Evaluation of the mechanical properties and diffusion coefficients of osmodehydrated melon cubes

The objective of this work was to evaluate the influence of osmotic agents, their concentration and temperature, on the mass transfer kinetics and mechanical properties of osmodehydrated melon cubes. Samples were immersed in a hypertonic solution of sucrose or maltose up to 8 h under controlled temperature and agitation. Water loss, sugar gain and mechanical properties were analysed throughout the process. Mass transfer kinetics was modelled according to Peleg and Fick equations. Higher water loss, lower sugar uptake and stress at rupture values more similar to fresh fruit were observed in samples treated with maltose solutions. Peleg’s model showed the best adjustment to all the experimental data, however the k₁ and k₂ parameters did not show a clear trend with the solution concentration or temperature increase. The effective diffusivity obtained using Fick’s equation varied from 3.93 × 10^?9 to 6.45 × 10^?9m² s^?1 for water loss and from 7.57 × 10^?10 to 3.14 × 10^?9m² s^?1 for sugar gain.     

Structure Conservation and Differential Expression of Farnesyl Diphosphate Synthase Genes in Euphorbiaceous Plants

Farnesyl diphosphate synthase (FPS) is a key enzyme of isoprenoids biosynthesis. However, knowledge of the FPSs of euphorbiaceous species is limited. In this study, ten FPSs were identified in four euphorbiaceous plants. These FPSs exhibited similar exon/intron structure. The deduced FPS proteins showed close identities and exhibited the typical structure of plant FPS. The members of the FPS family exhibit tissue expression patterns that vary among several euphorbiaceous plant species under normal growth conditions. The expression profiles reveal spatial and temporal variations in the expression of FPSs of different tissues from Euphorbiaceous plants. Our results revealed wide conservation of FPSs and diverse expression in euphorbiaceous plants during growth and development.     

A selective assay to detect chitin and biologically active nano-machineries for chitin-biosynthesis with their intrinsic chitin-synthase molecules

A new assay system for chitin has been developed. It comprises the chitin-binding protein ChbB in fusion with a His-tag as well as with a Strep-tag, the latter of which was chemically coupled to horseradish peroxidase. With the resulting complex, minimal quantities of chitin are photometrically detectable. In addition, the assay allows rapid scoring of the activity of chitin-synthases. As a result, a refined procedure for the rapid purification of yeast chitosomes (nano-machineries for chitin biosynthesis) has been established. Immuno-electronmicroscopical studies of purified chitosomes, gained from a yeast strain carrying a chitin-synthase gene fused to that for GFP (green-fluorescence protein), has led to the in situ localization of chitin-synthase-GFP molecules within chitosomes.     

Improved polyhydroxybutyrate (PHB) production in transgenic tobacco by enhancing translation efficiency of bacterial PHB biosynthetic genes

Polyhydroxybutyrate [P(3HB)] was produced in the transgenic tobacco harboring the genes encoding acetoacetyl-CoA reductase (PhaB) and polyhydroxyalkanoate synthase (PhaC) from Ralstonia eutropha (Cupriavidus necator) with optimized codon usage for expression in tobacco. P(3HB) contents in the transformants (0.2mg/g dry cell weight in average) harboring the codon-optimized phaB gene was twofold higher than the control transformants harboring the wild-type phaB gene. The immunodetection revealed an increased production of PhaB in leaves, indicating that the enhanced expression of PhaB was effective to increase P(3HB) production in tobacco. In contrast, codon-optimization of the phaC gene exhibited no apparent effect on P(3HB) production. This result suggests that the efficiency of PhaB-catalyzed reaction contributed to the flux toward P(3HB) biosynthesis in tobacco leaves.     

