Fish Skin Research Articles

Effects of fish skin collagen peptide on physicochemical properties of frozen dough and quality and antioxidant activity of steamed bread

Fish skin collagen peptide (FSCP), as a bioactive peptide, holds significant potential in the food industry, particularly in enhancing the quality and nutritional attributes of frozen dough products. This research examined the impacts of FSCP addition and freezing time on water distribution, rheo-fermentation, rheological, and structural properties of dough, as well as the textural properties, internal structure, and antioxidant activity of steamed bread. The results showed that adding FSCP inhibited water migration and reduced freezable water content. After 4 weeks of freezing, the freezable water content of the FSCP-added groups decreased by 0.42%–4.77% compared with the control. Rheo-fermentation analysis indicated that the total CO2 release volume, maximum dough development height, and CO2 retention volume initially increased with FSCP concentration, peaking at 1.5%, before decreasing with further increases in FSCP concentration. Moreover, FSCP effectively mitigated gluten freeze damage, resulting in a slower decline in disulfide bond content and viscoelasticity. Additionally, it improved the textural properties and antioxidant activity of the steamed bread. X-ray micro-CT images revealed that FSCP improved gas pore distribution and network density in the steamed bread. Overall, FSCP proved effective in improving the attributes of frozen dough and the final steamed bread, particularly at a 1.5% concentration. These findings suggest a promising application of FSCP in frozen dough-based products, especially in the development of functional foods.

Chemical, physical, and sensory properties of various fish skin gelatin fortified taro flour - seaweed based analogue rice

Chemical, physical, and sensory properties of various fish skin gelatin fortified taro flour - seaweed based analogue rice

Traditional Fish Leather Dyeing Methods with Indigenous Arctic Plants

Along the Arctic and sub-Arctic coasts of Alaska, Siberia, north-eastern China, Hokkaido, Scandinavia and Iceland, people have dressed in clothes or worn shoes made of fish skin for millennia. (Within this article, the terms fish skin and fish leather are used to indicate different processes of the same material. Fish skin: Skin indicates the superficial dermis of an animal. Fish skin is referred to as the historical raw material that is tanned following traditional methods such as mechanical, oiling and smoking tanning, using materials such as bark, brain, urine, fish eggs and corn flour. Fish leather is used to refer that the fish skin has passed one or more stages of industrial vegetable or chrome tanning production and is ready to be used to produce leather goods). These items are often decorated with a rich colour palette of natural dyes provided by nature. In this study, minerals and raw materials of plant origin were collected from riverbanks and processed by Arctic seamstresses who operated as designers, biochemists, zoologists, and climatologists simultaneously. During our research, an international team of fashion, tanning and education specialists used local Arctic and sub-Arctic flora from Sweden, Iceland, and Japan to dye fish leather. Several plants were gathered and sampled on a small scale to test the process and determine the colours they generated based on the historical literature and verbal advice from local experts. This paper describes the process and illustrates the historical use of natural dyes by the Arctic groups originally involved in this craft, building on the traditional cultural heritage that has enabled us to develop sustainable dyeing processes. The results are promising and confirm the applicability of these local plants for dyeing fish skins, providing a basis for a range of natural dye colours from local Arctic flora. The aim is to develop a moderate-sized industrial production of fish leather in this colour palette to replace current unsustainable chemical dyeing processes. This project represents an innovation in material design driven by traditional technologies, addressing changes in interactions between humans and with our environment. The results indicate that new materials, processes, and techniques are often the fruitful marriage of fashion and historical research of traditional methods, helping the industry move towards a more sustainable future.

Sws2 Gene Positively Regulates Melanin Production in Plectropomus leopardus Skin via Direct Regulation of the Synthesis of Retinoic Acid.

