Large Yellow Croaker Research Articles

Diagnosis of cryptocaryoniasis in large yellow croaker (Larimichthys crocea) by real-time object detection based on YOLOv3

With the introduction and deepening of the concept of sustainable aquaculture, the traditional aquaculture practices are gradually being supplemented and even replaced by advanced systems based on new technology. We here present an automated diagnostic method for diagnosis of cryptocaryoniasis in industrial marine aquaculture. It is based on computer image recognition technology targeting the typical clinical disease sign, white skin spots. A total of 800 images of healthy (400) and Cryptocaryon irritans infected (400) large yellow croaker (Larimichthys crocea) were obtained by cameras, and each type of image was enhanced to 1000. Based on the algorithm YOLOv3, the weights of the trained model yolov3.pt. were used to perform transfer learning on the enhanced image data set to establish the diagnosis model YOLOv3 of cryptocaryoniasis of L. crocea. Then, a visual real-time monitoring system for cryptocaryoniasis was developed. The results show that transfer learning could be well-applied to the training of the cryptocaryoniasis detection model. The accuracy of the final model was about 2% higher than that of the source model (average accuracy of YOLOv3 was 92%, recognition speed 36 frames/s). The algorithm YOLOv3 allows effective discrimination and recognition of cryptocaryoniasis in large yellow croaker. The visual real-time monitoring system allows the automatic and accurate diagnosis of cryptocaryoniasis in L. crocea aquaculture. The results illustrate the applicability of artificial intelligence for reduction of manpower expenditure in diagnostic work, shortening of detection time and elevation of accuracy and timeliness of problem recognition.

Protective effects of dietary Astragalus polysaccharides on large yellow croaker (Larimichthys crocea) against Vibrio alginolyticus infection

As one of the effective immunopotentiators, Astragalus polysaccharides (APS) are being used widely in prevention and control of fish bacteriosis. However, the understanding of the related immune protection mechanisms is still limited. In this study, the protective effects of dietary APS on large yellow croaker (Larimichthys crocea) following Vibrio alginolyticus infection were investigated. After continuous feeding for 42 d, fish in APS group exhibited higher survival rates against V. alginolyticus infection compared to the control group, and 500 mg/kg APS produced the highest relative percent survival (RPS) of 53.33%, therefore, 500 mg/kg (0.05%) supplementation was recommended in large yellow croaker farming from a standpoint of antibacterial infection. APS could enhance antioxidant level of fish by increasing serum T-AOC capacity and SOD activity and reducing MDA content, and improve innate immune response by increasing serum AKP and ACP activities. Head kidney differential transcriptome analysis between control group and 500 mg/kg APS group before and after V. alginolyticus infection corroborated the effects of APS on activation of antioxidant capacity and innate immunity by up-regulating the antioxidant-related genes and activating CTLR pathway, respectively. Additionally, APS could also activate fish adaptive immunity by reversing V. alginolyticus-induced inhibition on T and B cell receptor signaling pathways. All these findings suggested that APS may exert the protective effects against V. alginolyticus infection by improving antioxidant ability, innate and adaptive immune responses of large yellow croaker, thus providing insights into the protection mechanisms of APS in fish and highlighting their potential application in fish aquaculture.

Genetic linkage between swimming performance and disease resistance enables multitrait breeding strategies in large yellow croaker

