Salmon Protein Research Articles

Study the stability mechanism of Nano freezing-thawing on myofibrillar proteins in Atlantic salmon

Study the stability mechanism of Nano freezing-thawing on myofibrillar proteins in Atlantic salmon

Nutritional evaluation of an aqueous-processed canola protein concentrate in diets of Atlantic Salmon Salmo salar at different life stages

A novel aqueous processing method was applied on canola defatted meal to produce a protein concentrate (>76 % crude protein, dry matter basis). This aqueous-processed canola protein concentrate (ACPC) was evaluated in three experiments with Atlantic salmon. The objectives were to (1) estimate the nutrient digestibility of ACPC in juvenile fish, (2) appraise its nutrient digestibility in post-smolt salmon, and (3) evaluate the long-term effect of ACPC on growth, survival, nutrient utilization, body composition, fillet pigmentation and gut histology of post-smolt salmon. In the first study, one Reference and one test diet, which was a blend of 70 % Reference and 30 % ACPC (70:30 ratio), were fed to juvenile salmon (57 ± 7 g) and feces were collected using settling columns. In the second study, post-smolt salmon (228 ± 4 g) were fed one Reference and three test diets, which consisted of three Reference to ACPC ratios: 90:10, 80:20 and 70:30. Feces were collected by manual stripping. The long-term study (168 days) was designed as a 2 × 4 full factorial analysis with two types of formula (Americas, with processed animal proteins (PAPs), and Europe, without PAPs) and four inclusion levels of ACPC (0, 10, 15, 20 %) fed to post-smolt Atlantic salmon (228 ± 5 g). Fish were bulk weighed every 28 or 56 days. Distal intestine and fillet were sampled (10 fish/tank) at the end for histological examination and color measurement, respectively. All diets (43–49 % crude protein, 18–25 % crude lipid depending on studies) were extruded and fed to apparent satiation. The apparent digestibility coefficients (ADCs) of ACPC protein in juvenile and post-smolt salmon were 89 % and ≥ 94 %, respectively. The essential amino acids ADCs in juvenile and post-smolt salmon were 83–99 % and 91–99 %, respectively. ACPC protein digestibility was not significantly affected by its inclusion level (P = 0.470). In the third experiment, growth (TGC: 0.143–0.160) and feed intake (668–780 g/fish) were not significantly affected by ACPC inclusion (P ≥ 0.10). Feed conversion ratios varied between 1.04 and 1.08. An unexpected occurrence of disease caused 1.6 % mortality over three weeks during the 24-week long-term study and survival was significantly higher in salmon fed ACPC-containing diets (P < 0.001). ACPC inclusion significantly increased fillet redness (P < 0.001) and increased villus length of distal intestine (P < 0.001). In conclusion, ACPC was a safe and nutritive protein alternative in salmon diets, regardless of inclusion level.

Comparing feces collection methods for evaluating the apparent digestibility coefficient of brewers' spent yeast in juvenile Atlantic salmon (Salmo salar).

Brewer's spent yeast (BSY), derived from Saccharomyces cerevisiae used in beer production, is a valuable protein source for aquafeeds. Estimations of apparent digestibility coefficients (ADC) for nutrients in BSY are crucial for its inclusion in aquafeeds. ADC estimations for Saccharomyces cerevisiae protein in rainbow are hardly comparable from a methodological point of view, whereas the ADC estimations for BSY protein in Atlantic salmon are only based on stripped feces, which are known to produce underestimations. Therefore, new determinations of ADC of BSY nutrients are necessary for the inclusion of this ingredient in practical diets for salmonids. This study is focused on determining unbiased ADC values for protein and energy from BSY in juvenile Salmo salar. To reduce systematic biases, fecal samples were collected using stripping and decantation methods, which are known to produce under-and overestimations, respectively. 780 fish (25.16 ± 4.88 g) were stocked in six tanks. A reference diet (50% protein, 20% lipid, 1% Cr2O3) was provided to three tanks, and a test diet (70,30 reference diet to BSY) to the other three. ADC for BSY protein was 84.70 ± 1.04% (decantation) and 70.50 ± 4.03% (stripping). For gross energy, stripped feces yielded an ADC of 52.04 ± 5.30%, while decantation resulted in 63.80 ± 1.17%. Thus, ADC estimates were taken as the average of the stripping-value and the decantation-value, resulting in 77.6% for BSY crude protein, which is appreciably higher than previously measured values in S. salar fed undisrupted S. cerevisiae, and in 57.9% for gross energy.

