Solvent-Free Production of Bioflavors by Enzymatic Esterification of Citronella (<Emphasis Type="Italic">Cymbopogon winterianus</Emphasis>) Essential Oil

Enzymatic esterification of citronella essential oil towards the production of geranyl and citronellyl esters may present great scientific and technological interest due to the well-known drawbacks of the chemical-catalyzed route. In this context, this work reports the maximization of geranyl and citronellyl esters production by esterification of oleic and propionic acids in a solvent-free system using a commercial immobilized lipase as catalyst. Results of the reactions showed that the strategy adopted for the experimental design proved to be useful in evaluating the effects of the studied variables on the reaction conversion using Novozym 435 as catalyst. The operating conditions that maximized the production of each ester were determined, leading, in a general way, to conversions of about 90% for all systems. New experimental data on enzymatic esterification of crude citronella essential oil for geranyl and citronellyl esters production in solvent-free system are reported in this work.     

Nonparametric regression with warped wavelets and strong mixing processes

We consider the situation of a univariate nonparametric regression where either the Gaussian error or the predictor follows a stationary strong mixing stochastic process and the other term follows an independent and identically distributed sequence. Also, we estimate the regression function by expanding it in a wavelet basis and applying a hard threshold to the coefficients. Since the observations of the predictor are unequally distant from each other, we work with wavelets warped by the density of the predictor variable. This choice enables us to retain some theoretical and computational properties of wavelets. We propose a unique estimator and show that some of its properties are the same for both model specifications. Specifically, in both cases the coefficients are unbiased and their variances decay at the same rate. Also the risk of the estimator, measured by the mean integrated square error is almost minimax and its maxiset remains unaltered. Simulations and an application illustrate the similarities and differences of the proposed estimator in both situations.

     

Alkaloids from stems of Esenbeckia leiocarpa Engl. (Rutaceae) as potential treatment for Alzheimer disease

Esenbeckia leiocarpa Engl. (Rutaceae), popularly known as guarant?, goiabeira, is a native tree from Brazil. Bioactivity-guided fractionation of the ethanol stems extract afforded the isolation of six alkaloids: leiokinine A, leptomerine, kokusaginine, skimmianine, maculine and flindersiamine. All isolated compounds were tested for acetyl cholinesterase inhibition, in vitro and displayed anticholinesterasic activity. The alkaloid leptomerine showed the highest activity (IC?? = 2.5 mM), similar to that of the reference compound galanthamine (IC?? = 1.7 mM). The results showed for the first time the presence of alkaloids leptomerine and skimmianine in E. leiocarpa (Engl.) with potent anticholinesterasic activity.     

Carboxymethylchitosan/Poly(amidoamine) Dendrimer Nanoparticles in Central Nervous Systems‐Regenerative Medicine: Effects on Neuron/Glial Cell Viability and Internalization Efficiency

The applicability of CMCht/PAMAM dendrimer nanoparticles for CNS applications was investigated. AFM and TEM observations revealed that the nanoparticles possessed a nanosphere‐like shape with a size from 22.0 to 30.7 nm. The nanoparticles could be bound to fluorescent‐probe FITC for tracing purposes. Post‐natal hippocampal neurons and cortical glial cells were both able to internalize the FITC‐labeled CMCht/PAMAM dendrimer nanoparticles with high efficiency. The percentage of positive cells internalizing the nanoparticles varied, reaching a peak after 48 h of incubation. Further experiments for periods up to 7 d revealed that the periodical addition of FITC‐labelled CMCht/PAMAM dendrimer nanoparticles was needed to maintain the overall percentage of cells internalizing them. Finally, it was also observed that cell viability was not significantly affected by the incubation of dendrimer nanoparticles.

     

Screening of Pectinase-Producing Microorganisms with Polygalacturonase Activity

The aim of this work was to perform the screening of microorganisms, previously isolated from samples of agro-industrial waste and belonging to the culture collection of our laboratory, able to produce polygalacturonases (PG). A total of 107 microorganisms, 92 newly isolated and 15 pre-identified, were selected as potential producers of enzymes with PG activity. From these microorganisms, 20 strains were able to synthesize PG with activities above 3 U mL⁻¹. After the kinetic study, the enzyme activity was increased up to 13 times and the microorganism identified as Aspergillus niger ATCC 9642 and the newly isolated W23, W43, and D2 (Penicillium sp.) after 24 h of fermentation led to PG activities of 30, 41, 43, and 45 U mL⁻¹, respectively. The RAPD analysis demonstrated that the selected strains differs genetically, indicating that no duplication of strains among them in the experiments for polygalacturonases production was verified.     

Witness Trees in the Moser–Tardos Algorithmic Lovász Local Lemma and Penrose Trees in the Hard-Core Lattice Gas

We point out a close connection between the Moser–Tardos algorithmic version of the Lovász local lemma, a central tool in probabilistic combinatorics, and the cluster expansion of the hard-core lattice gas in statistical mechanics. We show that the notion of witness trees given by Moser and Tardos is essentially coincident with that of Penrose trees in the Cluster expansion scheme of the hard-core gas. Such an identification implies that the Moser–Tardos algorithm is successful in a polynomial time if the cluster expansion converges.     

Microstructures and magnetic domain configurations of NdFe<Subscript>11</Subscript>Ti and Nd<Subscript>2</Subscript>(Fe,Ti)<Subscript>17</Subscript> aggregates

Nd:11Fe:Ti alloys produced by arc melting and splat quenching have been investigated by scanning electron microscopy, transmission electron microscopy, magnetic force microscopy and magnetic measurements. Both the as-cast and splat-quenched materials crystallized adopting essentially the ThMn₁₂-type structure. However, the RFe₁₁M (where R is a rare-earth element and M is an early 3d element or other non-magnetic element) stoichiometry was not strictly followed and α-Fe(Ti) and Nd₂(Fe,Ti)₁₇ could be detected in the microstructures. Magnetic force microscopy showed that the critical size for single-domain behavior in the splat-quenched aggregates was close to 100 nm. Annealing treatments induced a NdFe₁₁Ti → Nd₂(Fe,Ti)₁₇+α-Fe(Ti) + Fe₂Ti reaction. Transmission electron microscopy investigations showed that this solid-state transformation produced a fine intergrowth of the two ternary rare-earth compounds with a specific crystallographic orientation relation. The lower saturation magnetization of the splat/annealed condition as compared to the splat-quenched condition may reflect the disorderly intergrown Nd₂(Fe,Ti)₁₇ phase in NdFe₁₁Ti. On the other hand the higher coercivity obtained for the splat-quenched condition seems related to the smaller scale of the microstructure due to a possible, albeit weak, pinning effect by the grain boundaries.     

Microorganism screening for limonene bioconversion and correlation with RAPD markers

The use of microorganisms for biotransformations of monoterpenes has stimulated the biotechnological market. Aiming at the highest efficiency in the process of strains screening, the application of molecular biology techniques have been proposed. Based on these aspects, the objective of this work was to select different strains able to convert limonene using fermentative process and random amplified polymorphic DNA (RAPD) markers. The results obtained in the fermentative screening, from 17 strains tested, pointed out that four microorganisms were able to convert limonene into oxygenated derivatives. The RAPD study showed a polymorphism of 96.02% and a similarity from 16.02 to 51.51%. Based on this it was possible to observe a high genetic diversity, even among strains of same species, concluding that the RAPD was not able to correlate the genetic characteristics of the microorganism with the results obtained from the biotransformation process.