Extraction of proteins with low fluoride level from Antarctic krill (Euphausia superba) and their composition analysis

The complex coacervation of gum Arabic and krill protein isolate and their application for Antarctic krill oil encapsulation

Antarctic krill oil (AKO) possesses potent bioactivities but has limited applications in the food industry due to its poor stability, strong off-flavor, and low bioavailability of contained astaxanthin. In this study, Antarctic krill protein isolate (AKPI) was separated from processing by-product of krill and utilized as a novel wall material via complexing it with gum Arabic (GA) to improve the limitations of AKO. The strong complex coacervation reaction between AKPI and GA was occurred at the pH of 3.8 and the ratioAKPI-to-GA of 3:1, while electrostatic interaction and hydrogen-bond interaction were determined to be the main driving forces of such reaction. The ratiowall-to-core was confirmed as 1:0.75 after comprehensively assessing the effect of AKO content on the various properties of AKPI-GA coacervated microcapsules, while the wall material concentration and pH were optimized at 1 % and 3.8, respectively. The obtained solid AKO microcapsules exhibited the encapsulation efficiency of 80.22 %. AKPI-GA coacervated microcapsules extremely masked the odor of AKO and achieved the controlled-release of AKO in the gastrointestinal tract. Meanwhile, the encapsulated AKO displayed higher astaxanthin retention and oxidative stability compared with non-encapsulated AKO during storage.

Enhancing Pseudomonas cell growth for the production of medium-chain-length polyhydroxyalkanoates from Antarctic krill shell waste

Antarctic krill shell waste (AKSW), a byproduct of Antarctic krill processing, has substantial quantity but low utilization. Utilizing microbial-based cell factories, with Pseudomonas putida as a promising candidate, offers an ecofriendly and sustainable approach to producing valuable bioproducts from renewable sources. However, the high fluoride content in AKSW impedes the cell growth of P. putida. This study aims to investigate the transcriptional response of P. putida to fluoride stress from AKSW and subsequently conduct genetic modification of the strain based on insights gained from transcriptomic analysis. Notably, the engineered strain KT+16840+03100 exhibited a remarkable 33.7-fold increase in cell growth, capable of fermenting AKSW for medium-chain-length-polyhydroxyalkanoates (mcl-PHA) biosynthesis, achieving a 40.3-fold increase in mcl-PHA yield compared to the control strain. This research advances our understanding of how P. putida responds to fluoride stress from AKSW and provides engineered strains that serve as excellent platforms for producing mcl-PHA through AKSW.

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.

Cloning and Characterization of Chitin Deacetylase from Euphausia superba

Chitin deacetylase (CDA) can catalyze the deacetylation of chitin to produce chitosan. In this study, we identified and characterized a chitin deacetylase gene from Euphausia superba (EsCDA-9k), and a soluble recombinant protein chitin deacetylase from Euphausia superba of molecular weight 45 kDa was cloned, expressed, and purified. The full-length cDNA sequence of EsCDA-9k was 1068 bp long and encoded 355 amino acid residues that contained the typical domain structure of carbohydrate esterase family 4. The predicted three-dimensional structure of EsCDA-9k showed a 67.32% homology with Penaeus monodon. Recombinant chitin deacetylase had the highest activity at 40 °C and pH 8.0 in Tris-HCl buffer. The enzyme activity was enhanced by metal ions Co2+, Fe3+, Ca2+, and Na+, while it was inhibited by Zn2+, Ba2+, Mg2+, and EDTA. Molecular simulation of EsCDA-9k was conducted based on sequence alignment and homology modeling. The EsCDA-9k F18G mutant showed a 1.6-fold higher activity than the wild-type enzyme. In summary, this is the first report of the cloning and heterologous expression of the chitin deacetylase gene in Euphausia superba. The characterization and function study of EsCDA-9k will serve as an important reference point for future application.