Diploid and triploid Chinook salmon (Oncorhynchus tshawytscha) exhibit differential immunological responses toacute thermal stress.

Exposure to temperatures outside of a fish's optimal range results in suppression of the immune system, ultimately leaving aquaculture stocks susceptible to disease outbreaks. This effect is exacerbated in triploid fishes, which demonstrate greater susceptibility to stress than their diploid counterparts. This study investigates the impacts of acute heat stress on the abundance of immune transcripts and proteins in diploid and triploid Chinook salmon (Oncorhynchus tshawytscha), an important finfish crop. This study also demonstrates that acute heat stress induces significant increases in the abundance hsp70, hsp90 and il1b transcripts in the head kidneys, gills and heart ventricles of both diploid and triploid Chinook salmon. Widespread dysregulation of antigen-presentation transcripts was also observed in fish of both ploidies. These results suggest that acute heat stress activates acute-phase responses in Chinook salmon and dysregulates antigen presentation, potentially leaving fish more susceptible to infection. At the protein level, IL-1β was differentially expressed in the head kidney and ventricles of diploid and triploid salmon following heat shock. Differential expression of two tapasin-like proteins in diploid and triploid salmon subjected to heat shock was also observed. Altogether, these data indicate that diploid and triploid Chinook salmon respond differently to acute thermal stressors.

Glucoregulatory Properties of a Protein Hydrolysate from Atlantic Salmon (Salmo salar): Preliminary Characterization and Evaluation of DPP-IV Inhibition and Direct Glucose Uptake In Vitro.

Metabolic disorders are increasingly prevalent conditions that manifest pathophysiologically along a continuum. Among reported metabolic risk factors, elevated fasting serum glucose (FSG) levels have shown the most substantial increase in risk exposure. Ultimately leading to insulin resistance (IR), this condition is associated with notable deteriorations in the prognostic outlook for major diseases, including neurodegenerative diseases, cancer risk, and mortality related to cardiovascular disease. Tackling metabolic dysfunction, with a focus on prevention, is a critically important aspect for human health. In this study, an investigation into the potential antidiabetic properties of a salmon protein hydrolysate (SPH) was conducted, focusing on its potential dipeptidyl peptidase-IV (DPP-IV) inhibition and direct glucose uptake in vitro. Characterization of the SPH utilized a bioassay-guided fractionation approach to identify potent glucoregulatory peptide fractions. Low-molecular-weight (MW) fractions prepared by membrane filtration (MWCO = 3 kDa) showed significant DPP-IV inhibition (IC50 = 1.01 ± 0.12 mg/mL) and glucose uptake in vitro (p ≤ 0.0001 at 1 mg/mL). Further fractionation of the lowest MW fractions (<3 kDa) derived from the permeate resulted in three peptide subfractions. The subfraction with the lowest molecular weight demonstrated the most significant glucose uptake activity (p ≤ 0.0001), maintaining its potency even at a dilution of 1:500 (p ≤ 0.01).

