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In order to investigate the influence of antifreeze peptide properties on its protective effect on myofibrillar proteins in frozen surimi, the present study was conducted to characterize the properties of three antifreeze peptides (sericin peptides, collagen peptides and silver carp hydrolysates), and we analyzed the changing pattern of myofibrillar protein properties under different freezing conditions, and constructed a correlation model between myofibrillar protein properties and frozen storage parameters and antifreeze peptide properties using least absolute shrinkage and selection operator (Lasso) regression. The results showed that all antifreeze peptides used in the study were “hyperactive” antifreeze peptides with thermal hysteresis activity (THA) (> 0.60 ℃), low molecular mass (< 10 000 Da), high hydrophilicity (θ < 30°) , and polar amino acid content of more than 60%; the antifreeze peptides were able to significantly mitigate the negative effects of frozen storage on myofibrillar proteins. The mean content of myofibrillar proteins in frozen surimi with added antifreeze peptides was 50.44–54.47 mg/g, the mean Ca2+-ATPase activity was 1.61–1.67 U/mg, the mean surface hydrophobicity index increased only by 39.91%–42.40% when compared with that of fresh surimi, and the rate of myofibrillar protein denaturation was much lower than that of the control group without antifreeze peptides. The Lasso regression model explained the effects of antifreeze peptide properties on changes in the properties of myofibrillar protein in frozen surimi, demonstrating that antifreeze peptides with lower molecular mass and higher THA contributed to slowing down the decline in myofibrillar protein content, Ca2+-ATPase activity, surface hydrophobicity, and characteristic indexes. The differences in the hydrophilicity/hydrophobicity of antifreeze peptides resulted in differences in their interactions with ice crystals and proteins, and consequently caused different effects on surimi myofibrillar proteins. This study provides a theoretical basis for the application of antifreeze peptides and the quality regulation of surimi products and also provides a direction for the development of novel efficient antifreeze agents.

Fermentation is a traditional way of fish storage. During the fermentation process, microorganisms in raw materials or the environment can promote the decomposition and utilization of carbohydrates, proteins, and fats through metabolism, thereby generating rich flavor substances. People in different regions make different types of fermented fish products with different flavors by using different raw materials and ingredients and controlling conditions such as salt content, fermentation temperature, and fermentation time. The differences in the microbial community composition in various types of fermented fish products result in different compositions of characteristic flavor substances. Therefore, the microbial community composition in different fermented fish products and the correlation between microbial metabolism and the formation of characteristic flavor compounds are current research hotspots. This review summarizes recent studies on the fermentation process, microbial community composition, characteristic flavor substances and their formation mechanisms in different types of fermented fish products in China, and analyzes the impact of fermentation conditions on the microbial community composition and flavor formation. Besides, this review compares the characteristics of research methods for the correlation between different microorganisms and flavor substances. This review will provide a reference and direction for exploring the formation mechanism of the flavor of fermented fish and for the precise regulation of fermented fish flavor in the future.

Objective: Explore the cryoprotective mechanism and structure-activity relationship of antifreeze peptides derived from silver carp parvalbumin. Methods: Using differential scanning calorimetry and molecular dynamics simulation to compare activity, structure and mode of action of two typical peptides. Results: Pv-AFP 1 （KAADSFNH KAFFAKVG） had a stable α-helix structure, while Pv-AFP 2 （KAADSFNHKAF） tended to exhibit random coil. The thermal hysteresis activity of Pv-AFP 1 was 0.87 ℃, which was higher than Pv-AFP 2 （0.74 ℃）. Molecular dynamics simulations showed that Pv-AFP 1 could interact with 53 water molecules, and could form 16 hydrogen bonds to adsorb onto the surface of ice crystals, with a binding energy of -1 514 kJ/mol, all were greater than Pv-AFP 2 （can bind 50 water molecules, adsorb on ice surface by forming 11 hydrogen bonds, with a binding energy of -805 kJ/mol）. Despite the similarity of the two peptide sequences, their major sites and modes of interactions with water molecules and ice crystals were somewhat different. In addition, both peptides could interact with ice/water interface and altered the curvature of the ice surface, thereby inhibiting water freezing. But Pv-AFP 1 showed a better inhibitory effect on ice surface growth than Pv-AFP 2, which was consistent with their thermal hysteresis activity. Conclusion: The activities of antifreeze peptides derived from silver carp parvalbumin might be related to their structural characters and their affinities, sites and modes of interaction with water molecules and ice crystals.

