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In this study, we devoted attention to the hepatoprotective functions of high Fischer ratio oligopeptides (HFOPs) from Antarctic krill (HFOPs-AK) on alcoholic liver injury of mice. The results indicated that HFOPs-AK significantly improved the pathological state of mice liver and kidney, reduced alanine aminotransferase (ALT) and aspartate transaminase (AST) activities, regulated lipid metabolism, and alleviated the burden on the liver. In addition, HFOPs-AK depicted anti-inflammatory and antioxidant effects by reducing tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) contents and increasing superoxide dismutase (SOD) and catalase (CAT) activities to reduce malondialdehyde (MDA) level. The hepatoprotective mechanism of HFOPs-AK was further revealed by quantitative reverse transcription PCR (RT-qPCR) analysis, and the results proved that HFOPs-AK had the ability to stimulate the adenosine 5‘-monophosphate-activated protein kinase (AMPK)/nuclearrespiratoty factor 2 (Nrf2)/inhibitor of NF-κB (IκBα) signaling pathways, thereby regulating the expression levels of downstream factors. The activation of these signaling pathways is essential for the regulation of lipid metabolism as well as anti-inflammatory and antioxidant functions. This finding offers a novel approach for the development of innovative hepatoprotective agents utilizing HFOPs-AK.

High Fischer ratio oligopeptides (HFOs) have a variety of biological activities, but their mechanisms of action for anti-fatigue are less systematically studied at present. This study aimed to systematically evaluate the anti-fatigue efficacy of HFOs from Antarctic krill (HFOs-AK) and explore its mechanism of action through establishing the fatigue model of endurance swimming in mice. Therefore, according to the comparison with the endurance swimming model group, HFOs-AK were able to dose-dependently prolong the endurance swimming time, reduce the levels of the metabolites (lactic acid, blood urea nitrogen, and blood ammonia), increase the content of blood glucose, muscle glycogen, and liver glycogen, reduce lactate dehydrogenase and creatine kinase extravasation, and protect muscle tissue from damage in the endurance swimming mice. HFOs-AK were shown to enhance Na+-K+-ATPase and Ca2+-Mg2+-ATPase activities and increase ATP content in muscle tissue. Meanwhile, HFOs-AK also showed significantly antioxidant ability by increasing the activities of superoxide dismutase and glutathione peroxidase in the liver and decreasing the level of malondialdehyde. Further studies showed that HFOs-AK could regulate the body's energy metabolism and thus exert its anti-fatigue effects by activating the AMPK signaling pathway and up-regulating the expression of p-AMPK and PGC-α proteins. Therefore, HFOs-AK can be used as an auxiliary functional dietary molecules to exert its good anti-fatigue activity and be applied to anti-fatigue functional foods. [ABSTRACT FROM AUTHOR]

Heat treatment reduces the quality of Antarctic krill (Euphausia superba) meat, thus greatly limiting its industrial application. It was found that L-Lys immersion pretreatment can effectively improve the quality of heat-treated Antarctic krill meat; the underlying mechanism is unclear. Therefore, this study aimed to investigate the effect of L-Lys concentrations (0, 25, 50, 100, and 200 mM) on the aggregation behavior and structure of Antarctic krill myofibrillar protein solution before and after heat treatment. Compared with the untreated group, L-Lys decreased the surface hydrophobicity and particle size of the heat-treated Antarctic krill protein by 2.38 times and 18.27 times while increasing the solubility by 3.59 times. Furthermore, L-Lys intervention inhibited the formation of disulfide bonds in myofibrillar protein of the heat-treated Antarctic krill, enhanced the intermolecular hydrogen bonding force, improved the orderliness of the secondary structure, and "exposed" the tyrosine residues of the protein molecule. As a result, the polarity of the microenvironment was enhanced while the tertiary structure of the protein was altered, thus inhibiting thermal aggregation. This study reveals the mechanism of L-Lys inhibition of thermal aggregation behavior of Antarctic krill myofibrillar protein. Our results provide insights into the development and utilization of Antarctic krill protein in the food industry. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study developed a soft candy with peptide-zinc chelates using low-fluorine protein hydrolysates derived from Antarctic krill powder. To achieve this, the enzymatic hydrolysis conditions of the protein isolates were optimized through single-factor experiments. Protein hydrolysates were used to produce Antarctic krill peptides (AKP) through ceramic membrane microfiltration at various pressure levels. AKP-zinc chelates (AKP-Zn) were prepared by mixing AKP and zinc sulfate, subsequent to characterized the resulting complex. Finally, we examined the tolerance of AKP-Zn and soft candy containing AKP-Zn (SC-AKP-Zn) to simulated gastrointestinal digestion in vitro. The optimal enzyme mix was a 1:1 ratio of alkaline and flavored protease, with 4000 U/g enzymes, pH 7.5 and 3 h, and the ceramic membrane microfiltration increased the protein content in AKP by approximately 85.34 ± 3.54 %. Characterization showed that AKP effectively interacts zinc ions through bonding with oxygen and nitrogen atoms, helps the strength of AKP-Zn in various pH levels and simulated digestive systems. AKP-Zn and SC-AKP-Zn showed higher bioavailability compared to zinc sulfate and zinc gluconate. These results provide a solid theoretical foundation for creating ready-to-eat food products with AKP-Zn and offer new insights into the potential applications of Antarctic krill proteins.

Enzymatic hydrolysis preparation process of angiotensin-I converting enzyme (ACE) inhibitory peptides from Antarctic krill (Euphausia superba) was optimized and its stability was evaluated. Using the degreased Antarctic krill meal as the substrate and the ACE inhibition rate of enzymatic hydrolysates as the evaluation index, alkaline protease was selected as the optimal protease for preparing ACE inhibitory peptides from Antarctic krill among six types of proteases. The optimum enzymatic hydrolysis conditions were determined through single factor and response surface experiments, which were finally confirmed as follows: Enzymatic hydrolysis time of 3.4 h, material liquid ratio of 1:7 (g/mL) and enzyme dosage of 1.6%. Under these conditions, the ACE inhibition rate of enzymatic hydrolysates was 74.37%±0.87%. The obtained ACE inhibitory peptides exhibited good thermal stability at temperatures ranging from 20 ℃ to 100 ℃ and were relatively stable under neutral and weak alkaline conditions. The ACE inhibitory activity of the peptides decreased significantly under pH8.0 conditions (P

