A method to estimate prey density from single-camera images: A case study with chinstrap penguins and Antarctic krill.

Estimating the densities of marine prey observed in animal-borne video loggers when encountered by foraging predators represents an important challenge for understanding predator-prey interactions in the marine environment. We used video images collected during the foraging trip of one chinstrap penguin (Pygoscelis antarcticus) from Cape Shirreff, Livingston Island, Antarctica to develop a novel approach for estimating the density of Antarctic krill (Euphausia superba) encountered during foraging activities. Using the open-source Video and Image Analytics for a Marine Environment (VIAME), we trained a neural network model to identify video frames containing krill. Our image classifier has an overall accuracy of 73%, with a positive predictive value of 83% for prediction of frames containing krill. We then developed a method to estimate the volume of water imaged, thus the density (N·m-3) of krill, in the 2-dimensional images. The method is based on the maximum range from the camera where krill remain visibly resolvable and assumes that mean krill length is known, and that the distribution of orientation angles of krill is uniform. From 1,932 images identified as containing krill, we manually identified a subset of 124 images from across the video record that contained resolvable and unresolvable krill necessary to estimate the resolvable range and imaged volume for the video sensor. Krill swarm density encountered by the penguins ranged from 2 to 307 krill·m-3 and mean density of krill was 48 krill·m-3 (sd = 61 krill·m-3). Mean krill biomass density was 25 g·m-3. Our frame-level image classifier model and krill density estimation method provide a new approach to efficiently process video-logger data and estimate krill density from 2D imagery, providing key information on prey aggregations that may affect predator foraging performance. The approach should be directly applicable to other marine predators feeding on aggregations of prey.

Correction of omega-3 fatty acid deficiency and improvement in disease activity in patients with systemic lupus erythematosus treated with krill oil concentrate: a multicentre, randomised, double-blind, placebo-controlled trial.

OBJECTIVE: Omega-3 polyunsaturated fatty acids (PUFAs) play a critical role in regulating inflammation and lipid metabolism. This study sought to ascertain the frequency of omega-3 deficiency in patients with SLE and investigate whether supplementation with krill oil concentrate (KOC) could replenish omega-3 levels and decrease SLE disease activity. METHODS: A multicentre, randomised, double-blind, placebo-controlled trial was conducted in adult patients with active SLE. Eligible patients were randomised to receive 4 g/day KOC or placebo (vegetable oil mixture) for the first 24 weeks, and thereafter patients could opt to enter an open-label extension. The primary end point was improvement of the red blood cell Omega-3 Index from baseline to week 24. Changes in clinical features, including SLE Disease Activity Index 2000 (SLEDAI-2K) disease activity scores, were also monitored. RESULTS: Seventy-eight patients met eligibility criteria and were randomised to a treatment group (n=39 per group). The baseline Omega-3 Index in the total SLE cohort was a mean 4.43% (±SD 1.04%). After 4 weeks of KOC treatment, the Omega-3 Index rapidly increased to 7.17%±1.48% (n=38) and after 24 weeks to 8.05%±1.79% (n=25) (each p<0.001 vs baseline), whereas no significant change from baseline was noted in patients receiving placebo. Increases in the Omega-3 Index in KOC-treated patients persisted through week 48. After patients switched from placebo to KOC at 24 weeks, the mean Omega-3 Index showed a rapid and significant increase (from 4.63%±1.39% at week 24 (n=26) to 7.50%±1.75% at week 48 (n=12); p<0.001). Although there were no changes in disease activity in the study population overall, SLEDAI-2K scores decreased significantly in the KOC group during the 24-week randomised period among those who had high disease activity at baseline (SLEDAI-2K ≥9) (p=0.04, p=0.02 and p=0.01 vs placebo at 4, 8 and 16 weeks, respectively; n=9 per group). KOC was well-tolerated, with no significant safety concerns. CONCLUSION: KOC corrected omega-3 deficiency in patients with SLE. Supplementation with KOC was safe and decreased disease activity in those with more active disease. These findings warrant further evaluation of omega-3 fatty acid supplementation with KOC in the management of SLE. TRIAL REGISTRATION NUMBER: NCT03626311.

