Isolation and identification of xylitol-producing yeasts from agricultural residues

Selected yeast strains isolated from corn silage and viticulture residues were screened for their capacities to convert D-xylose into xylitol A conventional TLC was adapted for easy determination of xylose and xylitol in the culture supernatant solutions. This technique is suitable for the first steps of a screening program to select xylitol-producing yeasts from natural environments. Candida tropicalis ASM III (NRRL Y-27290), isolated from corn silage, appears to be a promising strain for xylitol production with a high yield (0.88 g xylitol per g of xylose consumed).     

Isolation and characterization of cellulose nanofibrils from wheat straw using steam explosion coupled with high shear homogenization

Cellulose nanofibrils of diameter 10–50 nm were obtained from wheat straw using alkali steam explosion coupled with high shear homogenization. High shear results in shearing of the fiber agglomerates resulting in uniformly dispersed nanofibrils. The chemical composition of fibers at different stages were analyzed according to the ASTM standards and showed increase in α-cellulose content and decrease in lignin and hemicellulose. Structural analysis of steam exploded fibers was carried out by Fourier Transform Infrared (FT-IR) spectroscopy and X-ray diffraction (XRD). Thermal stability was higher for cellulose nanofibrils as compared to wheat straw and chemically treated fibers. The fiber diameter distribution was obtained using image analysis software. Characterization of the fibers by AFM, TEM, and SEM showed that fiber diameter decreases with treatment and final nanofibril size was 10–15 nm. FT-IR, XRD, and TGA studies confirmed the removal of hemicellulose and lignin during the chemical treatment process.     

Degradation of alkali-lignin residues from solid-state fermentation of wheat straw by streptomycetes

The ability of three Streptomyces strains to degradealkali-lignin, produced from the treatment of wheat straw by the same organisms, was examined. Decolourisation and loss of alkali-lignin was only detected in cultures supplemented with ammonium as an inorganic N source. The pH of cultures supplemented with inorganic N reached lower pH than in those supplemented with yeast extract. From FT-IR spectra corresponding to the alkali-lignin obtained from the same cultures, a degradation of carbohydrate component concomitant with a modification in the aromatic moiety of lignin could be inferred. The results indicate that streptomycetes are suitable for use in the treatment of alkali-lignin effluents from the biological treatment of wheat straw by the same organisms and therefore support the role for these organisms in the development of clean technologies in pulp and paper industry.     

酱醪中魏斯氏菌的分离及特性分析

【背景】魏斯氏菌广泛存在于发酵食品中,它们与食品发酵进程和风味物质的形成密切相关。酱油发酵过程酱醪中细菌的优势菌属是魏斯氏菌,研究魏斯氏菌的生理和代谢特性对于揭示菌株对环境的适应性和与酱油发酵相关的功能具有重要意义。【目的】从酱油酱醪中分离获得魏斯氏菌属中主要种的菌株,研究它们在酱油发酵过程的数量变化以及菌株的生理和生化特性,阐明菌株对酱油发酵体系的适应性和与酱油发酵相关的特性。【方法】通过菌株绝对数量的定量分析和耐受性比较,以及考察高盐条件下魏斯氏菌合成短链脂肪酸、胞外多糖、生物胺和氨基甲酸乙酯或其前体等特性,研究各类魏斯氏菌对酱油发酵和其安全性的影响。【结果】从高盐稀态酱油的酱醪中共分离得到16株魏斯氏菌,分别属于融合魏斯氏菌(Weissella confusa)、类肠膜魏斯氏菌(Weissellaparamesenteroides)和食窦魏斯氏菌(Weissellacibaria)。其中类肠膜魏斯氏菌可耐受高盐条件,是酱醪中魏斯氏菌属的主要菌种。它们合成短链脂肪酸的能力高于融合魏斯氏菌和食窦魏斯氏菌。酱醪来源的魏斯氏菌合成氨(胺)类危害物的特性区别较大,类肠膜魏斯氏菌的部分菌株产生物胺并可利用精氨酸积累瓜氨酸,食窦魏斯氏菌则能够降解多种生物胺。【结论】揭示了酱醪中主要魏斯氏菌的耐盐特性、在较低温度下生长情况和物质代谢规律,对于阐明魏斯氏菌与酱油发酵相关的功能和特性以及对酱油加工过程安全控制具有重要意义。     

Fractional and structural characterization of wheat straw hemicelluloses

Six hemicellulosic fractions were extracted successively from dewaxed wheat straw with sodium hydroxide at increasing strength from 0.25 to 2.00M, and the chemical composition are reported. The structure of the hemicellulosic fraction 2 was investigated using acid hydrolysis, methylation analysis and ¹³C-NMR experiments. The hemicelluloses were confirmed to be a (1→4)-linked β-D-xylan with D-glucopyranosyluronic acid (or 4-O-methyl--D-glucopyranosyluronic acid) group attached at position 2, and L-arabinofuranosyl and D-xylopyranosyl groups attached at position 3. For every 26 D-xylopyranosyl residues in the main chain, there was one uronic acid unit. For 13 such D-xylopyranosyl residues, there was one L-arabinofuranosyl group, and for 18 such D-xylopyranosyl residues, there was one D-xylopyranosyl group.     

