A Multiplex Assay to Assess the Transaminase Activity toward Chemically Diverse Amine Donors

The development of methods to engineer and immobilize amine transaminases (ATAs) to improve their functionality and operational stability is gaining momentum. The quest for robust, fast, and easy-to-use methods to screen the activity of large collections of transaminases, is essential. This work presents a novel and multiplex fluorescence-based kinetic assay to assess ATA activity using 4-dimethylamino-1-naphthaldehyde as an amine acceptor. The developed assay allowed us to screen a battery of amine donors using free and immobilized ATAs from different microbial sources as biocatalysts. As a result, using chromatographic methods, 4-hydroxybenzylamine was identified as the best amine donor for the amination of 5-(hydroxymethyl)furfural. Finally, we adapted this method to determine the apparent Michaelis-Menten parameters of a model immobilized ATA at the microscopic (single-particle) level. Our studies promote the use of this multiplex, multidimensional assay to screen ATAs for further improvement.     

Lessening polygalacturonase activity in a commercial enzyme preparation by exposure to pulsed electric fields

The effect of high-intensity pulsed electric field (HIPEF) treatments on polygalacturonase (PG) activity in an aqueous solution of a commercial enzyme preparation was evaluated. HIPEF treatments reduced PG activity notably. Exponentially decaying pulses of 40 and 160 µs generated by a laboratory scale device were applied in a batch processing and bipolar mode. Electric fields ranged from 5.18 to 19.39 kV/cm. The number of pulses ranged up to 400. Temperature was always below 25 °C. Maximum inactivation of PG activity (98%) required 32.4 ms HIPEF treatment at 10.28 kV/cm. PG activity depleted exponentially because of HIPEF treatments. The first order rate constants ranged from 32 to 590 µs ^-1 and increased exponentially with electric field intensity. PG activity decreased exponentially with input electric energy density.     

Assessment of the suitability of soil amendments to reduce 137Cs and 90Sr root uptake in meadows

In situ remediation strategies are an alternative approach in the management of radioactive contaminated areas, especially when based on modification of soil properties by the addition of amendments. Here, this strategy is applied to reduce 137Cs and 90Sr soil-plant transfer in meadows from areas of Russia, Belarus, and Ukraine affected by the Chernobyl fallout. Meadows were established on podzolic and peaty soils. Amendments covered a wide range of materials, such as loamy and sandy soils, polygorskite clay, phosphorite, turf, and sapropel. Field experiments showed the poor efficiency of most of the materials: only the polygorskite clay provoked a notable reduction (1.5-2-fold) in 137Cs root uptake. Subsequent laboratory characterization showed the lack of significant changes in the radiocesium interception potential and soil solution composition in the amended soils, a fact that helped to explain the lack of effect on the reduction of transfer. Moreover, a laboratory methodology based on the quantification of the adsorption potential of the amendments and the reversibility of the adsorption process was applied. This methodology was first proposed for the correct selection of the suitable materials to be used to decrease radionuclide root uptake in future remediation actions and then validated with data of the previous field experiments.     

Preparation of composites of laponite with alginate and alginic acid polysaccharides

Polymer/clay composites have several uses in fields such as engineering, agriculture, ceramics, surface coatings, absorbent materials, pharmaceuticals or catalysis. Polysaccharides, such as alginate and its acid derivatives, are biocompatible and biodegradable polymers, effective in the production of adsorbent systems, for encapsulation and controlled release of active ingredients such as drugs and fertilizers. In this work, alginate polysaccharide and alginic acid were used to form composites with laponite, both with the original clay or with clay previously functionalized with 3‐aminopropyltriethoxysilane. The properties of the composites prepared from laponite or functionalized laponite and alginic acid or alginate were compared. The interaction of laponite with alginic acid leads to composites with strong disorder in the clay structure. In all cases, composites with high contents of polysaccharides, with good thermal and mechanical properties, are obtained. Laponite‐derived composites showed high adsorption capability for Cr(III) and methylene blue from aqueous medium. Copyright © 2012 Society of Chemical Industry     

Rapid determination of soluble solids content and acidity of Black currant (Ribes nigrum L.) juice by mid-infrared spectroscopy performed in series