Antarctic krill (Euphausia superba) is the world's largest resource of animal proteins and is thought to be a high-quality resource for future marine healthy foods and functional products. Therefore, Antarctic krill was degreased and separately hydrolyzed using flavourzyme, pepsin, papain, and alcalase. Protein hydrolysate (AKH) of Antarctic krill prepared by trypsin showed the highest Ca-chelating rate under the optimized chelating conditions: a pH of 8.0, reaction time of 50 min, temperature of 50 °C, and material/calcium ratio of 1:15. Subsequently, fourteen Ca-chelating peptides were isolated from APK by ultrafiltration and a series of chromatographic methods and identified as AK, EAR, AEA, VERG, VAS, GPK, SP, GPKG, APRGH, GVPG, LEPGP, LEKGA, FPPGR, and GEPG with molecular weights of 217.27, 374.40, 289.29, 459.50, 275.30, 300.36, 202.21, 357.41, 536.59, 328.37, 511.58, 516.60, 572.66, and 358.35 Da, respectively. Among fourteen Ca-chelating peptides, VERG presented the highest Ca-chelating ability. Ultraviolet spectrum (UV), Fourier Transform Infrared (FTIR), and scanning electron microscope (SEM) analysis indicated that the VERG-Ca chelate had a dense granular structure because the N-H, C=O and -COOH groups of VERG combined with Ca2+. Moreover, the VERG-Ca chelate is stable in gastrointestinal digestion and can significantly improve Ca transport in Caco-2 cell monolayer experiments, but phytate could significantly reduce the absorption of Ca derived from the VERG-Ca chelate. Therefore, Ca-chelating peptides from protein hydrolysate of Antarctic krill possess the potential to serve as a Ca supplement in developing healthy foods. [ABSTRACT FROM AUTHOR]

High Fischer ratio oligopeptides (HFOs) have a variety of biological activities, but their mechanisms of action for anti-fatigue are less systematically studied at present. This study aimed to systematically evaluate the anti-fatigue efficacy of HFOs from Antarctic krill (HFOs-AK) and explore its mechanism of action through establishing the fatigue model of endurance swimming in mice. Therefore, according to the comparison with the endurance swimming model group, HFOs-AK were able to dose-dependently prolong the endurance swimming time, reduce the levels of the metabolites (lactic acid, blood urea nitrogen, and blood ammonia), increase the content of blood glucose, muscle glycogen, and liver glycogen, reduce lactate dehydrogenase and creatine kinase extravasation, and protect muscle tissue from damage in the endurance swimming mice. HFOs-AK were shown to enhance Na+-K+-ATPase and Ca2+-Mg2+-ATPase activities and increase ATP content in muscle tissue. Meanwhile, HFOs-AK also showed significantly antioxidant ability by increasing the activities of superoxide dismutase and glutathione peroxidase in the liver and decreasing the level of malondialdehyde. Further studies showed that HFOs-AK could regulate the body’s energy metabolism and thus exert its anti-fatigue effects by activating the AMPK signaling pathway and up-regulating the expression of p-AMPK and PGC-α proteins. Therefore, HFOs-AK can be used as an auxiliary functional dietary molecules to exert its good anti-fatigue activity and be applied to anti-fatigue functional foods.

The present study sought to evaluate the effect of basic amino acid (L-arginine (Arg), L-lysine (Lys), and L-histidine (His)) pretreatment on the quality of canned Antarctic krill. Additionally, the changes in krill meat at different pretreatment conditions and processing stages were measured. The Lys-pretreated krill meat exhibited 39.9% lower hardness, 19.8% lower chewiness, and 47.2% lower thiobarbituric acid reaction substances (TBARS) compared to the control group. The low-field nuclear magnetic resonance (LF-NMR) and the magnetic resonance imaging (MRI) analyses revealed that the Lys-pretreated krill meat showed a larger peak area of immobile water and a higher pseudo-color image brightness. The scanning electron microscopy (SEM) results showed that the microstructure of krill meat in the control group was broken and disordered, while the microstructural network of Lys-pretreated krill meat was more complete. This result indicated that Lys effectively improved the texture, water-holding capacity, and color of krill meat, protecting the microstructure and reducing the degree of oxidation. The sensory evaluation results showed that the Lys-treated canned Antarctic krill had a better flavor and texture than other canned products. Overall, Lys could be a potential regulatory strategy for effectively enhancing the quality of canned Antarctic krill. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba), an important group of marine zooplankton in the Southern Ocean, is the only fishery resource with extremely rich reserves and a low degree of development in the world. Antarctic krill is considered to be the greatest potential source of high-quality marine protein resources due to its abundant biomass and high protein content. Peptides prepared from Antarctic krill exhibit multiple physiological activities, including osteoporosis relief, glucose metabolism regulation, blood pressure amelioration, antioxidation, fatigue alleviation, and anti-aging activity. The production and development of Antarctic krill peptides has recently become an industry focus; however, existing research has been limited to the optimization of enzymatic hydrolysis processes, mainly involving the screening of suitable enzymes and the optimization of enzymatic hydrolysis conditions. Due to the high mineral content of Antarctic krill and the introduction of buffer salt in the process of enzymatic hydrolysis, current Antarctic krill peptides products have a high salt content, which leads to poor sensory experience and health risks. Hence, a process for desalination of Antarctic krill peptides is needed. Desalination methods for bioactive substances include dialysis, ultrafiltration, nanofiltration, electrodialysis, and macroporous resin adsorption. In the field of membrane separation, nanofiltration technology has been widely used in the purification, concentration, and desalination of food components owing to its advantages: low operation cost, no introduction of exogenous substances, no destruction of materials, and low rejection rate of monovalent ions. In order to improve product quality and ensure market expansion, the process of desalination of Antarctic krill peptides using nanofiltration technology was studied and optimized in this study.Defatted Antarctic krill powder was enzymatically hydrolyzed by alkaline protease to obtain Antarctic krill peptides for further use. The main factors affecting the desalination effect of Antarctic krill peptides (peptides concentration, nanofiltration pressure, and cycle times) were optimized by single-factor and orthogonal tests, using the desalination rate and protein loss rate as evaluation indexes. The experimental optimization ranges included peptides concentration of 1%~5%, nanofiltration pressure of 0.6~1.4 MPa and cycle times of 1~5. The salt contents of the samples before and after desalination were quantified using the silver nitrate titration method; the protein contents of the experimental samples were quantified using the Lowry colorimetric method. The quality indexes of the Antarctic krill peptides after treatment (including the basic nutritional composition: moisture content, protein content, ash content, salt content; amino acid composition; and molecular weight distribution) were systematically evaluated by the corresponding national standard methods. All experiments were performed in triplicate, and data were expressed as mean ± standard deviation. Excel 2016, IBM SPSS 20.0, and Origin 2018 were used for data analysis and chart drawing.Single-factor tests revealed that peptides concentration of 3%, nanofiltration pressure of 1.0 MPa and a cycle time of 2 could be selected as the design basis for the L9 (33) orthogonal test. The range value of the orthogonal test indicated that the degree of influence of the three factors on the desalination effect was as follows: peptides concentration > cycle times > nanofiltration pressure. The optimum conditions for desalting Antarctic krill peptides obtained by k value analysis were as follows: peptides concentration of 3.0%, nanofiltration pressure of 1.2 MPa and a cycle time of 3. Under the optimal condition, the desalination rate of the Antarctic krill peptides reached up to (86.35±2.11)%, and the protein loss rate was controlled at (9.10±0.35)%, demonstrating the feasibility of the process. The salt content of the Antarctic krill peptides after desalination was reduced to (1.14±0.12)% and the protein content was (92.73±2.29)%. The molecular weights of the Antarctic krill peptides after desalination were mainly distributed between 189 Da and 6500 Da, of which the proportion of peptides with molecular weight less than 3000 Da was (88.91±2.19)%, conforming to the molecular weight distribution range of bioactive peptides. The amount of essential amino acids in the Antarctic krill peptides after desalination accounted for (40.06±0.10)% of the total amino acids, and the ratio of essential amino acids to nonessential amino acids was (66.82±0.28)%. The amino acid compositions of the Antarctic krill peptides after desalination were ideal and met the standard stipulated by the FAO/WHO. The established nanofiltration desalination process presented good treatment effects, and the obtained peptides were of good quality and high nutritional value.The production of Antarctic krill protein-related products may be the next key development for the processing industry, since the sole high-value products of Antarctic krill at present are Antarctic krill oil and its derivatives. The established nanofiltration desalination process has practical application value and would provide technical support for the development of high-quality Antarctic krill peptides. This research provides scientific support for the efficient utilization of Antarctic krill resources.

