Lipase Production by Botryosphaeria ribis EC-01 on Soybean and Castorbean Meals: Optimization, Immobilization, and Application for Biodiesel Production

The effects of soybean and castorbean meals were evaluated separately, and in combinations at different ratios, as substrates for lipase production by Botryosphaeria ribis EC-01 in submerged fermentation using only distilled water. The addition of glycerol analytical grade (AG) and glycerol crude (CG) to soybean and castorbean meals separately and in combination, were also examined for lipase production. Glycerol-AG increased enzyme production, whereas glycerol-CG decreased it. A 2⁴ factorial design was developed to determine the best concentrations of soybean meal, castorbean meal, glycerol-AG, and KH₂PO₄ to optimize lipase production by B. ribis EC-01. Soybean meal and glycerol-AG had a significant effect on lipase production, whereas castorbean meal did not. A second treatment (2² factorial design central composite) was developed, and optimal lipase production (4,820 U/g of dry solids content (ds)) was obtained when B. ribis EC-01 was grown on 0.5 % (w/v) soybean meal and 5.2 % (v/v) glycerol in distilled water, which was in agreement with the predicted value (4,892 U/g ds) calculated by the model. The unitary cost of lipase production determined under the optimized conditions developed ranged from US$0.42 to 0.44 based on nutrient costs. The fungal lipase was immobilized onto Celite and showed high thermal stability and was used for transesterification of soybean oil in methanol (1:3) resulting in 36 % of fatty acyl alkyl ester content. The apparent K _m and V _max were determined and were 1.86 mM and 14.29 μmol min^?1 mg^?1, respectively.     

“Living” Radical Polymerization in Tubular Reactors, 2 – Process Optimization for Tailor‐Made Molecular Weight Distributions

“Living” radical polymerization is a relatively new polymerization process that can be used to prepare resins with controlled structures. In this work, a mathematical model developed previously to describe nitroxide‐mediated “living” radical polymerizations performed in tubular reactors is used for the optimization of the process and obtainment of tailor‐made MWDs. Operating conditions and design variables are determined with the help of optimization procedures in order to produce polymers with specified MWDs. It is shown that bimodal and trimodal MWDs, with given peak locations, can be obtained through proper manipulation of the operating conditions. This indicates that the technique discussed in this work is suitable for detailed design of the MWD of the final polymer.

     

Simple implementation of complex functionals: scaled self-consistency

We explore and compare three approximate schemes allowing simple implementation of complex density functionals by making use of self-consistent implementation of simpler functionals: (i) post-local-density approximation (LDA) evaluation of complex functionals at the LDA densities (or those of other simple functionals) (ii) application of a global scaling factor to the potential of the simple functional, and (iii) application of a local scaling factor to that potential. Option (i) is a common choice in density-functional calculations. Option (ii) was recently proposed by Cafiero and Gonzalez [Phys. Rev. A 71, 042505 (2005)]. We here put their proposal on a more rigorous basis, by deriving it, and explaining why it works, directly from the theorems of density-functional theory. Option (iii) is proposed here for the first time. We provide detailed comparisons of the three approaches among each other and with fully self-consistent implementations for Hartree, local-density, generalized-gradient, self-interaction corrected, and meta-generalized-gradient approximations, for atoms, ions, quantum wells, and model Hamiltonians. Scaled approaches turn out to be, on average, better than post approaches, and unlike these also provide corrections to eigenvalues and orbitals. Scaled self-consistency thus opens the possibility of efficient and reliable implementation of density functionals of hitherto unprecedented complexity.     

Is there a general rule for the gauche effect in the conformational isomerism of 1,2-disubstituted ethanes?

The stabilities of the gauche and anti conformations of butane, 1,2-dicyanoethane (DCE), and 1,2-dinitroethane (DNE) have been investigated through theoretical calculations. The gauche effect-the tendency of keeping close vicinal electronegative substituents (thetaX-C-C-X approximately 60 degrees ) in an ethane fragment-is expected to drive the conformational equilibrium of DCE and DNE toward the gauche conformation. It was found that, for butane, where the gauche effect is supposed to be poor/null, the hyperconjugation effect contributes mostly to the anti stabilization in opposition to the traditional sense that the methyl groups repel each other, and this should govern its conformational equilibrium. For DCE the equilibrium was shifted to the anti conformer, essentially due to a gauche repulsion, while for DNE, despite the higher electronic delocalization energies, a predominance of the gauche conformer was obtained, and this was attributed mainly to the attractive dipolar interaction between the two nitro groups. A full orbital energy analysis was performed using the natural bond orbital approach, which showed that bond bending and anti-C-H/C-X* hyperconjugation models, usually applied to explain the origin of the gauche effect in fluorinated derivatives, are not adequate to completely explain the conformational behavior of the titled compounds.     

