Fish muscle protein films were prepared from blue marlin (Makaira mazara Jordan & Evermann) meat which had been stored at 30 ° C to intentionally lower the meat quality. In this study, the effects of meat quality and pH on the formation of these protein films were investigated. Moreover, ε-polylysine was added to the film-forming solutions to reduce the microbial population of films. The mechanical properties of the films were slightly affected by acidic and alkaline pHs. However, the water vapor permeability of muscle protein films was not affected by either the quality of the fish meat or the pH of the film-forming solutions. SDS-PAGE (sodium dodecyl sulfate- polyacrylamide gel electrophoresis) showed the degradation of myosin heavy chain in acidic films and polymerization in alkaline films. It was revealed that biodegradable films can be produced even from very low quality fish meat, and that the bacterial population of films could be drastically reduced by the addition of ε-polylysine.
Category: Branches
Atlantic cod of initial mean weight ∼220 g were fed a control diet and three diets in which fish meal (FM) was replaced with increasing levels of full-fat soybean meal (FFS) supplied at 12, 24, and 36% of dry diet, for 12 weeks. There were no significant differences in final weights, but the specific growth rate (SGR) was significantly higher in fish fed the control (FFS0) diet compared to fish fed the FFS12 and FFS36 diets, and the feed conversion ratio (FCR) was significantly lower in fish fed the FFS0 diet compared to the other three treatments. The fatty acid (FA) compositions of the cod muscle and liver were highly affected by dietary treatment, and linear relationships between dietary and tissue FA concentrations were shown for some of these. Moreover, selective utilization or accumulation in the tissues of specific FA was suggested by the results.
The biochemical and genetic search for a bc 1 complex in Rhodothermus marinus was always fruitless; however, a functional equivalent, ie having quinol: cytochrome c oxidoreductase activity was characterized. Now, with the sequencing of R. marinus genome, it was possible to assign the N-terminal sequences of several proteins of this complex to its coding genes. The alternative complex III from R. marinus has the same genomic organization of the so-called MFIcc complexes, proposed to be oxidoreductases of the respiratory and photosynthetic electron transfer chains. In this report, we establish undoubtedly the existence of an alternative complex III, a functional substitute of the bc 1 complex, by its identification at both the biochemical and genomic level.
Trehalases play a central role in the metabolism of trehalose and can be found in a wide variety of organisms. A periplasmic trehalase (a, a-trehalose glucohydrolase, EC 3.2.1.28) from the thermophilic bacterium Rhodothermus marinus was purified and the respective encoding gene was identified, cloned and overexpressed in Escherichia coli. The recombinant trehalase is a monomeric protein with a molecular mass of 59 kDa.
Maximum activity was observed at 88C and pH 6.5. The recombinant trehalase exhibited a Km of 0.16 mM and a Vmax of 81 lmol of trehalose (min) 1 (mg of protein) 1 at the optimal temperature for growth of R. marinus (65C) and pH 6.5. The enzyme was highly specific for
trehalose and was inhibited by glucose with a Ki of 7 mM. This is the most thermostable trehalase ever characterized. Moreover, this is the first report on the identification and characterization of a trehalase from a
thermophilic bacterium.
The aerobic respiratory chain of the thermohalophilic bacterium Rhodothermus marinus has been extensively studied. In this study the isolation and characterization of a third oxygen reductase expressed in this organism are described. This newly isolated enzyme is a typical member of the type B family of haem-copper oxygen reductases, showing 43% amino acid sequence identity and 63% similarity with the ba3 oxygen reductase from Thermus thermophilus. It constitutes two subunits with apparent molecular masses of 42 and 38 kDa. It contains a low-spin B-type haem and a high-spin A-type haem. A stoichiometry of 1B: 1A haem per protein was obtained by spectral integration of UV-visible spectra. Metal analysis showed the presence of two iron and three copper ions, which is in agreement with the existence of a CuA center.
Taking advantage of having two spectroscopically distinct haems, the redox behavior of the ba3 oxygen reductase was analyzed and discussed in the framework of a model with interacting centers. Both haems, B and A, present two transitions, have unusually low reduction potentials of −65 mV and an interaction potential of −52.5 mV.