Objective To investigate the clinical outcome of 9 very preterm infants with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) and patent ductus arteriosus (PDA) after PDA ligation. Methods A retrospective analysis was performed for the clinical data of 9 very preterm infants with BPD-associated PH and PDA, and all infants underwent PDA ligation and were followed up regularly after surgery. Results After surgical treatment, 7 infants had normal pulmonary artery pressure and were discharged after successful ventilator weaning, and all these infants were regularly followed up to June 2022 at the outpatient service, among whom the oldest infant was aged 4 years; echocardiography showed that all infants had normal heart structure and function, pulmonary artery pressure, and growth and development, without recurrent respiratory infection. Two infants died. Conclusion Very preterm infants with BPD-associated PH and PDA often have critical situations, and in case of failed pharmacotherapy, timely PDA ligation is an important method to improve prognosis.

Objective: To solve the problems of an uncertain fermentation process, a long fermentation period, and the unstable quality of traditional naturally fermented preserved fish. Methods: The lactic acid bacteria were isolated from low-salt preserved red fish, and the inhibition ability, salt tolerance, and acid production ability of the strains were investigated. The lactic acid bacteria suitable for fermentation were screened out, and the fermentation of preserved red fish was intensified by inoculation. The amount of red rice flour added, the amount of salt added during curing, and the fermentation temperature were optimized in the fermentation process. Results: There were 22 strains of Pediococcus with inhibitory effect on Escherichia coli or Staphylococcus aureus were isolated, among which Pediococcus pentosaceus P-56 had the best inhibitory effect on Escherichia coli and higher tolerance to bile salt and acid; After inoculation fermentation and process optimization. The pH value of the Zhayu decreased to 4.42 at 4 days of fermentation, the TCA-soluble peptide content was 434.99 μmol/g and the sensory score reached 45.7. Conclusion: The optimal process conditions for the fermentation of preserved red fish with lactic acid bacteria were: 4% salt addition for curing, 4% red yeast rice flour addition and fermentation temperature of 32 ℃.

Esterases/lipases from the GDSL family have potential applications in the hydrolysis and synthesis of important esters of pharmaceutical, food, and biotechnical interests. However, the structural and functional understanding of GDSL enzymes is still limited. Here, we report the crystal structure of the GDSL family esterase EstL5 complexed with PMSF at 2.34 Å resolution. Intriguingly, the PMSF binding site is not located at the active site pocket but is situated in a surface cavity. At the active site, we note that there is a trapped crystallization solvent 1,6-hexanediol, which mimics the bound ester chain, allowing for further definition of the active site pocket of EstL5. The most striking structural feature of EstL5 is the presence of a unique channel, which extends approximately 18.9 Å, with a bottleneck radius of 6.8 Å, connecting the active-site pocket and the surface cavity. Replacement of Ser205 with the bulk aromatic residue Trp or Phe could partially block the channel at one end and perturb its access. Reduced enzymatic activity is found in the EstL5 S205W and EstL5 S205F mutants, suggesting the functional relevance of the channel to enzyme catalysis. Our study provides valuable information regarding the properties of the GDSL-family enzymes for designing more efficient and robust biocatalysts.