Improving the robustness of fish stock has become a key issue in the advancement of aquaculture, as diseases and harsh aquatic conditions impact industry sustainability and yield. In this study, we identify several genetic loci that link swimming performance to disease resistance in large yellow croaker, and apply genomic selection (GS) for swimming performance to generate offspring with both enhanced swimming performance and disease resistance. First, we classified our reference population as superior swimmers (SS) or inferior swimmers (IS) by swimming tests and assessed inherent disease resistance. Consistent with previous research, SS displayed enhanced resistance to the parasite Cryptocaryon irritans. Through genotyping of parental reference and candidate populations, we generated a single nucleotide polymorphism (SNP) database, containing 45832 high-quality SNPs in total. We applied multitrait genome-wide association study analysis of swimming performance and disease resistance to this dataset and identified three linked SNPs, which were associated with 48 potential candidate genes, including pp3r1b, mapk12b, mapk11, and tnfrsf11a. Next, we generated a GS model using the BayesB method and calculated the candidate population's genetic estimated breeding value (GEBV). Individuals with GEBV's in the top 12 ​% were selected as broodstocks for breeding selective lines (SL), and the remaining individuals were used as the control group (CG). We found that SL exhibited both increased swimming performance and resistance to C. irritans compared to CG. Our study reveals the genetic basis related to swimming performance and disease resistance. This work has implications for designing multitrait breeding strategies and improving whole-fish fitness, both of which are critical in aquaculture.

An aluminium adjuvant compound with ginseng stem leaf saponins enhances the potency of inactivated Pseudomonas plecoglossicida vaccine in large yellow croaker (Larimichthys crocea)

Large yellow croaker (Larimichthys crocea) farm industry in China suffered from huge economic loss caused by Pseudomonas plecoglossicida infection. Due to multi-antibiotic resistance, efficient vaccines are urgent to be developed to combat this pathogen. In this study, an inactivated vaccine was developed with an aluminium adjuvant (Alum) plus ginseng stem and leaf saponins (GSLS). As a result, the relative percentage survival (RPS) against P. plecoglossicida was up to 67.8 %. Comparatively, RPS of groups that vaccinated with only inactivated vaccine and vaccine containing Alum or Montanide™ 763A as adjuvant were 21.8 %, 32.2 % and 62.1 %, respectively. Assays for total serum protein and serum lysozyme activity in group vaccinated with inactivated vaccine plus Alum + GSLS adjuvant were significantly higher than that in control group. Moreover, specific antibody in serum elicited a rapid and persistent level. According to the expression of some immune related genes, inactivated vaccine plus Alum + GSLS adjuvant induced a stronger cellular immune response which was vital to defend against P. plecoglossicida. In conclusion, our study demonstrated that the compound Alum and GSLS adjuvant is a potential adjuvant system to develop LYC vaccine.

Stable chlorine dioxide combined with slightly acidic electrolyzed water: an effective way to delay protein deterioration of refrigerated large yellow croaker (Pseudosciaena crocea)

SummaryFish is susceptible to spoilage for enzymatic and microbial activities during storage, proteolysis of MPs by endogenous proteases played a crucial influence in the early postmortem decomposition of myosin. This study aimed to investigate the impact of stable chlorine dioxide (ClO2) combined with slightly acidic electrolyzed water (SAEW) on myofibrillar proteins (MPs) and endogenous proteases alterations in large yellow croaker (Pseudosciaena crocea) during cold storage. The results of Fourier‐transform infrared spectroscopy (FT‐IR) and intrinsic fluorescence intensity (IFI) showed that the ClO2 + SAEW treatment kept the structural stability of protein in fillets during cold storage. Moreover, ClO2 + SAEW treatment dramatically inhibited protein degradation and oxidation. The results of light microscopy further confirmed the results. Meanwhile, there was a tendency to first increase and then decrease on the activities of calpain and cathepsin B, L. According to the correlation analysis and principal component analysis, the activities of endogenous proteases (cathepsin B, D, L, and calpain) were significant (P < 0.01) positively correlated to myofibrillar fragmentation index and trichloroacetic acid‐soluble peptide, and were significant (P < 0.01) negative correlated with the contents of total sulfhydryl and Ca2+‐ATPase. The endogenous proteases activities and protein deterioration were strongly associated. Therefore, endogenous protease was affected by ClO2 and SAEW, which delayed protein degradation in large yellow croaker, especially ClO2 combined with SAEW treatment.

