The luxS deletion reduces the spoilage ability of Shewanella putrefaciens: An analysis focusing on quorum sensing and activated methyl cycle.

The luxS mutant strains of Shewanella putrefaciens (SHP) were constructed to investigate the regulations of gene luxS in spoilage ability. The potential regulations of AI-2 quorum sensing (QS) system and activated methyl cycle (AMC) were studied by analyzing the supplementation roles of key circulating substances mediated via luxS, including S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), methionine (Met), homocysteine (Hcy) and 4,5-dihydroxy-2,3-pentanedione (DPD). Growth experiments revealed that the luxS deletion led to certain growth limitations of SHP, which were associated with culture medium and exogenous additives. Meanwhile, the decreased biofilm formation and diminished hydrogen sulfide (H2S) production capacity of SHP were observed after luxS deletion. The relatively lower total volatile base nitrogen (TVB-N) contents and higher sensory scores of fish homogenate with luxS mutant strain inoculation also indicated the weaker spoilage-inducing effects after luxS deletion. However, these deficiencies could be offset with the exogenous supply of circulating substances mentioned above. Our findings suggested that the luxS deletion would reduce the spoilage ability of SHP, which was potentially attributed to the disorder of AMC and AI-2 QS system.

Mitochondria of Live Mizuhopecten yessoensis Scallops Can Sensitively Respond to Quality Changes during Dry/Reimmersed Storage as Determined by TMT-Labeled Proteomic Analysis.

Dry/reimmersed storage is often used in the transportation of live scallops. In this study, tandem mass tag (TMT)-labeled protein omics were used to quantitatively analyze the protein changes in scallops during dry/reimmersed stress. The results showed that during dry storage, scallops maintained cellular redox homeostasis through the upregulation of SCO1-like protein and thioredoxin domain-containing protein and reduced organic acids from the ATP synthetic process by the downregulation of NADH dehydrogenase, thereby reducing the damage caused during dry storage. During reimmersed storage, mitochondrial proteins underwent very sensitive changes. By upregulating aerobic respiration-related proteins (including proteins involved in glucose phosphate metabolism, glyceraldehyde 3-phosphate metabolism, etc.), the ATP synthesis ability was improved. However, the damage to the mitochondrial structure by dry storage could not be completely recovered, even by reimmersion. This included some apoptosis-related proteins that were obviously upregulated. In summary, compared with ATP-related indexes, mitochondria can respond more sensitively to dry storage stress.

Effect of Ca2+ on 3D printing accuracy and antioxidant efficacy of nano starch-lutein surimi: mechanical properties, chemical bonds and release rate.

BACKGROUND: Nano starch-lutein (NS-L) can be used in three-dimensional (3D) printed functional surimi. However, the lutein release and printing effect are not ideal. The purpose of this study was to facilitate the function and printing properties of surimi by adding the combination of calcium ion (Ca2+ ) and NS-L. RESULTS: Printing properties, lutein release and antioxidation of printed Ca2+ -NS-L-surimi were determined. The NS-L-surimi with 20 mM kg-1 Ca2+ had the best printing effects (fine accuracy, 99 ± 1%). Compared to NS-L-surimi, the structure became denser after adding Ca2+ , the gel strength, hardness, elasticity, yield stress (τ), water holding capacity of Ca2+ -NS-L-surimi increased by about 17 ± 4%, 3 ± 1%, 9 ± 2%, 20 ± 4%, 40 ± 5% respectively. These enhanced mechanical strength and self-supporting ability to resist binding deformation and improve printing accuracy. Moreover, salt dissolution and increased hydrophobic force by Ca2+ stimulated protein stretching and aggregation, leading to enhancement of gel formation. Decreased printing effects of NS-L-surimi with excessive Ca2+ (> 20 mM kg-1 ) caused by excessive gel strength and τ, leading to strong extrusion force and low extrudability. Additionally, Ca2+ -NS-L-surimi had higher digestibility and lutein release rate (increased from 55 ± 2% to 73 ± 3%), because Ca2+ made NS-L-surimi structure porous, which promoted contact of enzyme-protein. Furthermore, weakened ionic bonds reduced electron binding bondage that combined with released lutein to provide more electrons for enhancing antioxidation. CONCLUSION: Collectively, 20 mM kg-1 Ca2+ could better promote printing process and function exertion of NS-L-surimi, facilitating the application of 3D printed functional surimi. © 2023 Society of Chemical Industry.

Study on nucleotide, myofibrillar protein biochemical properties and microstructure of freeze-dried scallop striated muscle during storage and rehydration.