Opsins are a class of transmembrane proteins encoded by opsin genes, and they play a variety of functional roles. Short wavelength-sensitive opsin 2 (sws2), one of the five classes of visual opsin genes, mainly senses blue light. Previous research has indicated that sws2 is essential for melanocyte formation in fish; however, its specific role in skin color differentiation remains to be elucidated. Here, we identified the sws2 gene in a prized reef-dwelling fish, Plectropomus leopardus. The full-length P. leopardus sws2 gene encodes a protein consisting of 351 amino acids, and exhibits substantial homology with other fish species. The expression of the sws2 gene was widespread across P. leopardus tissues, with high expression in eye and skin tissues. Through immunohistochemistry and in situ hybridization analyses, we discovered that the sws2 gene was primarily localized in the rod and cone cells of the retina, and epidermal cells of the skin. Furthermore, dsRNA interference was used for sws2 gene knockdown in living P. leopardus to elucidate its function in skin color differentiation. Black-color-related genes, melanin contents, and tyrosinase activity in the skin significantly decreased after sws2 knockdown (p < 0.05), but red-color-related genes and carotenoid and lutein contents significantly increased (p < 0.05). Retinoic acid injection produced the opposite results. Our results suggested that the sws2 gene influences P. leopardus skin color regulation by affecting vitamin synthesis and melanin-related gene expression levels. This study establishes a foundation for elucidating the molecular mechanisms by which sws2 regulates melanocyte formation in fish skin.

Systemic immune responses do not affect significant immune responses in the skin

Fish skin plays an important role in defending against pathogens in water, primarily through the secretion of skin mucus containing various immune-related factors. Local immune responses in the skin activate systemic immune responses by inflammatory cytokines. However, it remains unclear whether immune responses in the skin occur after systemic immune responses caused by pathogen invasion into the fish body. This study aimed to clarify the relationship between systemic immune responses and skin responses after intraperitoneal injection of formalin-killed cells (FKC) of Vibrio anguillarum. Although systemic inflammatory responses were observed in the spleen after injection, expression changes in the skin did not show significant differences. In contrast, expression of hemoglobin subunit genes significantly increased in the skin after FKC injection, suggesting that erythrocytes infiltrate extravascularly.

Laser Ablating Biomimetic Periodic Array Fish Scale Surface for Drag Reduction.

Reducing resistance to surface friction is challenging in the field of engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions to adapt to their complex environments over centuries. Among these biological wonders, fish, one of the oldest in the vertebrate group, have garnered attention due to their exceptional fluid dynamics capabilities. Fish skin has inspired innovation in reducing surface friction due to its unique structures and material properties. Herein, drawing inspiration from the unique properties of fish scales, a periodic array of fish scales was fabricated by laser ablation on a polished aluminum template. The morphology of the biomimetic fish scale surface was characterized using scanning electron microscopy and a white-light interfering profilometer. Drag reduction performance was measured in a closed circulating water tunnel. The maximum drag reduction was 10.26% at a Reynolds number of 39,532, and the drag reduction performance gradually decreased with an increase in the distance between fish scales. The mechanism of the biomimetic drag reduction surface was analyzed using computational fluid dynamics. Streamwise vortices were generated at the valley of the biomimetic fish scale, replacing sliding friction with rolling friction. These results are expected to provide a foundation for in-depth analysis of the hydrodynamic performance of fish and serve as new inspiration for drag reduction and antifouling.

Dietary lipid and astaxanthin contents affect the pigmentation of Arctic charr (Salvelinus alpinus)

The most important quality parameter of salmonids is the red color of their skin and muscles. In this contribution, the effects of astaxanthin and dietary lipid content on the pigmentation of Arctic charr (Salvelinus alpinus) were studied. Charrs were fed on diets containing 40, 60, and 80 ppm synthetic astaxanthin together with 10, 18, and 26% dietary lipids for 24 weeks. Results indicated that the astaxanthin concentration in the belly skin and flesh of fish was strongly correlated with both carotenoid and dietary lipid contents, suggesting a significant interaction between diets and the total carotenoid concentration in the belly skin and flesh. The Hunter color L* values of the fillet and the belly skin were inversely related to their carotenoid levels, whereas their a* and b* values were strongly correlated with the total carotenoid concentration. The apparent digestibility coefficient of carotenoids was directly correlated with the level of dietary lipid but inversely correlated with carotenoid contents. A strong correlation between the content of carotenoids retained in the flesh and their digestibility was observed. Thus, the pigmentation of Arctic charr could improve the overall consumer acceptability as well as nutritional and potential market values of Arctic charr.Graphical

Sonic hedgehog (shh) gene from Pseudopleuronectes yokohamae (Teleostei: Pleuronectidae): Molecular cloning, characterization, and expression profile during early embryonic, juvenile, and adult stages.

