Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
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生物工程
No full textLignocellulose is one of the most abundant biological macromolecules, which could potentially produce renewable clean energy to replace the fossil fuels. Cellulosome secreted by anaerobic bacteria can efficiently degrade lignocelluloses, which promotes greatly the possibility for industrial consume of cellulose-based bioenergy. Cellulosome is an extracellular supramolecular of cellulase complex composed by polyproteins, keeping with a certain stoichiometric ratio of protein subunits, which may determine the degrading function of the molecule. However, the industrial-oriented modifications of cellulosome were limited due to the lack in further understanding of the regulatory mechanism of subfamilies. To help solve this problem, in this thesis we focused on the study on expression of cellulosome and its regulatory mechanism, to provide a breakthrough point and new direction for the artificial design and assembly of super cellulosome.
Firstly, we analyzed the expression pattern of cellulosome under different carbon sources to illuminate the stoichiometric ratio of cellulosome subunits. We analyzed the extracellular proteins of mesophilic Clostridium papyrosolvens under various carbon source (glucose, cellobiose, cellulose, cornstalk) by proteomic methods, and found the expressions of cellulosome-related proteins like glycoside hydrolase family, LacI transcriptional regulator and cellulosome anchoring protein differed a lot under different substrate.
Secondly, in order to elucidate the cause of different stoichiometric ratio among cellulosome subunits, this study mainly focused on the cleavage of cip-cel mRNA by RNase, based on the previous discovery of the selective RNA cleavage mechanism (selective RNA cleavage mechanism, SRPS), which precisely regulates different expression of each gene in cip-cel gene, the cellulosome gene cluster of Clostridium cellulolyticum. Furthermore, a series of mutations had been conducted in the cloned intergenic region of cip-cel gene cluster, indicateing that the unpaired bubble region and AT-rich region is the determinative sites for recognization and cleavage of cip-cel gene by RNase.
Finally, attempt has been made to determine the specific endonuclease participated in the process of neck ring structure recognition and cleavage. By transcriptional level analysis we have characterized a potential gene with the highest level of expression, as well as the highest homologous with other species endonuclease. Knockout plasmids of candidate gene Ccel_0605 were constructed by Targetron technology based on type II intron, and following experiments showed that the gene Ccel_0605 was probably a necessary gene for bacterial growth and once been knockout, C. cellulolyticum can not survive.
In this thesis, regulatory mechanism of the stoichiometric ratio of cellulosome subunits has been studied, and the expression difference of cellulosome under various substrates has been displayed. Meanwhile, gene structures for recognization and cleavage of cip-cel by RNase were identified and the specific RNase invovled was attempted to be validated. This study will be helpful to finnally elucidate the regulatory mechanism of cellulosome subunits, and provide more solid evidence for guiding the artificial ddesign of super cellulosome coplex, which could be used for promoting the cellulose-based bioenergy industries.
