Advanced Materials Research Vols. 690-693

Abstract: On the base of experimental observations of mass loss rate in dependence of temperature in isothermal condition in circulating air atmosphere was determined the activation energy of lignocellulosic materials degradation without and with retardants. Experiment was performed in an electrically heated hot-air furnace according to ISO 871 standard (Setchkin furnace) in conjunction with precision scales. Degradation of lignocellulosic materials was performed at various temperatures and various air-flow speeds. Pure cellulose as a model compound was impregnated by water solution of KHCO₃ and (NH₄)2HPO₄.

Abstract: The preparation, characterization, and environmental application of crosslinked porous chitosan films for Acid red (AR) adsorption have been investigated. The adsorbent was characterized by scanning electron microscope (SEM). The adsorption experiments were carried out in a batch system to optimize operation variables: contact time, Acid red concentration, temperature, and pH. The results indicated crosslinked porous chitosan films could successfully remove 96% of Acid red. The adsorption equilibrium isotherms showed that the sorption processes were better fitted by Langmuir equation.

Abstract: The asymmetric reduction of ethyl 4-chloro-acetoacetate (CAAE) to ethyl (R)-4-chloro-3- hydroxybutanoate (R-CHBE) biocatalysed by the aldehyde reductase of Sporobolomyces salmonicolor expressed in E. coli M15 (pQE30-alr) in combination with regeneration of NADPH by the glucose dehydrogenase of Bacillus megaterium expressed in E. coli M15 (pQE30-gdh) was reported. The bioreduction was carried out in a two-phase reaction system with n-butyl acetate as an organic solvent. Bioconversion of 300 mmol CAAE with a final yield of 97.5 % and an enantiometric excess of 99 % was achieved without the addition of cofactor NADPH.

Abstract: The effects of tea polysaccharides (TPS) and polyphenols (TPP) on the growth inhibition of hepatoma H22 cells in mice including the roles of them in immune stimulation were investigated. The results showed that TPS and TPP both significantly inhibited the growth of H22 transplantable tumor in mice without statistical difference, both remarkably decreased the spleen index and increased the thymus index compared with that of model group (p<0.05). In addition, TPS and TPP significantly improved the splenocyte proliferation induced by ConA or LPS, and notably enhanced the macrophage phagocytosis towards neutral red. The comparison showed the effect of TPS on immune stimulation was superior to that of TPP to some extent.

Abstract: The article used acid protease to remove the protein in wheat straw, and investigated the influence of wheat straw without the protein to enzymatic hydrolysis. By the single factor experiments, the cellulose degradation rate of wheat straw removed the protein was significantly higher than untreated, in the same conditions of enzymatic hydrolysis. It is shortening 24h of enzymatic hydrolysis time and reducing enzyme dosage 90mg/g. By the orthogonal experiments, the optimal reaction conditions for enzymatic hydrolysis of wheat straw with protein removed is the cellulase dosage 170mg, enzymatic time 56h, solid-liquid ratio 1:20, pH 4.8, the reaction temperature 50°C. Compared to the untreated, the cellulose degradation rate increased by 35.58%.

Abstract: The enzymolysis of walnut residue protein was investigated using trypsase, and the best process conditions were studied by one-factor experiment and orthogonal experiment. The result showed that the influential degree weakened as follows sequence: temperature, pH, enzyme quantity, and time. The optimum conditions were temperature 53 °C, pH 8.3, enzyme quantity 0.85%, and time 2.5 h. The enzymolysis liquid obtained was thickly fragrant, nigger-brown, and not bitter. Its ammonia-nitrogen content was 6.98 g/100 g, and hydrolysis degree was 15.76%.

Abstract: The immunostimulatory activity of porcine cartilage polysaccharide nanoparticles was evaluated by using in vivo animal models. The results demonstrated that porcine cartilage polysaccharide nanoparticles not only significantly prolonged the survival period in H₂₂ tumor-bearing mice and inhibiting H₂₂ cells proliferation, but also remarkably increased the spleen index and thymus index. These results suggest that porcine cartilage polysaccharide nanoparticles might be a strong natural immunomodulator and the antitumor effect of these nanoparticles is associated with its potent immunostimulating effect.

Abstract: This study discusses the stresses in alveolar bones with various thicknesses of cortical layer around the implanted fixed partial denture subject to occlusion or external load. The stresses induced by occlusion and external loads can vary with the condition of the bone. For verification, a physical model with identical shape to the digital model and with similar material properties, loads, and boundary conditions was built. The data obtained from the physical model agreed well with that obtained from the simulations performed on the digital model. After the reliability of the finite element method (FEM) digital model had been confirmed, stresses induced by occlusion and external loads were studied. The induced stress level on the cortical bone increased with the decrease in the cortical layer. When the cortical layer vanished, the induced stress level significantly dropped. The soft cancellous bone supported the implanted complex completely once the cortical layer had gone. However, the induced displacement continued to increase more rapidly as the cortical layer thickened or vanished. A lateral load applied to the complex was also studied. The movement between the natural bone and the implant increased with the decrease in the cortical layer. This could lead to the stability problem of the implant denture and osseointegration. The results indicate that patients with thinner cortical bone carried a higher risk of failure during the restoration.

Abstract: Vitamin A is an essential nutrient element in animal and human growth, which is usually produced by partially acetylating and transforming retinyl diol. The lipase-catalyzed mono-acetylation can obtain pure monoacetate compared with the classical chemistry process. In the current work, the synthesis of vitamin A precursor of Candida antarctica lipase B catalyzed by regioselective monoacetylation of primary hydroxyl of diol in n-hexane was studied. The reaction rate could be described in terms of the Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism and competitive inhibition by both substrates. A kinetic model was developed, and the apparent kinetic parameters were calculated as: V_max =8.45 mmol/ (L•h); K _{m, vinyl} =0.997 mmol/L; K _{m, diol} =161.28 mmol/L; K _{i, diol} =287.32 mmol/L; K _{i, monoacetate}=18.13 mmol/L; and K _{I, diol} =427.40 mmol/L. The current study indicates a competitive enzyme inhibition of highly concentrated diol during lipase-catalyzed acetylation reaction. When the diol concentration in the medium was low, there was a good conformity between the experimental and simulated values with 4.73% average relative error.

Abstract: To investigate the effect of drying temperature on the fermented soybean meal, we examined the water content, protein solubility, and kinetics and thermodynamics of small peptide elimination. Results showed that the drying process of the fermented soybean meal could reduce the water content to safe level, and higher temperature (> 70 °C) would shorten the drying time, but at the same time, decrease the protein solubility and the content of small peptides. Kinetic parameters indicated that the highest rate constant k at 90°C was 18.6 times of the lowest k at 50°C and temperature effect was stronger than the time effect in the reaction, as a result, reducing their content. Thermodynamic calculation appeared that there was the chemical endothermic reaction of peptides and higher temperature also accelerated the elimination of the small peptides in this drying system.