A Comparative Study on the Quality of Large Yellow Croaker (Larimichthys crocea) of Different Sizes Cultured in Different Cage Systems

This study analyzed the quality of large yellow croaker (Larimichthys crocea) of different sizes cultured in farmed floating sea-cage (common cage, CC) or deep-water cage (DWC) models. The quality was assessed based on several factors: condition factors, ventral color, texture, protein and lipid content, and fatty acid composition. In addition, we analyzed and identified taste characteristics and volatile substances. The results showed that large yellow croaker cultured in DWC had a better body shape than CC with lower condition factors and higher body length-to-height ratio. The DWC cultured fish were yellower with lower lipid content than the CC cultured fish. The springiness of the flesh from fishes cultured in DWC was significantly higher than those cultured in CC. The level of immobilized water and n-3 polyunsaturated fatty acid was higher in DWC. The DWC culture model contributed to the sweetness, saltiness, and umami of the flesh. The flesh from DWC had a higher content of aldehydes, such as pentanal, heptanal, and hexanal. The results demonstrated that the DWC culture model is a better choice to improve the quality of large yellow croaker in terms of organoleptic properties, nutritional value, and taste.

Molecular characterization and functional analysis of galectin-1 from silver pomfret (Pampus argenteus)

Galectins, as members of lectin families, exhibit a high affinity for β-galactosides and play diverse roles in biological processes. They function as pattern recognition receptors (PRRs) with important roles in immune defense. In this study, galectin-1, designated as SpGal-1, was identified and characterized from silver pomfret (Pampus argenteus). The SpGal-1 comprises an open reading frame (ORF) spanning 396 base pairs (bp) and encodes a deduced amino acid (aa) sequence containing a single carbohydrate recognition domain (CRD). Sublocalization analysis revealed that SpGal-1 was mainly expressed in the cytoplasm. The mRNA transcripts of SpGal-1 were ubiquitously detected in various tissues, with a higher expression level in the intestine. In addition, when exposed to Photobacterium damselae subsp. damselae (PDD) infection, both the liver and head kidney exhibited significantly increased SpGal-1 mRNA expression. The recombinant protein of SpGal-1 (named as rSpGal-1) demonstrated hemagglutination against red blood cells (RBCs) from Larimichthys crocea and P. argenteus in a Ca2+ or β-Mercaptoethanol (β-ME)-independent manner. Notably, rSpGal-1 could bind with various pathogen-associated molecular patterns (PAMPs) including D-galactose, D-mannose, lipopolysaccharide (LPS), and peptidoglycan (PGN), with highest affinity to PGN. Moreover, rSpGal-1 effectively interacted with an array of bacterial types encompassing Gram-positive bacteria (Staphylococcus aureus and Nocardia seriolae) and Gram-negative bacteria (PDD and Escherichia coli, among others), with the most robust binding affinity towards PDD. Collectively, these findings highlight that SpGal-1 is a crucial PRR with involvement in the host immune defense of silver pomfret.

The identification and expression of an interleukin-21 receptor in large yellow croaker (Larimichthys crocea).

We identified a homologue of IL-21R (LcIL-21R) in large yellow croaker (Larimichthys crocea, Lc). Our investigation focused on understanding the molecular structural features and immune function of LcIL-21R. We cloned the LcIL-21R gene from the genome of Larimichthys crocea by RT‒PCR, and the molecular and structural characteristics of LcIL-21R were analyzed by a series of protein analysis tools. We used real-time PCR to investigate the tissue distribution of LcIL-21R, and LcIL-21R gene expression regulation was also measured in head kidney leukocytes under trivalent bacterial vaccine or poly (I:C) stimulation. The open reading frame (ORF) of the LcIL-21R gene is 1629bp long and encodes a precursor protein of 542 amino acids (aa), with a 23-aa signal peptide and a 519-aa mature peptide containing four putative N-glycosylation sites. LcIL-21R has two fibronectin type III (FNIII)-like domains (D1 and D2), a transmembrane domain, and a cytoplasmic region. A conserved WSXWS motif was also found in the D2 domain. The predicted structure of the extracellular region of LcIL-21R (LcIL-21R-Ex) is highly similar to that of human IL-21R. LcIL-21R was constitutively expressed in all tissues examined, and LcIL-21R mRNA levels were increased in the head kidney and spleen upon inactivated trivalent bacterial vaccine or poly(I:C) stimulation. Our results suggest that LcIL-21R shares structural and functional properties with IL-21Rs found in other vertebrates, indicating its potential involvement in the IL-21-mediated immune response to pathogenic infections. These findings contribute to our understanding of the evolutionary conservation of IL-21 signaling and its role in the immune system.