The hedgehog signaling pathway plays an important role in early development and growth of most vertebrates. Sonic hedgehog (shh) gene is a critical regulator of embryonic development in many species, including humans. However, it is not clear what roles shh can play in the development of fish. In this paper, shh gene was cloned from Pseudopleuronectes yokohamae. The full-length complementary DNA (cDNA) of P. yokohamae sonic hedgehog gene (Pyshh) comprises 3194 bp, with a 1317-bp open reading frame (ORF) that encodes a polypeptide of 438 amino acids with a typical HH-signal domain and Hint-N domain. The conserved sequences of the protein among species were predicted by using multiple sequence comparison. The phylogenetic tree construction showed that PySHH is clustered in a branch of Pleuronectidae. To explore the expression of Pyshh gene in various tissues of P. yokohamae, we used real-time fluorescence quantitative PCR technology to detect it. The results showed that Pyshh gene is widely distributed in various tissues of P. yokohamae juveniles, different tissues of adult males and females, and is particularly expressed in immune organs. The Pyshh gene expression was higher in the muscle and brain of juvenile fish, and higher in bone, gill, and skin of male fish than that of female fish, suggesting that Pyshh might be involved in the formation of immune organs of P. yokohamae. The expression of Pyshh gene significantly upregulated from the gastrula stage to the hatching stage. Western blotting of the expression levels of PySHH during different embryonic development stages revealed that PySHH levels increased gradually during development stages from oosperm stage to hatching stage. These results indicate that Pyshh is highly conserved among species and plays a critical role in the complex process of embryonic development. Its precise regulation is essential for the proper formation of many organs and tissues in the body, and disruptions in its function may have serious consequences for the formation of immune organs in fish.

Polyculture of Genetically Improved Farmed Tilapia (GIF tilapia) and Penaeus vannamei Using Biofloc Technology – A Review

According to Food and Agriculture Organization of the United Nations (FAO), aquaculture has grown faster and its expansion aimed at meeting the increase of world fish demand, and preserving natural fish stocks. Currently, to produce fish in quantity and quality requires reduction of the environmental impact from aquaculture, through the improvement of culture systems. Disease is the major factor affecting the development and expansion in aquaculture. Losses due to disease in shrimp farming are high. Various approaches to minimize the impact of disease on production are possible. Another approach to keep the pathogen pressure low is polyculture of shrimp and finfish. This practice makes shrimp farming more sustainable by reducing the environmental impact and the incidence of shrimp disease. Antimicrobial peptides in the fish skin kill shrimp pathogens, keeping pathogen pressure of bacteria and viruses low. In polyculture, shrimps can eat tilapia faeces and unused fish feed, while tilapia filter phytoplankton, reducing the risk of low dissolved oxygen levels at night. In addition, shrimp bioturbation at the pond bottom returns nutrients to the water column, enhancing phytoplankton production and consequently the natural feed available for the tilapia. Biofloc technology (BFT) is one of the most applicable and promising systems for sustainable aquaculture development. This technology is essentially based on the recycling of nutrients via microorganisms, primarily (i) heterotrophic bacteria, which convert nitrogen compounds into microbial biomass, in addition to serves as a source of food for aquatic organisms, and (ii) chemoautotrophic bacteria, which convert ammonia to nitrite and nitrate.