Isolation and characterization of Z-DNA binding proteins from wheat germ

The preparation of a heterogeneous non-histone protein extract from wheat germ utilizing Br-poly(dG-dC).poly(dG-dC) (Z-DNA) affinity chromatography is described. The binding characteristics of antibodies against Z-DNA are used as a model system to define important criteria that the DNA binding behavior of a Z-DNA binding protein should display. We show that the wheat germ extract contains DNA binding proteins specific for left-handed Z-DNA by these criteria. The affinity of the proteins measured by competition experiments was approximately 10(5) greater for Br-poly(dG-dC).poly(dG-dC) (Z-DNA) than for poly(dG-dC).poly(dG-dC) (B-DNA). The affinity of the proteins for plasmid DNA increases with increasing negative superhelicity which is known to stabilize Z-DNA. The proteins are shown to compete with Z-DNA antibodies for binding to supercoiled plasmids. Finally, the affinity for two plasmids at a given superhelical density is greater for the plasmid containing an insert known to form Z-DNA than for a plasmid without the insert. The proteins exhibit a 2-3-fold greater affinity for stretches of (dC-dA)n.(dT-dG)n over stretches of (dG-dC)n.(dG-dC)n when both sequences are induced to form Z-DNA by supercoiling.     

Isolation and characterization of bacteria from the rhizosphere of wheat

In this study, we isolated bacteria from rhizosphere and endorhizophere of wheat crops of the central region of Argentina. The isolates were phenotypically characterized and the restriction patterns of 16S rDNA (ARDRA) using endonuclease AluI were analysed. Representative isolates were used to evaluate the effect of the inoculation on the growth of wheat under greenhouse conditions. The effects of plant growth-promoting bacteria on wheat plants were studied by evaluating shoot fresh and dry weights and root fresh and dry weights. One native strain increased the shoot and root dry biomass by 23% and 45% respectively. Other strains increased the shoot dry biomass. A 1.5 kb fragment of the 16S rRNA gene of one isolate was sequenced. This isolate showed high identity with different species of Pseudomonas.     

Isolation and characterization of photoactive complexes of NADPH:protochlorophyllide oxidoreductase from wheat

A photoactive substrate-enzyme complex of the NADPH:protochlorophyllide oxidoreductase (POR; EC 1. 3. 1. 33) was purified from etiolated Triticum aestivum L. by gel chromatography after solubilization of prolamellar bodies by dodecyl-maltoside. Irradiation by a 1-ms flash induced the phototransformation of protocholorophyllide a (Pchlide) with −196 °C absorbance and emission maxima at 640 and 643 nm, respectively. The apparent molecular weight of this complex was 112 ± 24 kDa, which indicates aggregation of enzyme subunits. By lowering the detergent concentration in the elution buffer, a 1080 ± 250-kDa particle was obtained which displayed the spectral properties of the predominant form of photoactive Pchlide in vivo (−196 °C absorbance and fluorescence maxima at 650 and 653 nm). In this complex, POR was the dominant polypeptide. Gel chromatography in the same conditions of an irradiated sample of solubilized prolamellar bodies indicated rapid disaggregation of the complex after Pchlide phototransformation. High performance liquid chromatographic analysis of the POR complexes obtained using two detergent concentrations indicates a possible association of zeaxanthin and violaxanthin with the photoactive complex. Received: 25 February 1998 / Accepted: 8 June 1998     

Isolation and characterization of novel atrazine-degrading microorganisms from an agricultural soil

Six previously undescribed microorganisms capable of atrazine degradation were isolated from an agricultural soil that received repeated exposures of the commonly used herbicides atrazine and acetochlor. These isolates are all Gram-positive and group with microorganisms in the genera Nocardioides and Arthrobacter, both of which contain previously described atrazine degraders. All six isolates were capable of utilizing atrazine as a sole nitrogen source when provided with glucose as a separate carbon source. Under the culture conditions used, none of the isolates could utilize atrazine as the sole carbon and nitrogen source. We used several polymerase-chain-reaction-based assays to screen for the presence of a number of atrazine-degrading genes and verified their identity through sequencing. All six isolates contain trzN and atzC, two well-characterized genes involved in the conversion of atrazine to cyanuric acid. An additional atrazine-degrading gene, atzB, was detected in one of the isolates as well, yet none appeared to contain atzA, a commonly encountered gene in atrazine impacted soils and atrazine-degrading isolates. Interestingly, the deoxyribonucleic acid sequences of trzN and atzC were all identical, implying that their presence may be the result of horizontal gene transfer among these isolates.     

