Marine microorganisms contribute to the health of the global ocean by supporting the marine food web and regulating biogeochemical cycles. Assessing marine microbial diversity is a crucial step towards understanding the global ocean. The waters surrounding Iceland are a complex environment where relatively warm salty waters from the Atlantic cool down and sink down to the deep. Microbial studies in this area have focused on photosynthetic micro- and nanoplankton mainly using microscopy and chlorophyll measurements. However, the diversity and function of the bacterial and archaeal picoplankton remains unknown. Here, we used a co-assembly approach supported by a marine mock community to reconstruct metagenome-assembled genomes (MAGs) from 31 metagenomes from the sea surface and seafloor of four oceanographic sampling stations sampled between 2015 and 2018. The resulting 219 MAGs include 191 bacterial, 26 archaeal and two eukaryotic MAGs to bridge the gap in our current knowledge of the global marine microbiome.
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Channel catfish (Ictalurus punctatus) muscle was subjected to 6 protein extraction and precipitation techniques using acid solubilization (pH 2.0, 2.5, and 3.0) or alkaline solubilization (pH 10.5, 11.0, 11.5) followed by precipitation at pH 5.5. The catfish protein isolate was compared with ground defatted white muscle. Alkali-processed catfish showed increased gel rigidity, gel strength, and gel flexibility compared to acid-processed catfish, which exhibited inconsistent functional performance, increasing and decreasing gel rigidity, gel strength, and gel flexibility. The gel rigidity (G′) at pH 3.0 in the absence of salt had the highest G′ of the acid treatments and was not significantly different from the alkaline-treated catfish muscle (P > 0.05). However in the presence of added salt pH treatment it had the lowest G′ and was different from alkaline treatments (P < 0.05) during break force testing. These results show that pH-shift processing of channel catfish muscle provides highly functional isolates with a potentially broad range of applications. This range of applications is possible due to the modification of the textural properties of catfish muscle protein produced using different acidic or alkaline pH solubility treatments.
The effect of using polyphosphates during prebrining and the effect of prebrining time of cold water shrimp (Pandalus borealis) was studied with low field nuclear magnetic resonance (LF-NMR) transverse relaxation time measurements (benchtop and unilateral) and near infrared (NIR) spectroscopy with the aim of improving shrimp processing. Strong calibrations were obtained for moisture content and water-holding capacity (WHC) using the NIR technique. Multivariate analysis indicated significant correlations between benchtop NMR parameters and moisture content and WHC, as measured with physicochemical methods and NIR spectroscopy. Significant correlations were also observed between NMR parameters and muscle pH, protein content, and phosphate content. The study showed that LF-NMR contribute to improved understanding of the shrimp brining process and to improved process control on-line or at-line, especially in combination with NIR measurements. However, optimization of the unilateral device is necessary.
Fish protein hydrolysates (FPH) possess various bioactivities making them a desirable ingredient in health foods. Saithe is an underutilized fish species and an excellent candidate for FPH. To produce high quality FPH removing undesirable components prior to the hydrolysis process is preferred and possible via the pH-shift process. The objective was to produce and investigate the properties of hydrolyzed protein isolates produced from minced saithe trimmings. Saithe trimmings were minced, homogenized in water and subjected to two variations of a pH shift process with (A) and without (B) dewatering. The latter process has the advantage of being less complicated and less expensive which is beneficial to the industry. Both systems were adjusted to 3% protein, pH 8 and 45 °C and subjected to enzyme hydrolysis. Both hydrolysis processes led to almost identical SDS-page peptide makeup. Both FPHs had similar antioxidative activities evaluated using oxygen radical absorbance capacity (ORAC), iron chelation ability and (DPPH) radical scavenging ability assays. FPH from process A had significantly higher ACE inhibition ability compared to FPH from process B.
These results demonstrate that saithe FPH has good antioxidative activities and a strong ability to inhibit ACE, and may thus have a potential as a bioactive food ingredient.
The quality and safety of food products is influenced by the presence of spoilage and pathogenic microorganisms. The presence and concentration of spoilage microorganisms is the main factor which determines the shelf life of a food product. The presence of pathogens could cause serious health problems. In order to simulate and predict the shelf life of Icelandic cod loins stored in styrofoam boxes in an actual supply chain from Iceland to France, a mathematical model for microbial growth is developed. Three specific spoilage organisms (SSO) are considered: Pseudomonas spp. (Ps), Photobacterium phosphoreum (Pp) and H2S-producing bacteria (H2S). The Baranyi and Roberts model is used for prediction of microbial growth in cod loins. The temperature dependence of the growth rate is taken into account through the square root model as a secondary model. Previous laboratory data are used for developing the primary and secondary models. The laboratory data from field trials, collected under dynamic temperature conditions, are used for calibration of the lag phase for each spoilage bacterium. Temperature recordings along with microbial and sensory analyses from the different cod groups are collected to test and validate the shelf life prediction (SLP) models. Finally, the model predictions are compared with shelf life data obtained by sensory evaluation of cooked products performed during the trials. Keywords: Icelandic cod, microbial growth models, shelf life prediction, field trials.