Characterization and in vitro calcium release of the novel calcium-loaded complexes using Antarctic krill protein and pectin: Effect of different blending sequences.

Food-grade biopolymer-based complexes are of particular interest in the field of biologic ingredient delivery owing to unique controlled-release properties. Herein, three calcium-loaded complexes using Antarctic krill protein (P) and pectin (HMP) with different blending sequences were designed, named P + Ca + HMP, P + HMP + Ca and HMP + Ca + P, respectively. The calcium-loaded capacity, structural properties, and in vitro gastrointestinal calcium release of the complexes were investigated. The results demonstrated that the calcium binding rate and content of the P + Ca + HMP complex were the highest, reaching to 90.3 % and 39.0 mg/g, respectively. Particularly, the P + Ca + HMP complex exhibited a more stable fruit tree-like structure. Furthermore, the structural analysis confirmed that the primary interaction forces involved hydrogen bond, electrostatic, hydrophobic and ionic bond interaction. Ultimately, the P + Ca + HMP complex demonstrated superior calcium delivery. In conclusion, a novel calcium delivery system was successfully developed based on optimized the self-assembly sequence, which held significant importance in promoting the high-value utilization of Antarctic krill protein and enhancing the in vitro bioaccessibility of calcium.

Geographical distribution of the mesozooplankton community in highly productive coastal polynyas of the Ross Sea region marine protected area (RSR MPA) during early summer.

We investigated the recent spatial variation in the mesozooplankton community on the broad shelf of the RSR MPA during the bloom season. The mesozooplankton community was geographically divided into three regions: the Terra Nova Bay polynya, the Ross Sea polynya, and the marginal polynya. Larval euphausiids were dominant in the two polynya regions, whereas copepods were predominant in the marginal polynya region. Salinity, sea ice, and dissolved oxygen related to the different water mass compositions were the most significant factors distinguishing the mesozooplankton community. The key environmental variable separating the three groups was salinity. In accordance with the relatively high mesozooplankton abundance in the polynya regions, the occurrence and size of the polynyas in the December Ross Sea are thought to affect the spatial distribution of mesozooplankton. Consequently, this study indicates that two polynyas in the Ross Sea are vital habitats for krill during summer. Our observation results provide fundamental information for evaluating marine ecosystems and establishing a management plan for the RSR MPA.

Krill Oil for Knee Osteoarthritis: A Randomized Clinical Trial.

Importance: Knee osteoarthritis is disabling, with few effective treatments. Preliminary evidence suggested that krill oil supplementation improved knee pain, but effects on knee osteoarthritis remain unclear. Objective: To evaluate efficacy of krill oil supplementation, compared with placebo, on knee pain in people with knee osteoarthritis who have significant knee pain and effusion-synovitis. Design, Setting, and Participants: Multicenter, randomized, double-blind, placebo-controlled clinical trial in 5 Australian cities. Participants with clinical knee osteoarthritis, significant knee pain, and effusion-synovitis on magnetic resonance imaging were enrolled from December 2016 to June 2019; final follow-up occurred on February 7, 2020. Interventions: Participants were randomized to 2 g/d of krill oil (n = 130) or matching placebo (n = 132) for 24 weeks. Main Outcomes and Measures: The primary outcome was change in knee pain as assessed by visual analog scale (range, 0-100; 0 indicating least pain; minimum clinically important improvement = 15) over 24 weeks. Results: Of 262 participants randomized (mean age, 61.6 [SD, 9.6] years; 53% women), 222 (85%) completed the trial. Krill oil did not improve knee pain compared with placebo (mean change in VAS score, -19.9 [krill oil] vs -20.2 [placebo]; between-group mean difference, -0.3; 95% CI, -6.9 to 6.4) over 24 weeks. One or more adverse events was reported by 51% in the krill oil group (67/130) and by 54% in the placebo group (71/132). The most common adverse events were musculoskeletal and connective tissue disorders, which occurred 32 times in the krill oil group and 42 times in the placebo group, including knee pain (n = 10 with krill oil; n = 9 with placebo), lower extremity pain (n = 1 with krill oil; n = 5 with placebo), and hip pain (n = 3 with krill oil; n = 2 with placebo). Conclusions and Relevance: Among people with knee osteoarthritis who have significant knee pain and effusion-synovitis on magnetic resonance imaging, 2 g/d of daily krill oil supplementation did not improve knee pain over 24 weeks compared with placebo. These findings do not support krill oil for treating knee pain in this population. Trial Registration: Australian New Zealand Clinical Trials Registry Identifier: ACTRN12616000726459; Universal Trial Number: U1111-1181-7087.