旨在为南极磷虾渔业捕捞以及陆基精准加工利用提供科学指导，研究了不同体长南极磷虾的脂质组成差异。以脂质含量、甘油酯含量、磷脂含量、胆固醇含量、游离脂肪酸含量、磷脂组成和脂肪酸组成为评价指标，结合多元统计分析技术比较不同体长（＜30 mm、30～40 mm、40～50 mm、＞50 mm）南极磷虾脂质组成的差异。结果显示：不同体长南极磷虾脂质含量占干基的（17.57±2.43）%～（24.35±0.31）%；甘油酯和磷脂是主要的脂质组分，分别占脂质的（41.40±1.22）%～（43.54±2.02）%和（39.70±0.70）%～（41.89±2.69）%；磷脂主要由磷脂酰胆碱（PC）、磷脂酰乙醇胺（PE）和溶血磷脂酰胆碱（LPC）组成，分别占总磷脂的（8004±0.73）%～（85.94±0.58）%、（13.13±0.59）%～（19.17±0.75）%、（0.79±0.05）%～（116±0.03）%；脂质中主要脂肪酸为C14∶ 0、C16∶ 0、C18∶ 1、C20∶ 5（EPA）、C22∶ 6（DHA），分别占总脂肪酸含量的（12.00±0.37）%~(12.85±0.15)%、（24.64±0.15）%～（27.11±0.16）%、（13.21±0.35）%～（15.09±0.14）%、（18.41±0.18）%～（18.86±0.56）%、（10.17±0.18）%～（12.84±0.16）%；不同体长南极磷虾的脂质含量、磷脂中PC和PE比例、脂肪酸中C16∶ 0、C18∶ 1和DHA比例等总体差异显著（p＜0.05）。结合聚类分析和主成分分析，根据体长可将南极磷虾样品明显区分为＜30 mm、30～40 mm、＞40 mm 3大类。研究结果表明南极磷虾的脂质组成与其体长关系显著。旨在为南极磷虾渔业捕捞以及陆基精准加工利用提供科学指导，研究了不同体长南极磷虾的脂质组成差异。以脂质含量、甘油酯含量、磷脂含量、胆固醇含量、游离脂肪酸含量、磷脂组成和脂肪酸组成为评价指标，结合多元统计分析技术比较不同体长（＜30 mm、30～40 mm、40～50 mm、＞50 mm）南极磷虾脂质组成的差异。结果显示：不同体长南极磷虾脂质含量占干基的（17.57±2.43）%～（24.35±0.31）%；甘油酯和磷脂是主要的脂质组分，分别占脂质的（41.40±1.22）%～（43.54±2.02）%和（39.70±0.70）%～（41.89±2.69）%；磷脂主要由磷脂酰胆碱（PC）、磷脂酰乙醇胺（PE）和溶血磷脂酰胆碱（LPC）组成，分别占总磷脂的（8004±0.73）%～（85.94±0.58）%、（13.13±0.59）%～（19.17±0.75）%、（0.79±0.05）%～（116±0.03）%；脂质中主要脂肪酸为C14∶ 0、C16∶ 0、C18∶ 1、C20∶ 5（EPA）、C22∶ 6（DHA），分别占总脂肪酸含量的（12.00±0.37）%~(12.85±0.15)%、（24.64±0.15）%～（27.11±0.16）%、（13.21±0.35）%～（15.09±0.14）%、（18.41±0.18）%～（18.86±0.56）%、（10.17±0.18）%～（12.84±0.16）%；不同体长南极磷虾的脂质含量、磷脂中PC和PE比例、脂肪酸中C16∶ 0、C18∶ 1和DHA比例等总体差异显著（p＜0.05）。结合聚类分析和主成分分析，根据体长可将南极磷虾样品明显区分为＜30 mm、30～40 mm、＞40 mm 3大类。研究结果表明南极磷虾的脂质组成与其体长关系显著。 The lipid compositions of Antarctic krill (Euphausia superba) with different body lengths were comparatively studied to provide scientific guidance for the fishery harvesting and land-based accurate utilization of the Antarctic krill. Antarctic krill samples were divided into four groups according to the body lengths (＜30 mm, 30-40 mm, 40-50 mm, ＞50 mm), and the lipid content, glyceride content, phospholipid content, cholesterol content, free fatty acid content, phospholipid composition as well as fatty acid composition of the samples were used as evalution indicators, the differences of the lipid compositions of the four group samples were compared combined with multivariate statistical analysis technology. The results showed that the lipid contents of the Antarctic krill with different body lengths were (17.57±2.43)% -(24.35±0.31)% of dry basis. Glyceride and phospholipid were the main lipid components, accounting for (41.40±1.22)%-(43.54±2.02)% and (39.70±0.70)%-(41.89±2.69)% of the lipid, respectively. Phospholipid was mainly composed of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and lysophosphatidylcholine(LPC), accounting for (80.04±0.73)%-(85.94±0.58)%, (13.13±0.59)%-(19.17±0.75)%, and (0.79±005)%-(1.16±0.03)% of the total phospholipid, respectively. The fatty acids of the lipid were mainly C14∶ 0, C16∶ 0, C18∶ 1, C20∶ 5 (EPA) and C22∶ 6 (DHA), accounting for (12.00±0.34)%-(12.85±0.15)%, (24.64±0.15)%-(27.11±0.16)%, (13.21±0.35)%-(15.09±0.14)%, (18.41±0.18)%-(18.86±0.56)%, (10.17±0.18)%-(12.84±0.16)% of the total fatty acids, respectively. There were overall significant differences in the lipid contents, the ratios of PC and PE in phospholipid, the ratios of C16∶ 0, C18∶ 1 and DHA in total fatty acids of the Antarctic krill with different body lengths (p＜0.05). Antarctic krill samples could be obviously divided into three categories ＜30 mm,30-40 mm,＞40 mm by the cluster analysis and principal component analysis according to body length. In conclusion, the lipid composition of Antarctic krill is significantly related to the body length.