Replacing fishmeal with salmon hydrolysate reduces the expression of intestinal inflammatory markers and modulates the gut microbiota in Atlantic salmon (Salmo salar)

The feed legislation allows the use of fish protein hydrolysates in feed for the same species in which it came from, since enzymatic hydrolysis degrades the proteins and eliminates potential prions, which have caused disease in mammals, but not in fish. In this trial, we investigated the effects of partially replacing dietary fishmeal (FM) with salmon protein hydrolysate (FPH) on the intestinal gene expression and microbiota. Atlantic salmon post smolts were either fed a control diet containing 30% fishmeal (FM), a 20% FM diet with 9% salmon hydrolysate (FPH-09) or a 10% FM diet with 18% salmon hydrolysate (FPH-18), until doubling of weight. Gene expression analysis by RNA sequencing of pyloric caeca (PC), midgut (MG) and hindgut (HG) revealed a downregulation of immunological genes involved in inflammation in the intestine of FPH-18 fed salmon compared to salmon fed the FM control. The gene expression of paralogous peptide transporters (PepT) was analyzed by real time quantitative PCR in PC, anterior midgut (AMG), posterior midgut (PMG) and HG of salmon fed all the three diets. The PepT1b paralog had highest relative expression levels in PC and AMG, suggesting that PepT1b is most important for peptide uptake in the anterior intestine. PepT1a was also mainly expressed in the PC and AMG, but at lower levels than PepT1b and PepT2b in the AMG. The PepT2b paralog had high levels of expression in AMG, PMG and HG indicating that it contributed significantly to peptide uptake in the posterior part of the gastrointestinal tract. The gut microbiota in the mucosa and digesta of the MG and HG, were dominated by the phyla Cyanobacteria and Proteobacteria, but also Firmicutes were present. The only dietary effect on the microbiota was the higher prevalence of the phyla Spirochaetes in the mucosa of FPH-18 fed salmon compared to the FM fed salmon. In conclusion, replacing FM with salmon hydrolysate reduced the expression of inflammatory markers in the Atlantic salmon intestine suggesting improved health benefits. The reduced inflammation may be related to the reduced FM content, potentially bioactive peptides in the hydrolysate and/or the altered gut microbial composition.

Influence of starch-protein interactions on the digestibility and chemical properties of a 3D-printed food matrix based on salmon by-product proteins

This study evaluated the influence of starch-protein interactions on the chemical properties and digestibility of a 3D-printed gel based on salmon by-product protein. Changes in the starch-protein interactions of the stable cornstarch (CS, 15%) and salmon protein isolate (SPI, 4%–12%) printable gels during the in vitro gastrointestinal digestion process were studied by principal component analysis. Protein-rich printed gels increased resistant starch content by 18.05%. Changes in chemical properties and the starch-protein concentration of the gels during the digestion process were highly correlated. The CS-SPI gels in the gastric and intestinal phases exhibited lower α-helix/β-sheet ratio and fluorescence intensity values, whereas surface hydrophobicity increased. This resulted in more ordered structures with a high level of molecular interaction that inhibited enzymatic hydrolysis. This study provides crucial information about the transformations of starch-protein interactions during the digestibility of 3D-printed food matrices as an alternative source of nutrients with a high nutritional quality.

Salmon protein gel enhancement for dysphagia diets: Konjac glucomannan and composite emulsions as texture modifiers

The growing prevalence of dysphagia among the aging population presents a significant challenge. Many highly nutritious foods, like salmon, are often unsuitable for the elderly due to their firm texture when heated. To address this concern, a combination of salmon myofibrillar protein (SMP), Konjac glucomannan (KGM), and different emulsion fillers—such as oil droplets, octenyl succinic anhydride (OSA)-modified potato starch emulsion, and high methoxylated pectin (HMP) emulsions—was selected to enhance the network of salmon protein gels with the aims to create potential applications as dysphagia-friendly foods. The International Dysphagia Dietary Standardization Initiative (IDDSI) test indicated that all gel samples were classified as level 5. The OSA-SMP-KGM gel exhibited notably higher cohesiveness (P < 0.05), reduced adhesion, and enhanced mouthfeel. The OSA-SMP-KGM gel exhibited a smooth surface and excellent water retention (92.4 %), rendering it suitable for individuals with swallowing difficulties, particularly those prone to experiencing dry mouth. The yield stress of OSA-SMP-KGM gel was 594.14 Pa and stable structure was maintained during chewing and swallowing (γe/γv = 62.5). This study serves as a valuable reference for developing salmon-based products that are not only highly nutritious but also fulfill the criteria for a desirable swallowing texture.

