Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
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Enrichment of low concentration rare earths from leach solutions of ion-adsorption ores by bubbling organic liquid membrane extraction using N1923
No full textMild oxalic acid-catalyzed hydrolysis as a novel approach to prepare cellulose nanocrystals.
No full textThe traditional method to isolate cellulose nanocrystals (CNCs) is to subject cellulosic materials to strong acid hydrolysis by mineral acids, which usually causes problems such as corrosion of equipment, the need for large amounts of water, the difficulty of acid recovery, and over-degradation of cellulose. Thus, a green and sustainable approach for the preparation of CNCs was developed where mild acid hydrolysis with diluted oxalic acid was used. The reaction kinetics of different preparation parameters, such as reaction temperature, oxalic acid dose, addition of HCl, and reaction time were thoroughly investigated. A high yield of up to 85 % was achieved by mild oxalic acid hydrolysis in comparison to the yield of 35 % using the most common approach with sulfuric acid hydrolysis. The CNCs from the above approach have a high thermal stability, that is, a maximum thermal degradation temperature of 350 °C in comparison to 200 °C when sulfuric acid hydrolysis was used. Importantly, oxalic acid solutions were readily recovered, and exhibited consistently high performance in several continuous runs of reaction. The hydrolysates contained mostly monomeric sugars, which could be further utilized for chemical or biofuel production
Additive-Modulated Switchable Reaction Pathway in the Addition of Alkynes with Organosilanes Catalyzed by a Supported Pd Nanoparticles: Hydrosilylation versus Semihydrogenation
No full textN-Alkylation vs O-Alkylation: Influence on the Performance of aPolymeric Field-Effect Transistors Based on a Tetracyclic Lactam Building Block
No full textLactam-containing conjugated molecules are important building blocks for conjugated polymers for high performance organic field-effect transistors (OFETs). The alkylation on conjugated lactam building blocks may preferably produce either O-alkylated or N-alkylated isomers, which might have different influences on the HOMO/LUMO energy levels, π−π stacking patterns and crystallinity of the corresponding polymers. However, the influence of Oalkylation and N-alkylation on the OFET performance of the resultant polymers has not been reported. Here, with an improved synthetic strategy, we prepared the N-alkylated isomer of dibenzonaphthyridinedione (DBND), a tetracyclic lactam building block that used to give O-alkylated product preferably, which gave us a chance to compare the influence of N-alkylated DBND (N-DBND) and O-alkylated DBND (O-DBND) on the OFET performance of the corresponding polymers. It was found that the polymer based on N-DBND exhibits a much higher hole mobility (0.55 cm2 V−1 s−1), almost 100 times greater than the one based on O-DBND (0.006 cm2 V−1 s−1). The reasons for such a huge difference were thoroughly investigated theoretically and experimentally. It was found that repeating unit in the polymer based on N-DBND exhibits a much higher dipole moment (1.56 D) than that based on O-DBND (0.49 D), which results in a much stronger intermolecular binding energy (−57.2 vs −30.0 kcal mol−1). Although both polymers exhibits very similar coplanarity and crystalline patterns, stronger intermolecular interaction of the polymer based on N-DBND leads to shorter π−π stacking distance (3.63 vs 3.68 Å), which results in a film with higher crystallinity and highly interconnected fibrillar domains, and accounts for its high charge carrier mobility, as evidenced by 2D-GIXD and AFM analysis. We come to the conclusion that the more polar amide bond in N-DBND is the major factor which governs the charge transport properties, which overwhelms the side-chain engineering effect that O-alkylation might bring in (the branching point of the side-chain of an O-DBND-based polymer is one more atom away from the polymer backbone and results in less steric hindrance)
生物工程
No full textHaematococcus pluvialis (Chlorohyceae) is generally regarded as one of the best biological source for astaxanthin which is widely used for health product, feed and medicine. However, the Haematococcus pluvialis through autotrophy is poor in biomass producty and costive when inudstrial production. Genetic engineering modification such as the construction of heterophic strains with glucose may solve the problems. This thesis had made an attempt to establish stable genetic transformation of Haematococcus pluvialis. Research work includes the analysis of the differentiation between motile cell and non-motile cell, the difference in cultivation and regeneration on solid plate for electrotransformation, biolistic transformation and PEG-mediated protoplast transformation.