Key Words: Clostridium papyrosolvens, Clostridium cellulolyticum, cellulosome, proteome analysis, cip-cel mRNA cleavage中文;英
中国国家博硕士学位论文数据库建设初探
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<span font-size:="" microsoft="" style="color: rgb(51, 51, 51); font-family: " text-align:="">信息社会高速发展,中国研究生培养规模宏大,学位论文社会需求日益迫切。文章在分析目前国内学位论文数据库的收录情况、社会公开情况和社会需求矛盾的基础上,提出建设"中国国家博硕士学位论文数据库"的构想,进而对学位论文公开的法律政策支持、数据库建设方案等进行分析,提出相应对策,力促国内学位论文社会公开,以期加强研究生培养的社会监督,发挥博硕士学位论文对科技发展的推动作用。 </span></p
Optimization of eucalyptus pretreatment by NH4Cl using response surface methodology
No full textThis work focused on the effect of NH4Cl on pretreatment of eucalyptus for xylose recovery rate. Response surface methodology (RSM) was applied to design the experiments, and the optimum pretreatment conditions were determined, resulting in 77.45% xylose recovery rate. A quadratic polynomial equation for predicting the xylose recovery rate was developed. The experimental results were in good agreement with predicted values. Composition analysis proved that NH4Cl pretreatment had a good effect on hemicellulose in eucalyptus, and the physical surface of the eucalyptus showed an apparently damaged surface after pretreatment with NH4Cl in scanning electron microscopy (SEM) images
Sensitive detection of maltose and glucose based on dual enzyme-displayed bacteria electrochemical biosensor
No full textGlucoamylase-displayed bacteria (GA-bacteria) and glucose dehydrogenase-displayed bacteria (GDH-bacteria) were co-immobilized on multi-walled carbon nanotubes (MWNTs) modified glassy carbon electrode (GCE) to construct GA-bacteria/GDH-bacteria/MWNTs/GCE biosensor. The biosensor was developed by optimizing the loading amount and the ratio of GA-bacteria to GDH-bacteria. The as prepared biosensor exhibited a wide dynamic range of 0.2-10 mM and a low detection limit of 0.1 mM maltose (S/N=3). The biosensor also had a linear response to glucose in the range of 0.1-2.0 mM and a low detection limit of 0.04 mM glucose (S/N=3). Interestingly, at the same concentration, glucose was 3.75-fold sensitive than that of maltose at the proposed biosensor. No interferences were observed for other possible mono- and disaccharides. The biosensor also demonstrated good long-term storage stability and repeatability. Further, using both GDH-bacteria/MWNTs/GCE biosensor and GA-bacteria/GDH-bacteria/MWNTs/GCE biosensor, glucose and maltose in real samples can be detected. Therefore, the proposed biosensor is capable of monitoring the food manufacturing and fermentation process. (C) 2016 Elsevier B.V. All rights reserved
High photodegradation ability of dyes by Fe(III)-tartrate/TiO2 nanotubular photocatalyst supported via photo-Fenton reaction
No full textPhoto-Fenton reactions are introduced into the decomposition process of methyl orange (MO) through modification of TiO2 nanotubes (TNT) by ferric tartrate. With respect to pure TNT, an enhanced photocatalytic activity of ferric tartrate/TNT is obtained. When the ferric tartrate content is about 5.0%, the degradation rate to MO solution is over 80% after 180 min UV-vis light irradiation. With excessive ferric tartrate introduced into the catalysts, this high photocatalytic performance is depressed. In addition, the photocatalytic activity of the nanocomposites can be optimized by varying the crystallized temperature of TNT precursor. In our experimental conditions, the optimal photocatalytic activity is achieved for the sample pre-crystalized at 773 K (with 5.0 at.% ferric tartrate). Its degradation efficiency to MO reaches 99% within 180 min UV-vis light irradiation. (C) 2016 Elsevier B.V. All rights reserved
Temporal and spacial dynamics of bioenergy-related CO2 emissions and underlying forces analysis in China
No full textWith increasing attention on energy shortage and global warming, bioenergy is a promising alternative energy to mitigate CO2 emissions. Despite the environmental friendly potential, a certain quantity of bioenergy-related CO2 is still emitted in China. This paper investigates the temporal dynamics of bioenergy-related CO2 emissions in 2000-2010 in China, and explores the underlying influence factors based on logarithmic mean Divisia index (LMDI). Then the core results are verified with a GIS-based approach from a spacial perspective. The results show that four impact factors: emission intensity, energy structure, energy efficiency and economic development have different impacts on bioenergy-related CO2 emissions, of which economic development is the major factor contributing to its increase, while energy efficiency is the major determinant for the decline. Per capita bioenergy-related CO2 emissions in different areas are verified in accordance with either economic development factor or energy efficiency factor to some extent. To achieve the dual purpose of sustainable development and CO2 emissions reduction, this paper provides a practical policy framework for rural bioenergy and economic development