No distinct local cuisines among humpback whales: A population diet comparison in the Southern Hemisphere.

Southern hemisphere humpback whale (Megaptera novaeangliae, SHHW) breeding populations follow a high-fidelity Antarctic krill (Euphausia superba) diet while feeding in distinct sectors of the Southern Ocean. Their capital breeding life history requires predictable ecosystem productivity to fuel migration and migration-related behaviours. It is therefore postulated that populations feeding in areas subject to the strongest climate change impacts are more likely to show the first signs of a departure from a high-fidelity krill diet. We tested this hypothesis by investigating blubber fatty acid profiles and skin stable isotopes obtained from five SHHW populations in 2019, and comparing them to Antarctic krill stable isotopes sampled in three SHHW feeding areas in the Southern Ocean in 2019. Fatty acid profiles and δ13C and δ15N varied significantly among all five populations, however, calculated trophic positions did not (2.7 to 3.1). Similarly, fatty acid ratios, 16:1ω7c/16:0 and 20:5ω3/22:6ω3 were above 1, showing that whales from all five populations are secondary heterotrophs following an omnivorous diet with a diatom-origin. Thus, evidence for a potential departure from a high-fidelity Antarctic krill diet was not seen in any population. δ13C of all populations were similar to δ13C of krill sampled in productive upwelling areas or the marginal sea-ice zone. Consistency in trophic position and diet origin but significant fatty acid and stable isotope differences demonstrate that the observed variability arises at lower trophic levels. Our results indicate that, at present, there is no evidence of a divergence from a high-fidelity krill diet. Nevertheless, the characteristic isotopic signal of whales feeding in productive upwelling areas, or in the marginal sea-ice zone, implies that future cryosphere reductions could impact their feeding ecology.

Metabolomics analysis of physicochemical properties associated with freshness degradation in frozen Antarctic krill (Euphausia superba).

This study aimed to determine the effect of different frozen temperatures during storage on the quality of Antarctic krill (Euphausia superba) and assess the change at the metabolite level via a combination of physicochemical property analysis, liquid chromatography-tandem mass spectrometry (LC-MS) based non-targeted metabolomics profiling. Regarding samples stored at -20 °C, the expressions of 7055 metabolites were elevated, while 2313 were downregulated. Lipids and lipid molecules had the highest proportion of differential metabolites. A total of 432 discriminatory metabolites with Kyoto Encyclopedia of Genes and Genomes (KEGG) IDs was obtained. We also observed that the concentrations of differential bitter free amino acids (FAAs) and oxidation products of arachidonic and linoleic acid increased. Moreover, as the storage temperature increased, the freshness, umami, and sweetness components were considerably reduced. Furthermore, results indicated that the color, pH and water-holding capacity (WHC) were potential indicators of quality deterioration, while inosinic acid was a probable biomarker for umami degradation of frozen Antarctic krill. In conclusion, this study demonstrates that storage at lower temperatures can be beneficial for maintaining the freshness of Antarctic krill from macro and micro perspectives.

Comparing trophic position estimates using bulk and compound specific stable isotope analyses: applying new approaches to mackerel icefish Champsocephalus gunnari.

