The effect of filtered wood smoke (FS) processing on microbial growth in yellowfin tuna steaks was investigated. Steaks were treated for 32 h and then subjected to aerobic storage for 8 days and levels of aerobic bacteria studied. The FS treatment was compared to untreated tuna (exposed to air), 100% nitrogen (N2) (to investigate the specific effect of oxygen exclusion), 100% carbon monoxide (CO) (to investigate the effect of the CO molecule) and artificial FS (to investigate a gas with all the same gas compounds except for the smoke compounds). A study was also conducted with 21% carbon dioxide (CO2) to investigate the effect of CO2, which is found in both FS and the artificial FS. The results show that all treatments effectively (p<0.05) reduced aerobic microorganisms compared to the untreated control after 32 h, possibly due to an oxygen exclusion effect as well as to the presence of other active compounds in the gases. However, only FS, artificial FS, 100% CO and 21% CO2 treatments had a significant (p> 0.05) residual antibacterial / bacteriostatic effect post-treatment. The FS treatment had the most significant residual effect (p<0.05), and this study strongly suggests this effect is due to the presence of CO2, smoke components and CO.
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Survival problems are encountered at early stages of intensive fish rearing and antibiotics are widely used to remedy the situation. Probiotics may provide a potential alternative method to protect larvae from opportunistic and pathogenic bacteria and promote a balanced environment. This study was designed to search for new probiotics to target this critical period in cod rearing. Potential probionts were selected from the natural microbiota of cod aquacultural environment. The selection was based on several criteria: pathogen inhibition potential, growth characteristics, strain identification, metabolite production and adhesion to fish cell lines. Our study demonstrated that 14% of screened bacteria (n = 188) had antagonistic properties towards fish pathogens. The majority of these isolates were Gram-positive (81%), belonging to Firmicutes (69.2%) and Actinobacteria (11.5%) phyla based on 16S rRNA gene sequencing. Only 6 (3.2%) of 188 isolates could inhibit all three pathogens tested: Vibrio anguillarum, Aeromonas salmonicida subsp. achromogenes and Vibrio salmonicida. Differences observed in activity intensity and spectrum among inhibitory isolates emphasize the need to develop probiotic mixtures for efficient prophylactic methods. Comparison of growth behavior of inhibitory isolates and pathogens at cod rearing temperatures, metabolite production and adhesion capacity were considered for final probiont selection. Four promising isolates that could be used as a mixed supplement to rearing water were identified as putative probiotic bacteria. This study emphasizes the importance and potential of lactic acid bacteria in aquaculture.
A speciation technique for arsenic (As) has been applied using ion pair reverse phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS). Six As-species (arsenite, arsenate, dimethylarsinic acid, dimethylarsinous acid, monomethylarsonic acid and monomethylarsonic acid) have been separated with isocratic elution within less than 6 minutes. A cation exchange column was used for separation of AsB, AsC, Tetra (Me4As+) and TMAsO. The As chemical form and oxidation state is highly important in respect to toxicity; therefore total As-determination is insufficient for a complete toxicological evaluation and risk assessment. Arsenic speciation has been studied on urine samples of children from an As-affected area in the Iron Quadrangle, Brazil. DMAsV and MMAsV were the major urinary metabolites in these samples. The mean value for total As-concentration of all samples (n = 15) was 26.3 ng As mL−1 with a range of 16.1 to 55.2 ng As mL−1. TMAsO and AsC (arsenocholine) were not detected in this study. In most samples, monomethylarsonous acid [MMAsIII] was detected up to 2.0 ng As mL−1. DMAsIII was not detected at any time, most probably due to volatilisation and some oxidation to DMAsV. The chromatographic recoveries, calculated from ([sum (species) × 100] / total As in urine samples), ranged from 77.4 to 94.9%. This work also contributes to the pertinent discussion regarding the reliability of MMAsIII/ DMAsIII speciation in urine.
A bit fishy: Six arsenolipids have been isolated from cod-liver oil and identified by HPLC and mass spectrometry as a series of arsenic-containing long-chain fatty acids (for example, see picture). These fatty acids account for about 20 % of the total arsenolipid content of cod-liver oil.
Epidemiological studies have indicated that exposure of humans to inorganic arsenic in drinking water is associated with the occurrence of bladder cancer. The mechanisms by which arsenic induces this malignancy are still uncertain; however, arsenic metabolites are suspected to play a pivotal role. The aim of the present study was the investigation of uptake capabilities of human urothelial cells (UROtsa) compared with primary human hepatocytes (phH) as well as the intracellular distribution of the arsenic species. Additionally, we were interested in the cyto- and genotoxic potential (comet assay, radical generation) of the different arsenic compounds in these two cell types. Our results show that UROtsa cells accumulate higher amounts of the arsenic species than the phH. Differential centrifugation revealed that the arsenic compounds are preferentially distributed into nuclei and ribosomes. After 24-h exposure, arsenic is mainly found in the ribosomes of UROtsa cells and in the nuclei and mitochondria of phH. In contrast to the pentavalent arsenic species, the trivalent species induced a 4- to 5-fold increase in DNA damage in hepatocytes. Radical generation, measured by thiobarbituric acid reactive substances, was more pronounced in hepatocytes than in urothelial cells. In summary, the uptake of arsenic compounds appears to be highly dependent upon cell type and arsenic species. The nonmethylating urothelial cells accumulate higher amounts of arsenic species than the methylating hepatocytes. However, cyto- and genotoxic effects are more distinct in hepatocytes. Further studies are needed to define the implications of the observed accumulation in cellular organelles for the carcinogenic activity of arsenic.