One Pot Synthesis of Nanofiber-Coated Magnetic Composites as Magnetic Dispersive Solid-Phase Extraction Adsorbents for Rapid Determination of Tetracyclines in Aquatic Food Products.

A magnetic adsorbent based on a C-nanofiber (Fe3O4@C-NFs) nanocomposite was synthesized using a simple one-pot co-precipitation method. The characterized results showed that the obtained C-nanofiber-coated magnetic nanoparticles had many attractive features such as a large specific surface area and a highly interwoven and branched mesoporous structure, as well as distinguished magnetism. The nanocomposite was then used as an adsorbent in the magnetic solid phase extraction (MSPE) of four typical tetracyclines (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) in aquatic products. The TCs in the extract were determined using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Experimental variables of MSPE, including the sorbent amount, pH condition, adsorption and desorption time, and desorption solvent, were investigated and optimized systematically. The method validation indicated that the developed method showed good linearity (R2 > 0.995) in the range of 1.0-200 ng/mL. The average recoveries at the spiked levels ranged from 90.7% to 102.7% with intra-day and inter-day relative standard deviations (RSDs, n = 6) ranging from 3.72% to 8.17% and 4.20% to 9.69%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for the four kinds of TCs were 0.7 μg/kg and 2.0 μg/kg, respectively. Finally, MSPE based on C-nanofiber-coated magnetic nanoparticles was successfully applied to TC analysis in real aquatic products (grass carp, large yellow croaker, snakehead, mandarin fish, Penaeus vannamei, swimming crab, etc.). Compared with traditional extraction methods, the proposed method for TC analysis in aquatic products is more sensitive, effective, recyclable, and environmentally friendly.

The application of ice glazing containing D-sodium erythorbate combined with vacuum packaging to maintain the physicochemical quality and sweet/umami non-volatile flavor compounds of frozen stored large yellow croaker (Pseudosciaena crocea)

Ice glazing containing 0.3 % D-sodium erythorbate (DSE), combined with vacuum packaging, was used as a method to maintain the quality of large yellow croaker during frozen storage. This study aimed to assess various aspects, including water properties (water holding capacity and moisture distribution), protein-related characteristics (secondary and tertiary structure of myofibrillar protein), freshness indicators (K value and total volatile base nitrogen (TVB-N)), and non-volatile flavor compounds (free amino acids (FAAs) and nucleotides) in samples stored for 300 days at –23 °C. The results showed that vacuum packaging had a significant inhibitory effect on the growth of ice crystal. Notably, it successfully maintained the cross-sectional area of nearly all ice crystals below 20,000 μm2, effectively curtailing water loss. Simultaneously, the combination of vacuum packaging with the complex ice glaze effectively mitigated the degradation of IMP and free amino acids, maintaining low levels of K value (12.85 %) and TVB-N (11.28 mg N/100 g) throughout the 300-day frozen storage, retaining first-class freshness. Among the various treatment modalities assessed, the combined application of vacuum packaging and 0.3 % DSE-infused ice glazing emerged as the most effective in terms of preservation outcomes. This efficacious combination shows promising potential for the frozen storage of aquatic products and is therefore recommended for practical implementation.

