Impact of different pretreatments on chemical compositions of Indian mackerel mince was studied. Mince prepared using washing / membrane removal / alkaline solubilization process (W – MR – Al) contained the lowest remaining myoglobin and haem iron content and also showed the lowest total lipid and phospholipid contents. When mince and W – MR – Al were hydrolyzed using Alcalase for up to 120 min, a higher degree of hydrolysis (DH) was found in W – MR – Al after 30 min of hydrolysis. Furthermore, hydrolyzate from W – MR – Al had lower peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and non-haem iron content throughout hydrolysis period (P <0.05). When hydrolyzate powder produced from mince and W – MR – Al (0–0.3% w / v) were fortified in milk, the former resulted in the lower likeness score (P <0.05) at all levels used. The addition of the latter, for up to 0.2%, had no effect on likeness of all attributes, compared with milk without fortification (P > 0.05). Therefore, the appropriate pretreatment of mince yielded hydrolyzate with lower fishy odor.
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The Atlantic salmon, Salmo salar, shows geographically structured differentiation at various classes of molecular genetic variation, among and within river stocks. Nuclear microsatellite locus variation at multiple loci has been exploited for more than a decade as a marker for the continental origin of fish caught at sea in distant-water fisheries. However, a simpler, more cost-effective, but still accurate, assignment can be obtained using a single microsatellite locus in combination with a mitochondrial DNA (mtDNA) single-nucleotide polymorphism (SNP) detected by restriction enzyme digestion. Following on from this, a preliminary study was made of the potential for using mtDNA SNP variation to enhance the resolving power and cost-effectiveness of within-continent assignment of European salmon as determined using microsatellites. Variation in 20 mtDNA regions, encompassing ∼43% of this genome, in 330 salmon from 29 rivers across Europe, was analyzed. High levels of inter-individual and inter-river variation were found, as well as evidence of regional differentiation paralleling observed microsatellite differentiation. The observations indicate scope for using mtDNA SNPs along with microsatellites for genetically based assignment of European salmon to region and river of natal origin, but further study is needed.
Fish protein hydrolysates (FPH) have gained increasing attention as nutritious fish products. Lipid oxidation associated with fishy odor in FPH limits its utility. Thus, an appropriate pretreatment of fish mince prior to hydrolysis by lowering pro-oxidants and lipid substrates could tackle such a problem. Different pretreatments of Nile tilapia minces including (1) washing (W), (2) washing and membrane removal (W-MR), and (3) washing / membrane removal followed by acid or alkaline solubilization (W-MR-Ac or W -MR-Al) were conducted prior to hydrolysis. During the hydrolysis process, degree of hydrolysis (DH) and chemical changes were monitored. Color and sensory properties of milk fortified with hydrolysates prepared from mince without and with pretreatment were also determined. Among the pretreated mince samples, W-MR-Al contained the lowest remaining myoglobin and heme iron contents and also showed the lowest total lipid and phospholipid contents (P<0.05). When mince and W-MR-Al were hydrolyzed using Alcalase for up to 120 min, higher DH were found in W-MR-Al. Furthermore, lower peroxide values, thiobarbituric acid reactive substances, and non-heme iron contents of hydrolysates from W-MR-Al were also observed (P <0.05). When FPH powder from mince and W-MR-Al (0.3% to 0.5%) were fortified in milk, the former yielded a lower likeness score (P<0.05) at all levels used. The addition of the latter up to 0.5% had no effect on likeness of all attributes, compared with control (without FPH). An appropriate pretreatment of mince was a promising approach to lower fishy odor problem, caused by lipid oxidation in FPH.
Freezing of herring (Clupea harengus) for human consumption is increasing in the Nordic herring industry, either onboard the fishing vessels or right after landing. The quality of frozen herring as a raw material does not only depend on the frozen storage conditions applied, but also on compositional features, something which in turn can vary with season and catching ground. To unravel the link between biological variations, basic muscle composition, and sensory properties of frozen herring, a unique herring raw material was caught by commercial fishing vessels at three locations: around Iceland, outside the Norwegian coast, and in Kattegat / Skagerrak. The samplings were done according to a specific scheme and conducted over several seasons and 2 years. The herring was converted into butterfly fillets, packed in cardboard boxes, frozen, and then stored at –20 ° C or –80 ° C for up to 18 mo. The sensory quality was characterized by objective sensory profiling. It was shown that two generalized sensory variables could be defined from a principal component analysis of the sensory data. Except for the expected pronounced effect from storage time, the most distinct variation followed the lipid content, which in turn varied with season. An unexpected conclusion was that catching location only had a minor affect on the changes in sensory quality of herring during frozen storage. Knowledge about how season and catching location affects herring during frozen storage will be useful for optimizing the utilization of herring for frozen storage for human consumption.