Firstly, based on the morphology of two main cell type - motile cell and non-motile cell in its complicated life history, the cell differentiation of all Haematococcus pluvialis cells to be single type or the majority of cells to be single type during the cultivation were observed. Results showed that motile cell occupied more than 80% in the first 4 days and non-motile cell occupied more than 80% when cultivated for 12 days in BYA medium which contains 2 g/L sodium acetate, 2 g/L yeast extration in BG11. Meanwhile the maximm cells density was 8×105 cells/mL. Under the centrifugation condition of 500 g × 5 min , all types of cells will be collected. In Tris-HCl buffer with 0.2 mmol/L CaCl2, motile cells were more stable while non-motile cells did without CaCl2. In addition, compared with direct coating for regeneration, double-layer plate was proved to be significantly more effective while starch embedding showed no advantage. Futher experiments indicates that the regeneration rate of motile cell was higher than non-motile cell, and colonies in TAP and BYA in which sodium acetate was added formated more quickly than 8P-BG11 and 3N-BBM. BYA was the best medium for cell regeneration and the regeneration rate was 52.8% and 31.5% for motile cell and non-motile cell respectively.
Secondly, the sensibility to spectinomycin and zeomycin of Haematococcus pluvialis in solid plates and liuqid medium was analyzed, and electrotransformation and biolistic transformation were conducted. The results suggested that appropriate screening concentration of spectinomycin and zeomycin to Haematococcus pluvialis was 200 µg/mL, 8 µg/mL in solid palte respectively while 20 µg/mL, 1 µg/mL respectively in liquid medimu. Motile cells were more sensitive than non-motile cell to electricity, and the survival rate was 40% when the voltage was about 1000 v/cm for motile cell, but for non-motile cell, the voltage was 2000 v/cm to reach the same survial rate. Unofortunately, the experimental repeatability was poor and recombinant transformant was not observed via Ble gene to zeomycin, however, transformant was found via addA gene to spectinomycin. PCR analysis had proved that the transgene was integrated into the chloroplast genome and chromosome repestively by pHpluS1 plasmid and 18s-pHpluS1-28s plasmid.
Finally, based on the optimized protocol for protoplast preparation and regeneration, protoplast transformatioin of Haematococcus pluvialis was constructed for the first time. Protoplast viability was significantly increased when 0.5 mmol/L CaCl2 was added into the buffer solution. Protease-k was proved to be the most effective enzyme for protoplast preparation, and when the cell density was 5×106 cells/mL, preparation rate and viability was 78.5% and 78.4% respectively at 35C for 120 min. Transformant was found by electrotransformation based on protoplast, but the colonies also could’t grow in liquid medium. With PEG (polyethylene glycol) -mediated protoplast transformation, fluorescence was observed. Besides, transformant were found via addA gene to spectinomycin, and it is confirmed that the transgene was integrated into the chloroplast genome and chromosome repestively by pHpluS1 plasmid and 18s-pHpluS1-28s plasmid which were linearized by PCR analysis.中
化学工程
No full textAerogels are widely used in fields of special garments, aviation and military industry, petrochemical, energy saving building due to its low density, high specific surface area, high porosity and low thermal conductivity. Bio-based aerogels prepared from nature polymers not only possess the characteristics of traditional aerogels, but also integrate with their own excellent properties such as good flexibility, renewability, environmental friendliness. As one kind of bio-materials, cellulose is an abundant biopolymer in nature. As a new generation, cellulose aerogels combine the advantages of cellulose and traditional aerogels. However, pure cellulose aerogels have poor mechanical strength because of their own structure. Combining with inorganic nano-materials not only can improve their mechanical strength, but also endow them with characteristics of conduction, lyophobic, antiflaming and other interesting properties. In this thesis, cellulose and its derivatives were used as research object, combined with different inorganic nanomaterials to prepare cellulose-based composite aerogels, and their mechanical and heat insulation properties were investigated. The main contents and results are as follows:
(1) Cotton cellulose was used as raw material, cheaper sodium silicate was used as precursor and LiOH/urea/H2O system was used as solvent for dissolving cellulose. Then composite hydrogels were fabricated via in situ formation of silica in cellulose hydrogel. Finally, composite aerogels were obtained after drying with supercritical CO2. The effect of preparation conditions such as Na2SiO3 mass fraction, HCl concentration and cellulose concentration on structure and properties of composite aerogels were studied. The results show that the specific surface area of composite aerogels is increased by 65%, pore diameter is decreased 1 times, and compressive strength and Young’s modulus are increased by 3 times and 4 times, respectively.