Identification and characteristics of temperature-sensitive sites of Pseudomonas plecoglossicida based on aptamers

Pseudomonas plecoglossicida can infect Pseudosciaena crocea and cause visceral white spot disease, resulting in substantial economic losses to the P. crocea industry. Pseudomonas plecoglossicida is a temperate-sensitive bacterium and only infects P. crocea below 22 ℃. Aptamers are oligonucleotide molecules selected by the systematic evolution of ligands by exponential enrichment (SELEX) and can identify all kinds of targets. In the present study, five aptamers (M17, M19, M48, M56 and M81) for P. plecoglossicida cultured at 18 ℃ were selected by SELEX and based on comparative analysis of the high frequency sequences. The five aptamers had significantly higher affinities for the pathogenic P. plecoglossicida at 18 ℃ than for the nonpathogenic P. plecoglossicida at 28 ℃ and the other six bacteria (Escherichia coli, Edwardsiella tarda, Aeromonas hydrophila, Vibiro harveryi, Vibiro alginolyticus, Pseudomonas aeruginosa) (P < 0.01). The affinity constants (Kd) and maximum affinity (Am) of these aptamers for P. plecoglossicida were determined, with Kd values of M17 (23.35 ± 6.40), M19 (66.37 ± 14.73), M48 (105.91 ± 21.41), M56 (31.16 ± 5.03) and M81 (52.63 ± 13.82) nmol/L and with Am values of M17 (1041.26 ± 57.08), M19 (2291.76 ± 171.96), M48 (1258.51 ± 21.41), M56 (1307.70 ± 54.01) and M81 (543.27 ± 44.16) nmol/L, respectively. The secondary structures of the aptamers were analyzed, and the aptamer binding proteins of the pathogenic P. plecoglossicida were isolated by magnetic separation and purified by polyacrylamide gel electrophoresis. Mass spectrometry revealed ribosomal proteins to be the main aptamer binding proteins. The secondary and tertiary structures and subcellular localization of these aptamer binding proteins were also studied and analyzed. These findings provide a foundation for the temperature-sensitive pathogenic mechanism of P. plecoglossicida in P. crocea. This is the first report on aptamers that recognize temperature-sensitive sites in P. plecoglossicida.

P38 MAPK involvement in the thermal stress response occurs via HSP27 and caspase3 in the large yellow croaker (Larimichthys crocea)

The p38 mitogen-activated protein kinase (p38 MAPK) is a multifunctional molecule that is involved in cellular response to various stressful stimuli. In the present study, the full-length cDNA sequence of p38 MAPK (Lcp38 MAPK) was identified from the large yellow croaker Larimichthys crocea, which encoded a polypeptide of 361 amino acid residues. The predicted Lcp38 MAPK protein contained a highly conserved Thr-Gly-Tyr (TGY) motif, a glutamate and aspartate (ED) site, a substrate binding site (Ala-Thr-Arg-Trp < ATRW>), and a serine/threonine kinase catalytic (S_TKc) domain characteristic of the MAPK family. The constitutive expression of Lcp38 MAPK was detected in most of the tissues examined with the strongest expression in intestine. Subcellular localization in LCK cells (kidney cell line from a L. crocea) revealed that Lcp38 MAPK existed in both the cytoplasm and cell nucleus. The expression of Lcp38 MAPK after temperature stress was tested in LCK cells. The results indicated that Lcp38 MAPK transcripts were significantly upregulated under both cold (10 °C) and heat stress (35 °C) (P < 0.05). Furthermore, the phosphorylation levels of p38 MAPK as well the transcriptional levels of heat shock protein 27 (HSP27) and caspase3 in LCK cells were significantly induced under thermal exposure (P < 0.05). However, the cold- and heat induced HSP27 and caspase3 expression was significantly suppressed by SB203580, a specific inhibitor of p38-MAPK (P < 0.05). These findings indicated that Lcp38 MAPK might be involved in the cellular stress response via HSP27 and caspase3 in large yellow croaker.

Development of electrospun fish gelatin film containing lauroyl arginate ethyl and its application in large yellow croaker (Pseudosciaena crocea) preservation

Development of electrospun fish gelatin film containing lauroyl arginate ethyl and its application in large yellow croaker (Pseudosciaena crocea) preservation

Flavor characteristics of semi-dried yellow croaker (Pseudosciaena crocea) with KCl and ultrasound under sodium-reduced conditions before and after low temperature vacuum heating.