High gene flow is considered the norm for most marine organisms and is expected to limit their ability to adapt to local environments. Few studies have directly compared the patterns of differentiation at neutral and selected gene loci in marine organisms. We analyzed a transcriptome-derived panel of 281 SNPs in Atlantic herring (Clupea harengus), a highly migratory small pelagic fish, for elucidating neutral and selected genetic variation among populations and to identify candidate genes for environmental adaptation. We analyzed 607 individuals from 18 spawning locations in the northeast Atlantic, including two temperature clines (5–12 ° C) and two salinity clines (5–35 ‰). By combining genome scan and landscape genetic analyzes, four genetically distinct groups of herring were identified: Baltic Sea, Baltic – North Sea transition area, North Sea / British Isles and North Atlantic; notably, samples exhibited divergent clustering patterns for neutral and selected loci. We found statistically strong evidence for divergent selection at 16 outlier loci on a global scale, and significant correlations with temperature and salinity at nine loci. On regional scales, we identified two outlier loci with parallel patterns across temperature clines and five loci associated with temperature in the North Sea / North Atlantic. Likewise, we found seven replicated outliers, of which five were significantly associated with low salinity across both salinity clines. Our results reveal a complex pattern of varying spatial genetic variation among outlier loci, likely reflecting adaptations to local environments. In addition to disclosing the fine scale of local adaptation in a highly vagile species, our data emphasize the need to preserve functionally important biodiversity.
The short and long term effects of short photoperiods on growth and maturity were investigated in 240 individually tagged juvenile Arctic charr (Salvelinus alpinus). The Arctic charr were reared at constant temperature (12 ° C) and on four different light regimes; one group on continuous light (LD24: 0) as control and three groups experienced a period of short day (LD8: 16) on a three subsequent 6 week periods ie 24th September – 6thNovember (LD8: 16Sep – Nov), 6th November – 19th December (LD8: 16Nov – Dec), 19th December-29th January (LD8: 16Dec – Jan). Before and after the short photoperiod treatment the groups were reared at continuous light. The growth of the fish was monitored over a period of 11 months. At the termination of the experiment in September 2009, the body mass of the three groups receiving a short day period (LD8: 16 Sep – Nov, LD8: 16 Nov – Dec and LD8: 16 Dec – Jan) was significantly higher (13.9% , 12.9% and 10.7% respectively) than that of the group reared at continuous light (LD24: 0). The three groups receiving the short photoperiod did not differ in weight at the end of the trial so the time of year at which the short photoperiod was applied did not seem to be of importance regarding the growth enhancement. The maturation rate did not appear to be affected by the photoperiod treatments. The improved growth was mainly a result of a higher feed intake and improved feed conversion efficiency for the period following transfer of the charr from a short photoperiod to the continuous light. Application of such a winter photoperiod during the juvenile phase can, therefore, be used as a tool to increase the biomass and growth rate in Arctic charr farming.
Illegal, Unreported and Unregulated fishing has had a major role in the overexploitation of global fish populations. In response, international regulations have been imposed and many fisheries have been 'eco-certified' by consumer organizations, but methods for independent control of catch certificates and eco-labels are urgently needed. Here we show that, by using gene-associated single nucleotide polymorphisms, individual marine fish can be assigned back to population of origin with unprecedented high levels of precision. By applying high differentiation single nucleotide polymorphism assays, in four commercial marine fish, on a pan-European scale, we find 93–100% of individuals could be correctly assigned to origin in policy-driven case studies. We show how case-targeted single nucleotide polymorphism assays can be created and forensically validated, using a centrally maintained and publicly available database. Our results demonstrate how application of gene-associated markers will likely revolutionize origin assignment and become highly valuable tools for fighting illegal fishing and mislabeling worldwide.