Study on the Sensitization and Antigenic Epitopes of Tropomyosin from Antarctic Krill (Euphausia superba)

Antarctic krill (Euphausia superba), a shrimp-like marine crustacean, has become a beneficial source of high-quality animal protein. Meanwhile, a special focus has been placed on its potential sensitization issue. In this study, a 35 kDa protein was purified and identified to be Antarctic krill tropomyosin (AkTM) by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The purified TM showed a strong IgE-binding capacity to shrimp/crab-allergic patients' sera, indicating that TM is the primary allergen in Antarctic krill. Simulated gastrointestinal digestion revealed that the digestion stability of TM to pepsin was higher than that to trypsin. The strong degranulation triggered by TM in RBL-2H3 cells suggested that AkTM has a strong sensitization capacity. The TM-sensitized BALB/c mice displayed severe anaphylactic symptoms; high levels of TM-specific IgE, sIgG1, and histamine; and increased IL-4, indicating that AkTM could provoke IgE-mediated allergic reactions. Bioinformatics prediction, indirect competition ELISA, and mast cell degranulation assay were used to map the antigenic epitopes of AkTM. Finally, nine peptides of T_43-58, T_88-101, T_111-125, T_133-143, T_144-155, T_183-197, T_223-236, T_249-261, and T_263-281 were identified as the linear epitopes of AkTM. The findings may help us develop efficient food processing techniques to reduce krill allergy and gain a deeper comprehension of the allergenicity of krill allergens.

Cloning and Characterization of Fructose-1,6-Bisphosphate Aldolase from Euphausia superba

Fructose-1,6-bisphosphate aldolase (EC 4.1.2.13) is a highly conserved enzyme that is involved in glycolysis and gluconeogenesis. In this study, we cloned the fructose-1,6-bisphosphate aldolase gene from Euphausia superba (EsFBA). The full-length cDNA sequence of EsFBA is 1098 bp long and encodes a 365-amino-acid protein. The fructose-1,6-bisphosphate aldolase gene was expressed in Escherichia coli (E. coli). A highly purified protein was obtained using HisTrap HP affinity chromatography and size-exclusion chromatography. The predicted three-dimensional structure of EsFBA showed a 65.66% homology with human aldolase, whereas it had the highest homology (84.38%) with the FBA of Penaeus vannamei. Recombinant EsFBA had the highest activity at 45 °C and pH 7.0 in phosphate buffer. By examining the activity of metal ions and EDTA, we found that the effect of metal ions and EDTA on EsFBA's enzyme activity was not significant, while the presence of borohydride severely reduced the enzymatic activity; thus, EsFBA was confirmed to be a class I aldolase. Furthermore, targeted mutations at positions 34, 147, 188, and 230 confirmed that they are key amino acid residues for EsFBA.

Antarctic krill peptide alleviates liver fibrosis via downregulating the secondary bile acid mediated NLRP3 signaling pathway

Liver fibrosis is a necessary process for liver disease. Recent studies have reported that the enterohepatic circulation of bile acid plays a vital role in developing liver fibrosis. The Antarctic krill peptide (AKP) has been proved to have a variety of activities such as antioxidant and anti-inflammatory, but any possible influence on liver fibrosis remains unclear. In the current study, the liver fibrosis mice were intraperitoneal injection of carbon tetrachloride (2.5%, 10 mL kg^-1) and oral administration AKP (400 mg kg^-1) for 30 days. The results showed that the AKP supplement decreased the serum ALT and AST levels, reduced the content of liver TNF-α and Collagen I, and improved liver inflammation and fibrosis, which was also confirmed by H&E and Masson staining. Bile acid is an important metabolite for the gut microbiota. We found that the AKP supplement alleviated the gut microbiota dysbiosis remarkably, as indicated by increased species richness and diversity, and decreased overgrowth of genera Bifidobacterium, Lactobacillus, Bacteroides, Clostridiales and Fusicatenibacter. Furthermore, AKP mediated gut microbiota improvement decreased the intestinal bile salt hydrolase and 7α-dehydroxylation activities, resulting in the decrease of secondary bile acid taurodeoxycholic acid (TDCA) and taurolithocholic acid (TLCA) concentrations. Mechanistically, AKP inhibited NLRP3 signal by downregulating the secondary bile acid, decreased cleaved Caspase-1 expression to suppress IL-1β-mediated hepatic stellate cell activation. This study reports for the first time that AKP improved liver fibrosis via improving the gut microbiota mediated bile acid-NLRP3 signaling, which might provide new ideas and evidence for Antarctic krill's high-value utilization.