This study investigated the flavor characteristics of semi-dried yellow croaker made by KCl instead of partial NaCl combined with ultrasound treatment before and after low temperature vacuum heating. The electronic tongue, electronic nose, free amino acids, 5'-nucleotides, and gas chromatography-ion mobility spectrometry were employed. Electronic nose and electronic tongue results showed that different treatment groups had different sensitive signals to smell and taste. The odor and taste of each group were mainly affected by Na+ and K+. The difference between the groups becomes larger after thermal treatment. Ultrasound and thermal treatment both changed the content of taste components. In addition, each group contained 54 volatile flavor compounds. Among them, the combined treatment method gave semi-dried large yellow croaker pleasant flavor characteristics. Besides, it also improved the content of flavor substances. In conclusion, the semi-dried yellow croaker under sodium-reduced conditions showed better performance in flavor characteristics.

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Dynamic Changes in the Microbial Composition and Spoilage Characteristics of Refrigerated Large Yellow Croaker (Larimichthys crocea) during Storage.

The quality changes, dynamic changes in microbial composition, and diversity changes in large yellow croaker (Larimichthys crocea) during 4 °C refrigeration were studied using 16S rDNA high-throughput sequencing technology, and the total viable count (TVC), total volatile basic nitrogen (TVB-N), and thiobarbituric acid-reactive substances (TBARS) were determined. The results revealed a consistent increase in TVC, TVB-N, and TBARS levels over time. On the 9th day, TVC reached 7.43 lg/(CFU/g), while on the 15th day, TVB-N exceeded the upper limit for acceptable quality, reaching 42.56 mg/100 g. Based on the 16S rDNA sequencing results, we categorized the storage period into three phases: early storage (0th and 3rd days), middle storage (6th day), and late storage (9th, 12th, and 15th days). As the storage time increased, both the species richness and diversity exhibited a declining trend. The dominant genus identified among the spoilage bacteria in refrigerated large yellow croaker was Pseudomonas, accounting for a high relative abundance of 82.33%. A comparison was carried out of the spoilage-causing ability of three strains of Pseudomonas screened and isolated from the fish at the end of storage, and they were ranked as follows, from strongest to weakest: P. fluorescen, P. lundensis, and P. psychrophila. This study will provide a theoretical basis for extending the shelf life of large yellow croaker.

The optimal feeding regime for large yellow croaker Larimichthys crocea, with an emphasis on obviating raw fish diet in commercial farming

Commercial farming of large yellow croaker Larimichthys crocea still relies on raw fish diet. The present study assessed the possibility to replace raw fish diet with a formulated diet containing 490 g/kg crude protein by optimizing feed and feeding management. In experiment I, fish weighing 10.8 g were fed with the formulated diet at either five frequencies (FF13, 1/3 meal/d; FF12, 1/2 meal/d; FF11, 1 meal/d; FF21, 2 meal/d; FF31, 3 meal/d) or at 1 meal/d but different times (FF11, at 6:00; FF11A, at 18:00), respectively. In experiment II, fish were fed at 2 meal/d with the formulated diet (FF21) or a quality raw fish diet (RF21). The final body weight (FBW), weight gain, feed intake and body lipid content, fish in/out ratio (FIFO) and waste outputs (nitrogen, phosphorus and carbon) were higher, whereas the nutrient and energy retention efficiencies (NRE, nitrogen; PRE, phosphorus; CRE, carbon; ERE, energy) were lower, in FF21 and FF31 than in FF13, FF12 and FF11. No significant differences were detected in FBW and weight gain either between FF21 and FF31 or between FF13, FF12 and FF11. The feed conversion ratio (FCR) and feed cost were higher in FF31 than in FF13, FF12 and FF11. The activities of superoxide dismutase (SOD) and catalase (CAT) in plasm, activities of glutathione peroxidase (GSH-PX) and CAT in liver, and malondialdehyde (MDA) content in plasm and liver were higher in FF31 than in FF11. No significant differences were detected in FBW, weight gain, NRE, PRE, CRE, ERE, body composition, feed cost, FIFO-, waste outputs, activities of antioxidant enzymes and MDA content in plasm and liver between FF11 and FF11A despite FF11A had higher feed intake and FCR compared with FF11. The FBW, weight gain, feed intake, FCR, body lipid content, feed cost, FIFO, waste outputs, activities of SOD and GSH-PX in liver, plasm CAT activity, and MDA content in plasm and liver were higher, whereas the survival, NRE, PRE and ERE were lower, in RF21 than in FF21. Our study indicates that 2 meal/d is the optimal feeding frequency for large yellow croaker, and completely replacing raw fish diet with the formulated diet in commercial farming benefits to increase fish survival and yield and to reduce feed cost, FIFO, waste outputs and body lipid deposition.