An α-l-rhamnosidase (EC 3.2.1.40) from a newly discovered thermophilic bacterium was expressed in Escherichia coli BL21 DE3 pRIL cells. The cells were immobilized in Ca2+-alginate beads. The temperature of 50 ° C used in reactions, appeared to be sufficient for making the mesophilic strain porous enough for the substrate to access the cloned thermostable enzyme. Pretreatment of cells with heat or lysozyme prior to bead formation did not improve the results. The best cell concentration (w / w) for bead preparation was found to be 0.0192 g ml−1 and stability of beads increased if CaCl2 concentration in buffers and substrate was kept at 50 mM. In a 60 min assay, the optimal pH of the entrapped cells was found to be 7.8 and the optimal temperature 60 ° C. By packing the beads in a column, a bioreactor for production of l-rhamnose from naringin was created. Full degradation of 7.9 mM naringin could be reached by running the reactor at 1 ml min−1 at 50 ° C. The optimal running temperature of the reactor was found to be 50 ° C and the reactor was fully stable over 3 days at that temperature. On the fourth day, substrate degradation capacity had decreased by 10–15%.
Organotin compounds have been widely used as stabilizers and anti-fouling agents with the result that they are ubiquitously distributed in the environment. Organotins accumulate in the food chain and potential effects on human health are disquieting. It is not known as yet whether cell surface adsorption or accumulation within the cell, or indeed both is a prerequisite for the toxicity of organotin compounds. In this study, the alkylated tin derivatives monomethyltin trichloride (MMT), dimethyltin dichloride (DMT), trimethyltin chloride (TMT) and tetramethyltin (TetraMT) were investigated for cyto- and genotoxic effects in CHO-9 cells in relation to the cellular uptake. To identify genotoxic effects, induction of micronuclei (MN), chromosome aberrations (CA) and sister chromatid exchanges (SCE) were analyzed and the nuclear division index (NDI) was calculated. The cellular uptake was assessed using ICP-MS analysis. The toxicity of the tin compounds was also evaluated after forced uptake by electroporation. Our results show that uptake of the organotin compounds was generally low but dose-dependent. Only weak genotoxic effects were observed after exposure of cells to DMT and TMT. MMT and TetraMT were negative in the test systems. After forced uptake by electroporation MMT, DMT and TMT induced significant DNA damage at non-cytotoxic concentrations. The results presented here indicate a considerable toxicological potential of some organotin species but demonstrate clearly that the toxicity is modulated by the cellular uptake capability.
The influence of factors in catching and processing of cod on fillet yield, gaping, number of nematodes and prevalence of bruises was studied in close cooperation with an Icelandic fisheries company. Data was collected onboard fishing vessels and in a fish processing plant in N-Iceland, for 29 months. Conditions during trawling and storing were recorded. Fishing ground had significant effect (95% significance limit) on fillet yield, gaping and number of parasites. Time of year had significant effect on all variables. The time-lag from catch to processing (age of the raw material) affected both gaping and bruises significantly. Fillet yield was closely correlated to both condition factor and head proportion. The results can be used for decision-making on where to direct the fishing boats and what to do with the catch after unloading it.
This paper describes the responses of consumers in six European countries (Greece, Italy, Spain, France, Iceland and United Kingdom) tasting meat from twelve different local types of lambs produced in those same six countries. Animals represented 10 breeds and crossbreeds, three sexes, several diets composed of either milk, concentrates and various forages as main ingredients and different slaughter ages, from 1 and 12 months, and carcass weights, from 5.5 to 30.4 kg. Tests were conducted by 36 volunteer families in each of the six countries involved in the study. Families were asked to roast the joints using their own cooking criteria, evaluating (from “dislike extremely” to “like extremely”) flavor, tenderness, juiciness and overall liking. Also the cook was asked to rate the odor during cooking. Country and lamb type and their interaction were statistically significant for all the variables analyzed. Results suggest a link between the assessments of a given lamb type and the consumers' culinary background, showing clear associations between country and lamb type preferences. It was possible to separate, independently of the country, different groups of families with similar preferences. Five family groups, which included 88 families (40,74%), had a clear Mediterranean origin and preferred types of lamb fed either milk or mainly concentrate diets. Seven family groups, which included 93 families (43.06%) with a clear northern origin, preferred types reared on grass or with grass included in the diet. The rest of the groups (four) that included 35 families (16.20%) had no clear composition (northern or Mediterranean), and they had a wider taste preference. It can clearly be seen that there are two categories of consumers of lamb in the analyzed European market: those who prefer “milk or concentrate taste” and those who prefer “grass taste”.
Lipid oxidation and functional properties were monitored in spray dried fish powder made from saithe (Pollachius virens) by-products. The fresh powder exhibited slight antioxidant activity in a model system of linoleic acid emulsion. The freshly made powder had low lipid extract-ability in polar solvents and over 30% free fatty acids (FFA). Further lipid oxidation took place during storage, independent of storage temperatures. Functional properties measured by color changes, water-binding capacity, apparent viscosity and protein solubilty changed more during storage at 30 ° C than 0 ° C.