Quantifying the tropic position (TP) of an animal species is key to understanding its ecosystem function. While both bulk and compound-specific analyses of stable isotopes are widely used for this purpose, few studies have assessed the consistency between and within such approaches. Champsocephalus gunnari is a specialist teleost that predates almost exclusively on Antarctic krill Euphausia superba. This well-known and nearly constant trophic relationship makes C. gunnari particularly suitable for assessing consistency between TP methods under field conditions. In the present work, we produced and compared TP estimates for C. gunnari and its main prey using a standard bulk and two amino acid-specific stable isotope approaches (CSI-AA). One based on the difference between glutamate and phenylalanine (TPGlx-Phe), and the other on the proline-phenylalanine difference (TPPro-Phe). To do that, samples from C. gunnari, E. superba and four other pelagic invertebrate and fish species, all potential prey for C.gunnari, were collected off the South Orkney Islands between January and March 2019, analyzed using standard isotopic ratio mass spectrometry methods and interpreted following a Bayesian approach. Median estimates (CI95%) for C. gunnari were similar between TPbulk (3.6; CI95%: 3.0-4.8) and TPGlx-Phe(3.4; CI95%:3.2-3.6), and lower for TPPro-Phe (3.1; CI95%:3.0-3.3). TP differences between C. gunnari and E. superba were 1.4, 1.1 and 1.2, all compatible with expectations from the monospecific diet of this predator (ΔTP=1). While these results suggest greater accuracy for Glx-Phe and Pro-Phe, differences observed between both CSI-AA approaches suggests these methods may require further validation before becoming a standard tool for trophic ecology.

A comprehensive study of the colloidal properties, biocompatibility, and synergistic antioxidant actions of Antarctic krill phospholipids.

Excipient selection is crucial to address the oxidation and solubility challenges of bioactive substances, impacting their safety and efficacy. AKPL, a novel ω-3 polyunsaturated fatty acids (PUFAs) esterified phospholipid derived from Antarctic krill, demonstrates unique antioxidant capabilities and synergistic effects. It exhibits pronounced surface activity and electronegativity at physiological pH, as evidenced by a critical micelle concentration (CMC) of 0.15 g/L and ζ-potential of -49.9 mV. In aqueous environments, AKPL self-assembles into liposomal structures, offering high biocompatibility and promoting cell proliferation. Its polyunsaturated bond-rich structure provides additional oxidation sites, imparting antioxidant properties superior to other phospholipids like DSPC and DOPC. Additionally, AKPL augments the efficacy of lipophilic antioxidants, such as alpha-tocopherol and curcumin, in aqueous media through both intermolecular and intramolecular interactions. In sum, AKPL emerges as an innovative unsaturated phospholipid, offering new strategies for encapsulating and delivering oxygen-sensitive agents.

Krill Oil and Its Bioactive Components as a Potential Therapy for Inflammatory Bowel Disease: Insights from In Vivo and In Vitro Studies.

Krill oil is extracted from krill, a small crustacean in the Antarctic Ocean. It has received growing attention because of krill oil's unique properties and diverse health benefits. Recent experimental and clinical studies suggest that it has potential therapeutic benefits in preventing the development of a range of chronic conditions, including inflammatory bowel disease (IBD). Krill oil is enriched with long-chain n-3 polyunsaturated fatty acids, especially eicosapentaenoic and docosahexaenoic acids, and the potent antioxidant astaxanthin, contributing to its therapeutic properties. The possible underlying mechanisms of krill oil's health benefits include anti-inflammatory and antioxidant actions, maintaining intestinal barrier functions, and modulating gut microbiota. This review aims to provide an overview of the beneficial effects of krill oil and its bioactive components on intestinal inflammation and to discuss the findings on the molecular mechanisms associated with the role of krill oil in IBD prevention and treatment.

Characterisation of a casein-/whey protein concentrate-Antarctic krill oil emulsion system and improvement of its storage stability.