Three-liquid-phase salting-out extraction of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)-rich oils from Euphausia superba

The TLPSOES parameters were optimized by response surface methodology using Box-Behnken design, which were 16.5% w/w of ammonium citrate, 17.5% w/w of ethanol, and 46% w/w of n-hexane at 70 min of stirring time. Under optimized conditions the extraction efficiency attained was 90.91 ± 0.97% of EPA, 90.02 ± 1.04% of DHA, and 91.85 ± 1.11% of KO in the top n-hexane phase. The highest extraction efficiency of proteins and flavonoids, i.e. 88.34 ± 1.35% and 79.67 ± 1.13%, was recorded in the solid interface and ethanol phase, respectively. The KO extracted by TLPSOES system consisted of lowest fluoride level compared to the conventional method and whole wet krill biomass. The TLPSOES is a potential candidate for nutraceutical industry of KO extraction from wet krill biomass.

Purification, identification, and molecular mechanism of DPP-IV inhibitory peptides from defatted Antarctic krill powder

Dipeptidyl peptidase-IV (DPP-IV) inhibitors can reduce the blood sugar levels of diabetic patients by preventing the rapid decomposition of incretin hormone and prolonging its physiological effects. In this study, DPP-IV inhibitory peptides FAGDDAPR and LAPPRGSL were isolated from defatted Antarctic krill powder (DAKP) protein by the sequential purification of ultrafiltration, gel filtration chromatography, and RP-HPLC, and IC₅₀ values of the two peptides were 349.70 ± 3.66 μM and 461.14 ± 0.87 μM, respectively. The FAGDDAPR and LAPPRGSL were identified by LC-MS/MS method, and the molecular models of DPP-IV and the two peptides were further constructed by AutoDock Vina software, the results revealed that the inhibition activity of FAGDDAPR and LAPPRGSL was mainly attributed to the formation of strong hydrophobic interactions and hydrogen bonds with amino acids of DPP-IV. PRACTICAL APPLICATIONS: DAKP is an economical by-product produced in the production of krill oil and contains high-quality protein, but these products were mainly used as fish feed and had low utility value in the past. DPP-IV inhibitors are an efficacious drug employed in the treatment of hyperglycemia processes. However, these drugs can cause undesirable side effects. Thus, the development of new natural hypoglycemic drugs with low side effects is a valuable strategy to be applied in therapeutic interventions.

Effects of different drying methods on the structures and functional properties of phosphorylated Antarctic krill protein

Antarctic krill protein (AKP) was extracted from Antarctic krill by an alkali dissolution-isoelectric precipitation method and then it was phosphorylated with sodium tripolyphosphate. The phosphorylated Antarctic krill protein (P-AKP) powder was obtained by spray-drying (SD), freeze-drying (FD), and hot-air drying (AD), and the effects of these drying methods on the structures and functional properties of proteins were investigated. The P-AKP powder dried by SD had the best sensory performance, and its particle size was much smaller than that of FD and AD. Scanning electron microscope displayed a uniform particle size of SD powder and the particles were uniformly dispersed. X-ray diffraction analysis showed a higher crystallinity of SD sample than AD and FD. Differential scanning calorimeter analysis revealed that SD sample had the best thermal stability and less protein denaturation (ΔH = 210.80 J/g), followed by FD (ΔH = 80.48 J/g) and AD (ΔH = 73.94 J/g; P < 0.05). Fourier transform infrared showed that SD sample contained more protein secondary structure. Compared with SD, the phosphorylated group-related chemical bonds in FD and AD samples were partially destroyed. SD sample had the highest protein solubility, oil absorption capacity, emulsifying, and foaming activities than FD and AD (P < 0.05). Although FD had the highest water absorption capacity, sample prepared with AD had the worst functional performance. Therefore, different drying methods used for preparation of the P-AKP can affect its physicochemical and associated functional properties, and SD could be an appropriate drying method for the industrial mass production of P-AKP powders with better functionalities. PRACTICAL APPLICATION: The optimal drying method for preparing the phosphorylated Antarctic krill protein (P-AKP) powder was proved to be spray-drying (SD), because the physicochemical and functional properties were better for P-AKP dried by SD than the other drying methods. Hence, SD was recommended for the industrial mass production of P-AKP powders with better functionalities. This research can provide theoretical guidance for the further processing and utilization of P-AKP, and offer technical reference for food processing and preservation.