Centrosomal protein of 192 kDa (Cep192) fragment possesses bactericidal and parasiticidal activities in Larimichthys crocea

A novel AMP Lc1773, derived from centrosomal protein of 192 kDa (Cep192), was isolated from Larimichthys crocea using a Bacillus subtilis system. After cDNA libraries construction, repeating selection of B. subtilis system, extraction of extracellular protein, and expression of recombinant protein, we found that B. subtilis 1773, extracellular protein, and rLc1773 had a strong potential to kill Vibrio. parahaemolyticus and V. vulnificus. Further analysis of the antibacterial mechanism revealed that rLc1773 not only disrupted the integrity of bacterial membrane (as confirmed by SEM, TEM, and confocal microscopy observation, and flow cytometry assays), resulting in bacterial cell membrane pore conformation, bacterial rupture, and leakage of cellular contents, but also targeted to block protein synthesis rather than damage nucleic acids (as confirmed by SDS-PAGE, enzyme expression, and gel retardation assays). In addition, rLc1773 had the ability to kill parasite Scuticociliatida in a high rate and low concentration. Critically, the antibacterial activity of rLc1773 had good thermal stability and UV radiation tolerance, but it was affected by pH 9–11 and diverse enzyme to some extent. Lc1773 had neither hemolysis on fish, shrimp, and rabbit erythrocytes，nor significant cytotoxicity. To our knowledge, Cep192 fragment was first demonstrated to possess bactericidal and parasiticidal activities.

Insight into the effect of large yellow croaker roe phospholipids on the physical properties of surimi gel and their interaction mechanism with myofibrillar protein.

The present study aimed to investigate the effects of large yellow croaker roe phospholipids (LYCRPLs) on the physical properties of surimi gels and to clarify their interaction mechanism with myofibrillar proteins (MPs) in terms of chemical forces and the spatial conformation. LYCRPLs could improve the gel strength, textural properties, rheological properties and water-holding capacity of surimi gels. Moreover, the interaction mechanism between LYCRPLs with MPs was revealed through intermolecular forces, Fourier transform infrared spectroscopy and ultraviolet visible absorption spectroscopy. The findings demonstrated that LYCRPLs enhanced the surface hydrophobicity and particle size of MPs, facilitating expansion and cross-linking of MPs. These results provide a theoretical basis for improving the characteristics of surimi gels and thus facilitate the application of LYCRPLs in the aquatic food industry. © 2023 Society of Chemical Industry.

The inhibitory effect of large yellow croaker roe phospholipid as a potential antioxidant on fish oil oxidation stability

Large yellow croaker roe phospholipid (LYCRPLs) is a potential antioxidant. In this study, the inhibition of LYCRPLs on fish oil (FO) oxidation was systematically investigated by evaluating peroxide value, acid value, p-anisidine value, thiobarbituric acid value, and volatile compounds in the accelerated oxidation reaction. The results showed that LYCRPLs presented remarkable antioxidant activity and extended FO shelf-life compared with soybean phospholipids. The analysis of volatile compounds elucidated that LYCRPLs mainly inhibited the formation of aldehyde volatile compounds and thus improved the oxidative stability of FO. Moreover, LYCRPLs could effectively improve the thermal stability of FO. This research provides new insights into LYCRPLs as a promising natural antioxidant in the food industry.