Predatory nature of the littoral amphipod Echinogammarus marinus: gut content analysis and effects of alternative food and substrate heterogeneity

Interspecific interactions are major structuring forces in marine littoral communities; however, it is unclear which of these interactions are exhibited by many key-component species. Gut content analysis showed that the ubiquitous rocky/cobble shore amphipod Echinogammarus marinas, often ascribed as a mesograzer, consumes both algae and macroinvertebrates. Further, laboratory experiments showed that E. marinus is an active predator of such macroinvertebrates, killing and consuming the isopod Jaera nordmanni and the oligochaete Tubificoides benedii. Predatory impacts of E. marinus were not alleviated by the presence of alternative food in the form of alga discs. However, in the presence of prey, consumption of alga by E. marinus was significantly reduced. Further, survival of prey was significantly higher when substrate was provided, but predation remained significant and did not decline with further increases in substrate heterogeneity. We conclude that such amphipods can have pervasive predatory impacts on a range of species, with implications for community structure, diversity and functioning.

The functional role of Gammarus (Crustacea, Amphipoda): shredders, predators, or both?

Gammarus spp. are traditionally viewed under the functional feeding group (FFG) concept as herbivorous 'shredders'. Although recent studies suggest that Gammarus should also be viewed as predators, this latter role remains contentious. Here, in a laboratory experiment, we objectively examine the balance between shredder and predator roles in a common freshwater species. Gammarus pulex preyed significantly on mayfly nymph, Baetis rhodani, in both the presence and absence of excess leaf material. There was no significant difference in predation where the alternative food, that is, leaf material, was present as compared to absent. Also, G. pulex shredded leaf material in the presence and absence of B. rhodani. However, shredding was significantly reduced where alternative food, that is, B. rhodani prey, was present as compared to absent. Further, G. pulex had a clear leaf species preference. Our results suggest that Gammarus function as both predators and shredders, with the balance of the two roles perhaps depending on food availability and quality. We discuss implications for the use of the FFG concept in assessing freshwater processes, and the role that Gammarus predation may play in structuring macroinvertebrate communities.

Evaluation of an alternative spectroscopic approach for aflatoxin analysis: Comparative analysis of food and feed samples with UPLC-MS/MS

Increasing research has highlighted the effects of changing climates on the occurrence and prevalence of toxigenic Aspergillus species producing aflatoxins. There is concern of the toxicological effects to human health and animal productivity following acute and chronic exposure that may affect the future ability to provide safe and sufficient food globally. Considerable research has focused on the detection of these toxins, based on the physicochemical and biochemical properties of the aflatoxin compounds, in agricultural products for human and animal consumption. As improvements in food security continue more regulations for acceptable levels of aflatoxins have arisen globally; the most stringent in Europe. These regulations are important for developing countries as aflatoxin occurrence is high significantly effecting international trade and the economy. In developed countries analytical approaches have become highly sophisticated, capable of attaining results with high precision and accuracy, suitable for regulatory laboratories. Regrettably, many countries that are affected by aflatoxin contamination do not have resources for high tech HPLC and MS instrumentation and require more affordable, yet robust equally accurate alternatives that may be used by producers, processors and traders in emerging economies. It is especially important that those companies wishing to exploit the opportunities offered by lucrative but highly regulated markets in the developed world, have access to analytical methods that will ensure that their exports meet their customers quality and safety requirements.

This work evaluates the ToxiMet system as an alternative approach to UPLC–MS/MS for the detection and determination of aflatoxins relative to current European regulatory standards. Four commodities: rice grain, maize cracked and flour, peanut paste and dried distillers grains were analysed for natural aflatoxin contamination. For B1 and total aflatoxins determination the qualitative correlation, above or below the regulatory limit, was good for all commodities with the exception of the dried distillers grain samples for B1 for which no calibration existed. For B1 the quantitative R² correlations were 0.92, 0.92, 0.88 (<250 μg/kg) and 0.7 for rice, maize, peanuts and dried distillers grain samples respectively whereas for total aflatoxins the quantitative correlation was 0.92, 0.94, 0.88 and 0.91. The ToxiMet system could be used as an alternative for aflatoxin analysis for current legislation but some consideration should be given to aflatoxin M1 regulatory levels for these commodities considering the high levels detected in this study especially for maize and peanuts

An evaluation of the capability of a biolayer interferometry biosensor to detect low-molecular-weight food contaminants