In Vivo Hepatoprotective Effects of a Peptide Fraction from Krill Protein Hydrolysates against Alcohol-Induced Oxidative Damage

Background: Krill (Euphausia superba) represent the largest animal biomass on earth, and are a rich source of high-quality protein with essential amino acids. Krill-derived peptides are renowned for their antioxidant activities. Hence, these peptides may have protective effects against oxidative stress. Alcoholic liver disease is a prevalent cause of death worldwide. The present study explores the hepatoprotective effects of krill peptide hydrolysate fractions against ethanol-induced liver damage in BALB/c mice. Methods: Hydrolysis was carried out by mimicking the gastrointestinal digestion environment and the filtrate was fractionated based on molecular weight (<1 kDa, 1–3 kDa, and >3 kDa). The 1–3 kDa fraction (KPF), which indicated the highest antioxidant effect, was further investigated for its effect on weight and survival rate increase in mice and its influence on serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, and liver cholesterol levels. Moreover, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) levels were measured, followed by Nrf2 and HO-1 expression. Histopathology studies were conducted to assess hepatic tissue damage. Results: KPF enhanced the weight and survival rate of mice while reducing serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, and liver cholesterol levels. Moreover, KPF upregulated SOD, CAT, and GPx in liver tissues, while downregulating tumor necrosis factor α and interleukin-6 mRNA expression. KPF further increased Nrf2 and HO-1 expression and suppressed ethanol-induced apoptotic proteins in the liver. Histopathology of KPF-treated mice showed less hepatic tissue damage compared to ethanol-treated mice. Conclusions: Hydrolysates and bioactive peptides prepared from krill can be employed as functional foods to enhance liver function and health. Further investigations of KPF could lead to the development of functional foods.

Effects of three products from Antarctic krill on the nitrogen balance, growth, and antioxidation status of rats

A few studies conducted over the past few decades have demonstrated the health benefits of a diet rich in marine products, but limited studies have investigated the effects of different krill products on the nitrogen balance and their potential health benefits. In our study, after a 14-day acclimation period, 50 female Sprague-Dawley rats were randomly assigned to five groups, each of which was fed a different diet, for 28 days. We then evaluated the effect of krill protein complex (KPC), krill powder, and defatted krill powder on the nitrogen balance, growth, and antioxidant activity through analyses of MDA, CAT, GSH-Px, and T-SOD. An in vivo analysis suggested that the nitrogen retention rate, protein digestibility, and bioutilization of krill products were equal to those of casein. Moreover, the KPC diet resulted in the highest nitrogen intake and retention among the groups, and the biological value and net protein utilization obtained with KPC were higher than those obtained with defatted krill powder, which was consistent with the weight gains observed for these two groups. The hematological test also showed that KPC contributed to the production of functional proteins in the body. The antioxidant activity analysis indicated that higher GSH-Px and T-SOD activities were obtained with krill products and KPC, respectively, compared with casein. The results from this study suggested that krill proteins could promote growth and improve the antioxidant status of an organism. Although further studies on the safety of krill products for human consumption are needed, this work provides insights into the use of krill proteins as a potential substitute for other proteins and restructured foods.