[Display omitted] • NIAAA method was used to establish a mouse model of alcoholic liver injury (ALI). • Protective mechanism of high Fischer ratio oligopeptides from Antarctic krill (HFOPs-AK) on ALI mice was studied. • HFOPs-AK could modulate lipid metabolism, anti-inflammatory and antioxidant effects. • Protective mechanism of HFOPs-AK is to regulate the AMPK/Nrf2/IκBα signaling pathways. In this study, we devoted attention to the hepatoprotective functions of high Fischer ratio oligopeptides (HFOPs) from Antarctic krill (HFOPs-AK) on alcoholic liver injury of mice. The results indicated that HFOPs-AK significantly improved the pathological state of mice liver and kidney, reduced alanine aminotransferase (ALT) and aspartate transaminase (AST) activities, regulated lipid metabolism, and alleviated the burden on the liver. In addition, HFOPs-AK depicted anti-inflammatory and antioxidant effects by reducing tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) contents and increasing superoxide dismutase (SOD) and catalase (CAT) activities to reduce malondialdehyde (MDA) level. The hepatoprotective mechanism of HFOPs-AK was further revealed by quantitative reverse transcription PCR (RT-qPCR) analysis, and the results proved that HFOPs-AK had the ability to stimulate the adenosine 5'-monophosphate-activated protein kinase (AMPK)/nuclearrespiratoty factor 2 (Nrf2)/inhibitor of NF-κB (IκBα) signaling pathways, thereby regulating the expression levels of downstream factors. The activation of these signaling pathways is essential for the regulation of lipid metabolism as well as anti-inflammatory and antioxidant functions. This finding offers a novel approach for the development of innovative hepatoprotective agents utilizing HFOPs-AK. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba) is the world’s largest resource of animal proteins and is thought to be a high-quality resource for future marine healthy foods and functional products. Therefore, Antarctic krill was degreased and separately hydrolyzed using flavourzyme, pepsin, papain, and alcalase. Protein hydrolysate (AKH) of Antarctic krill prepared by trypsin showed the highest Ca-chelating rate under the optimized chelating conditions: a pH of 8.0, reaction time of 50 min, temperature of 50 °C, and material/calcium ratio of 1:15. Subsequently, fourteen Ca-chelating peptides were isolated from APK by ultrafiltration and a series of chromatographic methods and identified as AK, EAR, AEA, VERG, VAS, GPK, SP, GPKG, APRGH, GVPG, LEPGP, LEKGA, FPPGR, and GEPG with molecular weights of 217.27, 374.40, 289.29, 459.50, 275.30, 300.36, 202.21, 357.41, 536.59, 328.37, 511.58, 516.60, 572.66, and 358.35 Da, respectively. Among fourteen Ca-chelating peptides, VERG presented the highest Ca-chelating ability. Ultraviolet spectrum (UV), Fourier Transform Infrared (FTIR), and scanning electron microscope (SEM) analysis indicated that the VERG-Ca chelate had a dense granular structure because the N-H, C=O and -COOH groups of VERG combined with Ca2+. Moreover, the VERG-Ca chelate is stable in gastrointestinal digestion and can significantly improve Ca transport in Caco-2 cell monolayer experiments, but phytate could significantly reduce the absorption of Ca derived from the VERG-Ca chelate. Therefore, Ca-chelating peptides from protein hydrolysate of Antarctic krill possess the potential to serve as a Ca supplement in developing healthy foods.

Summary: The aim of the study was to investigate the autolysis phenomenon in Antarctic krill during the buffer storage under refrigeration (after harvesting and before processing), groups of whole krill (WK) and of tail (TL) were stored at 4 °C and evaluated at 0, 6, 24, 36 and 48 h. The changes observed in visual appearance, sensory evaluation and meat yield jointly proved that severe autolysis had occurred, and this was more pronounced in the WK group than in the TL group. Meanwhile, the hardness of WK and TL groups decreased by 51.2% and 23.3%, and the shear force also decreased significantly from 3.26 N to 1.77 N and 2.28 N, respectively. Combined with the disrupted muscle microstructure and the conversion of bound water to immobilised water, the muscle tissue was found to be less stable as affected by the autolysis. The properties and structure of myofibrillar protein were dramatically changed, as revealed by the increased myofibril fragmentation index, decreased sulfhydryl content, and fluorescence intensity. Therefore, Antarctic krill can be deemed susceptible to autolysis during the buffer storage, especially whole krill. The information gained in this study improves our understanding of the effect of autolysis on muscle stability and its protein basis in Antarctic krill. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba) is an important source of biomass and high-quality protein. However, heat treatment negatively impacts the quality of Antarctic krill and compromises its utilization in the food industry. This study aimed to investigate the mechanisms underlying changes in Antarctic krill meat characteristics and physicochemical properties treated at different temperatures and holding times. Our findings indicated that hardness and cooking loss of Antarctic krill meat increased dramatically at higher temperatures and holding times. The low-field nuclear magnetic resonance (LF-NMR) analysis revealed that the loss of immobilized water increased, whereas the SDS-PAGE analysis showed that the content of myosin heavy chain decreased significantly and that protein degradation occurred. Fourier transform infrared spectroscopy (FT-IR) and intrinsic fluorescence spectra suggested that α-helix motifs were transformed into β-sheets and that more hydrophobic groups were exposed. The scanning electron microscopy (SEM) results showed that Antarctic krill meat formed corrugated folded regions after heat treatment without forming a three-dimensional water-entrapped structure, which led to significant water loss, resulting in rapid deterioration of Antarctic krill meat. These results provide the basis for a deeper understanding of the processing characteristics of Antarctic krill meat. [ABSTRACT FROM AUTHOR]