Efeito do tratamento térmico nas características do concentrado proteico proveniente da carne mecanicamente separada de salmão do atlântico

The objective of the study was to develop protein concentrates from mechanically separated meat of Atlantic salmon, as well as to evaluate the influence of different heat treatments, namely: electric oven, conventional gas oven and microwave oven, on the chemical characteristics of the final product. The oven and microwave generated potentially more stable products, with lower water and moisture activity and higher protein contents. In general, all treatments originated salmon protein concentrates with expressive attributes for the development of new fortified products, being an attractive ingredient for the reuse of waste from the fish industry.

Murine model identifies tropomyosin as IgE cross-reactive protein between house dust mite and coho salmon that possibly contributes to the development of salmon allergy.

Recently, we have developed a method to identify IgE cross-reactive allergens. However, the mechanism by which IgE cross-reactive allergens cause food allergy is not yet fully understood how. In this study, we aimed to understand the underlying pathogenesis by identifying food allergens that cross-react with house dust mite allergens in a murine model. Allergenic protein microarray analysis was conducted using serum from mice intraperitoneally injected with Dermatophagoides pteronyssinus (Der p) extract plus alum or alum alone as controls. Der p, Dermatophagoides farinae (Der f), coho salmon extract-sensitized and control mice were analyzed. Serum levels of IgE against Der p, Der f, coho salmon extract, protein fractions of coho salmon extract separated by ammonium sulfate precipitation and anion exchange chromatography, and recombinant coho salmon tropomyosin or actin were measured by an enzyme-linked immunosorbent assay. A murine model of cutaneous anaphylaxis or oral allergy syndrome (OAS) was established in Der p extract-sensitized mice stimulated with coho salmon extract, tropomyosin, or actin. Protein microarray analysis showed that coho salmon-derived proteins were highly bound to serum IgE in Der p extract-sensitized mice. Serum IgE from Der p or Der f extract-sensitized mice was bound to coho salmon extract, whereas serum IgE from coho salmon extract-sensitized mice was bound to Der p or Der f extract. Analysis of the murine model showed that cutaneous anaphylaxis and oral allergic reaction were evident in Der p extract-sensitized mice stimulated by coho salmon extract. Serum IgE from Der p or Der f extract-sensitized mice was bound strongly to protein fractions separated by anion exchange chromatography of coho salmon proteins precipitated with 50% ammonium sulfate, which massively contained the approximately 38 kDa protein. We found that serum IgE from Der p extract-sensitized mice was bound to recombinant coho salmon tropomyosin. Der p extract-sensitized mice exhibited cutaneous anaphylaxis in response to coho salmon tropomyosin. Our results showed IgE cross-reactivity of tropomyosin between Dermatophagoides and coho salmon which illustrates salmon allergy following sensitization with the house dust mite Dermatophagoides. Our method for identifying IgE cross-reactive allergens will help understand the underlying mechanisms of food allergies.