Composition and content analysis of fluoride in inorganic salts of the integument of Antarctic krill (Euphausia superba)

Ash of Antarctic krill integument (AAKI) was prepared by sintering the integument at 550°C under air atmosphere for 4 hours, and its composition was analyzed by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and electron dispersive spectroscopy (EDS). XRD results showed that the major phase in AAKI was ascribed to apatite. Besides, it was noticed that the (300) peak of AAKI shifted to 33.07°, which was coincident with that of fluorapatite (FA). The FTIR results confirmed the presence of phosphate ions, and the absence of -OH. The EDS results confirmed the presence of Ca, P, O and F elements in the ash sample. The content of FA in the ash was determined to be 50.4%, and the proportion of fluorine in the form of FA to the total fluorine in the integument was 40.5%. Based on the XRD, FTIR and EDS results, it can be concluded that FA was the main form of fluoride in the integument of Antarctic krill.

Comparing different dehydration methods on protein quality of krill (Euphausia Pacifica)

Krill, (Euphausia pacifica) contains a high protein content (>15.4%) and an estimated biological value higher than many animal protein sources. Thus it is considered to be an important source of high-quality protein. However, commercial processing of krill is limited due to problems such as presence of hydrolytic enzymes (proteases, carboxypeptidases, nucleases, and phospholipases), and its small size. These enzymes are released immediately upon krill harvesting, resulting in autolysis, and rapid spoilage. Herein we compared different dehydration methods of krill on its protein quality. We processed Krill using air-drying (AD), vacuum microwave drying at low temperature (VD) and freeze-drying (FD), and also treated krill with chitinase prior to drying (HZ). AD-processed krill displayed the lowest in-vitro digestibility (P < 0.05) along with low apparent in-vivo protein digestibility compared to VD and FD, respectively. This result corresponded to lower available lysine in AD dried krill (5.6 mg/100 mg protein) compared to VD (8.5 mg Lysine /100 mg protein), FD (8.5 mg/100 mg protein), and HZ (8.9 mg/100 mg protein). Using a two-week metabolic study with rats, we found that apparent urinary nitrogen losses and net protein utilization were low in krill, compared to a casein control. The addition of chitinase to krill prior to drying significantly increased protein quality measures. A high fluoride concentration was also detected in dehydrated krill, irrespective of the drying method. It is expected that the fluoride content of krill is an additional factor that will affect protein utilization.

Peptides from Antarctic Krill ( Euphausia superba) Improve Osteoarthritis via Inhibiting HIF-2α-Mediated Death Receptor Apoptosis and Metabolism Regulation in Osteoarthritic Mice

Osteoarthritis (OA) is a prevalent debilitating disease which is predominantly characterized by cartilage degeneration. In the current study, destabilization of the medial meniscus (DMM) mouse model was used to investigate the effects of Antarctic krill peptides (AKP) on cartilage protection. As observed, AKP clearly ameliorate cartilage degeneration as evidenced by increased cartilage thickness and cartilage area and decreased histological Osteoarthritis Research Society International (OARSI) scores. Toluidine blue staining showed that AKO remarkably inhibited the loss of cartilage matrix in mice with OA. Hypoxia-inducible factor-2α (HIF-2α) has a key role in catabolic regulation and inflammation cascades which are the main causes of OA. AKP can down-regulate the expression of HIF-2α and its downstream genes such as MMP-13, Adamts-5, IL-1β, iNOS, CXCL-1, and NOS₂. Consistent with this, anabolic genes such as Acan and Col2α1 were restored after treatment with AKP. Chondrocyte apoptosis and the reduction in cartilage cell viability are also involved in the process of OA. The HIF-2α-mediated death receptor apoptosis signaling pathway has been involved in the regulation of chondrocyte apoptosis. AKP can reduce the expressions of key pro-apoptosis genes in Fas-FasL and DR3-DR3L signaling pathways such as Fas, FasL, FADD, caspase8, caspase3, DR3, DR3L, RIP, and NF-κB. In addition, expressions of antiapoptosis genes such as c-AIP and c-FLIP were increased significantly. These findings indicate that AKP can be used as a new functional factor in the development of functional foods and chondroprotective drugs.