AIMS: To develop Antarctic krill oil emulsions with casein and whey protein concentrate (WPC) and study their physicochemical properties and storage stability. METHODS: Emulsions were prepared by homogenisation and ultrasonication. The properties of the emulsions were investigated via ultraviolet ray spectroscopy, dynamic light scattering, confocal laser scanning microscope, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, Fourier transform infra-red spectrometer, and fluorescence spectrum. Shelf life was predicted by the Arrhenius model. RESULTS: Casein- and WPC-krill oil emulsions were well formed; the mean particle diameters were less than 128.19 ± 0.64 nm and 158 ± 1.56 nm, the polymer dispersity indices were less than 0.26 ± 0.01 and 0.27 ± 0.01, and the zeta potential were around -46.88 ± 5.02 mV and -33.51 ± 2.68 mV, respectively. Shelf life was predicted to be 32.67 ± 1.55 days and 29.62 ± 0.65 days (40 °C), 27.69 ± 1.15 days and 23.58 ± 0.14 days (50 °C), 24.02 ± 0.15 days and 20.1 ± 0.08 days (60 °C). CONCLUSION: The prepared krill oil emulsions have great potential to become a new krill oil supplement.

Digestive and Absorptive Properties of the Antarctic Krill Tripeptide Phe-Pro-Phe (FPF) and Its Auxiliary Memory-Enhancing Effect.

Aging and stress have contributed to the development of memory disorders. Phe-Pro-Phe (FPF) was identified with high stability by mass spectrometry from simulated gastrointestinal digestion and everted gut sac products of the Antarctic krill peptide Ser-Ser-Asp-Ala-Phe-Phe-Pro-Phe-Arg (SSDAFFPFR) which was found to have a positive impact on memory enhancement. This study investigated the digestive stability, absorption, and memory-enhancing effects of FPF using nuclear magnetic resonance spectroscopy, simulated gastrointestinal digestion, in vivo fluorescence distribution analysis, mouse behavioral experiments, acetylcholine function, Nissl staining, immunofluorescence, and immunohistochemistry. FPF crossed the blood-brain barrier into the brain after digestion, significantly reduced shock time, working memory errors, and reference memory errors, and increased the recognition index. Additionally, FPF elevated ACh content; Nissl body counts; and CREB, SYN, and PSD-95 expression levels, while reducing AChE activity (P < 0.05). This implies that FPF prevents scopolamine-induced memory impairment and provides a basis for future research on memory disorders.

Characterization and Hydrolysis Mechanism Analysis of a Cold-Adapted Trypsin-Like Protease from Antarctic Krill.

Cold-adapted proteases are capable of efficient protein hydrolysis at reduced temperatures, which offer significant potential applications in the area of low temperature food processing. In this paper, we attempted to characterize cold-adapted proteases from Antarctic krill. Antarctic krill possesses an extremely active autolytic enzyme system in their bodies, and the production of peptides and free amino acids accompanies the rapid breakdown of muscle proteins following the death. The crucial role of trypsin in this process is recognized. A cold-adapted trypsin named OUC-Pp-20 from Antarctic krill genome was cloned and expressed in Pichia pastoris. Recombinant trypsin is a monomeric protein of 26.8 ± 1.0 kDa with optimum reaction temperature at 25 °C. In addition, the catalytic specificity of OUC-Pp-20 was assessed by identifying its hydrolysis sites through LC-MS/MS. OUC-Pp-20 appeared to prefer Gln and Asn at the P1 position, which is an amino acid with an amide group in its side chain. Hydrolysis reactions on milk and shrimp meat revealed that it can effectively degrade allergenic components in milk and arginine kinase in shrimp meat. These findings update the current knowledge of cold-adapted trypsin and demonstrate the potential application of OUC-Pp-20 in low temperature food processing.

Advances in encapsulation systems of Antarctic krill oil: From extraction to encapsulation, and future direction.