Mutation of mpv17 results in loss of iridophores due to mitochondrial dysfunction in tilapia

Abstract Mpv17 (mitochondrial inner membrane protein MPV17) deficiency causes severe mitochondrial DNA depletion syndrome in mammals and loss of pigmentation of iridophores and a significant decrease of melanophores in zebrafish. The reasons for this are still unclear. In this study, we established an mpv17 homozygous mutant line in Nile tilapia. The developing mutants are transparent due to the loss of iridophores and aggregation of pigment granules in the melanophores and disappearance of the vertical pigment bars on the side of the fish. Transcriptome analysis using the skin of fish at 30 dpf (days post fertilization) revealed that the genes related to purine (especially pnp4a) and melanin synthesis were significantly downregulated. However, administration of guanine diets failed to rescue the phenotype of the mutants. In addition, no obvious apoptosis signals were observed in the iris of the mutants by TUNEL staining. Significant downregulation of genes related to iridophore differentiation was detected by qPCR. Insufficient ATP, as revealed by ATP assay, α-MSH treatment, and adcy5 mutational analysis, might account for the defects of melanophores in mpv17 mutants. Several tissues displayed less mtDNA and decreased ATP levels. Taken together, these results indicated that mutation of mpv17 led to mitochondrial dTMP deficiency, followed by impaired mtDNA content and mitochondrial function, which in turn, led to loss of iridophores and a transparent body color in tilapia.

Distribution of extended-spectrum β-lactamase producing Escherichia coli genes in an integrated poultry-fish farming system in Bogor, Indonesia.

The excessive use of antimicrobials in livestock farming leads to the emergence and dissemination of antimicrobial-resistant organisms. This study aimed to detect extended-spectrum β-lactamase (ESBL)-producing Escherichia coli genes in integrated poultry-fish farms in Bogor, Indonesia. A total of 256 samples were collected from six poultry-fish farms. One hundred and seventy-five chicken cloaca swabs, 60 fish skin swabs, six pond water samples, and 15 farmer's hand swabs. ESBL-producing E. coli was confirmed through double-disk diffusion. The specific primers and probe genes for quantitative polymerase chain reaction detection of ESBL-producing E. coli targeted blaTEM, blaCTX-M, blaSHV, and blaOXA-48 genes. Among the 256 samples tested, 145 (56.6%) were positive for E. coli, and 67.6% (98/145) were identified as ESBL-producing E. coli. The most ESBL-producing E. coli isolates were obtained from chicken cloaca (78.3%, 72/92), followed by pond water (66.7%, 4/6), fish skin (47.6%, 20/42), and farmer's hand swabs (40%, 2/5). About 100% of the isolates carried the genes blaTEM and blaCTX-M, whereas 17.3% and 24.5% carried blaSHV and blaOXA-48, respectively. ESBL-producing E. coli genes were investigated in chicken cloaca, fish, pond water, and farmers' hands within an interconnected poultry-fish farming operation. The ESBL-producing E. coli in chickens can transfer resistant genes to aquatic environments. The transfer could harm other aquatic species and food chains, potentially threatening human health.

Epidermal mucus as a potential biological and biochemical matrix for fish health analysis

Fish reside in ecosystems teeming with pathogens, so their mucus has developed antimicrobial properties that help inhibit these pathogens. The fish's epidermal mucus serves as the initial line of defense against pathogens. This study aimed to characterize the antibacterial activity and biochemical makeup of fish skin mucus against various bacterial strains. The analysis was conducted on Labeo rohita, a fish species chosen for its mucus sample. The mucus was tested for its antibacterial activity against multiple Gram-positive and Gram-negative bacteria. The results showed that the crude mucus extract had higher activity than the saline mucus extract. The fish mucus's antimicrobial potential was assessed using the well diffusion method. The crude mucus extract displayed slightly better antibacterial activity against Gram-negative bacteria like Escherichia coli and Pasterulla multocida, as well as Gram-positive bacteria like Staphylococcus aureus and Bacillus subtilis, compared to the saline mucus extract of Labeo rohita. The samples were also tested for their hemolytic and thrombolytic activities. The activity of antioxidants in fish mucus was evaluated using DPPH, reducing power, TPC, and TFC assays. Additionally, biochemical analysis was performed, including measurements of CAT, POD, SOD, and protein content. Advanced techniques such as Fourier infrared spectroscopy (FTIR) and UV spectroscopy were employed for the characterization of fish mucus. FTIR analysis of fish mucus revealed the presence of aliphatic primary amines (N-H) and alkenes as functional groups at various peaks in the spectrum. The results were analyzed using mean and standard deviations.

