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This study reports the importance of physicochemical characteristics of the core-shell structured polymer-coated Fe 3 O 4 cluster@SiO 2 nanocomposite particles for designing the biocatalysts used for transesterification of soybean oil. To demonstrate this issue, two different types of polymer molecules such as polyethylenimine (PEI) and polyacrylic acid (PAA) each with two different molecular weights are employed. The highest fatty acid methyl esters (FAMEs) synthesis yield values are achieved by the lipases immobilized onto the low- and high-molecular-weight PEI-coated particles as compared to those of the low- and high-molecular-weight PAA-coated particles ( i.e., ∼64.8% and ∼73.1% versus ∼51.5% and ∼46.4%, respectively). The lipases immobilized onto the PEI-coated particles also exhibit excellent stabilities over five repeated uses. The solvent content assays of the particles immersed in water, methanol and soybean oil reveal that the PEI-coated particles have the highest tendency to absorb the oil and the least ones to absorb water and methanol. Thus, those particles increase the substrate molecules accessibility to the immobilized lipases in the reaction medium, leading to the superior transesterification efficiency. This study provides insight into the highly effective enzymatic production of biodiesel with considering the physicochemical properties of support particles used for enzymes immobilization. [ABSTRACT FROM AUTHOR]

It is reported for the first time, the selection of an industrial centrifuge with the optimized geometry and operational conditions to efficiently separate the diphtheria bacterial cell debris from the culture medium and particularly to harvest the purified bacterial toxin by using the computational fluid dynamics (CFD) simulation and experimental approaches. The industrial-scale tubular and disc stack centrifuges each with two different sizes were first simulated to quantify their complex hydrodynamics. An optimal balance among the rotational speed, feed flow rate, and possible cell damages was required to efficiently separate the bacterial cells. It was also revealed that both large-sized tubular and disc stack centrifuges perform remarkably better than the smaller ones. Ultimately, according to the CFD simulation results, among four centrifuges, the large-sized disc stack centrifuge with the rotational speeds upper than 5500 rpm and the feed flow rates lower than 100 L h−1 was a potential candidate to utilize in the real process. Through performing experiments by using an industrial disc stack centrifuge, a good agreement was found between the CFD and experimental data in terms of the optimized rotational speed and feed flow rate required for the separation of cells. The Ramon flocculation assay confirmed the preserved quality and quantity of the main product of this bioseparation process, 'the bacterial toxin purified from the bacterial cell debris'. [Display omitted] • CFD simulation is used to optimize industrial disc stack and tubular centrifuges. • Optimal rotational speed and flow rate are required to separate cells without damage. • Large-sized centrifuges show remarkably better performance compared to smaller ones. • Experiments validated simulation results to obtain toxin purified from cells. • Large disc stack centrifuge can be a potential candidate to separate bacterial cells. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Pd on activity enhancement of perovskite catalysts for oxidation of CH4 and CO emitted from natural-gas fueled vehicles is investigated using a synthetic stoichiometric exhaust gas mixture. Various LaBO3 and LaBPd0.05O3 (B=Mn, Fe, Co and Ni) perovskite-type nanocatalysts were prepared via a solution combustion synthesis, calcined at 700°C for 5h, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area measurement, H2 temperature programmed reduction (TPR) and O2 temperature programmed desorption (TPD). XRD results, confirms the presence of PdO in Pd-containing samples, which is highly active for CO and CH4 oxidation. TPR and TPD results show that Pd significantly facilitates the reducibility of B in LaBPd0.05O3 pervoskites and enhances the mobility of lattice oxygen in the prepared samples, which results in activity enhancement for Pd-containing catalysts. Oxidation activity results reveal that Pd effect is more pronounced for CO oxidation as compared to that for CH4, probably due to the Pd transition from PdO to metallic Pd and/or its incorporation into the pervoskite structure occurred at elevated temperatures, which both seem to reduce its activity. Among the prepared samples, LaFePd0.05O3 catalyst shows the highest activity for CO and CH4 oxidation, T 90 of which occur at 165 and 558°C, 191 and 40°C lower than that for LaFeO3 respectively. [ABSTRACT FROM AUTHOR]

In this study, we prepared various anionic magnetic adsorbents through the carboxyl functionalization of core/shell-structured Fe 3 O 4 /SiO 2 (FS) particles by either succinic anhydride (FSC), low-molecular-weight (MW 1800) polyacrylic acid (PAA) (FSP1), or high-molecular-weight (MW 100,000) PAA (FSP2), and then, investigated the effect of the structure of adsorbents and operational parameters on their performance for the lysozyme separation. The type and size of functional molecules have significant effects on the surface concentration of functional carboxyl groups onto the adsorbent particles (increase in the order of FSP2 > FSP1 > FSC), and consequently on the adsorption efficiency (AE) (∼100, 98, and 62%, respectively) and adsorption capacity (AC) (∼1000, 980, and 621 mg·g -1 , respectively) of the adsorbents. However, the loss of the antibacterial activity of separated lysozyme molecules due to the molecular conformational change increased in the order of FSP2 > FSP1 = FSC, as compared to the free lysozyme. The application of basic buffer solutions for the elution of adsorbed enzyme molecules resulted in more adverse effects on the enzyme activity. The obtained results recommend that FSP1 can be used as a suitable anionic adsorbent for the isolation of positively charged proteins, owing to its high adsorption capacity, excellent reusability, and structural stability, as well as the high purity, structural stability, and activity recovery of the isolated proteins.