BACKGROUND: The quality deterioration of Antarctic krill (Euphausia superba) after thermal processing limits its industrial application. This study sought to improve the texture characteristics of Antarctic krill after heat treatment through pre‐soaking using l‐lysine (Lys) solution and sodium tripolyphosphate (STPP). Moreover, the effects of Lys on heat‐treated Antarctic krill were explored. RESULTS: Lys significantly reduced the cooking loss and improved the texture characteristics of Antarctic krill during heat treatment. The low‐field nuclear magnetic resonance results showed that Lys reduced the water loss of Antarctic krill during heat treatment. Additionally, the surface hydrophobicity, Fourier transform infrared spectroscopy, and endogenous fluorescence spectroscopy results showed that Lys could inhibit the structural damage of Antarctic krill protein under the thermal denaturation condition and enhance the thermal stability of the protein. The scanning electron microscopy results showed that Lys could protect the structural integrity of Antarctic krill muscle fibers during heat treatment. CONCLUSION: The cooking loss in the Lys added groups was better than the sodium tripolyphosphate added group, and 2.0% Lys solution could minimize the cooking loss of Antarctic krill. The secondary and tertiary structures of the Antarctic krill protein were actively protected by Lys during heat treatment. Overall, the study will provide insights into the application of Lys in the food industry as a natural additive and an alternative to phosphate. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In Antarctica, abundant consumers rely on Antarctic krill for food, but krill are also the subject of a commercial fishery. The fishery overlaps in time and space with the foraging areas of these consumers, thus potential competition between krill fisheries and krill consumers is a major management concern. The fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources with an ecosystem approach, according to which fishing should not interfere with either the population growth of krill, or krill-dependent consumers. Krill catches have become increasingly spatially concentrated in a small number of hotspots, raising concerns about how local depletion of krill impacts consumers. Such concentrated fishing demonstrates that there is a mismatch between the spatial and temporal scale at which krill fisheries are currently managed, and that at which fisheries operate and consumers forage. Information on the seasonal dynamics of predator abundance and their foraging behaviour is fundamental to future precautionary management of the krill fishery. We analysed the spatiotemporal distribution of two major krill consumers – humpback and minke whales – and that of krill fishing, off the Western Antarctic Peninsula. We used whale tracking data (58 humpback whale tracks and 19 minke whale tracks) to develop spatial random forest models predicting the monthly distribution of whale foraging areas from January-July. Using these predictions, we calculated spatiotemporally-explicit geographic overlap between whales and fisheries, the latter represented by krill fishing effort and catch data. Over the krill fishing season, fishing effort and catch hotspots shifted to the southwest, into the Bransfield Strait where effort and catch was highest. Predicted humpback whale foraging areas increased in the Bransfield Strait over the same period, while predicted minke whale foraging areas showed an opposite trend. For both we predicted a whale-fishing interaction hotspot in the Bransfield Strait, strongest in April and May. Our results illustrate the fine spatial scale of likely interactions between baleen whales and the krill fishery, and their concentration over the season, underlining the need for fishery management more closely aligned to the spatiotemporal scale of likely predator-fishery interactions.

The aim of this study was to purify and identify antioxidant peptides from Antarctic Krill hydrolysate and elucidate their cytoprotection mechanisms on H2O2-induced oxidative stress in Chang liver cells. Using ultrafiltration and chromatographic methods, twelve peptides were purified from the Antarctic Krill hydrolysate and identified as AEK, VEK, VEKT, AEKTR, IEN, VEKGK, LKPGN, IEKG, LQP, ATH, IEKT, and IDSQ. LKPGN and LQP exhibited high scavenging activities on HO·, DPPH·, and O2−·. Moreover, LKPGN and LQP can protect Chang liver cells against H2O2-induced oxidative stress by increasing cell viability and decreasing the apoptosis rate. The mechanism indicated that LKPGN and LQP could concentration-dependently increase the antioxidant enzyme (SOD and GSH-PX) levels to scavenge excess ROS, increase mitochondrial membrane potential, and decrease DNA damage and MDA content. Therefore, LKPGN and LQP from Antarctic Krill could serve as promising candidates applied in health-promoting products.

For utilizing the largest source of marine proteins, Antarctic krill (Euphausia superba) proteins were defatted and hydrolyzed separately using pepsin, alcalase, papain, trypsin, and netrase, and alcalase hydrolysate (EPAH) showed the highest DPPH radical (DPPH·) and hydroxyl radical (HO·) scavenging activity among five hydrolysates. Using ultrafiltration and chromatography methods, fifteen antioxidant peptides were purified from EPAH and identified as Asn-Gln-Met (NQM), Trp-Phe-Pro-Met (WFPM), Gln-Asn-Pro-Thr (QNPT), Tyr-Met-Asn-Phe (YMNF), Ser-Gly-Pro-Ala (SGPA), Ser-Leu-Pro-Tyr (SLPY), Gln-Tyr-Pro-Pro-Met-Gln-Tyr (QYPPMQY), Glu-Tyr-Glu-Ala (EYEA), Asn-Trp-Asp-Asp-Met-Arg-Ile-Val-Ala-Val (NWDDMRIVAV), Trp-Asp-Asp-Met-Glu-Arg-Leu-Val-Met-Ile (WDDMERLVMI), Asn-Trp-Asp-Asp-Met-Glu-Pro-Ser-Phe (NWD-DMEPSF), Asn-Gly-Pro-Asp-Pro-Arg-Pro-Ser-Gln-Gln (NGPDPRPSQQ), Ala-Phe-Leu-Trp-Asn (AFLWA), Asn-Val-Pro-Asp-Met (NVPDM), and Thr-Phe-Pro-Ile-Tyr-Asp-Tyr-Pro-Gln (TFPIYDPQ), respectively, using a protein sequencer and ESI/MS. Among fifteen antioxidant peptides, SLPY, QYPPMQY and EYEA showed the highest scavenging activities on DPPH· (EC50 values of 1.18 ± 0.036, 1.547 ± 0.150, and 1.372 ± 0.274 mg/mL, respectively), HO· (EC50 values of 0.826 ± 0.027, 1.022 ± 0.058, and 0.946 ± 0.011 mg/mL, respectively), and superoxide anion radical (EC50 values of 0.789 ± 0.079, 0.913 ± 0.007, and 0.793 ± 0.056 mg/mL, respectively). Moreover, SLPY, QYPPMQY and EYEA showed strong reducing power, protective capability against H2O2-damaged plasmid DNA, and lipid peroxidation inhibition ability. Furthermore, SLPY, QYPPMQY, and EYEA had high stability under temperatures lower than 80 °C, pH values ranged from 6–8, and simulated GI digestion for 180 min. The results showed that fifteen antioxidant peptides from alcalase hydrolysate of Antarctic krill proteins, especially SLPY, QYPPMQY and EYEA, might serve as effective antioxidant agents applied in food and health products.