Biocompatible supercapacitor engineered from marine collagen impregnated with polypyrrole and tungsten disulfide

There is an urgent demand for highly stable energy storage systems that are biocompatible, environmentally friendly, and made from affordable, sustainable materials. Research on biologically sourced materials as green energy storage devices such as supercapacitor (SC) technologies are emerging, but they are often expensive, complicated to manufacture, and fail to meet the required performance levels. This article presents a simple and innovative method to fabricate a human skin comfortable SC electrode using collagen extracted from hoki (Macruronus novaezelandiae) fish skin. Polypyrrole and tungsten disulfide nanoparticles were incorporated into the collagen matrix via early wetness impregnation to provide the required electrical properties. Electrochemical investigations revealed that the areal capacitance of the composite material was 348 mF cm−2 and cyclic testing showed that the capacitance retention is 98 % after 50,000 cycles. The collagen-based composite demonstrated excellent biocompatibility to HEK293 cells grown over a 1-week period. This novel technique for producing biodegradable and biocompatible SC electrodes from renewable source paves opportunities to utilize other sources of biomaterials for smart electronic applications.

Development Of Novel Processed Tilapia Products For The Group Of Female Fish Farmers In The Village Of Ranu Klakah Lumajang

Floatingfish cages are utilized in fish farming systems using public water bodies such as lakes and seas, with tilapia being a widely cultivated fish in Indonesia due to its economic and nutritional value. Ranu Klakah, a volcanic lake in East Java, is explored as a site for tilapia cultivation. Upwelling, the process of nutrient-rich deep water rising to the surface due to wind-induced currents, is examined for its effects on water quality and fish productivity. The activity focuses on the impact of upwelling on tilapia, including reduced water quality, scarcity of natural fish food, physiological stress, disease susceptibility, and decreased fish production. To address the challenges posed by upwelling, it suggests processing tilapia into value-added products, like fish nuggets and skin chips, to enhance market value. Community service activities involving training for making these processed fish products are described, aiming to empower women in the fish farming sector and improve family income. We concludewith insights into the potential benefits of these activities and their positive impact on the local community.

Characterization of biodegradable films prepared from gelatin extracted from jellyfish Acromitus flagellates using hot water extraction and microwave-assisted extraction

This study investigated the characteristics of biodegradable films prepared from gelatin derived from jellyfish Acromitus flagellatus using hot water extraction (F-JFG-HW) and microwave-assisted extraction (F-JFG-MW), in comparison to the cold-water fish skin gelatin (F-FG) and porcine skin gelatin (F-PG) based films. Both jellyfish gelatin films were darker compared to F-PG and F-FG. The tensile strength of jellyfish gelatin-based films was lower than that of F-PG but higher than that of F-FG. Both jellyfish-gelatin film types exhibited higher elongation at break, water vapour transmission rates, and antioxidant potential compared to F-FG and F-PG. The scanning electron microscopic analysis revealed that jellyfish gelatin films exhibited granular and porous surface structures and less compact internal structures compared to F-FG and F-PG. Both jellyfish gelatin-based films and F-FG films were 100 % water soluble and completely biodegradable after 24 h of incorporation in soil, while F-PG films biodegraded completely after 2 days.

Biomimicry in construction: Glycoprotein-stabilised adobe bricks for enhanced compressive strength inspired by termites mounds