In this study, the effects of soybean oil addition (1%, 3%, 5% and 7%) on the structure of surimi gels during freeze-thaw were investigated, and the first-order Ogden model was used to describe the relationship between the true stress and the true strain of surimi gels with different mass fractions of soybean oil under large compression deformation (stretch ratio of 0.4–1). The results showed that the addition of soybean oil to fresh surimi reduced the gel strength and enlarged the pores of the gel network. It was found that the addition of 5% and 7% soybean oil had a protective effect on the gel network structure of surimi after six freeze-thaw cycles. The gel strength of surimi with 5% and 7% soybean oil (319.30 and 338.64 g · cm, respectively) was significantly higher (P < 0.05) than that (286.04 g · cm) of the control group (without soybean oil), and the gel network structure was more complete than that of the latter. The Ogden model was fitted well to the true stress-strain compression response curves of fresh and freeze-thawed surimi gels with the addition of soybean oil (R2 = 0.916–0.998). The model fitting results showed that the initial shear modulus changes of fresh and freeze-thawed surimi gels were consistent with the gel strength results. This study suggested that the addition of soybean oil at 5% and 7% can reduce the damage caused to the surimi gel structure by freeze-thaw cycles. The Ogden model can well describe the effect of soybean oil addition on the large deformation behavior of fresh and frozen-thawed surimi gels. These findings may provide theoretical and technical support for the quality improvement of surimi products and the control of transportation and storage conditions.

Silver carp (Hypophthalmichthys molitrix) surimi was heated after freeze-thaw cycles at different freezing temperatures, and the changes of nonanal, 1-octene-3-alcohol, endogenous fluorescent substances, protein subunits, lysine, α-dicarbonyl compounds (glyoxal, GO and methylglyoxal, MGO), Nε-carboxylmethyl-lysine (CML) as an advanced glycation end product (AGE) and fluorescent AGEs in surimi during freeze-thaw and heating treatment were determined. The results showed that freezing temperature had no significant effect on any of the parameters measured (P > 0.05). As the number of freeze-thaw cycles increased, the levels of nonanal, 1-octene-3-ol, endogenous fluorescent substances, CML and fluorescent AGEs in surimi increased significantly, the content of lysine increased, and the levels of GO and MGO decreased significantly (P < 0.05). The levels of 1-octene-3-ol, GO, MGO, CML and fluorescent AGEs increased significantly during heat processing, the content of lysine increased at first and then decreased, the level of endogenous fluorescent substances decreased significantly (P < 0.05), and the myosin heavy chain was gradually degraded into smaller proteins. The above results showed that freeze-thaw treatment provided a large number of precursors for the formation of AGEs in surimi. Thermal processing promoted fat oxidation and protein degradation, stimulating the formation of AGEs in surimi through various pathways, which could in turn affect the safety of surimi.

To give full play to the role of fatigue supervision of intelligent monitoring platforms, We consider the shortage of the traditional management model of enterprises. The management game model of enterprises and drivers is built from the benefits of drivers. Taking 79 drivers of enterprise A in Jiaozuo City as an example, the number of fatigue violations of each driver in each of the six consecutive months was counted. Combined with the system clustering method, the drivers are classified according to the trend of the number of violations. Finally, different regulatory measures were proposed for different categories of drivers according to the evolution of the regulatory game system. The model evolution simulation results show that when the cost paid by the driver for violating the law (c) is greater than the additional benefit generated by the violation (d), the driver will choose not to drive fatigued to protect his benefits. The classification results show that drivers can be divided into four categories:① class no fatigue violation records; ② class fatigue violation records show a downward trend; ③ class fatigue violation records show wavy changes, indicating repeated violations; ④ class fatigue violation records show an upward trend. The number of violations varies for different categories of drivers. The d increases as the number of violations increases. Therefore, different management measures are proposed to increase c for the 4-type drivers so that the parameters of each type of driver satisfy the range of values of c>d. Thus, the driver evolves in the direction of no-fatigue driving. It can effectively regulate fatigue driving and improve driving safety.