Salmon hydrolysate as a protein source for Atlantic salmon; prion content and effects on growth, digestibility and gut health

Feeding unhydrolyzed protein to the same species from which it came from have caused prion disease in some mammals, but this has not been observed in fish. In this study, we characterized a salmon protein hydrolysate (FPH) for prion content and investigated how partially replacing fish meal with salmon hydrolysate, affected growth, digestibility and gut health of Atlantic salmon (Salmo salar). The salmon hydrolysate was analysed for prion content by shotgun and targeted proteomics, but no prions were found. Atlantic salmon post smolts were fed one of the following: a control diet containing 30% fish meal (FM), a 20% FM with 9% salmon hydrolysate diet (FPH-09) or a 10% FM with 18% salmon hydrolysate diet (FPH-18). Salmon fed the hydrolysate diets had higher specific growth rate over the first 25 days. The FPH-18 diet contained more digestible proteins and amino acids than the FM diet, and the ash digestibility increased linearly with the FPH content, indicating increased mineral uptake. Histological analysis of midgut and hindgut did not reveal any significant differences between the FM and FPH-18 diets, and the intestines were assessed to be normal and healthy. These results imply that salmon hydrolysate is a promising novel feed ingredient for Atlantic salmon, due to its excellent amino acid profile and high digestibility.

Increased Thermostability of an Engineered Flavin-Containing Monooxygenase to Remediate Trimethylamine in Fish Protein Hydrolysates.

Protein hydrolysates made from marine by-products are very nutritious but frequently contain trimethylamine (TMA), which has an unattractive fish-like smell. Bacterial trimethylamine monooxygenases can oxidize TMA into the odorless trimethylamine N-oxide (TMAO) and have been shown to reduce TMA levels in a salmon protein hydrolysate. To make the flavin-containing monooxygenase (FMO) Methylophaga aminisulfidivorans trimethylamine monooxygenase (mFMO) more suitable for industrial application, we engineered it using the Protein Repair One-Stop Shop (PROSS) algorithm. All seven mutant variants, containing 8 to 28 mutations, displayed increases in melting temperature of between 4.7°C and 9.0°C. The crystal structure of the most thermostable variant, mFMO_20, revealed the presence of four new stabilizing interhelical salt bridges, each involving a mutated residue. Finally, mFMO_20 significantly outperformed native mFMO in its ability to reduce TMA levels in a salmon protein hydrolysate at industrially relevant temperatures. IMPORTANCE Marine by-products are a high-quality source for peptide ingredients, but the unpleasant fishy odor caused by TMA limits their access to the food market. This problem can be mitigated by enzymatic conversion of TMA into the odorless TMAO. However, enzymes isolated from nature must be adapted to industrial requirements, such as the ability to tolerate high temperatures. This study has demonstrated that mFMO can be engineered to become more thermostable. Moreover, unlike the native enzyme, the best thermostable variant efficiently oxidized TMA in a salmon protein hydrolysate at industrial temperatures. Our results present an important next step toward the application of this novel and highly promising enzyme technology in marine biorefineries.

Evaluation of physicochemical properties of starch-protein gels: Printability and postprocessing

The impact of physicochemical properties and printing parameters on starch-protein gel printability was evaluated to achieve stable 3D-printed gels suitable for individuals with special nutritional needs. The effect of postprocessing (oven/freeze-drying) on physical properties of printed gels was assessed. Corn starch (CS, 10%–15%) and salmon protein isolate (SPI, 2%–4%) were used to obtain stable printed gels; rheological and thermal properties were determined. The texture profile and dimensional stability of the printed gels were studied to determine the optimal printing parameters. The postprocessed gels were analyzed to evaluate their possible use as food with modified texture for dysphagic patients. Different CS-SPI concentrations influenced gel shear recovery by increasing protein denaturation temperature. The best dimensional and textural stability occurred with 15% CS and 3%–4% SPI using 0.91 mm nozzle diameter and 30 mm/s printing speed. Post-processed gels showed that freeze-drying managed to maintain excellent shape fidelity (94.66%–99.22%), while rehydrated gels had modified textures that made them suitable for use in dysphagic people. This study demonstrated that CS-SPI gels provide a promising alternative for 3D-printed foods especially for individuals with specific nutritional needs.

L-plastin levels are associated with mortality during cardiomyopathy syndrome in farmed Atlantic salmon (Salmo salar L.)