Earth is a green building material with very low embodied energy and almost zero greenhouse gas emissions. However, it lacks strength and durability when used without stabilisation. By incorporating responsibly sourced stabilisers, it is possible to enhance the strength of this material. In this study, adobe bricks stabilised using bio-inspired stabilisers were investigated. This research was inspired by the high strength and durability of termite mounds, exploring the stabiliser behind such robust natural constructions. Termites build their mounds by incorporating a glycoprotein from their saliva to cement the sub-soil particles together. Biomimicry has been employed to investigate the potential use of the termites' construction stabiliser in adobe bricks. Three glycoproteins from meat and fish industry waste were identified as potential stabilisers in adobe bricks. Bovine serum albumin (BSA) from cows' blood, mucin from the porcine stomach, and gelatine from cold-water fish skin were the three stabilisers used in this study. Two soils were used to prepare adobe bricks for testing. The primary soil used in this study was from Devon in the United Kingdom (UK). The second soil was obtained from the Mayo neighbourhood in Khartoum, Sudan, and used only in key tests. Adobe bricks were made and stabilised with different concentrations of these bio-inspired stabilisers. Controlled unstabilised adobe bricks were used for comparison. The bricks were tested for their unconfined compressive strength. The main conclusion of this study is that BSA has proven its potential to be used as a stabiliser in earth construction. Using 0.5 % BSA resulted in a 17 % and 41 % increase in the unconfined compressive strength of the British and Sudanese adobe bricks, respectively. In addition, using 5 % BSA resulted in a 203 % and 97 % increase in the unconfined compressive strength of the British and Sudanese adobe bricks, respectively. The compressive strength of BSA-stabilised adobe bricks is higher than that of earth bricks stabilised using 5 % cement and 5 % lime reported in the literature. Furthermore, the compressive strength of the 5 % BSA-stabilised adobe bricks is higher than the lower recommended compressive strength for the hollow concrete blocks in the UK. Hence, these BSA-stabilised adobe bricks could substitute hollow concrete blocks to construct internal walls. The other stabilisers tested did not significantly improve the unconfined compressive strength of the adobe bricks. The study underscores the value of biomimicry and proposes glycoproteins as viable natural stabilisers in earth construction, with further recommendations for in-depth research to optimise application methods and formulations.

Identification and characterization of circular RNAs in the skin of rainbow trout (Oncorhynchus mykiss) infected with infectious hematopoietic necrosis virus

Rainbow trout (Oncorhynchus mykiss) is an economically significant freshwater-farmed fish worldwide, and the frequent outbreaks of infectious hematopoietic necrosis (IHN) in recent years have gravely compromised the healthy growth of the rainbow trout aquaculture industry. Fish skin is an essential immune barrier against the invasion of external pathogens, but it is poorly known about the role of circRNAs in rainbow trout skin. Therefore, we examined the expression profiles of circRNAs in rainbow trout skin following IHNV infection using RNA-seq. A total of 6607 circRNAs were identified, of which 34 circRNAs were differentially expressed (DE) and these DE circRNA source genes were related to immune-related pathways such as Toll-like receptor signaling pathway, NOD-like receptor signaling pathway, Cytokine-cytokine receptor interaction, ubiquitin mediated proteolysis, and ferroptosis. We used qRT-PCR, Sanger sequencing, and subcellular localization to validate the chosen DE circRNAs, confirming their localization and expression patterns in rainbow trout skin. Further, 12 DE circRNAs were selected to construct the circRNA-miRNA-mRNA regulatory network, finding one miRNA could connect one or more circRNAs and mRNAs, and some miRNAs were reported to be associated with antiviral immunity. The functional prediction findings revealed that novel_circ_002779 and novel_circ_004118 may act as sponges for miR-205-z and miR-155-y to regulate the expression of target genes TLR8 and PIK3R1, respectively, and participated in the antiviral immune responses in rainbow trout. These results shed light on the immunological mechanism of circRNAs in rainbow trout skin and offer fundamental information for further research on the innate immune system and breeding rainbow trout resistant to disease.

Investigation into Potential Allergenicity and Digestion-Resistant Linear Epitopes of Fish Skin Gelatin in Cell-Cultured Meat Scaffolds.

As a key component of cell-cultured fish, fish skin gelatin (FSG)-based cell scaffold provides support structures for cell growth, proliferation, and differentiation. However, there are potential allergenicity risks contained in FSG-based scaffolds. In this study, 3D edible scaffolds were prepared by phase separation method and showed a contact angle of less than 90°, which indicated that the scaffolds were favorable for cell adhesion. Besides, the swelling ratio was greater than 200%, implying a great potential to support cell growth. The sequence homology analysis indicated that FSG was prone to cross-reaction with collagen analogues. Additionally, a food allergic model was constructed and represented that mice gavaged with cod FSG exhibited higher levels of specific antibodies, mast cell degranulation, vascular permeability, and intestinal barrier impairment than those gavaged with pangasius and tilapias FSG. Its higher allergenicity might be attributed to a higher number of digestion-resistant linear epitopes. Moreover, the higher hydrolysis degree linked to the exposure of linear epitopes to promote the combination with IgE, which was also responsible for maintaining the higher allergenicity of cod FSG. This study clarifies allergenic risks in cell-cultured fish and further study will focus on the allergenicity reduction of FSG-based cell scaffolds.