Decomposition of wheat straw and rye residues as affected by particle size

Effects of contact between the soil and crop residues on the processes of residue decomposition are still poorly understood. The objective of this study was to investigate the effects of residue particle size on the decomposition of wheat (Triticum aestivum L.) straw (C/N=270) and green rye (Secale cereale) residues (C/N=9). Residue particle size was used as a means to vary the contact between crop residues and the soil. Carbon mineralization was measured during 102 d for straw and 65 d for rye, on residues ranging in sizes from laboratory model (0.03 cm) to field-scale (10 cm). The soil was a silt (Typic Hapludalf) and the incubation was performed at 15 °C. The effects of particle size on C mineralization varied for the two residues. In the first two days of incubation, decomposition rate of rye increased with decreasing particle size but thereafter, the trend was reversed. In 65 days, 8% more C was decomposed in the 7-cm residues than in the 0.03-cm ones. For wheat straw, early decomposition (3–17 days) was faster for the small-sized particles (0.06 and 0.1 cm). Thereafter, the largest size classes (5 and 10 cm) decomposed faster. After 102 days, the very fine particles ( 0.1 cm) showed the greatest and the intermediate size classes (0.5 and 1 cm), the lowest amount of C mineralized. We hypothesized that greater availability and accessibility of N was responsible for the higher rates of decomposition observed for finely-ground wheat straw while a physical protection of finely ground residues was probably involved in the observed reverse effect for rye.     

Isolation and characterization of kelch repeat-containing F-box proteins from colored wheat

Molecular Biology Reports - F-box proteins play important roles in the regulation of various developmental processes in plants. Approximately 1796 F-box genes have been identified in the wheat...     

Isolation, purification and characterization of hyaluronan from human umbilical cord residues

The main objective of this paper is to discuss new procedures of the isolation of Hyaluronan. Hyaluronic acid can be obtained from human umbilical cord residual, which is obtained from other biopharmaceutical productions. The route involves treatment of human umbilical cord residuals with sodium chloride solution, followed by ammonium quaternary salt solution precipitation; the solid is re-suspended in calcium chloride solution in order to dissociate the hyaluronan ammonium quaternary salt complex followed by ethanol-induced precipitation to give a product. The product was purified four times by chloroform extraction, and characterized by chemical methods such as the Blumenkrantz and Asboe-Hansen uronic technique for uronic acid determination, Elson Morgan qualitative tests for hexosamines, intrinsic viscosity, ion-exchange chromatography, and ¹³C NMR spectroscopy. The results showed that the product might be used in the formulation of ointment, lotion and cream for the treatment of skin diseases.     

Isolation and characterization of three TaYUC10genes from wheat

YUCCA protein participates in a key rate-limiting step in the tryptophan-dependent pathway for auxin biosynthesis and is involved in numerous processes during plant development. In this study, the genomic and cDNA sequences of three TaYUC10 homoeologous genes were isolated. These sequences showed a very high conservation in coding region and the exon/intron structure, whereas their intron lengths were different. The cDNA and polypeptide chains of the three TaYUC10 genes were highly similar. These genes were most homologous to BdYUC10. Location analysis showed that TaYUC10.1 was present in chromosome 5BL. TaYUC10.3 was expressed in all parts of the wheat, but was predominant in the reproductive organs of mature wheat, such as flowering spikelets or fertilized embryos. In the fertilized embryos 28 d post-anthesis, expression of TaYUC10.3 was clearly increased with the development of seeds. This indicates that TaYUC genes may play a vital role in seed development. TaYUC10.3 overexpressed in Arabidopsis had a typical phenotype, excessive auxin accumulation also seen in higher plants, and showed increased spacing of silique and downward curling of the blade margin. Sterility was observed in adult transgenic plants, becoming more severe in late development. The floral structures of sterile plants were not integrated. TaYUC10 may be required for numerous wheat growth processes, including flower and seed development.     

Levulinic acid production from wheat straw

Studies were carried out on the effects of temperature, acid concentration, liquid:solid ratio and reaction time on levulinic acid production from wheat straw using response surface methodology. The P-value of the coefficient for acid concentration was 0.0002, suggesting that this was highly significant. The quadratic effects of temperature and liquid:solid ratio were also significant and their P-values were <0.0001 and 0.0027, respectively. The coefficient determination (R(2)) was good for the second-order model. The optimal conditions for levulinic acid production from wheat straw were 209.3 degrees C, 3.5% acid concentration, 15.6 liquid:solid ratio and 37.6 min of reaction time resulted 19.86% yield.     

Glutamyl-tRNA synthetases from wheat. Isolation and characterization of three dimeric enzymes

Three dimeric glutamyl-tRNA synthetases (GluRS) were isolated from extracts of quiescent wheat germ and wheat chloroplasts. The chloroplast enzyme (Mr = 110 000), called GluRS C, exhibits a prokaryotic (Escherichia coli) tRNA specificity. Two enzymes were found in the quiescent germ and were separated on phosphocellulose P11: one called GluRS P, probably the mitochondrial enzyme, has the same tRNA specificity as GluRS C; the other, called GluRS E, has eukaryotic (wheat germ) tRNA specificity. Both enzymes exhibit a molecular weight close to 160 000. Each of these enzymes co-eluate on hydroxyapatite and phosphocellulose chromatographies with an unstable active monomer whose molecular weight is approximately half that of the corresponding dimer. Two assumptions are discussed about these monomers.