The biochemical properties and microstructural changes of freeze-dried Japanese scallop (Patinopecten yessoensis) striated muscle during room temperature storage and rehydration were investigated. The results showed that the content of ATP in freeze-dried scallop muscle remained stable with no significant difference (p > 0.05). However, ATP was rapidly decomposed and AMP accumulated within 1.5 min of rehydration, and HxR and Hx were gradually produced from AMP decomposition with the extension of rehydration time. Besides, the results of chymotryptic digestion patterns demonstrated that the rod of myosin was unstable after dehydration, reflecting lower salt solubility than that of frozen-thawed scallop. In contrast, the myosin subfragment-1 (S-1) was stable, as indicated by the constant of Ca2+-ATPase activity of freeze-dried scallops throughout the storage and rehydration (p > 0.05). Furthermore, the microstructural analysis revealed that the Z line of the freeze-dried scallop was broken after dehydration process. This study might be useful for developing high-quality dehydrated scallops in the future.

Identification of novel antioxidant peptide from porcine plasma hydrolysate and its effect in in vitro digestion/HepG2 cells model.

A novel antioxidant peptide EDEQKFWGK from porcine plasma hydrolysate (PPH) was separated by chromatography, HPLC, and identified by LC-MS/MS. Results showed that EDEQKFWGK had better antioxidant ability (Hydroxyl RAS 32.19%, ABTS RAS 92.93% and DPPH RAS 26.76%) compared with glutathione (30.11%, 82.01%, 26.44%) due to the presence of hydrophobic, aromatic acids (F, W) and acidic amino acids (E, D), decreasing ROS by providing hydrogen atom and chelating metal ions. Furthermore, the antioxidant properties of synthetic EDEQKFWGK still significant despite in vitro digestion because of the production of smaller active peptide. Additionally, it could increase SOD, CAT, GSH-Px to resist oxidative damage in HepG2 cells by inhibiting ROS (O2- , OH·), forming complexes to prevent OH· from destroying DNA and binding to ARE to promote antioxidase expression. Thereby, the novel peptide EDEQKFWGK from porcine plasma had much stable antioxidant properties and hade great potential in formulating functional foods. PRACTICAL APPLICATIONS: This research isolated a novel antioxidant peptide. Moreover, the antioxidant effects of peptide were confirmed under the in vitro digestion model and oxidative damage HepG2 cells model. The results showed the antioxidant peptide could play better effect after digestion and protect the cells from oxidative damage. These data could expand the sequence data of antioxidant peptides and promote the high-value utilization of PPH.

Differentiation between fresh and frozen-thawed scallop adductor muscle as raw materials for sashimi during cold storage.

The changes of sensory and biochemical characteristics on the fresh and frozen-thawed scallop adductor muscle during storage at 4°C were discussed in this study. The Quality Index Method (QIM) scheme for evaluating scallop adductor muscle as raw materials for sashimi was proposed for the first time. The results of sensory evaluation showed that frozen-thawed scallop adductor muscle within zero to one day of refrigeration can be happily accepted by consumers, indicating the superiority of freezing for long-distance transportation, although the triangle test confirmed that there are still sensorial differences between fresh and frozen-thawed scallop adductor muscle. The microscopic observation of myofibrils extracted from scallop adductor muscle suggested that the myofibrillar protein which constitutes myofibrils has suffered some extent change due to freezing and thawing, even though the head region of myosin remained stable judging by the fact that there was no significant difference in Ca2+ -ATPase activity (p > 0.05). The changes of adenosine triphosphate (ATP) and its related compounds, and pH value during storage can be regarded as indicators to differentiate fresh and frozen-thawed scallop adductor muscle. The changes of Mg2+ -ATPase activity indicated that the interaction between myosin and actin was weakened by the freezing and thawing process. Practical Application: The QIM scheme can be used to evaluate the scallop adductor muscle as raw materials for sashimi. The mechanism of quality changes in the frozen-thawed scallop adductor muscle was discussed in combination with the destruction of myofibrils, ATP degradation and the decrease of pH value. This study has positive significance for improving the quality of frozen-thawed scallop adductor muscle by combining the changes of sensory and biochemical characteristics.

A new sulfated triterpene glycoside from the sea cucumber Colochirus quadrangularis, and evaluation of its antifungal, antitumor and immunomodulatory activities.

Our continuing search for marine bioactive secondary metabolites led to the screening of crude extracts of sea cucumbers by the model of Pyricularia oryzae. A new sulfated triterpene glycoside, coloquadranoside A (1), together with four known triterpene glycosides, philinopside A, B, E and pentactaside B (2-5) were isolated from the sea cucumber Colochirus quadrangularis, and their structures were elucidated using extensive spectroscope analysis (ESI-MS, 1D and 2D NMR) and chemical methods. Coloquadranoside A possesses a 16-acetyloxy group in the holostane-type triterpene aglycone with a 7(8)-double bond, a double bond (25,26) at its side chain, and two ß-d-xylose in the carbohydrate chain. Coloquadranoside A exhibits in vitro some antifungus, considerable cytotoxicity (IC50 of 0.46-2.03 µM) against eight human tumor cell lines, in vivo antitumor, and immunomodulatory activity.

Condition-dependent adenosine monophosphate decomposition pathways in striated adductor muscle from Japanese scallop (Patinopecten yessoensis).