Food-borne listeriosis, caused by Listeria monocytogenes (Lm), is relatively rare but the relatively high rate of fatality (20–30%) compared to other food-borne microbial pathogens such as Salmonella makes it a serious disease. The foodstuff is recognised as the primary route of transmission for human exposure. A wide variety of food or raw material may become contaminated with Lm but the majority of listeriosis cases are related to ready-to-eat (RTE) food. The important factor related to food-borne listeriosis is that Lm can grow under low (refrigerated) temperatures when given sufficient time. Therefore, RTE products with long shelf life are under risk with respect to growth of Lm to critical concentrations. A stochastic model for the growth of Lm with the inhibiting effect of lactic acid bacteria (LAB) in cold smoked salmon (CSS) was developed. An existing deterministic model for the growth of Lm was adapted by adding the Winner stochastic process in order to simulate the growth of Lm. The Poisson distribution is used to represent the initial count (occurrence) of Lm. A deterministic model for growth of LAB is used and the inhibiting effects of Lm and LAB on each other are taken into account. The Beta-Poisson model is used for estimating the dose response. The model has been tested during field trials with CSS performed in August 2010. The salmon was slaughtered in Norway and transported to France where it was processed. The model, implemented within the QMRA module, indicated that growth of Lm would occur in the CSS samples investigated.
The aim of this work was to develop an approach for chromosomal engineering of the thermophile Rhodothermus marinus. A selection strategy for R. marinus had previously been developed; this strategy was based on complementing a restriction-negative trpB strain with the R. marinustrpB gene. The current work identified an additional selective marker, purA, which encodes adenylosuccinate synthase and confers adenine prototrophy. In a two-step procedure, the available Trp+ selection was used during the deletion of purA from the R. marinus chromosome. The alternative Ade+ selection was in turn used while deleting the endogenous trpB gene. Since both deletions are unmarked, the purA and trpB markers may be reused. Through the double deletant SB-62 (ΔtrpB ΔpurA), the difficulties that are associated with spontaneous revertants and unintended chromosomal integration of marker-containing molecules are circumvented. The selection efficiency in R. marinus strain SB-62 (ΔtrpB ΔpurA) was demonstrated by targeting putative carotenoid biosynthesis genes, crtBI, using a linear molecule containing a marked deletion with 717 and 810 bp of 5′ and 3′ homologous sequences, respectively. The resulting Trp+ transformants were colorless rather than orange-red. The correct replacement of an internal crtBI fragment with the trpB marker was confirmed by Southern hybridization analysis of the transformants. Thus, it appears that target genes in the R. marinus chromosome can be readily replaced with linear molecules in a single step by double-crossover recombination.
Low field Nuclear Magnetic Resonance (LF-NMR) relaxation time measurements were used to evaluate the effect of different pre-salting methods (brine injection of salt and/or phosphates followed by brining, solely brining, pickling and kench salting) on the protein denaturation and change in muscle properties during the production steps of dry salted cod fillets followed by rehydration. The NMR relaxation curves were affected by the salting method and represented well the structural differences between the salting methods at each processing step. Significant correlations were observed between the NMR relaxation parameters and all physicochemical quality properties measured, except the cooking yield, when samples from all processing stages were analyzed together. The longitudinal relaxation time T1, and the faster relaxing transverse relaxation time T21 were shown to be especially sensitive to protein denaturation in the fillets. The water distribution indicated that the salting and rehydration processes changed the cells irreversibly. The study indicated that pre-brining by brine injection followed by brining, with low salt concentrations, led to the least protein denaturation during the dry salting and rehydration process.
The oxidative stability of mahi mahi red muscle dipped in tilapia protein hydrolysates was evaluated. Alkali solubilised tilapia protein isolate was hydrolysed using Flavourzyme to 13% degree of hydrolysis. Whole tilapia protein hydrolysate and ultrafiltered fraction <10 kDa were used as dip solutions. Mahi mahi red muscle was dip treated either for 2 or 4 min and stored at 4 °C. Lipid hydroperoxides (PV), thiobarbituric acid reactive substances (TBARS) and a∗ value were measured at regular intervals. Results showed that dip treatments significantly decreased (p < 0.05) the formation of PV and TBARS over 90 h storage time. There was no significant (p > 0.05) difference between WH and <10 kDa fractions, and between 2 and 4 min treatments. Red colour of treated samples measured as a∗ value decreased with storage time, but was not significantly different from the control. It could be concluded that dip treatment for 2 min in whole tilapia protein hydrolysate may be used as a potential antioxidant treatment for improving oxidative stability of fish fillets.
Epidemics often result in organizational, policy and technical changes within a country. In 1999, an epidemic of campylobacteriosis was reported in Iceland. The recent availability of fresh poultry products in the marketplace was suggested as the source of infection. This paper reports on the context of the epidemic, reviews interventions implemented to prevent campylobacteriosis, and discusses lessons learned. A retrospective study of interventions implemented in Iceland from June 1995 to December 2007 was conducted by interviewing key informants and reviewing Iceland’s literature. Cumulative incidence rates of domestic campylobacteriosis by year and average incidence rates per epidemic period were calculated. Interventions included on-farm surveillance of Campylobacter, producer education, enhanced biosecurity measures, changes in poultry processing, a leak-proof packaging policy, a freezing policy for products from Campylobacter-positive poultry flocks, consumer education, and the creation of a legislated inter-organizational response committee. These interventions appear to have collectively contributed to a decrease in campylobacteriosis’ incidence rate near pre-epidemic baseline levels. Expert consultations revealed that the implementation of a Campylobacter surveillance program in poultry and the freezing policy were critical to controlling the disease in the Icelandic population. It was also recognized that new multidisciplinary collaborations among public health, veterinary, and food safety authorities and a sustained co-operation from the poultry industry were integral factors to the mitigation of the epidemic. Iceland’s response to the campylobacteriosis epidemic is a lesson learned of inter-disciplinary and inter-organizational precautionary public health action in the face of a complex public health issue.