(2) Composite aerogels with excellent mechanical property were prepared by using CMC as raw materials, 2D graphene oxide (GO) nano-sheet as reinforcement, boric acid (BA) as cross-linker. By controlling the heat transfer rate, composite aerogels with isotropy and anisotropy structure were prepared, and the mechanical property and heat insulating were studied. The results show that the composite aerogel with isotropy structure has compression strength of 110 kPa, which is 5 times the axial and 14 times the radial of anisotropy structure composite aerogels, and thermal conductivity is lower than those of two directions of anisotropy structure composite aerogels. And the effect of GO content in isotropy composite aerogels on their properties was also discussed. The results show that the mechanical property of composite aerogel increases with the increase of GO content. When GO content is up to 5 wt%, the compressive strength and Young’s modulus of composite aerogels reach 349 kPa and 1029 kPa, respectively, which are 1.6 and 4.5 times that of CMC aerogels, respectively. However, the increased content of graphene oxide in composite aerogels also increases their thermal conductivity.中
生物工程
No full textAs the most abundant renewable resource on the earth, plant cell wall has numerous applications in various aspects of human living and industry servering as the main source of energy, fiber, building materials and papermaking materials. Thus, in-depth analysis of the composition, structure and biosynthesis mechanisms of plant cell wall, and optimization of the composition, structure and connections between different components by genetic engineering to improve the saccharification efficiency , is hot topics in the research of plant cell wall.
Arabidopsis thaliana seed coat cells synthesize and secrete large amounts of mucilage ploysaccarides (mainly composed of rhamnogalactoside I, RG I) to the extracellular at specific satges during the seed coat differentiation.Besides pectic RG I, mucilage also consists a small amount of cellulose and hemicellulose (e.g. heteroxylansand glactoglucomannan) components, thus mucilage represnet a specialized cell wall. Seed coat mucilage is not necessary for the germination or growth of plants, in addition, seed coat mucilage can be easily extracted and the defect phenotype can be readily identified, so it can be utilized as an ideal model system for the study of biosynthesis, modification and regulation of cell wall polysaccharides.
Previous study identified a transcription factor gene, HOMODOMAIN GLABROUS 2 (HDG2) . HDG2 belongs to homeobox subfamily HD-Zip IV. This study mainly focused on the mechanism of HDG2 in the regulation of seed coat mucilage structure.The main results are as follows: 1) Real-time quantitative PCR (qRT-PCR), in situ hybridization and promoter GUS activity analysis showed that HDG2 was specifically expressed in the seed coat, and its peak was observed at 10 days after pollination (10 DPA). 2) The transcriptional activation activity of HDG2 and its transcriptional activation domain was analyzed in yeast cell. The truncation test was performed according to the conserved domain of HDG2 protein (HD, LZ, START and SAD). The results indicated that HDG2 had transcriptional activation activity, and its transcriptional activation is located in the leucine zipper (LZ) domain. 3) Ruthenium red staining was carried out for T-DNA insertion mutants of HDG2(hdg2-2 and hdg2-3). The results showed that seed coat mucilage of hdg2 can be normally released, and no significant changes in total amount was observed. However, the mucilage layers of hdg2 was easily shaked off, leaving thinner adherent inner mucilage than that of the wild type (WT). 4) The hdg2 and WT seeds were dissected from 4 DPA-13 DPA and observed by resin embedding and slicing, the results showed that epidermal cells of hdg2-3 seed were normally developed and the secretion and the amount of mucilage displayed no significant differences compared to the WT. 5) The content, composition and structure of hdg2-3 mucilage was analyzed, and it was found that the total amount of hdg2-3 mucilage had no significant differences with that of the WT. The composition of monosaccharide showed that the contents of monosaccharides，which affect the mucilage structure (e.g. xylose, mannose) had no significant differences with the WT. 6) In situ immunohistochemical analysis showed that the crystalline cellulose content was significantly reduced in hdg2-3 compare with the WT, which was confirmed by the quantification of crystalline cellulose contents. Thus it can be conclueded that the decrease of crystalline cellulose led to the mucilage defect in hdg2-3. 7) To further confirm if HDG2 is involved in the modulation of crystalline cellulose, qRT-PCR analysis of hdg2 and WT seeds at different stages was performed. The results showed that CESA5, a key gene affecting cellulose synthesis in seed coat mucilage, was significantly decreased in hdg2-3. EMSA and yeast one hybridization analysis confirmed that HDG2 protein could bind to the L1-box motif located in CESA5 promoter. In addition, protoplast transcriptional activation assay showed that HDG2 could activate the expression of CESA5.
In summary, the molecular mechanisms of HDG2 transcription factor in the regulation of mucilage structure were characterzide in this study. A series of physiological and biochemical evidence suggested that HDG2 regulates the synthesis or assembly of cellulose by direct activation of CESA5 to maintain the normal structure of the seed coat mucilage. In contrast, HDG2 mutations inhibit the expression of CESA5, the synthesis or assembly of crystalline cellulose is blocked and finally showing a defective phenotype of the seed coat mucilage. The results obtained will help to deepen our understanding of the molecular mechanisms and regulation networks underlying cellulose synthesis and assembly, which lay a theoretical foundation for the future custom-design of the cell wall by genetic engineering means.中