内插旋流片的缩放管内糖液自然对流的传热研究

The natural convection heat transfer of a 60% sucrose solution in a vertical converging-diverging tube （CD） withregularly-spaced twisted tapes （RSTT） has been investigated numerically and experimentally. The effects of wall temperatureand number of RSTT on the Nusselt number were studied in detail. The distributions of velocity and temperature inthe 60% sucrose solution were studied and the simulated results of CD with RSTT were compared with those of the smoothtube. The influence of Rayleigh number and RSTT on the Nusselt number was conducted experimentally. The results indicatethat the Nusselt number of the 60% sucrose solution obviously increased with the number of RSTT but increased inconspicuouslywith 2 and more twisted tapes. The simulation shows that the distance for achieving an optimal heat transferperformance is 46 times the diameter of the tube. The mechanism of the natural convection heat transfer enhancement of the60% sucrose solution in relationship with the CD and the RSTT was analyzed, and the change of average tangential velocitywith the axial distance was presented to demonstrate that the enhancement of heat transfer was realized mainly because of the increase in tangential velocity.     

Preparation and characterization of non-random YBa2Cu3O7-Ag composite

Silver addition to the highT _c superconductor, YBa₂Cu₃O₇ (YBCO) is known to improve its mechanical properties and critical current (J _c) characteristics. We have synthesized the superconductor-metal composite YBCO-Ag by an electroless process at room temperature (using sucrose or hydrazine hydrate in an alkaline medium). The latter method produces a non-random coating whereby each grain of YBCO is coated uniformly by silver. The intrinsic highT _c of 90 K of YBCO can be recovered by compaction of the composite and subsequent heat treatment (900°C and 600°C) in oxygen.     

Isolation of σ-(L-α-aminoadipyl)-L-cysteinyl-D-valine from culture broths by covalent chromatography

An efficient procedure for the isolation of reduced -(L-α-aminoadipyl)-L-cysteinyl-D-valine (ACV) from culture supernatants of β-lactam antibiotic-producing microorganisms is described. The method utilises covalent chromatography to isolate thiols from culture broths that have been deproteinised and undergone borohydride reduction. 2-Pyridyl disulphide activated thiopropyl Sepharose was employed batchwise to isolate the thiols present in such broths from cultures of the known ACV excreter Cephalosporium acremonium N2 and the penicillin producer Penicillium chrysogenum P2. ACV was separated from these mixtures of thiols by gel permeation chromatograhy. Reversed-phase HPLC analysis showed the ACV to be of a high purity unless isolated from a highly complex culture medium.     

Exposure to Diflubenzuron Results in an Up-Regulation of a Chitin Synthase 1 Gene in Citrus Red Mite,Panonychus citri (Acari: Tetranychidae)

Chitin synthase synthesizes chitin, which is critical for the arthropod exoskeleton. In this study, we cloned the cDNA sequences of a chitin synthase 1 gene, PcCHS1, in the citrus red mite, Panonychus citri (McGregor), which is one of the most economically important pests of citrus worldwide. The full-length cDNA of PcCHS1 contains an open reading frame of 4605 bp of nucleotides, which encodes a protein of 1535 amino acid residues with a predicted molecular mass of 175.0 kDa. A phylogenetic analysis showed that PcCHS1 was most closely related to CHS1 from Tetranychus urticae. During P. citri development, PcCHS1 was constantly expressed in all stages but highly expressed in the egg stage (114.8-fold higher than in the adult). When larvae were exposed to diflubenzuron (DFB) for 6 h, the mite had a significantly high mortality rate, and the mRNA expression levels of PcCHS1 were significantly enhanced. These results indicate a promising use of DFB to control P. citri, by possibly acting as an inhibitor in chitin synthesis as indicated by the up-regulation of PcCHS1 after exposure to DFB.     

复配改良剂对马铃薯米线质构品质的影响

为探索马铃薯米线中品质改良剂应用的可行性,以质构品质为评价指标,研究不同品质改良剂(黄原胶、蔗糖酯和玉米淀粉)对马铃薯米线品质的改良效果,并在单因素实验基础上通过正交实验确定品质改良剂的最佳配比。实验结果表明:以原料质量为基准,当添加黄原胶0.4 g/100 g、蔗糖酯0.3 g/100 g和玉米淀粉6 g/100 g复配使用时,马铃薯米线的质构品质得到明显改良,弹性提高至0.988,硬度和咀嚼性分别为2271 g和2013 g。