Reliability-Based Optimization Using Differential Evolution and Inverse Reliability Analysis for Engineering System Design

In this contribution, a new methodology based on a double-loop iteration process is proposed for the treatment of uncertainties in engineering system design. The inner optimization loop is used to find the solution associated with the highest probability value (inverse reliability analysis), and the outer loop is the regular optimization loop used to solve the considered reliability problem through differential evolution and multi-objective optimization differential evolution algorithms. The proposed methodology is applied to mathematical functions and to the design of classical engineering systems according to both mono- and multi-objective contexts. The obtained results are compared with those obtained by classical approaches and demonstrate that the proposed strategy represents an interesting alternative to reliability design of engineering systems.     

Monitoring thermal,structural properties,methotrexate release and biological activity from biocompatible spray-dried microparticles

Boron phosphates (BPs) with different acidities were prepared by regulating the calcination temperatures for the reaction products of boric acid and phosphoric acid. The crystal structure, morphology, surface acidity, and thermal stability were characterized by X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), chemical absorbed apparatus, and thermogravimetric analysis (TG). The effects of BPs on the combustion behavior and catalyzing the carbonization of bisphenol-A epoxy resin (EP) were investigated by the limiting oxygen index (LOI) and cone calorimetry test. Upon loading 5 mass% BP prepared at 300 °C, the LOI value of the EP/BP composites increased to 29.6%, and moreover, the peak heat release rate and average specific extinction area decreased by 43 and 25%, respectively. A possible catalyzing carbonization mechanism was explored by TG coupled with Fourier transform infrared spectroscopy (TG–FTIR), TG, FTIR, SEM, Raman spectroscopy (Raman), and XPS. The results demonstrated that BP catalyzed EP to degrade at relatively low temperature, and the yield, compactness, and graphitization degree of the char residue were obviously enhanced with an increase in the ratio of Brønsted and Lewis acid sites (B/L value) and the total surface acid sites on the BP surface. Therefore, the catalyzing carbonization flame retardancy of the EP/BP composites can be improved through regulating the surface acidity of BP.     

Random walks on free products of cyclic groups

Let G be a free product of a finite family of finite groups,with the set of generators being formed by the union of thefinite groups. We consider a transient nearest-neighbour randomwalk on G. We give a new proof of the fact that the harmonicmeasure is a special Markovian measure entirely determined bya finite set of polynomial equations. We show that in severalsimple cases of interest, the polynomial equations can be explicitlysolved to get closed form formulae for the drift. The examplesconsidered are /2 /3, /3 /3, /k /k and the Hecke groups /2 /k.We also use these various examples to study Vershik's notionof extremal generators, which is based on the relation betweenthe drift, the entropy and the growth of the group.     

Crystalline properties and decomposition kinetics of cellulose fibers in wood pulp obtained by two pulping processes

In this study two cellulose fibers, Eucalyptus grandis (CEG) and Pinus taeda (CPT), obtained through the kraft and sulfite pulping processes, respectively, were characterized. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were carried out. From the XRD analysis the interplanar distance, crystallite size and crystallinity index were calculated and the degradation kinetics parameters were determined by TGA at heating rates of 5, 10, 20 and 40 °C min⁻¹ using the Avrami, Flynn-Wall-Ozawa (FWO) and Criado methods. The results obtained by FTIR showed that the composition of the fibers is similar, while from the XRD analysis slight differences in the crystallinity were observed. The thermogravimetric analysis showed higher thermal stability for CPT than CEG while the values for the activation energy (E_a) were higher for CEG than CPT. The results obtained by Avrami and Criado methods showed that the degradation mechanism in the CEG samples involves a diffusion process while in the case of CPT the degradation process is a phase boundary controlled reaction. The degradation mechanisms demonstrated that the difference between thermal stability and E_a may be due to differences in the type of crystalline structure of the samples obtained through the two pulping processes.     

Solution structure and conformational dynamics of deoxyxylonucleic acids (dXNA): an orthogonal nucleic acid candidate

Orthogonal nucleic acids are chemically modified nucleic acid polymers that are unable to transfer information with natural nucleic acids and thus can be used in synthetic biology to store and transfer genetic information independently. Recently, it was proposed that xylose-DNA (dXNA) can be considered to be a potential candidate for an orthogonal system. Herein, we present the structure in solution and conformational analysis of two self-complementary, fully modified dXNA oligonucleotides, as determined by CD and NMR spectroscopy. These studies are the initial experimental proof of the structural orthogonality of dXNAs. In aqueous solution, dXNA duplexes predominantly form a linear ladderlike (type-1) structure. This is the first example of a furanose nucleic acid that adopts a ladderlike structure. In the presence of salt, an equilibrium exists between two types of duplex form. The corresponding nucleoside triphosphates (dXNTPs) were synthesized and evaluated for their ability to be incorporated into a growing DNA chain by using several natural and mutant DNA polymerases. Despite the structural orthogonality of dXNA, DNA polymerase β mutant is able to incorporate the dXNTPs, showing DNA-dependent dXNA polymerase activity.