Antarctic krill oil (AKO) is highly sought after by consumers and the food industry due to its richness in a variety of nutrients and physiological activities. However, current extraction methods are not sufficient to better extract AKO and its nutrients, and AKO is susceptible to lipid oxidation during processing and storage, leading to nutrient loss and the formation of off-flavors and toxic compounds. The development of various extraction methods and encapsulation systems for AKO to improve oil yield, nutritional value, antioxidant capacity, and bioavailability has become a research hotspot. This review summarizes the research progress of AKO from extraction to encapsulation system construction. The AKO extraction mechanism, technical parameters, oil yield and composition of solvent extraction, aqueous enzymatic extraction, supercritical/subcritical extraction, and three-liquid-phase salting-out extraction system are described in detail. The principles, choice of emulsifier/wall materials, preparation methods, advantages and disadvantages of four common encapsulation systems for AKO, namely micro/nanoemulsions, microcapsules, liposomes and nanostructured lipid carriers, are summarized. These four encapsulation systems are characterized by high encapsulation efficiency, low production cost, high bioavailability and high antioxidant capacity. Depending on the unique advantages and conditions of different encapsulation methods, as well as consumer demand for health and nutrition, different products can be developed. However, existing AKO encapsulation systems lack relevant studies on digestive absorption and targeted release, and the single product category of commercially available products limits consumer choice. In conjunction with clinical studies of AKO encapsulation systems, the development of encapsulation systems for special populations should be a future research direction.

A Novel Tetrapeptide Ala-Phe-Phe-Pro (AFFP) Derived from Antarctic Krill Prevents Scopolamine-Induced Memory Disorder by Balancing Lipid Metabolism of Mice Hippocampus.

Memory impairment is a serious problem with organismal aging and increased social pressure. The tetrapeptide Ala-Phe-Phe-Pro (AFFP) is a synthetic analogue of Antarctic krill derived from the memory-improving Antarctic krill peptide Ser-Ser-Asp-Ala-Phe-Phe-Pro-Phe-Arg (SSDAFFPFR) after digestion and absorption. The objective of this research was to assess the neuroprotective effects of AFFP by reducing oxidative stress and controlling lipid metabolism in the brains of mice with memory impairment caused by scopolamine. The 1H Nuclear magnetic resonance spectroscopy results showed that AFFP had three active hydrogen sites that could contribute to its antioxidant properties. The findings from in vivo tests demonstrated that AFFP greatly enhanced the mice's behavioral performance in the passive avoidance, novel object recognition, and eight-arm maze experiments. AFFP reduced oxidative stress by enhancing superoxide dismutase activity and malondialdehyde levels in mice serum, thereby decreasing reactive oxygen species level in the mice hippocampus. In addition, AFFP increased the unsaturated lipid content to balance the unsaturated lipid level against the neurotoxicity of the mice hippocampus. Our findings suggest that AFFP emerges as a potential dietary intervention for the prevention of memory impairment disorders.

Estimated summer abundance and krill consumption of fin whales throughout the Scotia Sea during the 2018/2019 summer season.

