Continuous fixed bed biosorption of Cu2+ ions: application of a simple two parameter mathematical model

Biomass from two fungi of the Mucorales order, laboratory cultured and immobilised Rhizopus arrhizus, and industrial waste Mucor miehei, was tested for capacity to adsorb copper from solution in batch and continuous‐flow column systems. Maximum uptake levels were c 400 and 300 mmol g⁻¹ (dry weight) respectively. Immobilisation of Rhizopus arrhizus in polyvinyl formal to cell loadings of 60% (w/w) did not diminish metal uptake levels. In continuous‐flow columns both biosorbents adsorbed copper to levels equal or approaching the batch uptake values. Column breakthrough curves were fitted to a two parameter model and each of the parameters, σ and t₀ , were linearly correlated with column operating parameters. Predicted breakthrough curves agreed closely with experimental values. © 1999 Society of Chemical Industry     

Activity and selectivity of a {\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}} catalytic membrane in the partial hydrogenation reactions of acetylene and 1,3-butadiene

A ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane supported on a macroporous $\alpha {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ tube was prepared by sol–gel processing and used in the partial hydrogenation of acetylene and 1,3-butadiene. The average pore diameter of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was 3.6 nm. The gases were separated by Knudsen diffusion. The activity and selectivity of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was compared to that of ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ catalysts used in a conventional packed bed reactor. The highest selectivity to the partially hydrogenated products occurred when the reactant was premixed with H₂ and was passed through the membrane wall.     

Prevalence and characterization of Salmonella enterica serovar Weltevreden from imported seafood

During 2001-2005, 210 Salmonella enterica strains were isolated from seafood samples imported into US. Strains of S. enterica serovar Weltevreden were the most predominantly found among the 64 different serovars isolated. A total of 37 Salmonella Weltevreden isolates were characterized by pulsed-field gel electrophoresis (PFGE), plasmid profiles and antibiotic susceptibility to assess genetic diversity. Our results showed a low frequency of antibiotic resistance; 35 of the 37 isolates were sensitive to ampicillin, tetracycline, chloramphenicol, gentamicin, sulfisoxazole, streptomycin and kanamycin. Only two isolates, from samples originating in the Philippines and India, showed resistance to ampicillin and tetracycline and to streptomycin, sulfisoxazole and tetracycline, respectively. Of the 37 isolates, two isolates did not carry any plasmid and 35 isolates harbored several small and mega-plasmids. These isolates were differentiated into 10 distinct types based on plasmid profiles. Four different PFGE clusters were obtained with a genetic similarity of 66-76%. Four groups of isolates (formed by two or three isolates each) showed 100% similarity in the PFGE profiles. One of these groups included strains isolated in Vietnam in 2003, 2004 and 2005 from fish and shrimp. The other groups included strains isolated in Vietnam, Indonesia and Thailand in 2000, 2004 and 2005 from snail, shrimp and fish. Our findings show genetic diversity and temporal persistence of S. enterica serovar Weltevreden in recently monitored seafood imports.     

Economic comparison of long-term nuclear fuel cycle management scenarios: The influence of the discount rate

This article presents some main economic results obtained by the CEA in the DERECO project, which aimed to evaluate the global cost of contrasted and long-term nuclear fuel cycle scenarios. The scenarios have been studied for the period 2000–2150 in the French context. They all assume a sustainable nuclear development. These scenarios must not be considered as forecasts and do not reflect any industrial strategy. The article focuses on the comparison of five scenarios including the Generation IV fast reactors and their associated fuel cycles. Common trends as well as specific features can be identified. The article describes the scenarios with the replacement of the nuclear power and the associated fuel cycle. It details the main technical and economic assumptions common to all the scenarios, and exposes some main key results, concerning the flows and inventories as well as concerning economic evaluation. Economic results are given in a comparative manner due to the level of uncertainties at this time horizon. The key economic elements described in the article deal with the sensitivity of the results to the choice of the discount rate.     

Green hydropower: a new assessment procedure for river management

Hydropower is the most important renewable electricity source worldwide. It shows clear advantages for the global CO₂ balance but creates serious ecological impacts on a local scale. As a consequence, concern for the conservation of natural river ecosystems is growing within society and more people are willing to pay extra for so‐called ‘green electricity’. The definition of ‘green’, however, is not straightforward and customers cannot directly examine the quality of electricity products. Therefore, credible certification of high ecological standards is essential for successful green electricity marketing. In this paper we introduce a new assessment procedure for evaluating environmentally compatible hydropower production. This so‐called ‘Green Hydro’ concept was developed in the context of a multidisciplinary case study on a 400 MW hydropower scheme in the Southern Alps of Switzerland. The concept guarantees both general standards for different schemes operating in different types of watersheds and flexibility for local particularities. We developed an environmental management matrix that considers basic criteria and eco‐investments and covers five environmental areas of concern (i.e. hydrological character, connectivity, morphology, landscape, and biological communities). The ecological perspective is complemented by five management domains (i.e. instream flow regimes, hydropeaking, reservoir and bedload management, and power plant structures). Applying assessment and modelling tools for the Green Hydro procedure showed that dynamic habitat models allowed quantification of the effects of different instream flow regulations at morphologically distinct sites. In this case, morphological restoration could be more beneficial than increasing the minimum flow. The first experience with the Green Hydro certification is encouraging. So far, 13 facilities have successfully passed the certification procedure. They produce a total of 186 GWh green electricity per year, which is sufficient for the supply of almost 40 000 households in Switzerland. Copyright © 2004 John Wiley & Sons, Ltd.     