Cardiomyopathy syndrome (CMS) is a severe infectious cardiac disease affecting Atlantic salmon (Salmo salar L.). The disease is chief cause of sudden death in Norwegian fish farms and poses serious economical and fish welfare challenges to all salmon-producing countries. Although urgently needed, there are currently no treatments or effective preventive tools available. To achieve this, an in-depth understanding of the biological mechanisms leading to CMS is first required. Proteomic-based blood plasma analysis of inflammatory and immune response proteins recently identified L-plastin as an acute response protein in salmon. Here, we investigated whether L-plastin is associated with piscine myocarditis virus (PMCV) infection and mortality during CMS. By comparing heart and blood plasma samples from surviving and deceased fish from a confirmed CMS outbreak site, we observed that L-plastin expression was elevated in cardiac tissue while circulating free L-plastin levels were reduced in deceased fish. Interestingly, a higher molecular weight band positive for L-plastin was detected in plasma from deceased fish and correlated with L-plastin expression in the heart. In addition, cardiac L-plastin levels correlated with cardiac histopathological changes, mononuclear cell infiltration and necrosis of cardiomyocytes in the heart. Our findings set the base for further investigation of L-plastin as a potential biomarker for mortality risk during PMCV infection and for understanding the course of CMS in farmed salmon.

Development of Salmon Protein Based Shelf Stable Snacks and Improving Their Storage Quality Using Solanum nigrum, a Natural Immune Booster

ABSTRACT The aim of the present study was to develop salmon protein-based shelf stable snacks and to improve their storage quality using Solanum nigrum extract. The products were developed by incorporating different levels of salmon protein powder viz. 20% (T1), 30% (T2), 40% (T3), and 0.0% (control). The snacks containing optimum level of protein powder (30%) were incorporated with S. nigrum extract (1.0%) and stored at room temperature (25 ± 1°C) for 75 days. Incorporation of salmon protein powder significantly increased the protein and fat contents and decreased the carbohydrate content. The snacks containing 30% salmon protein powder showed highest scores for all sensory characteristics. The total phenolic content and DPPH-radical scavenging (% inhibition) of S. nigrum extract was 380 mg GAE/100 g and 79.0, respectively. Addition of S. nigrum extract significantly (P < .05) improved the lipid stability (reduced TBARS and free fatty acids) and microbial quality (total-plate and yeast/moulds), while enhancing the sensory quality of the snacks during storage. Salmon protein powder and S. nigrum can be used for the development of highly nutritive shelf stable snacks with improved lipid oxidative and microbial stability. The immune boosting properties of S. nigrum can be of health importance during this pandemic of SARS-CoV-2.

Environmental performance of insect protein: a case of LCA results for fish feed produced in Norway

In this article, life cycle assessments for six insect protein production cases are examined, and their life cycle inventories are systematically combined to create consistent data and results for the environmental performance of insect protein. The LCAs are on mealworms farmed in the Netherlands or France, fed on cereals or vegetable waste food and brewery side stream (four cases); and black soldier fly larvae farmed in Germany, fed on brewery side stream or brewery side stream with vegetable waste (two cases). The focus is on those insect proteins which can be utilised as fish feed with use in Norway as an example. Special attention is paid to obtain consistent system boundaries, method choices, background data, and indicators. The results show that the insect diet is crucial for all the analysed environmental indicators for insects fed a diet of high economic value vegetables. Emissions from the utilisation of insect manure for biogas, fertilisers or similar, and direct insect greenhouse gas emissions, seem to have little importance. The article further shows results compared with the greenhouse gas emissions for the most important salmon protein feed ingredients in Norway. Insect protein based on vegetables with low economic value has the potential to compete in environmental performance with existing protein sources for fish feed and can also cover 10 to 15% of the volumes of crude protein currently imported to the EU.

Functional characterization of Atlantic salmon (Salmo salar L.) PepT2 transporters.