Among large cetaceans in the Southern Hemisphere, fin whales were the most heavily exploited in terms of numbers taken during the period of intense industrial whaling. Recent studies suggest that, whilst some humpback whale populations in the Southern Hemisphere appears to have almost completely recovered to their estimated pre-whaling abundance, much less is known about the status of Southern Hemisphere fin whales. Circumpolar estimates in the 1990s suggest an abundance of about 5500 animals south of 60° S, while the IDCR/SOWER-2000 survey for the Scotia Sea and Antarctic Peninsula areas estimated 4670 fin whales within this region in the year 2000. More recent studies in smaller regions indicate higher densities, suggesting that previous estimates are overly conservative and/or that fin whales are undergoing a substantial increase. Here we report findings from a recent multi-vessel single-platform sightings survey carried out as part of the 2019 Area 48 Survey for Antarctic krill. While fin whales were encountered throughout the entire survey area, which covered the majority of CCAMLR Management Area 48, they were particularly abundant around the South Orkney Islands and the eastern Bransfield Strait. Large feeding aggregations were also encountered within the central Scotia Sea between South Orkney Islands and South Georgia. Distance sampling analyses suggest an average fin whale density throughout the Scotia Sea of 0.0256 ( CV = 0.149 ) whales per km2, which agrees well with recent density estimates reported from smaller sub-regions within the Scotia Sea. Design-based distance sampling analyses resulted in an estimated total fin whale abundance of 53,873 (CV = 0.15, 95% CI 40,233-72,138), while a density surface model resulted in a slightly lower estimate of 50,837 (CV: 0.136, 95% CI 38,966-66,324). These estimates are at least an order of magnitude greater than the previous estimate from the same region based on the IDCR/SOWER-2000 data, suggesting that fin whales are undergoing a substantial abundance increase in the South Atlantic. This may have important implications for the assessment of cetacean population trends, but also for CCAMLRs spatial overlap analysis process and efforts to implement a Feedback Management system for Antarctic krill. Our abundance estimate suggests an annual summer krill consumption by fin whales in the Antarctic Peninsula and Scotia Sea area of 7.97 (95% CI 4.94-11.91) million tonnes, which would represent around 20 times the total krill catch taken by the commercial fishery in Area 48 in the same season, or about 12.7% of the 2019 summer krill standing stock estimated from data collected during the same survey. This highlights the crucial importance of including cetacean krill predators in assessment and management efforts for living marine resources in the Southern Ocean, and particularly stresses the urgent need for a re-appraisal of abundance, distribution and ecological role of Southern Hemisphere fin whales.

Engineering marine phospholipid nanoliposomes via glycerol-infused proliposomes: Mechanisms, strategies, and versatile applications in scalable food-grade nanoliposome production.

This study presents a novel approach using polyol-based proliposome to produce marine phospholipids nanoliposomes. Proliposomes were formulated by blending glycerol with phospholipids across varying mass ratios (2:1 to 1:10) at room temperature. Analysis employing polarized light microscopy, FTIR, and DSC revealed that glycerol disrupted the stacked acyl groups within phospholipids, lowering the phase transition temperature (Tm). Krill oil phospholipids (KOP) proliposomes exhibited superior performance in nanoliposomes formation, with a mean diameter of 125.60 ± 3.97 nm, attributed to the decreased Tm (-7.64 and 7.00 °C) compared to soybean phospholipids, along with a correspondingly higher absolute zeta potential (-39.77 ± 1.18 mV). The resulting KOP proliposomes demonstrated liposomes formation stability over six months and under various environmental stresses (dilution, thermal, ionic strength, pH), coupled with in vitro absorption exceeding 90 %. This investigation elucidates the mechanism behind glycerol-formulated proliposomes and proposes innovative strategies for scalable, solvent-free nanoliposome production with implications for functional foods and pharmaceutical applications.

Molecular Mechanisms of Iron Transport and Homeostasis Regulated by Antarctic Krill-Derived Heptapeptide-Iron Complex.

In this study, the molecular mechanisms of iron transport and homeostasis regulated by the Antarctic krill-derived heptapeptide-iron (LVDDHFL-iron) complex were explored. LVDDHFL-iron significantly increased the hemoglobin, serum iron, total iron binding capacity levels, and iron contents in the liver and spleen to normal levels, regulated the gene expressions of iron homeostasis, and enhanced in vivo antioxidant capacity in iron-deficiency anemia mice (P < 0.05). The results revealed that iron ions within LVDDHFL-iron can be transported via the heme transporter and divalent metal transporter-1, and the absorption of LVDDHFL-iron involved receptor-mediated endocytosis. We also found that the transport of LVDDHFL-iron across cells via phagocytosis was facilitated by the up-regulation of the high mobility group protein, heat shock protein ß, and V-type proton ATPase subunit, accompanied by the regulatory mechanism of autophagy. These findings provided deeper understandings of the mechanism of LVDDHFL-iron facilitating iron absorption.

Extraction, identification, and molecular mechanisms of α-glucosidase inhibitory peptides from defatted Antarctic krill (Euphausia superba) powder hydrolysates.