The purpose of this study was to confirm inosine monophosphate (IMP) generation and to clarify the decomposition pathway of adenosine monophosphate (AMP) by investigating the properties of AMP, IMP, and adenosine (AdR) decomposition enzymes in Japanese scallop (Patinopecten yessoensis). The results showed that IMP accumulated due to AMP decomposition via endogenous enzymes in scallops stored at both 4 °C and 20 °C. The AMP decomposition rate was highest in the supernatant of homogenized scallop adductor muscle, followed by the suspended solution and precipitate, while IMP could not be decomposed in scallop. The results indicated that the activity of AdR deaminase was very high, and this enzyme was involved in an intracellular process in scallop. Moreover, 1 min of heating exerted little influence on the AMP and AdR decomposition rates, while 5 min of heating induced enzyme denaturation. The IMP generation rate increased dramatically in scallop crude enzyme solution containing 5 mM ethylenediaminetetraacetic acid (EDTA). This suggests that the major pathway of AMP decomposition might change with variations in metal ion concentrations in Japanese scallop. PRACTICAL APPLICATION: IMP generation in Japanese scallop (Patinopecten yessoensis) caused by endogenous enzymes was confirmed. IMP is very important for the umami taste (a pleasant savory taste) of aquatic products. As IMP accumulation might be achieved by changing the concentration of divalent metal ions and no IMP 5'-nucleotidase activity was detected in scallop, a suitable process to produce good flavor scallops with high IMP contents might be developed.

The preservation effect of CGA-Gel combined with partial freezing on sword prawn (Parapenaeopsis hardwickii).

Effects of Chlorogenic acid-Gelatin (CGA-Gel) combined with partial freezing on quality change of sword prawn (Parapenaeopsis hardwickii) stored at -5 °C were evaluated for 23 days. Changes in sensory score, total viable counts (TVC), and physiochemical indexes including pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS) and Ca2+-ATPase were examined. All shrimp treated with CGA and CGA-Gel had lower total viable counts compared to control (P < 0.05). The value of TVB-N and TBA of CGA-Gel treated group at day 13 were 18.4 mg N/100 g and 0.175 mg/100 g respectively, both below the proposed safe limits and values of CGA treated group. All the results demonstrated that Chlorogenic acid can inhibit growth of microorganism, lipid oxidation and protein degradation. CGA-Gel treated samples presented better quality preservation effects than CGA treated alone. Therefore, CGA-Gel combined with partial freezing is promising in sword prawn shelf life extension.

Antioxidant and antibacterial properties of coating with chitosan-citrus essential oil and effect on the quality of Pacific mackerel during chilled storage.

The goal of the study was to investigate whether chitosan-citrus essential oil composite works as an efficient preservative in Pacific mackerel (Pneumatophorus japonicus) during chilling storage. FT-IR analysis showed that chitosan-citrus essential oil coating was successfully prepared. Our results demonstrated that chitosan-citrus essential oil coating possessed significantly higher capability of scavenging reactive oxygen species ( O 2 - and OH-) than chitosan. Furthermore, Pacific mackerel coated with chitosan-citrus essential oil composite could significantly reduce parameters of corruption including physicochemical (drop loss, biogenic amine, and thiobarbituric acid-reactive substances) and microbiological parameters (total viable count), as compared with untreated and chitosan groups after 12 days of storage at -3°C. These results indicated that CS-CEOs could work as efficient preservative for Pacific mackerel storage through ameliorating redox state and inhibiting microbial growth and suggested that chitosan-citrus essential oil composite has great potential in preservation of aquatic products during superchilled storage.

Characterization of myosin subfragment-1 of summer and winter silver carp (Hypophthalmichthys molitrix) muscle.

UNLABELLED: Myosin subfragment-1 (S1) was prepared from myofibrils of summer and winter silver carp by chymotryptic digestion in the presence of ethylenediaminetetraacetic acid (EDTA). Two S1 heavy chain isoforms with different molecular sizes of 91 kDa and 95 kDa were detected in the fast skeletal muscle from summer and winter silver carp, respectively. ATPase inactivation assay indicated that winter S1 was about 20-fold unstable comparing to summer S1. Matrix-assisted laser desorption/ionization time-of-flight/mass spectrometry (MALDI-TOF MS) further confirmed that summer and winter myosin S1 heavy chain isoforms were homologous to myosin high-temperature type and myosin low-temperature type S1 heavy chain, respectively. Moreover, both types of myosin S1 heavy chain isoforms were identified at the intermediate stage. The results indicated that myosin was expressed in a season-specific manner; different types of myosin isomer expressed in different seasons, showing different thermostabilities. PRACTICAL APPLICATION: Silver carp, Hypophthalmichthys molitrix, is one of the most abundant freshwater fish species in China. The structure thermal stability of myosin rod from silver carp was affected by season change. The gel-forming abilities of surimi prepared in different seasons were different. This study investigated the seasonal differences in structure thermal stability of myosin S1 which is vital for gel formation of myosin. The results of this study will aid understanding of the relationship between the structure and function of myosin, and effective production of surimi from freshwater fish species in different seasons.