The high‐affinity/low‐capacity system Slc15a2 (PepT2) is responsible for the reuptake of di/tripeptides from the renal proximal tubule, but it also operates in many other tissues and organs. Information regarding PepT2 in teleost fish is limited and, to date, functional data are available from the zebrafish (Danio rerio) only. Here, we report the identification of two slc15a2 genes in the Atlantic salmon (Salmo salar) genome, namely slc15a2a and slc15a2b. The two encoded PepT2 proteins share 87% identity and resemble both structurally and functionally the canonical vertebrate PepT2 system. The mRNA tissue distribution analyses reveal a widespread distribution of slc15a2a transcripts, being more abundant in the brain and gills, while slc15a2b transcripts are mainly expressed in the kidney and the distal part of the gastrointestinal tract. The function of the two transporters was investigated by heterologous expression in Xenopus laevis oocytes and two‐electrode voltage‐clamp recordings of transport and presteady‐state currents. Both PepT2a and PepT2b in the presence of Gly‐Gln elicit pH‐dependent and Na+ independent inward currents. The biophysical and kinetic analysis of the recorded currents defined the transport properties, confirming that the two Atlantic salmon PepT2 proteins behave as high‐affinity/low‐capacity transporters. The recent structures and the previous kinetic schemes of rat and human PepT2 qualitatively account for the characteristics of the two Atlantic salmon proteins. This study is the first to report on the functional expression of two PepT2‐type transporters that operate in the same vertebrate organism as a result of (a) gene duplication process(es).Key points Two slc15a2‐type genes, slc15a2a and slc15a2b coding for PepT2‐type peptide transporters were found in the Atlantic salmon. slc15a2a transcripts, widely distributed in the fish tissues, are abundant in the brain and gills, while slc15a2b transcripts are mainly expressed in the kidney and distal gastrointestinal tract.Amino acids involved in vertebrate Slc15 transport function are conserved in PepT2a and PepT2b proteins.Detailed kinetic analysis indicates that both PepT2a and PepT2b operate as high‐affinity transporters.The kinetic schemes and structures proposed for the mammalian models of PepT2 are suitable to explain the function of the two Atlantic salmon transporters.

Salmon Protein Hydrolysate Potentiates the Growth Inhibitory Effect of Bicalutamide on Human Prostate Cancer Cell Lines LNCaP and PC3 by Modulating Iron Homeostasis.

Prostate cancer is a common cause of cancer death in men. In advanced stages of prostate cancer, androgen deprivation therapy (ADT) is initiated. Despite ADT, prostate cancers invariably progress to become androgen independent. A growing body of evidence implicates iron dysmetabolism in prostate cancer progression. A bioactive peptide-rich salmon protein hydrolysate (SPH) has previously been demonstrated to modulate iron homeostatic mechanisms. In the present study, the anticancer effect of SPH and bicalutamide co-treatment on LNCaP and PC3 prostate cancer cell proliferation was investigated. Our results found that SPH potentiates the anti-proliferative effect of bicalutamide in a dose-dependent manner for both cell lines. In the presence of 160 µg/mL SPH, co-treatment with 1.0 µM bicalutamide decreased LNCaP cells’ relative colony survival from 25% (1.0 µM bicalutamide monotreatment) to 2% after culturing for 12 days. For PC3 cells, the relative colony survival diminished from 52% (10.0 µM bicalutamide) to 32% at an SPH concentration of 160 µg/mL. Gene expression profiling, employing quantitative real-time PCR, revealed that the inhibitory effects were related to significant FTH1 up-regulation with a concomitant TFRC down-regulation. In conclusion, our results provide in vitro evidence that SPH potentiates the growth inhibitory effect of bicalutamide on prostate cancer cells by modulating iron homeostasis mechanisms.

Properties of peptides released from salmon and carp via simulated human-like gastrointestinal digestion described applying quantitative parameters.