Sublethal sanitizer stress and adaptive response of Escherichia coli O157:H7

The effect of sublethal exposure to peroxyacetic acid (PAA) sanitizer on adaptation to peroxidative stress and development of thermal cross-resistance was investigated in Escherichia coli O157:H7. Acute sublethal PAA sanitizer exposure was used to represent a contact scenario. Cultures were grown in Trypticase soy-yeast extract broth. Acute treatment cultures were pretreated with 0.1% PAA, then all cultures were challenged at either 80 mM H202 or 54 degrees C. Acute and peroxide control cultures showed substantially increased peroxidative tolerance (D80mM > 2 h) versus negative control cultures not exposed to sanitizer (D80mM = 0.19+/-0.03 h). The inactivation rate of the acetic acid control (D80mM = 0.21+/-0.05 h) was similar to the negative control rate. Acute (D54 degrees C = 0.55+/-0.07 h) cultures did not exhibit increased thermal resistance versus the control (D54 degrees C = 0.54+/-0.07 h). Thermal injury was determined as difference in D54 degrees C value (deltaD54 degrees c) obtained on pyruvate and deoxycholate media. Thermal-induced injury was not observed in either control (deltaD54 degrees C = 0.04 h) or acute (deltaD54 degrees C = 0.05 h) cultures.     

How to deal with negative power price spikes?—Flexible voluntary curtailment agreements for large-scale integration of wind

For the large-scale integration of electricity from renewable energy sources (RES-E), the German system seems to reach its limits. In 2009, the electricity wholesale market experienced serious negative prices at times of high wind and low demand. The feed-in system in Germany consists of a fixed feed-in price, a take-off obligation and a RES priority rule, and in practice only very restrictive use of RES-E curtailment. Exactly the latter is the problem. We argue that the overall performance of the system would improve seriously by lifting the restrictions on the use of voluntary curtailment agreements, while retaining the priority rule as such. Since generators of RES-E can only improve under this system reform, investment conditions improve, leading to higher installed RES-E capacity. This in turn implies that reduced wind output due to curtailment can actually be offset by higher wind output in all periods in which there is no problem.     

Enzyme activities in cocoa beans during fermentation

The activities of endoprotease, aminopeptidase, carboxypeptidase, invertase (cotyledon and pulp), polyphenol oxidase and glycosidases were studied during heap fermentation of ICS-95 cocoa beans. These enzymes are of key importance in flavour precursor formation and in pigment degradation during cocoa fermentation. Optimal extraction and assay conditions were established to characterise the enzymes reactions and to quantify and compare enzyme activities during cocoa fermentation. The enzymes exhibited large differences in pH optima and stability during fermentation. Aminopeptidase, invertase (cotyledon and pulp) and polyphenol oxidase were strongly inactivated, carboxypeptidase was partly inactivated, whereas endoprotease and glycosidases remained active throughout the fermentation. Since many enzymes are inactivated during fermentation, it is generally recognised that the actual period of enzyme action is short. Although our results confirmed total inactivation for some enzymes, we show that several key enzymes are not completely inactivated during fermentation. Therefore, some enzyme reactions can continue throughout the whole fermentation process. Only polyphenol oxidase was strongly inactivated during sun and artificial drying of the beans. The other enzymes were stable during the drying process. Enzymes like endoprotease and glycosidases are still active in properly fermented and dried beans. © 1998 SCI.     

Potent odorants causing the warmed-over flavour in boiled beef

Summary The flavour compounds showing higher odour units resulting from peroxidation of unsaturated fatty acids were analysed comparatively in freshly boiled beef and in a stored (48 h, 4° C) sample exhibiting warmed-over flavour. The results obtained by aroma extract dilution analysis revealed that this flavour was mainly caused by hexanal, 1-octen-3-one, (E)- and (Z)-2-octenal, (Z)-2-nonenal, (E, E)-2,4-nonadienal andtrans-4,5-epoiiy-(E)-2-decenal.

---

Intensive Geruchsstoffe des Warmed-over Flavour (WOF) von gekochtem Rindfleisch

Zusammenfassung Die Aromastoffe mit hohen Aromawerten, die aus der Peroxidation ungesättigter Fettsäuren hervorgehen, wurden in frisch gekochtem Rindfleisch und in einer gelagerten (48 h, 4 °C) Probe mit WOF analysiert. Ein Vergleich der Ergebnisse von Aromaextraktverdünnungsanalysen ergab, daß der WOF hauptsächlich durch Hexanal, 1-Octen-3-on, (E)- und (Z)2-Octenal, (Z)-2-Nonenal, (E, E)-2,4-Nonadienal sowietrans-4,5-Epoxy-(E)-2-decenal verursacht wird.