Amyloid-graphene oxide as immobilization platform of Au nanocatalysts and enzymes for improved glucose-sensing activity
No full textTwo-dimensional GO nanosheets and one-dimensional lysozyme nanofibrils were hybridized through electrostatic interaction to get a novel amyloid-GO composite, which promised a biocompatible immobilization platform for Au nanocatalysts as well as enzymes. The immobilization platform could load a large and tunable amount of Au NPs while maintaining their high catalytic activity. The immobilized catalysts showed high electrochemical behaviors, being ideal as glucose sensing systems. Furthermore, enzymes could also be immobilized on the residual bare surfaces of amyloid-GO, and served by a colorimetric method for a sensitive and selective analytical glucose-detecting platform. The introduction of amyloid fibrils with super large aspect ratios (>10(3)) on GO nanosheets offers an unprecedented possibility of designing and developing novel biomimetic catalysts for broad applications in biotechnology. (C) 2016 Elsevier Inc. All rights reserved
Enhancing reducing ability of alpha-zein by fibrillation for synthesis of Au nanocrystals with continuous flow catalysis
No full textGreen low-cost synthesis and efficient recyclability are two major hindrances for Au nanocrystals as catalysts applying in diverse industrial reaction processes. By the use of low-cost alpha-zein (i.e. a major storage protein of corn) as the reductant, capping agent and stabilizer, Au nanocrystals with tunable catalytic activity were synthesized in a wet-chemical approach. Fibrillation of alpha-zein further enhanced its reducing ability due to larger specific surface area and more hydrophilic groups exposed on the surfaces. The obtained Au nanocrystals had biocompatibility, high stability in various solvents, unique solubility in aqueous alcohol and high catalytic ability, being able to detect ethanol composition in aqueous ethanol as well as H2O2 for diagnosis of diabetes mellitus. These advantages also enable efficient recyclability of Au nanocrystals with continuous flow catalysis in different solvents and environments. Thus, the use of alpha-zein offered Au nanocrystals not only with green low-cost synthesis, but also with tunable catalytic activities, ethanol-responsiveness and efficient recyclability, which may be applicable in diverse fields. (C) 2016 Published by Elsevier Inc
CH3NH2 gas induced (110) preferred cesium-containing perovskite films with reduced PbI6 octahedron distortion and enhanced moisture stability
No full textWe report here the discovery of a fancy interaction between cesium iodide (CsI) and methylamine (CH3NH2) due to the presence of the hydrogen bond. The formed CsI center dot xCH(3)NH(2) is a liquid phase, which facilitates the large scale fabrication of highly uniform cesium-containing perovskite films with strong (110) preferred orientation by the CH3NH2 gas healing process. With this method, at most 10% nonpolar Cs cations could fully dope into the crystal lattice and extremely enhance the interaction of the inorganic framework with a more symmetrical PbI6 octahedron, resulting in obvious improvement in moisture stability under continuous illumination
Engineered Kluyveromyces marxianus for pyruvate production at elevated temperature with simultaneous consumption of xylose and glucose
No full textXylose and glucose from lignocellulose are sustainable sources for production of pyruvate, which is the starting material for the synthesis of many drugs and agrochemicals. In this study, the pyruvate decarboxylase gene (KmPDC1) and glycerol-3-phosphate dehydrogenase gene (KmGPD1) of Kluyveromyces marxianus YZJ051 were disrupted to prevent ethanol and glycerol accumulation. The deficient growth of PDC disruption was rescued by overexpressing mutant KmMTH1-Delta T. Then pentose phosphate pathway and xylitol dehydrogenase SsXYL2-ARS genes were overexpressed to obtain strain YZB053 which produced pyruvate with xylose other than glucose. It produced 24.62 g/L pyruvate from 80 g/L xylose with productivity of 0.51 g/L/ h at 42 degrees C. Then, xylose-specific transporter ScGAL2-N376F was overexpressed to obtain strain YZB058, which simultaneously consumed 40g/L glucose and 20 g/L xylose and produced 29.21 g/L pyruvate with productivity of 0.81 g/L/h at 42 degrees C. Therefore, a platform for pyruvate production from glucose and xylose at elevated temperature was developed. (C) 2016 Elsevier Ltd. All rights reserved