The safety of our food is an essential requirement of society. One well-recognised threat is that of chemical contamination of our food, where low-molecular-weight compounds such as biotoxins, drug residues and pesticides are present. Low-cost, rapid screening procedures are sought to discriminate the suspect samples from the population, thus selecting only these to be forwarded for confirmatory analysis. Many biosensor assays have been developed as screening tools in food contaminant analysis, but these tend to be electrochemical, fluorescence or surface plasmon resonance based. An alternative approach is the use of biolayer interferometry, which has become established in drug discovery and life science studies but is only now emerging as a potential tool in the analysis of food contaminants. A biolayer interferometry biosensor was assessed using domoic acid as a model compound. Instrument repeatability was tested by simultaneously producing six calibration curves showing replicate repeatability (n = 2) ranging from 0.1 to 6.5 % CV with individual concentration measurements (n = 12) ranging from 4.3 to 9.3 % CV, giving a calibration curve midpoint of 7.5 ng/ml (2.3 % CV (n = 6)). Reproducibility was assessed by producing three calibration curves on different days, giving a midpoint of 7.5 ng/ml (3.4 %CV (n = 3)). It was further shown, using assay development techniques, that the calibration curve midpoint could be adjusted from 10.4 to 1.9 ng/ml by varying assay parameters before the simultaneous construction of three calibration curves in matrix and buffer. Sensitivity of the assay compared favourably with previously published biosensor data for domoic acid. © 2013 Springer-Verlag Berlin Heidelberg.

The identification of potential alternative biomarkers of nitrofurazone abuse in animal derived food products

Semicarbazide (SEM) was considered to be a characteristic protein-bound side-chain metabolite of the banned veterinary drug nitrofurazone and used as a marker of nitrofurazone abuse. It was recently discovered that SEM can arise in food from sources other than nitrofurazone. This uncertainty over the source of SEM may be overcome if alternative markers specific to tissue-bound nitrofurazone residues can be determined. The structure of nitrofurazone metabolites in vivo and particular proteins to which they are bound are not known. These proteins with altered structure due to the presence of the drug metabolites can be considered as potential alternative biomarkers of nitrofurazone abuse. The proteins implicated in the in vivo binding of nitrofurazone were separated and identified. A crude mixture of proteins extracted from the liver of a rat treated with the drug was separated using a series of different techniques such as preparative isoelectric focusing and size exclusion HPLC. Multiple fractions were assayed by LC-MS/MS to detect the presence of SEM. The proteins containing SEM residues were identified by peptide mass mapping using trypsin digestion and MALDI-TOF. The first protein identified as containing high concentration of SEM was albumin. It was also shown that low molecular weight species within a protein mixture whose main constituent was glutathione S-transferase contained a high concentration of SEM. The chemical composition of these components is under investigation. Preliminary data suggest the SEM forms part of a nitrofurazone metabolite conjugated to glutathione. (C) 2008 Elsevier Ltd. All rights reserved.

Surface plasmon resonance biosensing: Approaches for screening and characterising antibodies for food diagnostics

Research in biosensing approaches as alternative techniques for food diagnostics for the detection of chemical contaminants and foodborne pathogens has increased over the last twenty years. The key component of such tests is the biorecognition element whereby polyclonal or monoclonal antibodies still dominate the market. Traditionally the screening of sera or cell culture media for the selection of polyclonal or monoclonal candidate antibodies respectively has been performed by enzyme immunoassays. For niche toxin compounds, enzyme immunoassays can be expensive and/or prohibitive methodologies for antibody production due to limitations in toxin supply for conjugate production. Automated, self-regenerating, chip-based biosensors proven in food diagnostics may be utilised as rapid screening tools for antibody candidate selection. This work describes the use of both single channel and multi-channel surface plasmon resonance (SPR) biosensors for the selection and characterisation of antibodies, and their evaluation in shellfish tissue as standard techniques for the detection of domoic acid, as a model toxin compound. The key advantages in the use of these biosensor techniques for screening hybridomas in monoclonal antibody production were the real time observation of molecular interaction and rapid turnaround time in analysis compared to enzyme immunoassays. The multichannel prototype instrument was superior with 96 analyses completed in 2h compared to 12h for the single channel and over 24h for the ELISA immunoassay. Antibodies of high sensitivity, IC50's ranging from 4.8 to 6.9ng/mL for monoclonal and 2.3-6.0ng/mL for polyclonal, for the detection of domoic acid in a 1min analysis time were selected. Although there is a progression for biosensor technology towards low cost, multiplexed portable diagnostics for the food industry, there remains a place for laboratory-based SPR instrumentation for antibody development for food diagnostics as shown herein.

Evaluation of the antidiabetic activity of DPP IV resistant N-terminally modified versus mid-chain acylated analogues of glucose-dependent insulinotropic polypeptide

Glucose dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone with therapeutic potential for type 2 diabetes due to its insulin-releasing and antihyperglycaemic actions. However, development of GIP-based therapies is limited by N-terminal degradation by DPP IV resulting in a very short circulating half-life. Numerous GIP analogues have now been generated exhibiting DPP IV resistance and extended bioactivity profiles. In this study, we report a direct comparison of the long-term antidiabetic actions of three such GIP molecules, N-AcGIP, GIP(LyS(37)PAL) and N-AcGIP(LyS(37)PAL) in obese diabetic (ob/ob) mice. An extended duration of action of each GIP analogue was demonstrated prior to examining the effects of once daily injections (25 nmol kg(-1) body weight) over a 14-day period. Administration of either N-AcGIP, GIP(LyS(37)PAL) or N-AcGIP(LyS37PAL) significantly decreased non-fasting plasma glucose and improved glucose tolerance compared to saline treated controls. All three analogues significantly enhanced glucose and nutrient-induced insulin release, and improved insulin sensitivity. The metabolic and insulin secretory responses to native GIP were also enhanced in 14-day analogue treated mice, revealing no evidence of GIP-receptor desensitization. These effects were accompanied by significantly enhanced pancreatic insulin following N-AcGIP(Lys(37)PAL) and increased islet number and islet size in all three groups. Body weight, food intake and circulating glucagon were unchanged. These data demonstrate the therapeutic potential of once daily injection of enzyme resistant GIP analogues and indicate that N-AcGIP is equally as effective as related palmitate derivatised analogues of GIP. (c) 2006 Elsevier Inc. All rights reserved.