Multi-stage countercurrent process for extracting protein from Antarctic Krill (Euphausia superba)

To systematically study multi-stage countercurrent process for Antarctic krill protein extracting and to optimize the multi-stage countercurrent technology, the solubility of Antarctic krill proteins after multi-step dissolution was explored firstly; multi-step extraction was investigated; and then multi-stage countercurrent system for protein extraction was carried out. In single step extraction, krill-to-water ratio and pH were chosen as 1:10 and 12.5 respectively, in order to extract more protein. In the multi-step dissolution process, the protein solubility of aqueous solution at pH 12.5 was 33.0 ± 0.8 mg/mL. Multi-step cross-flow processing testified the feasibility of multi-stage countercurrent assumption. Three-stage countercurrent method using krill-to-water ratio 1:10 extracted, 95.1 ± 0.6% protein from krill, where almost the same water as previous works. The total recovery yield of 67.9 ± 1.6% was achieved after precipitation at pH 4.5.

Antarctic seals: Molecular biomarkers as indicators for pollutant exposure, health effects and diet

Weddell (Leptonychotes weddellii), Ross (Ommatophoca rossii) and crabeater seals (Lobodon carcinophaga) are phocid seals with a circumpolar distribution around Antarctica. As long-lived and large top predators, they bioaccumulate contaminants and are considered as sentinels of ecosystem health. Antarctic seals are increasingly exposed to climate change, pollution, shipping and fisheries. To reveal and understand possible anthropogenic impacts on their immune and health status, this study investigates sensitive biomarkers of the xenobiotic metabolism and immune system in relation to mercury (Hg) burden. Gene-transcription studies using minimally-invasive blood samples are useful to monitor physiological processes in wildlife that can be related to different stressors. Blood samples of 72 wild-caught seals (Weddell n=33; Ross n=12; crabeater n=27) in the Amundsen and Ross Seas in 2008-2011 were investigated. Copy numbers per μl mRNA transcription of xenobiotic biomarkers (aryl hydrocarbon receptor (AHR)), aryl hydrocarbon receptor nuclear translocator (ARNT) and peroxisome proliferator-activated receptor (PPARα) and immune relevant cell mediators (cytokines interleukin-2 (IL-2), interleukin-10 (IL-10) and heat-shock-protein 70 (HSP70)) were measured using reference genes Tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta polypeptide (YWHAZ) and ribosomal protein L4 (RPL4) by real time RT-qPCR. Hg concentration was analysed in fur. Hg concentration increased with body weight and standard length in all species. Crabeater seals showed a lower Hg concentration than Ross and Weddell seals. Species-specific differences in gene-transcription were found between all species with highest levels of AHR, ARNT and PPARα in crabeater seals. Ross seals showed highest IL-10 and HSP70 transcription, while HSP70 was exceptionally low in crabeater seals. Between Hg and HSP70 a clear negative relationship was found in all species. The species-specific, age and sex-dependent gene-transcription probably reflect dietary habits, pollutant exposure and immune status.

A Phospholipid-Protein Complex from Krill with Antioxidative and Immunomodulating Properties Reduced Plasma Triacylglycerol and Hepatic Lipogenesis in Rats

Dietary intake of marine omega-3 polyunsaturated fatty acids (n-3 PUFAs) can change the plasma profile from atherogenic to cardioprotective. In addition, there is growing evidence that proteins of marine origin may have health benefits. We investigated a phospholipid-protein complex (PPC) from krill that is hypothesized to influence lipid metabolism, inflammation, and redox status. Male Wistar rats were fed a control diet (2% soy oil, 8% lard, 20% casein), or diets where corresponding amounts of casein and lard were replaced with PPC at 3%, 6%, or 11% (wt %), for four weeks. Dietary supplementation with PPC resulted in significantly lower levels of plasma triacylglycerols in the 11% PPC-fed group, probably due to reduced hepatic lipogenesis. Plasma cholesterol levels were also reduced at the highest dose of PPC. In addition, the plasma and liver content of n-3 PUFAs increased while n-6 PUFAs decreased. This was associated with increased total antioxidant capacity in plasma and increased liver gene expression of mitochondrial superoxide dismutase (Sod2). Finally, a reduced plasma level of the inflammatory mediator interleukin-2 (IL-2) was detected in the PPC-fed animals. The present data show that PPC has lipid-lowering effects in rats, and may modulate risk factors related to cardiovascular disease progression.