Apart from the classical (experimental) methods, biologically active peptides can be studied via bioinformatics approach, also known as in silico analysis. This study aimed to verify the following research hypothesis: ACE inhibitors and antioxidant peptides can be released from salmon and carp proteins during simulated in silico human-like gastrointestinal digestion. The potential to release biopeptides was evaluated using the BIOPEP-UWM quantitative criteria including the profile of biological activity, frequency of the occurrence (A)/release (AE) of fragments with an ACE inhibitory or antioxidant activity by selected enzymes, and relative frequency of release of bioactive fragments with a given activity by selected enzymes (W). Salmon collagen and myofibrillar proteins of carp turned out to be the best potential source of the searched peptides–ACE inhibitors and antioxidant peptides. Nonetheless, after digestion, the highest numbers of ACE inhibitors and antioxidant peptides were potentially released from the myofibrillar proteins of salmon and carp. Peptide Ranker Score, Pepsite2, and ADMETlab platform were applied to evaluate peptides’ bioactivity potential, their safety and drug-like properties. Among the 63 sequences obtained after the simulated digestion of salmon and carp proteins, 30 were considered potential biopeptides. The amino acid sequences of ACE-inhibiting and antioxidant peptides were predominated by P, G, F, W, R, and L. The predicted high probability of absorption of most analyzed peptides and their low toxicity should be considered as their advantage.

Yeast as a novel protein source - Effect of species and autolysis on protein and amino acid digestibility in Atlantic salmon (Salmo salar)

Yeasts are gaining increasing attention as alternative protein sources in fish feeds. The nutritional value of yeast depends on cultivation conditions, yeast species and processing conditions used after harvesting. The objective of the current study was to evaluate the effect of autolysis on apparent digestibility coefficients (ADCs) of crude protein and amino acids (AA) of different yeasts species in Atlantic salmon (Salmo salar). Three yeast species (i.e. Cyberlindnera jadinii, Blastobotrys adeninivorans and Wickerhamomyces anomalus) produced from hydrolysates of pre-treated wood and chicken products were used. After harvesting, each yeast was either directly heat-inactivated with spray-drying or autolyzed at 50 °C for 16 h followed by spray-drying. The treatments consisted of a high-quality fishmeal-based reference diet and six test diets containing 30% of each of the yeast product and 70% of the reference diet. The results showed that protein and AA digestibility differed among the yeast species and that the effect of autolysis on nutrient digestibility was inconsistent among the three yeast species. The ADCs of protein in inactivated yeasts were 63%, 72%, 66% in C. jadinii, B. adeninivorans and W. anomalus, respectively. Autolysis increased the ADCs of protein by 12% and 9% in C. jadinii and W. anomalus, respectively, while it remained unchanged for B. adeninivorans. The ADCs of lysine were 67%, 79% and 72% in inactivated C. jadinii, B. adeninivorans and W. anomalus, respectively. Autolysis improved the ADCs of lysine by 15%, 7% and 13% in C. jadinii, B. adeninivorans and W. anomalus, respectively. The ADCs of methionine in inactivated yeasts was 47% in C. jadinii, 81% in B. adeninivorans and 74% in W. anomalus. After autolysing the yeasts, the ADC of methionine improved by 26% and 4% in C. jadinii and B. adeninivorans, respectively, while it slightly reduced by 2% in W. anomalus. Data from regression analyses showed that digesta viscosity, digesta dry matter and nitrogen solubility are important determinants of protein digestibility of yeasts in fish. In addition, cell wall porosity as demonstrated by nitrogen solubility test, had a larger impact on nutrient digestibility of yeasts compared to the cell wall thickness. In conclusion, the digestibility of protein and AA of yeasts in Atlantic salmon depends on type of yeasts and down-stream processing applied after harvesting. Also, the particular in vitro digestibility method used in the current study did not adequately reflect the protein digestibility of yeasts in Atlantic salmon.