Exploitation of multiple host-derived nutrients by the yellow catfish epidermal environment facilitates Vibrio mimicus to sustain infection potency and susceptibility

Infection with Vibrio mimicus in the Siluriformes has demonstrated a rapid and high infectivity and mortality rate, distinct from other hosts. Our earlier investigations identified necrosis, an inflammatory storm, and tissue remodeling as crucial pathological responses in yellow catfish (Pelteobagrus fulvidraco) infected with V. mimicus. The objective of this study was to further elucidate the impact linking these pathological responses within the host during V. mimicus infection. Employing metabolomics and transcriptomics, we uncovered infection-induced dense vacuolization of perimysium; Several genes related to nucleosidase and peptidase activities were significantly upregulated in the skin and muscles of infected fish. Concurrently, the translation processes of host cells were impaired. Further investigation revealed that V. mimicus completes its infection process by enhancing its metabolism, including the utilization of oligopeptides and nucleotides. The high susceptibility of yellow catfish to V. mimicus infection was associated with the composition of its body surface, which provided a microenvironment rich in various nucleotides such as dIMP, dAMP, deoxyguanosine, and ADP, in addition to several amino acids and peptides. Some of these metabolites significantly boost V. mimicus growth and motility, thus influencing its biological functions. Furthermore, we uncovered an elevated expression of gangliosides on the surface of yellow catfish, aiding V. mimicus adhesion and increasing its infection risk. Notably, we observed that the skin and muscles of yellow catfish were deficient in over 25 polyunsaturated fatty acids, such as Eicosapentaenoic acid, 12-oxo-ETE, and 13-Oxo-ODE. These substances play a role in anti-inflammatory mechanisms, possibly contributing to the immune dysregulation observed in yellow catfish. In summary, our study reveals a host immune deviation phenomenon that promotes bacterial colonization by increasing nutrient supply. It underscores the crucial factors rendering yellow catfish highly susceptible to V. mimicus, indicating that host nutritional sources not only enable the establishment and maintenance of infection within the host but also aid bacterial survival under immune pressure, ultimately completing its lifecycle.

Elucidating the rheological and thermal properties of mixed fish and pork skin gelatin gels: Effects of cooling conditions and incubation times

Gelatin is an important hydrocolloid in food and biotechnological applications. There are two basic sources of gelatins; mammalian and fish-derived gelatins, but fish gelatins are less appreciated due to their weak gel properties. Hence, to reinforce the gel properties of fish gelatin, mixtures of gelatins are used. In this study, the mixtures of cold-water ocean fish scale (OFS) and pork skin (PS) gelatin were studied via rheological measurements, micro differential scanning calorimetry (DSC), and particle tracking at different cooling conditions and incubation times to understand the gelation mechanism and the network structure of the gels. The rheological and micro-DSC measurements provide a detailed understanding of the gelation mechanism of gelatin gels under different cooling conditions while particle tracking revealed the local physical properties of the gels. A single or two-step melting was demonstrated in the mixed gelatin gels depending on the cooling conditions suggesting that the aggregation of PS in the mixtures influences the physical and thermal properties of the gels. Under rapid cooling, co-aggregation of OFS and PS chains is considered to cause a single-step melting of the mixed gels. Under gradual cooling, conversely, the PS may form aggregates independently before the OFS. This is evidenced by a two-step decrease in moduli and two clear endothermic peaks in the micro-DSC measurement. Particle tracking further reveals information on the local physical properties of pure and mixed gelatin gels on reheating, indicating that the local structures of mixed gels resemble those of pure PS gels. This suggests that mixed OFS and PS gels may form a cooperative aggregation, thereby improving the physical and thermal properties of the mixed gelatin gels.