Immobilization and Stabilization of Beta-Xylosidases from Penicillium janczewskii

β-Xylosidases are critical for complete degradation of xylan, the second main constituent of plant cell walls. A minor β-xylosidase (BXYL II) from Penicillium janczewskii was purified by ammonium sulfate precipitation (30% saturation) followed by DEAE-Sephadex chromatography in pH 6.5 and elution with KCl. The enzyme presented molecular weight (MW) of 301 kDa estimated by size exclusion chromatography. Optimal activity was observed in pH 3.0 and 70–75 °C, with higher stability in pH 3.0–4.5 and half-lives of 11, 5, and 2 min at 65, 70, and 75 °C, respectively. Inhibition was moderate with Pb⁺² and citrate and total with Cu⁺², Hg⁺², and Co⁺². Partially purified BXYL II and BXYL I (the main β-xylosidase from this fungus) were individually immobilized and stabilized in glyoxyl agarose gels. At 65 °C, immobilized BXYL I and BXYL II presented half-lives of 4.9 and 23.1 h, respectively, therefore being 12.3-fold and 33-fold more stable than their unipuntual CNBr derivatives (reference mimicking soluble enzyme behaviors). During long-term incubation in pH 5.0 at 50 °C, BXYL I and BXYL II glyoxyl derivatives preserved 85 and 35% activity after 25 and 7 days, respectively. Immobilized BXYL I retained 70% activity after 10 reuse cycles of p-nitrophenyl-β-D-xylopyranoside hydrolysis.

     

Swelling behaviors of poly(dodecyl methacrylate-co-methyl eugenol) and poly(dodecyl methacrylate-co-methyl chavicol) gels in essential oil components

Poly(dodecylmethacrylate-co-methyleugenol) P(DDMA-co-Meu) and poly(dodecylmethacrylate-co-methylchavicol) P(DDMA-co-Mch) gels were synthesized in ethanol using free radical cross-linking polymerization method at 60 °C for 24 h in the presence of azobisisobutyronitrile (AIBN) and triethylene glycol dimethacrylate (TEGDMA) as initiator and cross-linker, respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the gels. These gels were used to investigate swelling behaviors in linalool and methyl eugenol, in essential oil mixture of phenyl propanoid and terpenoid, and also in various solvents. While the equilibrium swelling values (ESV) of both gels were higher in linalool than in methyl eugenol, the result was vice versa in the case of essential oil mixture. ESVs of both gels were also obtained in various solvents with different functional groups and the highest ESV of both gels were obtained in toluene, and the lowest ESV of P(DDMA-co-Meu) and P(DDMA-co-Mch) was in methanol and in ethylene glycol, respectively. While P(DDMA-co-Meu) is sensitive to carbon number change in alcohol, P(DDMA-co-Mch) is less sensitive. In the case of esters, increase of carbon number in functional group causes a more significant change in ESV than an increase of carbon number in aliphatic chain. Experimental results were correlated by the first-order and second-order models. The second-order model was more suitable than the other. While P(DDMA-co-Meu) gel swelled in linalool exhibits a Fickian diffusion character, the diffusion mechanism of the gel in methyl eugenol is a non-Fickian one. In the case of P(DDMA-co-Mch), the result is vice versa.     

Effect of heterocyclic ring system on formation of dimeric quinolones under catalyst-free conditions: a green approach

The intermediate-dependent green and efficient synthesis of dimeric quinolones 4a–l and 7a–l by the Knoevenagel condensation followed by Michael-type addition of 4-hydroxy-1-methylquinolin-2(1H)-one 1a, b to indole-3-aldehydes 2a–f and aromatic aldehydes 5a–l in water through the condensed compound 3a–l under catalyst-free conditions is described. This reaction was found to be environmentally friendly, has easy-workup and shorter reaction times giving good yields of the product without the need for its isolation using column chromatography.     

Synthesis of RE Y zeolite for formulation of FCC catalyst and the catalytic performance in cracking of n-hexadecane

Research on Chemical Intermediates - This study presents the synthesis of rare earth-doped Y (RE Y) zeolite, its application in formulation of a fluid catalytic cracking (FCC) catalyst and the...     

In Metric-measure Spaces Sobolev Embedding is Equivalent to a Lower Bound for the Measure

We study Sobolev inequalities on doubling metric measure spaces. We investigate the relation between Sobolev embeddings and lower bound for measure. In particular, we prove that if the Sobolev inequality holds, then the measure μ satisfies the lower bound, i.e. there exists b such that μ(B(x,r))≥b r ^α for r∈(0,1] and any point x from metric space.     

On parallel Branch and Bound frameworks for Global Optimization

Branch and Bound (B&B) algorithms are known to exhibit an irregularity of the search tree. Therefore, developing a parallel approach for this kind of algorithms is a challenge. The efficiency of a B&B algorithm depends on the chosen Branching, Bounding, Selection, Rejection, and Termination rules. The question we investigate is how the chosen platform consisting of programming language, used libraries, or skeletons influences programming effort and algorithm performance. Selection rule and data management structures are usually hidden to programmers for frameworks with a high level of abstraction, as well as the load balancing strategy, when the algorithm is run in parallel. We investigate the question by implementing a multidimensional Global Optimization B&B algorithm with the help of three frameworks with a different level of abstraction (from more to less): Bobpp, Threading Building Blocks (TBB), and a customized Pthread implementation. The following has been found. The Bobpp implementation is easy to code, but exhibits the poorest scalability. On the contrast, the TBB and Pthread implementations scale almost linearly on the used platform. The TBB approach shows a slightly better productivity.     

Matrix-analytic solution of infinite,finite and level-dependent second-order fluid models

This paper presents a matrix-analytic solution for second-order Markov fluid models (also known as Markov-modulated Brownian motion) with level-dependent behavior. A set of thresholds is given that divide the fluid buffer into homogeneous regimes. The generator matrix of the background Markov chain, the fluid rates (drifts) and the variances can be regime dependent. The model allows the mixing of second-order states (with positive variance) and first-order states (with zero variance) and states with zero drift. The behavior at the upper and lower boundary can be reflecting, absorbing, or a combination of them. In every regime, the solution is expressed as a matrix-exponential combination, whose matrix parameters are given by the minimal nonnegative solution of matrix quadratic equations that can be obtained by any of the well-known solution methods available for quasi birth death processes. The probability masses and the initial vectors of the matrix-exponential terms are the solutions of a set of linear equations. However, to have the necessary number of equations, new relations are required for the level boundary behavior, relations that were not needed in first-order level dependent and in homogeneous (non-level-dependent) second-order fluid models. The method presented can solve systems with hundreds of states and hundreds of thresholds without numerical issues.     

Optimization method in problems of acoustic cloaking of material bodies

Optimization problems for a three-dimensional model of acoustic scattering are formulated and studied. These problems arise in designing tools for cloaking material bodies by applying the wave flow method. The cloaking effect is achieved due to an optimal choice of variable parameters of the inhomogeneous isotropic medium occupying the sought shell. The solvability of direct and optimization problems for the acoustic scattering model is proved, and sufficient conditions ensuring the uniqueness and stability of optimal solutions are established.     

New polymer composites based on keratin and polyethylene

New biodegradable composites based on keratin and polyethylene have been produced under shear deformation. It has been demonstrated that the introduction of keratin leads to an increase in elastic modulus and to a decrease in ultimate tensile strength and elongation at break of the compositions. Elongation at break ε_b depends on the keratin dispersity; the highest ε_b values are observed for the compositions containing the smallest keratin particles. It has been shown that the compositions are susceptible to mold fungi; i.e., they are biodegradable.