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Highlights: [•] High potential of the strategy PVA/DMSO lens-shaped particles for immobilization. [•] Naringinase PVA biocatalyst displayed high operational stability and volumetric productivity. [•] Operational stability of NGase-PVA was reproduced throughout different scales. [•] The half-life of the naringinase PVA was about 48days at 45°C, in a PBR. [•] Naringinase PVA showed high operational and mechanical stability, in a PBR. [ABSTRACT FROM AUTHOR]

A finite two-dimensional (2D) foam sample bounded by walls contains inner bubbles (I-bubbles) and peripheric or edge bubbles (E-bubbles). We derive equations for the rate of area change of both types of bubbles, which depend linearly on the number of neighbours of a bubble but are, in general, not scale independent. From these equations we obtain global kinetic laws for the two aggregates (I- and E-) of bubbles. The topological operations that occur during coarsening of E-bubbles are identified and the effect of curvature of the wall on coarsening is discussed. Experimental results obtained with 2D (monolayer) foams are presented which, combined with theory, give a reasonable picture of the effect of boundaries on foam coarsening. A disturbance due to the bounding walls was not experimentally detected: I- and E-bubbles were found to grow in pace, their average areas remaining equal, with a global parabolic growth law. However, this property could not be inferred from the growth equations for individual I- and E-bubbles. [ABSTRACT FROM AUTHOR]

Experimental observations of the deformation of a monodisperse twodimensional (2D) monolayer foam in tension/compression are reported. The foam samples are bound by two parallel walls at a variable separation, w. At critical values of w, dislocations (5/7 pairs) nucleate at the periphery of the foam which then glide along directions at 60o to the walls. The dislocations may suffer reflection at the walls, with a change in Burgers vector. As a result of the glide process, the number of close-packed rows of cells parallel to the walls changes by one and a neck develops. Rearrangements of the bubbles to more stable configurations are also observed, following dislocation glide. A detailed analysis of the topology of nucleation, glide and reflection of dislocations is undertaken. The stress-strain relation is derived and used to calculate the yield stress of the honeycomb foam from the experimentally measured strains at which topological transitions occur. The yield stress is considerably lowered by the nucleation of dislocations and is affected by the liquid fraction in the foam. [ABSTRACT FROM AUTHOR]

Herein is reported an innovative and reproducible systemic approach for the fabrication of customized 3D hollow microspheres of polyvinyl alcohol (PVA) based on the use of aromatic boronic acids (ABAs) as crosslinkers. A dedicated experimental set-up was developed to enable microsphere formulation. Most of the boronic acids tested were able to produce hollow microspheres. Depending on the ABA used and the production conditions, hollow PVA/ABA microspheres with different morphologies, mass transfer characteristics and unprecedented thermal (up to 121 °C) stability were obtained. The crosslinking temperature proved to be an operational parameter to control membrane thickness. The hollow microspheres were evaluated in biocatalysis, with naringin hydrolysis as model system, using encapsulated naringinase. The results highlighted a naringinase high operational stability, namely in PVA microspheres crosslinked with 1,4-phenylenediboronic acid and with phenylboronic acid, with no evident loss of activity throughout seven consecutive runs, theoretically resulting in an infinite half-life. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA) electrospun nanofibers were produced using an electrospinning technique. Key parameters (e.g. collectors, distance from needle tip to collector, among others) that influence the structure and morphology of fibers were optimized. The naringinase entrapped in PVA nanofibers retained over 100% of its initial activity after 212 h of operation, at 25 °C. Chemical crosslinking with several boronic acids further increased the hydrolysis temperature (up to 85 °C) and yielded nanofibers with thermal stability up to 121 °C. A mini packed bed reactor (PBR) developed to establish the feasibility for continuous enzymatic operation, ran for 16 days at 45 °C. Highest naringenin biosynthesis was attained at a flow rate of 10 mL h −1 . Highest volumetric (78 mol L −1 h −1 ) and specific (26 mol h −1 g enzyme −1 ) productivities were attained at 30 mL h −1 . The activity of NGase in electrospun nanofibers remained constant for almost 16 days of operation at 10 mL h −1 . [ABSTRACT FROM AUTHOR]

Abstract: Novel ionic liquid (IL) sol–gel materials development, for enzyme immobilization, was the goal of this work. The deglycosylation of natural glycosides were performed with α-l-rhamnosidase and β-d-glucosidase activities expressed by naringinase. To attain that goal ILs with different structures were incorporated in TMOS/Glycerol sol–gel matrices and used on naringinase immobilization. The most striking feature of ILs incorporation on TMOS/Glycerol matrices was the positive impact on the enzyme activity and stability, which were evaluated in fifty consecutive runs. The efficiency of α-rhamnosidase expressed by naringinase TMOS/Glycerol@ILs matrices increased with cation hydrophobicity as follows: [OMIM]>[BMIM]>[EMIM]>[C2OHMIM]>[BIM] and [OMIM]≈[E2-MPy]≫[E3-MPy]. Regarding the imidazolium family, the hydrophobic nature of the cation resulted in higher α-rhamnosidase efficiencies: [BMIM]BF4 ≫[C2OHMIM]BF4 ≫[BIM]BF4. Small differences in the IL cation structure resulted in important differences in the enzyme activity and stability, namely [E3-MPy] and [E2-MPy] allowed an impressive difference in the α-rhamnosidase activity and stability of almost 150%. The hydrophobic nature of the anion influenced positively α-rhamnosidase activity and stability. In the BMIM series the more hydrophobic anions (PF6 −, BF4 − and Tf2N−) led to higher activities than TFA. SEM analysis showed that the matrices are shaped lens with a film structure which varies within the lens, depending on the presence and the nature of the IL. The kinetics parameters, using naringin and prunin as substrates, were evaluated with free and naringinase encapsulated, respectively on TMOS/Glycerol@[OMIM][Tf2N] and TMOS/Glycerol@[C2OHMIM][PF6] and on TMOS/Glycerol. An improved stability and efficiency of α-l-rhamnosidase and β-glucosidase expressed by encapsulated naringinase on TMOS/Glycerol@[OMIM][Tf2N] and TMOS/Glycerol@[C2OHMIM][PF6] were achieved. In addition to these advantageous, with ILs as sol–gel templates, environmental friendly processes can be implemented. [Copyright &y& Elsevier]