Pilot-scale evaluation of the application of low pH-inducible polyphosphate accumulation to the biological removal of phosphate from wastewaters.

To investigate the possible biotechnological application of the phenomenon of low pH-inducible phosphate uptake and polyphosphate accumulation, previously reported using pure microbial cultures and under laboratory conditions, a 2000 L activated sludge pilot plant was constructed at a municipal sewage treatment works. When operated as a single-stage reactor this removed more than 60% of influent phosphate from primary settled sewage at a pH of 6.0, as opposed to approximately 30% at the typical operational pH for the works of 7.0-7.3-yet without any deleterious effect on other treatment parameters. At these pH values the phosphorus content of the sludge was, respectively, 4.2% and 2.0%. At pH 6.0 some 33.9% of sludge microbial cells were observed to contain polyphosphate inclusions; the corresponding value at pH 7.0 was 18.7%. Such a process may serve as a prototype for the development of alternative biological and chemical options for phosphate removal from wastewaters.

A critical evaluation of Raman spectroscopy for the analysis of lipids: fatty acid methyl esters.

The work presented here is aimed at determining the potential and limitations of Raman spectroscopy for fat analysis by carrying out a systematic investigation of C-4-C-24 FAME. These provide a simple, well-characterized set of compounds in which the effect of making incremental changes can be studied over a wide range of chain lengths and degrees of unsaturation. The effect of temperature on the spectra was investigated over much larger ranges than would normally be encountered in real analytical measurements. It was found that for liquid FAME the best internal standard band was the carbonyl stretching vibration nu(C = O), whose position is affected by changes in sample chain length and physical state; in the samples studied here, it was found to lie between 1729 and 1748 cm(-1). Further, molar unsaturation could be correlated with the ratio of the nu(C = O) to either nu(C = C) or delta(H-C = ) with R-2 > 0.995. Chain length was correlated with the delta(CH2)(tw)/nu(C = O) ratio, (where "tw" indicates twisting) but separate plots for odd- and even-numbered carbon chains were necessary to obtain R-2 > 0.99 for liquid samples. Combining the odd- ani even-numbered carbon chain data in a single plot reduced the correlation to R-2 = 0.94-0.96, depending on the band ratios used. For molal unsaturation the band ratio that correlated linearly with unsaturation (R-2 > 0.99) was nu(C = C)/delta(CH2)(SC) (where "sc" indicates scissoring). Other band ratios show much more complex behavior with changes in chemical and physical structure. This complex behavior results from the fact that the bands do not arise from simple vibrations of small, discrete regions of the molecules but are due to complex motions of large sections of the FAME so that making incremental changes in structure does not necessarily lead to simple incremental changes in spectra.

Evaluation of Serpa cheese proteolysis by nitrogen content and capillary zone electrophoresis

Proteolysis of Serpa cheese produced traditionally (B) and semi-industrially (C) was evaluated for the first time by determination of nitrogen content and capillary zone electrophoresis (CZE). A citrate dispersion of cheese was fractionated to determine the nitrogen in pH 4.4, trichloroacetic and phosphotungstic acid soluble fractions (pH 4.4-SN, TCA-SN and PTA-SN, respectively). The pH 4.4-SN was significantly higher for B ( P <0.001), while TCA-SN was significantly higher for C ( P <0.001). PTA-SN was also higher for C but at 60 days ripening no significant difference was found between B and C. Degradation of alpha(s1) - and beta-caseins evaluated by CZE was in good agreement with the maturation index (pH 4.4-SN/TN).

Evaluation of a new peat-based sorbent for metals capture

A new peat-based sorbent was evaluated for the capture of heavy metals from waste streams. The media is a pelletted blend of organic humic material targeted for the capture of soluble metals from industrial waste streams and stormwater. The metals chosen for the media evaluation were Cd, Cu, Ni, and Zn due to their occurrence and abundance in waste streams and runoff. Sorption tests included an evaluation of the rate and extent of metals capture by the media, single versus multicomponent metals uptake, pH, anion influence, leaching effects and the effect of media moisture content on uptake rate and capacity. Isotherms of the sorption results showed that the presence of multiple metals increased the total sorption capacity of the media compared to the single component metal capacity; a result of site selectivity within the media. However the capacity for an individual metal in a multicomponent metal matrix was reduced compared to its single component capacity, due to competition for sites. Evidence of ion exchange behavior was observed but did not account for all metals capture. The media also provided a buffering action to counter the pH drop typically associated with metals capture.