Arsenic-containing hydrocarbons have been identified for the first time as natural components of fish oil.
Pseudomonas spp. is a group of microorganisms commonly found in fish and other fresh foods and is involved in their spoilage process. The aim of this study was to develop a rapid and accurate quantitative assay for Pseudomonas spp. in fish using real-time PCR. The assay targets the carbamoyl phosphate synthase gene (carA) with SYBR green based real-time PCR. The selectivity of the assay was confirmed using 24 Pseudomonas strains and 55 non-pseudomonad strains. A linear quantification was established over seven orders of magnitude, from 40 - 47 copies reaction−1. The assay was validated on cod samples collected during two shelf life trials and showed a high degree of correlation to the plate count method (rP = 0.891) where the difference between the methods was 0.04 log10CFU g−1 on average. The study shows that it is possible to accurately quantify the specific spoilage organisms belonging to the genus Pseudomonas in fish using real-time PCR. The method takes less than 5 h from sampling to results. The short detection time of the method can provide the fish industry with an important tool for quality control and processing management.
Six glycoside hydrolase (GH) family 13 members, classified under the polyspecific neopullulanase subfamily GH13_20 (also termed cyclomaltodextrinase) were analyzed. They originate from thermophilic bacterial strains (Anoxybacillus flavithermus, Laceyella sacchari, and Geobacillus thermoleovorans) or from environmental DNA, collected after in situ enrichments in Icelandic hot springs. The genes were isolated following the CODEHOP consensus primer strategy, utilizing the first two of the four conserved sequence regions in GH13. The typical domain structure of GH13_20, including an N-terminal domain (classified as CBM34), the catalytic module composed of the A-and B-domains, and a C-terminal domain, was found in five of the encoded enzymes (abbreviated Amy1 , 89, 92, 98 and 132). These five enzymes degraded cyclomaltodextrins (CDs) and starch, while only three, Amy92 (L. sacchari), Amy98 (A. flavithermus) and Amy132 (environmental DNA), also harbored neopullulanase activity. The L. sacchari enzyme was monomeric, but with CD as the preferred substrate, which is an unusual combination. The sixth enzyme (Amy29 from environmental DNA), was composed of the ABC domains only. Preferred substrate for Amy29 was pullulan, which was degraded to panose, and the enzyme had no detectable activity on CDs. In addition to its different activity profile and domain composition, Amy29 also displayed a different conservation (LPKF) in the fifth conserved region (MPKL) proposed to identify the subfamily. All enzymes had apparent temperature optima in the range 50–65 ° C, while thermostability varied, and was highest for Amy29 with a half-life of 480 min at 80 ° C. Calcium dependent activity or stability was monitored in four enzymes, but could not be detected for Amy29 or 98. Tightly bound calcium can, however, not be ruled out, and putative calcium ligands were conserved in Amy98.
Development of new technologies and preservation methods to offer conveniently packed fish with sufficient keeping quality is important to meet increasing demand for value-added fresh fish products on the market. The aim of this study was to investigate the effect of combined application of modified atmosphere packaging (MAP) and superchilled storage on the shelf life of fresh cod loins. Fresh cod loins were packed in polystyrene boxes and in MA (CO2/ N2/ O2: 50% / 45% / 5%) on day 3 postcatch and stored at chilled (1.5 ° C) and superchilled (−0.9 ° C) temperatures. Quantitative descriptive analysis (QDA) and physical, chemical, and microbial analyzes were carried out during the 21 d of storage. Superchilled storage alone compared to traditional chilled storage in polystyrene boxes increased the total shelf life (days from catch) of cod loins from 9 to 16 or 17 d. Chilled MA packaging increased the shelf life from 9 to 14 d and when MAP and superchilled storage were combined, a synergistic effect was observed and the shelf life was further extended to at least 21 d. It is noteworthy that the characteristic fresh and sweet taste can be maintained longer under such conditions. This could contribute to enhanced eating quality of fresh cod fillets for consumers in distant markets. However, MAP combined with superchilled storage resulted in different textural properties. Superchilled MA packed cod loins had more meaty texture compared to other sample groups after 7-d storage.
The effect of salinity on growth, feed conversion efficiency and blood physiology was investigated by rearing Atlantic halibut Hippoglossus hippoglossus (initial weight 25.5 ± 0.8 g, mean ± SEM) at salinities of 15, 25 or 32 ‰ for 4 months at 12 ° C. The final mean weight of the fish reared at 15 ‰ (135.9 ± 5.1) and 25. (130.8 ± 5.1) was significantly larger than that of fish reared at 32. (107.6 ± 5.2). Similarly, the specific growth rates (SGR) and feed conversion efficiency (FCE) were significantly higher at both 15 ‰ (SGR: 1.29 ± 0.03; FCE: 1.21 ± 0.04) and 25 ‰ (SGR: 1.25 ± 0.04; FCE: 1.18 ± 0.06) compared to 32 ‰ (SGR: 1.16 ± 0.04; FCE: 0.97 ± 0.10). Of the osmoregulatory and metabolic parameters analyzed in plasma Na+ and glucose were significantly lower in fish reared at 15 ‰ compared to both 25 ‰ and 32 ‰. The acid – base balance was influenced by the salinity treatment as there was a general trend towards higher pH, pCO2 and HCO3- in the full salinity group compared to the 15 ‰ group. The results clearly show that the optimum conditions for farming Atlantic halibut, both with respect to growth rate and feed conversion, is at salinities lower than 32 ‰. This is an important finding for the halibut industry.