Bioaccumulation of perfluorochemicals in sediments by the aquatic oligochaete Lumbriculus variegatus

Bioaccumulation of perfluoroalkyl sulfonates, perfluorocarboxylates, and 2-(N-ethylperfluorooctane sulfonamido) acetic acid (N-EtFOSAA) from laboratory-spiked and contaminated field sediments was assessed using the freshwater oligochaete, Lumbriculus variegatus. Semistatic batch experiments were conducted to monitor the biological uptake of these perfluorochemicals (PFCs) over 56 days. The elimination of PFCs was measured as the loss of PFCs in L. variegatus exposed to PFC-spiked sediment for 28 days and then transferred to clean sediment. The resultant data suggest that PFCs in sediments are readily bioavailable and that bioaccumulation from sediments does not continually increase with increasing perfluorocarbon chain length. Perfluorooctane sulfonate (PFOS) and perfluorononanoate were the most bioaccumulative PFCs, as measured by laboratory-based estimated steady-state biota sediment accumulation factors (BSAFs) and BSAFs measured using contaminated field sediments. Elimination rate constants for perfluoroalkyl sulfonates and perfluorocaroboxylates were generally smaller than those previously measured for other organic contaminants. Last, a PFOS precursor, N-EtFOSAA, accumulated in the worm tissues and appeared to undergo biotransformation to PFOS and other PFOS precursors. This suggests that N-EtFOSAA, which has been detected in sediments and sludge often at levels exceeding PFOS, may contribute to the bioaccumulation of PFOS in aquatic organisms.     

Brominated and chlorinated dioxins, PCBs and brominated flame retardants in Scottish shellfish: methodology, occurrence and human dietary exposure

The most commonly consumed shellfish species produced in Scotland - mussels, oysters and scallops - were investigated for the occurrence of a range of brominated and chlorinated contaminants in order to establish current levels and estimate human dietary exposure. Flesh from individual sub-samples was representatively pooled and 35 composites were analysed for brominated and chlorinated dioxins (PBDD/Fs, PCDD/Fs), brominated and chlorinated biphenyls (PBBs, PCBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs) and tetrabromobisphenol A (TBBPA). The analytical methodology used (13)C(12) labelled surrogates of the target compounds, with GC coupled to (usually) high resolution MS, and LC-MS/MS for HBCD and TBBPA analysis. Positive identifications were made in the majority of samples for most analytes with the exception of TBBPA and most PBDD congeners measured. None of the levels detected for PCDD/F and PCB were above the maximum permitted levels specified in European Union regulations. The levels of brominated furans predominated over brominated dioxins, reflecting the environmental distribution and source emission profiles of these contaminants, and relatively high levels of the tri-brominated congeners were observed. Levels of the flame retardant chemicals reflected current and legacy use, with appreciable concentrations of PBDEs and HBCDs (predominantly alpha-HBCD) but far lower levels of PBBs. TBBPA was not detected in any of the species. In general, mussels and oysters displayed relatively higher levels of contamination than scallops, although the gonad tissue of the latter showed significant levels of brominated dioxins. The estimated adult dietary intakes of PCDD/Fs and PCBs arising from the consumption of a typical portion of these foods in combination with an otherwise average UK diet were in the range 0.5-0.6 pg World Health Organisation (WHO)-toxic equivalent (TEQ)(2005)/kg bodyweight per day. These estimated dietary intakes are well within the Tolerable Daily Intake for dioxins and dioxin-like PCBs of 2 pg WHO-TEQ(2005)/kg bodyweight/day endorsed by the independent expert Committee on Toxicology of Chemicals in Food, Consumer Products and the Environment. The corresponding intakes for sumPBDEs and sumHBCDs were 5.6-6.1 and 5.9-7.9 ng/kg bodyweight/day respectively.     

Discrimination between defective and non-defective Brazilian coffee beans by their volatile profile

The coffee roasted in Brazil is considered to be of low quality, due to the presence of defective coffee beans that depreciate the beverage quality. In view of the fact that coffee flavour is directly related to the volatile compounds produced during roasting, the objective of the present study was to perform a comparative evaluation of the volatile fraction of defective (black, immature, sour) and healthy coffee beans, in order to find possible chemical markers for detection of defective coffee beans in roasted coffee. Volatiles extraction and concentration was performed by solid phase micro-extraction (SPME) of the roasted coffee headspace, using a triple phase (divinylbenzene/carboxen/polydimethylsiloxane) fiber. Analysis of the volatile profiles was performed by GC–MS. The results obtained showed that the proposed methodology was adequate for extraction, concentration and analysis of the coffees volatile profile. Several substances were identified as possible markers for differentiating black, sour and immature beans from healthy coffee beans. Statistical analysis of the data by principal components (PCA) demonstrated that the volatile profile enables the differentiation of healthy and defective coffees. The data were separated into two major groups, one represented by immature and black beans and the other by healthy and sour coffee beans. Such results indicated that black and sour beans can be associated to fermentation of immature and of healthy beans, respectively.     