In this report, eight antihypertensive peptides were isolated from protein hydrolysate of Antarctic krill (Euphausia superba) using ultrafiltration and chromatography consecutively, and their sequences were identified as Trp-Phe, Tyr-Arg-Lys-Glu-Arg, Tyr-Arg-Lys, Val-Asp, Tyr-Lys-Asp, Phe-Gln-Lys, Phe-Ala-Ser, and Phe-Arg-Lys-Glu. The IC 50 values of Trp-Phe (0.32 ± 0.05 mg/mL) and Phe-Ala-Ser (0.15 ± 0.02 mg/mL) on ACE inhibitory activity were significantly (p ≤.05) lower than those of the other six peptides. Furthermore, Trp-Phe, Tyr-Arg-Lys, Phe-Gln-Lys, and Phe-Ala-Ser did not only increase the nitric oxide (NO) concentration and decreased the content of endothelin-1 (ET-1) in the medium of human umbilical vein endothelial cells (HUVECs) in a dose-dependent manner after 24 h, but also significantly reversed the decreased production of NO in the presence of 0.5 μM norepinephrine and the effect of NE on ET-1 production. These results indicate that the isolated antihypertensive peptides can correct the endothelial cell dysfunction induced by norepinephrine. Unlabelled Image • Protein hydrolysate (AKH) of Antarctic Krill was prepared using trypsin. • Eight antihypertensive peptides from AKH were identified. • FAS with IC 50 of 0.15 ± 0.02 mg/mL showed the highest ACE inhibitory activity. • WF, VRK, FQK, and FAS can regulate the levels of NO and ET-1 in the medium of HUVEC. • WF, VRK, FQK, and FAS can correct the endothelial cell dysfunction. [ABSTRACT FROM AUTHOR]

The world-famous Antarctic krill (Euphausia superba) plays a fundamental role in the Antarctic food chain. It resides in cold environments with the most abundant biomass to support the Antarctic ecology and fisheries. Here, we performed the first genome survey of the Antarctic krill, with genomic evidence for its estimated genome size of 42.1 gigabases (Gb). Such a large genome, however, is beyond our present capability to obtain a good assembly, although our sequencing data are a valuable genetic resource for subsequent polar biomedical research. We extracted 13 typical protein-coding gene sequences of the mitochondrial genome and analyzed simple sequence repeats (SSRs), which are useful for species identification and origin determination. Meanwhile, we conducted a high-throughput comparative identification of putative antimicrobial peptides (AMPs) and antihypertensive peptides (AHTPs) from whole-body transcriptomes of the Antarctic krill and its well-known counterpart, the whiteleg shrimp (Penaeus vannamei; resident in warm waters). Related data revealed that AMPs/AMP precursors and AHTPs were generally conserved, with interesting variations between the two crustacean species. In summary, as the first report of estimated genome size of the Antarctic krill, our present genome survey data provide a foundation for further biological research into this polar species. Our preliminary investigations on bioactive peptides will bring a new perspective for the in-depth development of novel marine drugs.

Krill oils (KOs) were prepared using different extraction methods (hexane and supercritical carbon dioxide), different materials (heat-dried krill powder, freeze-dried krill powder, and freeze-dried krill tail meat powder), and different standing times during hexane extraction. The fluoride concentrations in the KOs were positively correlated with the protein concentrations. Absorbents were employed to remove fluoride from KO. Activated clay achieved the highest fluoride removal rate (70.66%), followed by calcium oxide (14.49%), activated carbon (11.97%), calcium chloride (9.32%), activated alumina (0.94%), and chitosan (0.52%). Meanwhile, the protein removal rates of the above absorbents were positively correlated with the fluoride removal rates. [ABSTRACT FROM PUBLISHER]

Antarctic krill (Euphausia superba) has a very high economic value due to its enormous production, higher protein content, and nutritional value. This study presents a detailed optimization of the analysis of volatile flavor compounds from Antarctic krill by combining headspace solid-phase microextraction (HS-SPME) as the extracting method and gas chromatography/mass spectrometry (GC-MS) as the analysis. An optimal solid-phase microextraction (SPME) fiber was selected, and the microextraction conditions were optimized using the response surface method (RSM). The Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) fiber showed the highest extraction efficiency and was selected for further optimization of extraction temperature, extraction time, and sodium chloride concentration. Forty-two types of volatile substances producing characteristic flavors were detected, seven of which contributed significantly to the flavor of Antarctic krill. Ethers, pyrazine, and aldehyde compounds contribute to the main flavor of Antarctic krill. The compounds 2-ethyl-3, 5-dimethyl-pyrazine, 2, 3, 5-trimethyl-6-ethylpyrazine, and 3-ethyl-2, 5-dimethyl-pyrazine produce the roasted flavor and the characteristic nutty odor. Moreover (E, Z)-2, 6-nonadienal adds a cucumber fragrance. The compounds 3-methyl-butanal and 3-methional play an important role in determining the overall flavor. [ABSTRACT FROM AUTHOR]

BACKGROUND Despite their abundance, Antarctic krill are underutilized because of numerous difficulties in their commercial processing. Ideally, fermentation technology can be applied to transform them into a popular condiment. In addition to the exploration of protease properties, the present study aimed to evaluate proteinase activity, pH, amino nitrogen, and histamine formation during fermentation at different temperatures and salt treatments. RESULTS Even though the activity of Antarctic krill protease reached a maximum at 40 °C and pH 7, it was stable at 30 °C and pH 7-9. Among the metal ions tested, Ca2+, Mg2+ and K+ increased protease activity, in contrast to Zn2+ and Cu2+. Within each treatment, the highest protease activity and amino nitrogen content, as well as the lowest histamine level, were observed on day 12 of fermentation. Treatment at 35 °C with 180 g kg-1 salt led to the production of maximum amino nitrogen (0.0352 g kg-1) and low histamine (≤0.0497 g kg-1). CONCLUSION Krill paste fermented for 12 days at 35 °C with 180 g kg-1 salt exhibited the optimal quality and properties, suggesting an efficient method for fermentation of Antarctic krill and other aquatic resources. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• Impact of climate shift in 2000 on krill recruitments at two regions of the Antarctic. • At Antarctic Peninsula, krill offset unfavorable winter for recruits with favorable fall. • At South Georgia, krill recruit source changed from Antarctic Peninsula to Scotia Sea. • Recruit adaptability to the climate shift resulted in maintaining krill stock levels. We examined how the climate regime shift around 2000 affected Antarctic krill recruitment variability at the North Antarctic Peninsula (NAP) and South Georgia (SG) during the period of 1990s through to 2000s. We used sea surface temperature (SST) as a proxy of the monthly sea ice extent and related it to the recruitment index (proportion of 1-year-old krill) of each succeeding year for NAP and SG by examining the correlation of the time series before and after 2000. For NAP, recruitment index was negatively correlated with winter SST at NAP in the 1990s but with autumn SST in the 2000s, suggesting that good recruitment was supported by extensive winter sea-ice in the 1990s but by extensive autumn sea-ice in the 2000s. This was attributed to the regime shift featured by winter warming and autumn cooling after 2000. For SG, recruitment was negatively correlated with winter SST at NAP in the 1990s but positively correlated with autumn SST in the southern Scotia Sea (SSS) in the 2000s. According to particle tracking experiment from NAP to SG in relation to the sea-ice extent and position of SACCF (Southern Antarctic Circumpolar Current Front), less sea-ice extent in 2000s meant less larvae distributing as north as SACCF, resulting in much fewer larval being transported to SG. Hence, we hypothesized that the regime shift weakened the connection between NAP and SG, but instead SSS became the main driver of recruitment at SG. We presume the krill population demonstrated adaptability to the regime shift by offsetting the unfavorable winter condition with the favorable autumn condition at NAP and for SG, replacing the source of recruits with those closer to it. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba) has a very high economic value due to its enormous production, higher protein content, and nutritional value. This study presents a detailed optimization of the analysis of volatile flavor compounds from Antarctic krill by combining headspace solid-phase microextraction (HS-SPME) as the extracting method and gas chromatography/mass spectrometry (GC-MS) as the analysis. An optimal solid-phase microextraction (SPME) fiber was selected, and the microextraction conditions were optimized using the response surface method (RSM). The Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) fiber showed the highest extraction efficiency and was selected for further optimization of extraction temperature, extraction time, and sodium chloride concentration. Forty-two types of volatile substances producing characteristic flavors were detected, seven of which contributed significantly to the flavor of Antarctic krill. Ethers, pyrazine, and aldehyde compounds contribute to the main flavor of Antarctic krill. The compounds 2-ethyl-3, 5-dimethyl-pyrazine, 2, 3, 5-trimethyl-6-ethyl-pyrazine, and 3-ethyl-2, 5-dimethyl- pyrazine produce the roasted flavor and the characteristic nutty odor. Moreover (E, Z)-2, 6-nonadienal adds a cucumber fragrance. The compounds 3-methyl-butanal and 3-methional play an important role in determining the overall flavor. [ABSTRACT FROM AUTHOR]