Black currant juice quality is a prime importance for growers and industrials. Such quality relies on the empirical and destructive measurements of soluble solids content and acidity. These measurements are time consuming and expensive. The serial analysis of the Black currant juice quality could allow the valuation of the product for the producer and saving of time for the manufacturer. Our objective was to develop predictive models of soluble solids content and acidity based on the mid-infrared spectroscopy performed in series.We showed that infrared spectroscopy allowed determining efficiently the quality of Black currant juices and that such technique could be performed in series. Soluble solids content were determined with a R²-value of 0.97 and an RMSECV of 1.14°Brix for a range of values comprised between 12.9°Brix and 16.42°Brix. Acidity content was determined with a R²-value of 0.96 and an RMSECV of 2.61 g L⁻¹ in a large range of values comprised between 14.87 g L⁻¹ and 36.27 g L⁻¹.These results allow asserting that the soluble solids content and the acidity of Black currant juice can be accurately determined by infrared spectroscopy. Furthermore, a large number of measures can be performed in series, what opens perspectives for a practical application.     

Failures of harbour walls at Malaga and Barcelona

The paper describes the failure of harbour walls which occurred at Malaga on 4th July 2004 and at Barcelona on 1st January 2007, associated with an inadequate consideration of the ground conditions in the light of the marine environment. At Malaga, there was an existing breakwater hence the new harbour was protected from the effect of the waves while at Barcelona, the construction of the quay wall proceeded at a faster rate than the breakwater. In both cases the wharf backfill was placed rapidly on the soft muds, progressing from the inland side. The paper discusses the importance of an overview including the ground investigation, engineering design, construction method and speed of construction.     

Coalescence of Levitated He II Drops

We describe experiments to study the coalescence of He II drops levitated in a magnetic trap. Using a high speed CCD camera, we have produced movies of drops coalescing at temperatures as low as 0.7 K. We examine some interesting features of the motion during and following coalescence.     

Toward Jeffersonian research programmes in ergonomics science

Thomas Jefferson believed that scientific research could lead to a fuller understanding of nature, while simultaneously addressing a persistent social problem of national or global interest. The two-fold ideals of this 'Jeffersonian research programme' fit well with the inherently practical aims of ergonomics science. However, in the past, basic and applied concerns have not always been well integrated in the discipline. This article makes a contribution, by proposing a novel metascientific framework consisting of a two-dimensional research space that addresses this problem. One dimension is methodological, representing the trade-off between experimental control and representativeness, while the other dimension is intentional, representing the trade-off between knowledge- and market-oriented purposes. The framework helps explain why it has frequently been difficult to integrate basic and applied concerns, and, at the same time, it shows that a Jeffersonian research programme for ergonomics science can be achieved by opening up degrees of freedom for research that have been comparatively unexplored. The importance of demonstrating contributions to fundamental understanding and to applied practice within the same research programme may be essential for survival and success in a climate of restricted research funding.     

Operating conditions for the electrolytic disinfection of process wash water from the fresh-cut industry contaminated with E. coli o157:H7

The effect of operating conditions (current density, recirculation flow rate and electrode doping level) on the efficacy of boron-doped diamond (BDD) electrodes to inactivate microorganisms and decrease chemical oxygen demand (COD) was studied in lettuce process wash water with a COD of 725 mg/L and inoculated with a 5-strain cocktail of Escherichia coli O157:H7. Changes in pathogen population, COD, pH, temperature, redox potential, and free and total chlorine were monitored in process wash water during treatments. Considering the specific characteristics of the washing step included in the fresh-cut processing, the disinfection of process wash water should be of fast action. A biphasic with a shoulder model was used to estimate shoulder length (Sl), log-linear inactivation rates (k_max1, k_max2), lowest population (N_f) and highest log reduction (HLR). Current density clearly influenced Sl, and k_max2; recirculation flow rate influenced Sl, k_max1, k_max2 and COD depletion; and doping level influenced N_f. No relationship was observed between inactivation parameters and chlorine concentration. Conditions including high current density (180 mA/cm²), high flow rate (750 l/h) and high doping level (8 000 μmol/mol) seems to provide a disinfection efficiency suitable to decrease the chance of bacterial cross contamination in the fresh-cut industries while saving on water consumption and decreasing the amount of wastewater effluents.