Effect of chitosan on physical and chemical processes during bread baking and staling

The objective of this research was to investigate the effect of chitosan on the interaction of water with bread ingredients and on the rate of staling. The changes in freezable bound water and total water contents in bread crumb were assessed by differential scanning calorimetry from water melting and evaporation endothermic peak areas. It was found that freezable water content and total water content in bread crumb decrease during staling more rapidly in the presence of chitosan. The weak interaction of freezable water with protein and starch polymeric chains in bread crumb becomes stronger, but the interaction of nonfreezable bound water with protein and starch molecules in bread crumb becomes weaker in the course of staling during bread storage. Two stages of bread crumb staling were indicated. Chitosan increases the rate of bread staling during both stages. It was suggested that during bread staling chitosan increases water migration rate from crumb to crust, prevents amylose-lipid complexation, and increases dehydration rate both for starch and gluten.     

Modelling of the lignin peroxidase LIII of Phlebia radiata: use of a sequence template generated from a 3-D structure

A model of the lignin peroxidase LIII of Phlebia radiata wasconstructed on the basis of the structure of cytochrome c peroxidase(CCP). Because of the low percentage of amino acid identitybetween the CCP and the lignin peroxidase LIII of Phlebia radiata,alignment of the sequences was based on the generation of atemplate from a knowledge of the 3-D structure of CCP and consensussequences of lignin peroxidases. This approach gave an alignmentin which all the insertions in the lignin peroxidase were placedat loop regions of CCP, with a 21.1% identity for these twoproteins. The model was constructed using this alignment andthe computer program COMPOSER, which assembles the model asa series of rigid fragments derived from CCP and other proteins.Manual intervention was required for some of the longer loopregions. The -helices forming the structural framework, andespecially the haem environment of CCP, are conserved in theLIII model and the core is close packed without holes. A possiblesite of the substrate oxidation at the haem edge of LIII isdiscussed.     

Cholesterol oxidation in heated lard enriched with two levels of cholesterol

Cholesterol oxidation in lard containing two levels of added cholesterol was monitored using capillary gaschromatography. Loss of cholesterol and formation of cholesterol oxidation products (COPs) were measured. Lard samples with 10 times (Test I) and 2 times (Test II) the amount of cholesterol originally found in each batch of lard were heated at 180°C for 10 hr a day for 240 and 160 hr, respectively. Cholesterol steadily decreased throughout the heating period in both tests. Cholesterol loss followed a first-order reaction rate, with a rate constant (k) of −1.18×10⁻³ h⁻¹ for Test I and −9.45×10⁻³ h⁻¹ for Test II. The COPs accumulated during both heating tests. But the amount of COPs formed did not total the amount of cholesterol lost. During heating, thermal degradation of cholesterol likely occurred, and those products were not detected. During cooling, hydroperoxides formed, which further oxidized into the COPs that were detected. The 7-ketocholesterol and 5α,6α-epoxycholesterol were the predominant COPs formed. The isomeric 7α-and 7β-hydroxycholesterols also accumulated in the heating tests. The 3β,5α,6β-cholestantriol was found in very small amounts and the 25-hydroxycholesterol was not detected. Presented in part at the 80th AOCS Annual Meeting, Cincinnati, OH, in May, 1989.     

PARAFAC modeling of three-way hyperspectral images: Endogenous fluorophores as health biomarkers in aquatic species

Demand for a renewable liquid-phase fuel has reinvigorated interest in the development of novel biofuels from algae. The effects of fluctuating nutrients, temperature, and predation which arise in algal aquaculture necessitate novel analytical methods to assess and optimize the health of these cultures. In this article we describe the use of trilinear modeling to these ends, using imaging data of endogenous fluorescence from the marine diatom, Thalassiosira pseudonana, collected on a hyperspectral fluorescence confocal microscope (HSF-CM). By combining the spatial and spectral data with the additional physical parameter introduced by the varying photobleach rates of endogenous fluorophores, we obtain a means for employing trilinear analysis in this system. In this case, analysis was implemented using the method of parallel factors analysis (PARAFAC) which alleviates the rotational ambiguities involved in multivariate analysis of 2-way data. By imposing a nutrient limitation in our diatom culture, and collecting single cell microscopy data at various time points during the nutritional stress, PARAFAC results reveal evolution of the spectral emission characteristics of six components and a background as a result of incremental photobleaching. Although the underlying mechanisms for these observations are not addressed, the differences observed between nutritively normal and nutritively stressed cells provide signatures for early detection of health deterioration in the algal culture. Finally, the combination of hyperspectral fluorescence microscopy with PARAFAC is generally applicable for the study of complex biological systems with endogenous fluorescence.