Decision-makers charged with implementing ecosystem-based management (EBM) rely on scientists to predict the consequences of decisions relating to multiple, potentially conflicting, objectives. Such predictions are inherently uncertain, and this can be a barrier to decision-making. The Convention on the Conservation of Antarctic Marine Living Resources requires managers of Southern Ocean fisheries to sustain the productivity of target stocks, the health and resilience of the ecosystem, and the performance of the fisheries themselves. The managers of the Antarctic krill fishery in the Scotia Sea and southern Drake Passage have requested advice on candidate management measures consisting of a regional catch limit and options for subdividing this among smaller areas. We developed a spatially resolved model that simulates krill-predator-fishery interactions and reproduces a plausible representation of past dynamics. We worked with experts and stakeholders to identify (1) key uncertainties affecting our ability to predict ecosystem state; (2) illustrative reference points that represent the management objectives; and (3) a clear and simple way of conveying our results to decision-makers. We developed four scenarios that bracket the key uncertainties and evaluated candidate management measures in each of these scenarios using multiple stochastic simulations. The model emphasizes uncertainty and simulates multiple ecosystem components relating to diverse objectives. We summarize the potentially complex results as estimates of the risk that each illustrative objective will not be achieved (i.e., of the state being outside the range specified by the reference point). This approach allows direct comparisons between objectives. It also demonstrates that a candid appraisal of uncertainty, in the form of risk estimates, can be an aid, rather than a barrier, to understanding and using ecosystem model predictions. Management measures that reduce coastal fishing, relative to oceanic fishing, apparently reduce risks to both the fishery and the ecosystem. However, alternative reference points could alter the perceived risks, so further stakeholder involvement is needed to identify risk metrics that appropriately represent their objectives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Twelve antioxidant peptides were purified from hydrolysate of Antarctic Krill. • LKPGN and LQP showed high radical scavenging and cytoprotective activities. • LKPGN and LQP could increase cell viability, antioxidant enzyme levels and MMP. • LKPGN and LQP could reduce the ROS content, MDA levels, and apoptosis rate. • LKPGN and LQP could protect DNA from H 2 O 2 -induced oxidative damage. The aim of this study was to purify and identify antioxidant peptides from Antarctic Krill hydrolysate and elucidate their cytoprotection mechanisms on H 2 O 2 -induced oxidative stress in Chang liver cells. Using ultrafiltration and chromatographic methods, twelve peptides were purified from the Antarctic Krill hydrolysate and identified as AEK, VEK, VEKT, AEKTR, IEN, VEKGK, LKPGN, IEKG, LQP, ATH, IEKT, and IDSQ. LKPGN and LQP exhibited high scavenging activities on HO, DPPH, and O 2 − . Moreover, LKPGN and LQP can protect Chang liver cells against H 2 O 2 -induced oxidative stress by increasing cell viability and decreasing the apoptosis rate. The mechanism indicated that LKPGN and LQP could concentration-dependently increase the antioxidant enzyme (SOD and GSH-PX) levels to scavenge excess ROS, increase mitochondrial membrane potential, and decrease DNA damage and MDA content. Therefore, LKPGN and LQP from Antarctic Krill could serve as promising candidates applied in health-promoting products. [ABSTRACT FROM AUTHOR]

For utilizing the largest source of marine proteins, Antarctic krill (Euphausia superba) proteins were defatted and hydrolyzed separately using pepsin, alcalase, papain, trypsin, and netrase, and alcalase hydrolysate (EPAH) showed the highest DPPH radical (DPPH·) and hydroxyl radical (HO·) scavenging activity among five hydrolysates. Using ultrafiltration and chromatography methods, fifteen antioxidant peptides were purified from EPAH and identified as Asn-Gln-Met (NQM), Trp-Phe-Pro-Met (WFPM), Gln-Asn-Pro-Thr (QNPT), Tyr-Met-Asn-Phe (YMNF), Ser-Gly-Pro-Ala (SGPA), Ser-Leu-Pro-Tyr (SLPY), Gln-Tyr-Pro-Pro-Met-Gln-Tyr (QYPPMQY), Glu-Tyr-Glu-Ala (EYEA), Asn-Trp-Asp-Asp-Met-Arg-Ile-Val-Ala-Val (NWDDMRIVAV), Trp-Asp-Asp-Met-Glu-Arg-Leu-Val-Met-Ile (WDDMERLVMI), Asn-Trp-Asp-Asp-Met-Glu-Pro-Ser-Phe (NWD-DMEPSF), Asn-Gly-Pro-Asp-Pro-Arg-Pro-Ser-Gln-Gln (NGPDPRPSQQ), Ala-Phe-Leu-Trp-Asn (AFLWA), Asn-Val-Pro-Asp-Met (NVPDM), and Thr-Phe-Pro-Ile-Tyr-Asp-Tyr-Pro-Gln (TFPIYDPQ), respectively, using a protein sequencer and ESI/MS. Among fifteen antioxidant peptides, SLPY, QYPPMQY and EYEA showed the highest scavenging activities on DPPH· (EC50 values of 1.18 ± 0.036, 1.547 ± 0.150, and 1.372 ± 0.274 mg/mL, respectively), HO· (EC50 values of 0.826 ± 0.027, 1.022 ± 0.058, and 0.946 ± 0.011 mg/mL, respectively), and superoxide anion radical (EC50 values of 0.789 ± 0.079, 0.913 ± 0.007, and 0.793 ± 0.056 mg/mL, respectively). Moreover, SLPY, QYPPMQY and EYEA showed strong reducing power, protective capability against H2O2-damaged plasmid DNA, and lipid peroxidation inhibition ability. Furthermore, SLPY, QYPPMQY, and EYEA had high stability under temperatures lower than 80 °C, pH values ranged from 6–8, and simulated GI digestion for 180 min. The results showed that fifteen antioxidant peptides from alcalase hydrolysate of Antarctic krill proteins, especially SLPY, QYPPMQY and EYEA, might serve as effective antioxidant agents applied in food and health products. [ABSTRACT FROM AUTHOR]

