimizing fermentation condition.These results indicated that the host WHS9 was more beneficial for the recombinant expression of 6-α-glucosyltransferase and the total soluble enzyme activity could achieve 2.11 U/mL at 20 ℃, including intracellular and extracellular.After adding 20 mmol/L trehalose, the total enzyme activity could reach 2.21 U/mL at 25 ℃ for 48 h.Then the fermentation period was optimized, and it was found that the highest enzyme activity could reach 3.14 U/mL at 36 h, which was 196 times higher than in WHS9 before optimization.This study firstly achieves recombinant expression of 6-α-glucosyltransferase in B.subtilis.

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.

‘Cuixiang’ kiwifruit are usually hard when purchased and need to be stored to soften before they can be eaten.However, kiwifruit are respiratory leaps that are prone to concentrated ripening, and the uncontrollable evolution of kiwifruit fruit quality during home storage can lead to a poor consumer experience and a reduced desire to buy.In this paper, the evolution of fruit quality of ‘Cuixiang’ kiwifruit under home storage conditions was systematically analyzed based on the dimensions of physicochemical characteristics, organoleptic quality, and aroma characteristics.In terms of physicochemical characteristics, titratable acid content and hardness of kiwifruit decreased significantly during home storage, while the content of total soluble solids, sugar-acid ratio, and weight loss tended to increase significantly.Based on the correlation of the above indexes, hardness was chosen to establish a zero-level kinetic shelf-life prediction model, and the model had good accuracy and reliability.Meanwhile, the artificial sensory evaluation showed that, except for the appearance score, which continued to decrease during the storage period, the scores of other sensory indexes, such as color, aroma, taste, texture, etc., increased significantly and peaked on the 11th day.Therefore, the total artificial sensory scores of ‘Cuixiang’ kiwifruit were the highest on the 11th day of home storage, which was the most suitable for consumption at this time.Gas chromatography-mass spectrometry was used to evaluate the aroma profile of kiwifruit, and a total of 513 volatile organic compounds were detected, with ester concentrations accounting for the highest percentage of kiwifruit samples at different stages of home storage, and terpenes showing the highest percentage of species.On the 1st day and the 7th day, the volatiles were more abundant and the aroma was more complex, with the highest content of aldehydes and a prominent herbaceous note.On the 11th day, the proportion of esters in the total volatiles was significantly higher than that on the 1st day and the 7th day, and the fruity and sweet flavors were more intense.

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.

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.

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.

In this study, the mycelia of Ganoderma sessile were used to prepare mycelium base composites (MBCs), C-MBCs (corn stalks), and H-MBCs (hemp stalks), respectively.To obtain more active mycelium seeds, the liquid cultivation conditions were optimized.The study included the effects of carbon sources, nitrogen sources, initial pH, temperature, G.sessile content, liquid volume, and rotating speed on the mycelial biomass of fermented products.Both C-MBCs and H-MBCs were measured for scanning electron microscope, compressive strength, and thermogravimetric characteristics.Results showed that the best mycelium cultivation medium was 25 g/L corn flour, 14 g/L soybean powder, 3 g/L KH₂PO₄, and 3 g/L 7H₂O·MgSO₄.The optimized fermentation conditions were fermentation temperature at 28 ℃, initial pH 5.5, G.sessile content with 5%, liquid volume 150 mL/500 mL flask, and rotating speed 180 r/min.Under the optimized conditions, the mycelial biomass in the cultural broth was 18.73 g/L, which increased by 34%, compared with those before optimization.The compressive strength and thermogravimetric characteristics of C-MBCs and H-MBCs were both better than expanded polystyrene.It’s concluded that this result will provide a reference for the application of MBCs instead of foam plastics in cushioning packaging.

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。

Squid belongs to the cephalopod class of mollusks, with short survival time, fast reproduction speed, comprehensive nutrition, high protein content, low-fat content, and low-calorie content.Squid skin accounts for 8%-13% of squid processing waste, and full utilization of squid skin can prevent resource waste.This article reviewed the nutritional components, peeling methods, extraction methods of collagen and gelatin from squid skin, as well as the preparation methods of squid skin collagen peptides with antioxidant activity, anti-hypertension, anti-skin aging, anti-tumor activity, and anti-freezing activity.The application of squid skin collagen products in industries such as food, medicine, cosmetics, and cosmeceuticals was also introduced.This article provided a systematic introduction to the research progress in the processing and utilization of squid skin, aiming to provide a theoretical basis for the deep processing of squid skin and promote the sustainable and healthy development of China’s aquatic product processing industry.In the future, the research should focus on optimizing the extraction process of squid skin collagen, improving the targeting of its target peptide screening, and conducting active clinical validation studies, to provide reference for the development and high-value utilization of squid skin.

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.

Astaxanthin is widely used in industries such as cosmetics, feed additives, and healthcare due to its antioxidant, coloring, and health-promoting properties.The traditional production process of astaxanthin mainly includes natural extraction and chemical synthesis.However, they cannot meet the growing market demand and consumer demand for natural products.With the rapid development of synthetic biology, the synthesis of astaxanthin by microbial fermentation is a more efficient way.Many naturally occurring sources of astaxanthin, such as Xanthophyllomyces dendrorhous and genetically engineered yeasts such as Saccharomyces cerevisiae, Yarrowia lipolyticus, and Kluyveromyces marxianus, have been isolated and constructed.To improve the efficiency of astaxanthin production through industrial yeast fermentation, researchers used a variety of strategies such as mutagenesis, genetic modification, and fermentation regulation, and explored ways to synthesize astaxanthin using different cheap substrates.Therefore, this study systematically reviews the research progress of yeast astaxanthin synthesis, analyzes the main factors affecting astaxanthin synthesis from the metabolic pathway of yeast and the current status of astaxanthin synthesis using different raw materials, and proposes methods and strategies for yeast to produce astaxanthin.

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.

The combination of meal and wine has always been one of people’s pursuits for a better life.The academic community’s interest in the study of meal and wine pairing is rapidly growing, but there is still a lack of scientific empirical evidence.For the first time, this study adopted a within-subjects design and used correlation analysis, ANOVA and other methods to explore consumer preferences for taste and Baijiu pairings.Results showed that four typical Baijiu (elegant-flavor Baijiu, chi-flavor Baijiu, strong-flavor Baijiu, and sauce-flavor Baijiu) could significantly weaken sweet and sour taste.In addition, strong-flavor Baijiu could weaken bitter taste, while sauce-flavor Baijiu could weaken umami taste.Consumer preferences for different types of Baijiu and taste pairings were significantly different, and preferences were significantly related to taste intensity changes, purchase intention, and recommendation.Four types of Baijiu had the highest preference for pairing with a sour taste, but there were differences in other tastes suitable for different types of Baijiu.In addition to the sour taste, the combinations of chi-flavor Baijiu and elegant-flavor Baijiu with sweet and salty taste were more satisfactory, while strong-flavor Baijiu and sauce-flavor Baijiu were more suitable for sweet and umami taste.In this study, a taste solution was used to induce a basic taste experience and to explore the matching preference between it and different types of Baijiu, which laid the foundation for further research on meal and wine pairing.