Reusable composite membranes for highly efficient chromium removal from real water matrixes.

Natural or industrial hexavalent chromium water pollution continues to be a worldwide unresolved threat. Today, there is intense research on new active and cost-effective sorbents for Cr(VI), but most still exhibit a critical limitation: their powdered nature makes their recovery from water cost and energy consuming. In this work, Al(OH)3, MIL-88-B(Fe), and UiO-66-NH2 Cr(VI) sorbents were immobilized into a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymeric substrate to develop an easily reactivable and reusable water filtering technology. The immobilization of the sorbents into the PVDF-HFP porous matrix modified the macro and meso-porous structure of the polymeric matrix, tuning in parallel its wettability. Although a partial blocking of the Cr(VI) adsorptive capacity was observed for of Al(OH)3 and MIL-88-B(Fe) when immobilized into composite membranes, PVDF-HFP/UiO-66-NH2 filter (i) exceeded the full capacity of the non-immobilized sorbent to trap Cr(VI), (ii) could be reactivated and reusable, and (iii) it was fully functional when applied in real water effluents.

Processing Strategies to Obtain Highly Porous Silk Fibroin Structures with Tailored Microstructure and Molecular Characteristics and Their Applicability in Water Remediation.

The present work reports on the control of silk fibroin (SF) porous structures performance through various processing methods. The study includes the analysis of two dissolving techniques (CaCl2/H2O/EtOH ternary and LiBr/H2O binary solutions), three regeneration methods (gelation, lyophilization and gas foaming) and one post-processing (EtOH). In all the cases, followed steps lead to SF structures with porosity values above 94% and large surface areas. Also, results about samples microstructure, secondary organization, crystallinity and water behavior, reveal a direct correlation between processing and SF properties. Thanks to the achieved progress, the SF varying porous structures were evaluated for metalloids (As5+ and As3+) and heavy metals (Cr6+ and Cr3+) adsorption, observing a direct relationship between samples processing and ionic species adsorption ability. Thus, it is shown that the control of the properties of SF based porous structures through processing, represents a suitable and ecofriendly approach for the development of bio-based materials for environmental applications.

On the mineral core of ferritin-like proteins: structural and magnetic characterization.

It is generally accepted that the mineral core synthesized by ferritin-like proteins consists of a ferric oxy-hydroxide mineral similar to ferrihydrite in the case of horse spleen ferritin (HoSF) and an oxy-hydroxide-phosphate phase in plant and prokaryotic ferritins. The structure reflects a dynamic process of deposition and dissolution, influenced by different biological, chemical and physical variables. In this work we shed light on this matter by combining a structural (High Resolution Transmission Electron Microscopy (HRTEM) and Fe K-edge X-ray Absorption Spectroscopy (XAS)) and a magnetic study of the mineral core biomineralized by horse spleen ferritin (HoSF) and three prokaryotic ferritin-like proteins: bacterial ferritin (FtnA) and bacterioferritin (Bfr) from Escherichia coli and archaeal ferritin (PfFtn) from Pyrococcus furiosus. The prokaryotic ferritin-like proteins have been studied under native conditions and inside the cells for the sake of preserving their natural attributes. They share with HoSF a nanocrystalline structure rather than an amorphous one as has been frequently reported. However, the presence of phosphorus changes drastically the short-range order and magnetic response of the prokaryotic cores with respect to HoSF. The superparamagnetism observed in HoSF is absent in the prokaryotic proteins, which show a pure atomic-like paramagnetic behaviour attributed to phosphorus breaking the Fe-Fe exchange interaction.

Detection of Clostridium tyrobutyricum spores using polyclonal antibodies and flow cytometry.

AIMS: The present work investigates the feasibility of using flow cytometry (FCM) combined with fluorescent-labelled specific polyclonal antibodies for the detection and presumptive identification of Clostridium tyrobutyricum spores in bovine milk. METHODS AND RESULTS: Two fluorescent molecules (fluorescein isothiocyanate and Alexa Fluor 488) were conjugated to antispores polyclonal antibodies. Side scatter and forward scatter profiles of the Cl. tyrobutyricum spores marked with fluorescent antibodies permitted the detection of spores and differentiated them from other related microbial species. The detection limit of this method was 10(3) spores per 100 ml of milk, and results could be achieved in 2 h. CONCLUSIONS: FCM combined with fluorochrome-conjugated antibodies, especially Alexa Fluor, could be an efficacious means to detect and provide presumptive identification of Cl. tyrobutyricum spores, as well as differentiation from other Clostridium species that can also cause late blowing in cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the basis for the development of a method suitable for analysis of milk destined for cheese manufacture that would permit the detection of Cl. tyrobutyricum spores in a short period. This would enable the industry to use contaminated milk for dairy products other than cheese where Cl. tyrobutyricum does not cause a problem.

Kinetic and thermodynamic parameters for heat denaturation of Cry1a(b) protein from transgenic maize (Zea mays).

The effect of heat treatment on the denaturation of Cry1A(b) protein expressed in transgenic maize was studied over a temperature range of 69 to 77 degrees C. Denaturation of Cry1A(b) protein was measured by the loss of reactivity with its specific antibodies using a sandwich ELISA. The process of denaturation was studied by analyzing the values of inmunoreactive protein after each heat treatment by kinetic analysis. Denaturation of Cry1A(b) protein was best described assuming a reaction order of 1.5. D-values calculated were 4338, 2350, 1272, 734, and 601 s at 69, 71, 73, 75, and 77 degrees C, respectively. Z-value was estimated to be 9.0 degrees C and the activation energy value was 266.15 kJ/mol. Thermodynamic parameters for the process of denaturation of Cry1A(b) protein were also calculated. The high values of the enthalpy of activation and the positive values of the entropy of activation obtained for Cry1A(b) protein are typical of a reaction in which the denaturation of the protein is the rate-determining process that predominates over an aggregation process during heating.

Development of two immunoassay formats to detect beta-lactoglobulin: influence of heat treatment on beta-lactoglobulin immunoreactivity and assay applicability in processed food.

Milk proteins are commonly used as ingredients in the food industry because of their functional properties, but they can cause severe reactions in milk-allergic individuals. In this work, two enzyme-linked immunosorbent assay (ELISA) formats were developed to detect bovine beta-lactoglobulin. The indirect competitive ELISA involved the use of anti-beta-lactoglobulin antisera, and the sandwich ELISA involved the use of specific antibodies isolated using a beta-lactoglobulin immunosorbent material. The effect of heat treatment on immunoreactivity of the protein in buffer and in milk was determined with both assays. The amount of immunoreactive protein in buffer and in milk decreased as determined by the sandwich ELISA, whereas the amount increased when measuring with the competitive ELISA. Several food products, including meat, bakery products, sauces, and snacks, were analyzed. With both assays, 10 of 11 products in which the ingredient list included the terms "powdered milk" or "milk proteins" contained beta-lactoglobulin. However, the beta-lactoglobulin concentration in these products obtained with the competitive ELISA were much higher than those obtained with the sandwich ELISA. These differences could be explained by the fact that the determination of beta-lactoglobulin concentration by immunoassay is influenced by differences in antibody recognition of the protein present in highly processed foods. Therefore, the antigen-binding properties of antibodies used in a particular immunoassay are important for a correct interpretation of results obtained in food processed at high temperature.