• The preparation process of Antarctic krill peptides-zinc chelate was optimized. • Chelating sites were carboxyl oxygen and amino nitrogen atoms of the peptides. • Differences of characterization between peptides and peptides-zinc chelate were given. • Chelate showed excellent stability against to various pH and gastrointestinal digestion. In the study, a novel kind of peptides-zinc (AKP-Zn) chelate was obtained using the Antarctic krill (Euphausia superba) peptides (AKP) as raw material, the reaction was carried out with the mass ratio of the AKP to ZnSO 4 ·7H 2 O of 1:2 at pH 6.0 and 60 °C for 10 min. The structure and composition of the AKP, including particle size, Zeta potential, molecular weight distribution, amino acid composition, microstructure and surface elemental composition, changed significantly after chelating with zinc. The result of Fourier transform infrared spectroscopy indicated that zinc could be chelated by carboxyl oxygen and amino nitrogen atoms of the AKP. Furthermore, compared with zinc sulfate and zinc gluconate, the AKP-Zn chelate was more stable at various pH conditions and the simulated gastrointestinal digestion experiment. These findings would provide a scientific basis for developing new zinc supplements and the high-value utilization of Antarctic krill protein resource. [ABSTRACT FROM AUTHOR]

The world-famous Antarctic krill (Euphausia superba) plays a fundamental role in the Antarctic food chain. It resides in cold environments with the most abundant biomass to support the Antarctic ecology and fisheries. Here, we performed the first genome survey of the Antarctic krill, with genomic evidence for its estimated genome size of 42.1 gigabases (Gb). Such a large genome, however, is beyond our present capability to obtain a good assembly, although our sequencing data are a valuable genetic resource for subsequent polar biomedical research. We extracted 13 typical protein-coding gene sequences of the mitochondrial genome and analyzed simple sequence repeats (SSRs), which are useful for species identification and origin determination. Meanwhile, we conducted a high-throughput comparative identification of putative antimicrobial peptides (AMPs) and antihypertensive peptides (AHTPs) from whole-body transcriptomes of the Antarctic krill and its well-known counterpart, the whiteleg shrimp (Penaeus vannamei; resident in warm waters). Related data revealed that AMPs/AMP precursors and AHTPs were generally conserved, with interesting variations between the two crustacean species. In summary, as the first report of estimated genome size of the Antarctic krill, our present genome survey data provide a foundation for further biological research into this polar species. Our preliminary investigations on bioactive peptides will bring a new perspective for the in-depth development of novel marine drugs. [ABSTRACT FROM AUTHOR]

In this work, alcalase and flavorzyme were chosen as the hydrolase for preparing high Fischer ratio oligopeptides from Antarctic krill (Euphausia superba) (HFP) using sequential enzyme hydrolysis process, and their hydrolysis conditions were optimized using single factor experiment. According to the Fischer ratio, granular activated carbon of XHJ‐200 (200 mesh) showed the best way to remove aromatic amino acids and its optimal parameters were pH value of 6.0, adsorption time of 2.5 hr, temperature of 25°C, and solid–liquid ratio of 1:20. The Fischer ratio and average molecular weight of HFP were 21.12 (>20) and 779.9 Da, respectively. In addition, the peptide profile of HFP was established using RP‐HPLC and 23 oligopeptides isolated from HFP including 6 dipeptides, 9 tripeptides, 3 tetrapeptides, and 5 pentapeptides were identified using protein amino acid sequence analyzer and mass spectrum. Furthermore, HFP exhibited high radical scavenging activity, reducing power, and lipid peroxidation inhibition capability. Practical applications: High Fischer ratio oligopeptides (HFO) is a kind of small peptide mixture with the mole ratio of branched‐chain amino acids (BCAA) to aromatic amino acids (AAA) higher than 20, which has drawn a great attention due to its great potential in clinical nutrition approaches for the treatment of liver disease when amino acid composition is out of proportion characterized by low levels of BCAA and high levels of AAA in the systemic blood. Antarctic krill is regarded as the largest animal protein resource for various food and pharmaceutical products. However, there is no report on the preparation of HFO of Antarctic krill (HFP). Therefore, the aim of the present study was to investigate the preparation process, peptide profiles and in vitro antioxidant activity of HFP. This study will potentially enhance the value‐added utilization of Antarctic krill by making it an important raw material in the health‐promoting functional products. [ABSTRACT FROM AUTHOR]

Antarctic krill ( Euphausia superba) obtained from the huge biomass in Antarctic waters is an important food product in Japan. Antarctic krill peptide powder (AKPP) prepared from the tail meat by enzymatic hydrolysis significantly decreased the systolic blood pressure in spontaneously hypertensive rats by a single oral administration (1, 10, or 100 mg). Presumably, the effect of AKPP was through inhibition of the conversion of angiotensin, which mediates blood pressure elevation, from its inactive propeptide to the mature angiotensin. Two potent angiotensin I-converting enzyme (ACE) inhibitory peptides were isolated from AKPP by high-performance liquid chromatography (HPLC) and identified as Val-Trp (IC50= 2.75 μg/mL; 12.9 μM) and Leu-Lys-Tyr (IC50= 4.26 μg/mL; 10.1 μM). Val-Trp and Leu-Lys-Tyr comprised 0.025%± 0.0023% (w/w) and 0.018%± 0.0023% (w/w) of AKPP, respectively, as measured by electrospray ionization mass spectrometry (ESI-MS). The contributions of Val-Trp and Leu-Lys-Tyr to the ACE inhibitor activity of AKPP were 17.7%± 1.60% and 8.04%± 1.03%, respectively, suggesting that these 2 peptides constitute a substantial portion of the overall ACE inhibitor potential of AKPP. [ABSTRACT FROM AUTHOR]