The introduction of Next Generation Sequencing (NGS) has revolutionized population genetics, providing studies of non-model species with unprecedented genomic coverage, allowing evolutionary biologists to address questions previously far beyond the reach of available resources. Furthermore, the simple mutation model of Single Nucleotide Polymorphisms (SNPs) permits cost-effective high-throughput genotyping in thousands of individuals simultaneously. Genomic resources are scarce for the Atlantic herring (Clupea harengus), a small pelagic species that sustains high revenue fisheries. This paper details the development of 578 SNPs using a combined NGS and high-throughput genotyping approach. Eight individuals covering the species distribution in the eastern Atlantic were bar-coded and multiplexed into a single cDNA library and sequenced using the 454 GS FLX platform. SNP discovery was performed by again sequence clustering and contig assembly, followed by the mapping of reads against consensus contig sequences. Selection of candidate SNPs for genotyping was conducted using an in silico approach. SNP validation and genotyping were performed simultaneously using an Illumina 1,536 GoldenGate assay. Although the conversion rate of candidate SNPs in the genotyping assay cannot be predicted in advance, this approach has the potential to maximize cost and time efficiencies by avoiding expensive and time-consuming laboratory stages of SNP validation. Additionally, the in silico approach leads to lower ascertainment bias in the resulting SNP panel as marker selection is based only on the ability to design primers and the predicted presence of intron-exon boundaries. Consequently SNPs with a wider spectrum of minor allele frequencies (MAFs) will be genotyped in the final panel. The genomic resources presented here represent a valuable multi-purpose resource for developing informative marker panels for population discrimination, microarray development and for population genomic studies in the wild. +
The ethanol production capacity from sugars and lignocellulosic biomass hydrolysates by Thermoanaerobacter strain AK5 was studied in batch cultures. The strain converts various carbohydrates to acetate, ethanol, hydrogen, and carbon dioxide. Maximum ethanol yields on glucose and xylose were 1.70 and 1.35 mol (mol sugars)−1, respectively. Increased initial glucose concentration inhibited glucose degradation and end-product formation leveled off at 30 mM. Cultivation of the strain with decreased liquid – gas (LG) ratios on glucose resulted in a shift to more acetate and less ethanol. End-product formation from glucose was further manipulated by adding extracellular electron acceptor (thiosulfate) or using a coculture of hydrogenotrophic methanogen. In both cases, the hydrogen-scavenging systems resulted in a dramatic shift from ethanol to acetate. Ethanol production from 4.5 g L–1 of complex biomass hydrolysates (grass, hemp, wheat straw, newspaper, and cellulose) pretreated with acid (0.50% H2SO4), alkali (0.50% NaOH), and without acid / alkali (control) and the enzymes Celluclast and Novozymes 188 (0.1 mL g–1 dry weight (dw); 70 and 25 U g–1 of Celluclast and Novozyme 188, respectively) was investigated. Highest ethanol yields (27.5 mM; 5.5 mM (g biomass)−1) were obtained on cellulose but lowest on hemp leafs (5.1 mM; 0.8 mM g–1). Chemical pretreatment increased ethanol yields substantially from lignocellulosic biomass but not from cellulose. The most-pronounced increase was on straw hydrolysates, where ethanol production increased from 5.5 mM to 15.2 mM on alkali-pretreated biomass. Ethanol yields were increased from 5.5 mM to 7.7 mM g–1 on cellulose by decreasing the hydrolyzate concentration to 2.25 g L–1, because of incomplete glucose degradation in the higher-loaded system.
AsaP1 is a toxic aspzincin metalloendopeptidase secreted by the fish pathogen Aeromonas salmonicida subsp. achromogenes. The protease is highly immunogenic and antibodies against AsaP1 evoke a passive protection against infection with A. salmonicida subsp. achromogenes. The protease is expressed as 37 kDa pre-pro-protein and processed to an active enzyme of 19 kDa in A. salmonicida subsp. achromogenes. Recombinant expression of AsaP1rec in E. coli results in a protease of 22 kDa that is not secreted. AsaP1rec induces comparable pathological changes in Atlantic salmon (Salmo salar L.) to native AsaP1wt. The aim of the study was to construct AsaP1 toxoids by exchanging catalytically important amino acids in the active site region of the protease.
Four different AsaP1 mutants (AsaP1E294A, AsaP1E294Q, AsaP1Y309A, and AsaP1Y309F) were successfully constructed by one step site directed mutagenesis, expressed in E. coli BL21 C43 as pre-pro-proteins and purified by His-tag affinity chromatography and gel filtration. Three of the resulting mutants (AsaP1E294A, AsaP1E294Q, and AsaP1Y309A) were not caseinolytic active and were detected as unprocessed pre-pro-proteins of 37 kDa. Caseinolytic active AsaP1rec and a mutant with reduced activity, AsaP1Y309F, were processed to a size of 22 kDa. Furthermore, AsaP1rec is able to process the inactive mutants to the mature size of 22 kDa, allowing the conclusion that AsaP1 is autocatalytically processed.
All four mutants AsaP1E294A, AsaP1E294Q, AsaP1Y309A and AsaP1Y309F are non-toxic in fish but induce a specific anti-AsaP1 antibody response in Arctic charr (Salvelinus alpinus L.) and are therefore true toxoids and possible vaccine additives.