Screening of microorganisms from deep-sea mud for Antarctic krill (Euphausia superba) fermentation and evaluation of the bioactive compounds

Twelve kinds of strains were isolated from deep-sea mud which can use Antarctic krill powder as the sole carbon/nitrogen source. These strains were identified by 16s rDNA sequence analysis and grouped into eight different genera, including Bacillus, Shewanella, Psychrobacter, Klebsiella, Macrococcus, Aeromonas, Acinetobacter, and Saccharomyces. After fermentation of Antarctic krill powder using these strains, bioactive compounds including total phenolics, free amino acids, and enzyme activities were investigated. Meanwhile, antioxidant activities of the fermentation liquors were also detected. Results showed that bioactive compounds could be effectively produced through fermentation process by these strains, of which three strains (Bacillus subtilis OKF04, Macrococcus caseolyticus OKF09, and Aeromonas veronii OKF10) could produce more than 650 mg/L total phenolics or 2000 mg/L total free amino acids. In terms of enzyme activities, almost all of the strains showed protease activity and amylase activity, but only Bacillus cereus OKF01 and Bacillus megaterium OKF05 performed lipase activity and chitinase activity, respectively. All of the fermentation liquors showed antioxidant activity, within which Bacillus megaterium OKF05, Macrococcus caseolyticus OKF09, and Aeromonas veronii OKF10 displayed it more prominently. These results demonstrate that the Antarctic krill powder could be effectively converted by microorganisms isolated from deep-sea mud for production of bioactive compounds mixture.

Effects of krill oil intake on plasma cholesterol and glucose levels in rats fed a high-cholesterol diet

BACKGROUND

In this study, whole krill oil (WKO) and phospholipid-type krill oil (PKO) with different lipid composition were prepared. The effects of KO intake on plasma cholesterol and glucose levels in Wistar rats fed a high-cholesterol diet (HCD) were investigated.

RESULTS

WKO contained 37.63% triglycerides, 48.37% phospholipids, 13.54% free fatty acids and 0.66% cholesterol, whereas the corresponding values for PKO were 0.59, 69.80, 28.53 and 1.09% respectively. Meanwhile, PKO contained much more polyunsaturated fatty acids (PUFA, 37.76%) than WKO (28.36%). After 4 weeks of HCD consumption, plasma levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and glucose increased significantly, but that of high-density lipoprotein cholesterol (HDL-C) decreased significantly. The intake of PKO and WKO for 4 weeks caused a significant reduction in body weight gain and plasma levels of TC and LDL-C in HCD-fed rats. Compared with WKO, PKO was more effective in decreasing plasma TC and LDL-C levels.

CONCLUSION

PKO showed better overall cholesterol-lowering effects than WKO, which may be due to its higher n-3 PUFA levels.

Seafood consumption and components for health

In recent years, in developed countries and around the world, lifestyle-related diseases have become a serious problem. Numerous epidemiological studies and clinical trials have demonstrated that diet is one of the major factors that influences susceptibility to lifestyle-related diseases, especially the middle-senile state. Studies examining dietary habits have revealed the health benefits of seafood consumption. Seafood contains functional components that are not present in terrestrial organisms. These components include n-3-polyunsaturated fatty acids, such as eicosapentaenoic acid and docosahexsaenoic acid, which aid in the prevention of arteriosclerotic and thrombotic disease. In addition, seafood is a superior source of various nutrients, such as protein, amino acids, fiber, vitamins, and minerals. This review focuses on the components derived from seafood and examines the significant role they play in the maintenance and promotion of health.