The objective of this study was to explore the potential of Antarctic krill-derived peptides as α-glucosidase inhibitors for the treatment of type 2 diabetes. The enzymolysis conditions of α-glucosidase inhibitory peptides were optimized by response surface methodology (RSM), a statistical method that efficiently determines optimal conditions with a limited number of experiments. Gel chromatography and LC-MS/MS techniques were utilized to determine the molecular weight (Mw) distribution and sequences of the hydrolysates. The identification and analysis of the mechanism behind α-glucosidase inhibitory peptides were conducted through conventional and computer-assisted techniques. The binding affinities between peptides and α-glucosidase were further validated using BLI (biolayer interferometry) assay. The results revealed that hydrolysates generated by neutrase exhibited the highest α-glucosidase inhibition rate. Optimal conditions for hydrolysis were determined to be an enzyme concentration of 6 × 103 U/g, hydrolysis time of 5.4 h, and hydrolysis temperature of 45 °C. Four peptides (LPFQR, PSFD, PSFDF, VPFPR) with strong binding affinities to the active site of α-glucosidase, primarily through hydrogen bonding and hydrophobic interactions. This study highlights the prospective utility of Antarctic krill-derived peptides in curtailing α-glucosidase activity, offering a theoretical foundation for the development of novel α-glucosidase inhibitors and related functional foods to enhance diabetes management.

Rich microbial and depolymerising diversity in Antarctic krill gut.

With almost a quadrillion individuals, the Antarctic krill processes five million tons of organic carbon every day during austral summer. This high carbon flux requires a broad range of hydrolytic enzymes to decompose the diverse food-derived biopolymers. While krill itself possesses numerous such enzymes, it is unclear, to what extent the endogenous microbiota contribute to the hydrolytic potential of the gut environment. Here we applied amplicon sequencing, shotgun metagenomics, cultivation, and physiological assays to characterize the krill gut microbiota. The broad bacterial diversity (273 families, 919 genera, and 2,309 species) also included a complex potentially anaerobic sub-community. Plate-based assays with 198 isolated pure cultures revealed widespread capacities to utilize lipids (e.g., tributyrin), followed by proteins (casein) and to a lesser extent by polysaccharides (e.g., alginate and chitin). While most isolates affiliated with the genera Pseudoalteromonas and Psychrobacter, also Rubritalea spp. (Verrucomicrobia) were observed. The krill gut microbiota growing on marine broth agar plates possess 13,012 predicted hydrolyses; 15-fold more than previously predicted from a transcriptome-proteome compendium of krill. Cultivation-independent and -dependent approaches indicated members of the families Flavobacteriaceae and Pseudoalteromonadaceae to dominate the capacities for lipid/protein hydrolysis and to provide a plethora of carbohydrate-active enzymes, sulfatases, and laminarin- or porphyrin-depolymerizing hydrolases. Notably, also the potential to hydrolyze plastics such as polyethylene terephthalate and polylactatide was observed, affiliating mostly with Moraxellaceae. Overall, this study shows extensive microbial diversity in the krill gut, and suggests that the microbiota likely play a significant role in the nutrient acquisition of the krill by enriching its hydrolytic enzyme repertoire.IMPORTANCEThe Antarctic krill (Euphausia superba) is a keystone species of the Antarctic marine food web, connecting the productivity of phyto- and zooplankton with the nutrition of the higher trophic levels. Accordingly, krill significantly contributes to biomass turnover, requiring the decomposition of seasonally varying plankton-derived biopolymers. This study highlights the likely role of the krill gut microbiota in this ecosystem function by revealing the great number of diverse hydrolases that microbes contribute to the krill gut environment. The here resolved repertoire of hydrolytic enzymes could contribute to the overall nutritional resilience of krill and to the general organic matter cycling under changing environmental conditions in the Antarctic sea water. Furthermore, the krill gut microbiome could serve as a valuable resource of cold-adapted hydrolytic enzymes for diverse biotechnological applications.