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Wang Q.,Jiangsu University | Wang Q.,Key Laboratory of Development and Application of Rural Renewable Energy | Wei W.,Jiangsu University | Kingori G.P.,Jiangsu University | Sun J.,Jiangsu University

Pretreatments of wheat straw by NaOH/urea solvent at low temperature were investigated. To understand the cell wall disruption during this low temperature process, and its impacts on enzymatic hydrolysis, morphology, cellulose crystal structure, and chemical properties were investigated by using the following instruments: optical microscopy, confocal laser scanning microscopy, Fourier transform infrared spectra, and X-ray diffraction. The results implied that the deconstruction of plant cell wall at low temperature was attributed to disruption of the hydrogen bonds in cellulose and solubilization of hemicellulose and lignin. Meanwhile, the pretreatment approach resulted in almost full recovery of cellulose, approximately 60 % of lignin and 70 % of xylan removal, respectively. It’s interesting to note that cellulose I crystal structure in the substrate pretreated at a solid loading of 10 % was partially changed to cellulose II structure, while wheat straw pretreated at a higher solid loading of 20 %, retained the cellulose I structure. Almost complete saccharification (>95 %) of cellulose in pretreated substrates was achieved at a relatively low cellulase loading of 10 FPU/g substrates within 48 h. The loss of xylan in pretreated substrate had a negative effect on the total sugar recovery. © 2015 Springer Science+Business Media Dordrecht Source

He M.-X.,China Institute of Technology | He M.-X.,Key Laboratory of Development and Application of Rural Renewable Energy | Wu B.,China Institute of Technology | Shui Z.-X.,China Institute of Technology | And 9 more authors.
Biotechnology for Biofuels

Background: High tolerance to ethanol is a desirable characteristics for ethanologenic strains used in industrial ethanol fermentation. A deeper understanding of the molecular mechanisms underlying ethanologenic strains tolerance of ethanol stress may guide the design of rational strategies to increase process performance in industrial alcoholic production. Many extensive studies have been performed in Saccharomyces cerevisiae and Escherichia coli. However, the physiological basis and genetic mechanisms involved in ethanol tolerance for Zymomonas mobilis are poorly understood on genomic level. To identify the genes required for tolerance to ethanol, microarray technology was used to investigate the transcriptome profiling of the ethanologenic Z. mobilis in response to ethanol stress. Results: We successfully identified 127 genes which were differentially expressed in response to ethanol. Ethanol up- or down-regulated genes related to cell wall/membrane biogenesis, metabolism, and transcription. These genes were classified as being involved in a wide range of cellular processes including carbohydrate metabolism, cell wall/membrane biogenesis, respiratory chain, terpenoid biosynthesis, DNA replication, DNA recombination, DNA repair, transport, transcriptional regulation, some universal stress response, etc. Conclusion: In this study, genome-wide transcriptional responses to ethanol were investigated for the first time in Z. mobilis using microarray analysis.Our results revealed that ethanol had effects on multiple aspects of cellular metabolism at the transcriptional level and that membrane might play important roles in response to ethanol. Although the molecular mechanism involved in tolerance and adaptation of ethanologenic strains to ethanol is still unclear, this research has provided insights into molecular response to ethanol in Z. mobilis. These data will also be helpful to construct more ethanol resistant strains for cellulosic ethanol production in the future. © 2012 He et al.; licensee BioMed Central Ltd. Source

He M.X.,China Institute of Technology | He M.X.,Key Laboratory of Development and Application of Rural Renewable Energy | Wu B.,China Institute of Technology | Qin H.,China Institute of Technology | And 11 more authors.
Biotechnology for Biofuels

Biosynthesis of liquid fuels and biomass-based building block chemicals from microorganisms have been regarded as a competitive alternative route to traditional. Zymomonas mobilis possesses a number of desirable characteristics for its special Entner-Doudoroff pathway, which makes it an ideal platform for both metabolic engineering and commercial-scale production of desirable bio-products as the same as Escherichia coli and Saccharomyces cerevisiae based on consideration of future biomass biorefinery. Z. mobilis has been studied extensively on both fundamental and applied level, which will provide a basis for industrial biotechnology in the future. Furthermore, metabolic engineering of Z. mobilis for enhancing bio-ethanol production from biomass resources has been significantly promoted by different methods (i.e. mutagenesis, adaptive laboratory evolution, specific gene knock-out, and metabolic engineering). In addition, the feasibility of representative metabolites, i.e. sorbitol, bionic acid, levan, succinic acid, isobutanol, and isobutanol produced by Z. mobilis and the strategies for strain improvements are also discussed or highlighted in this paper. Moreover, this review will present some guidelines for future developments in the bio-based chemical production using Z. mobilis as a novel industrial platform for future biofineries. © 2014 He et al.; licensee BioMed Central Ltd. Source

Shui Z.-X.,China Institute of Technology | Qin H.,China Institute of Technology | Wu B.,China Institute of Technology | Ruan Z.-Y.,Chinese Academy of Agricultural Sciences | And 9 more authors.
Applied Microbiology and Biotechnology

Furfural and acetic acid from lignocellulosic hydrolysates are the prevalent inhibitors to Zymomonas mobilis during cellulosic ethanol production. Developing a strain tolerant to furfural or acetic acid inhibitors is difficul by using rational engineering strategies due to poor understanding of their underlying molecular mechanisms. In this study, strategy of adaptive laboratory evolution (ALE) was used for development of a furfural and acetic acid-tolerant strain. After three round evolution, four evolved mutants (ZMA7-2, ZMA7-3, ZMF3-2, and ZMF3-3) that showed higher growth capacity were successfully obtained via ALE method. Based on the results of profiling of cell growth, glucose utilization, ethanol yield, and activity of key enzymes, two desired strains, ZMA7-2 and ZMF3-3, were achieved, which showed higher tolerance under 7 g/l acetic acid and 3 g/l furfural stress condition. Especially, it is the first report of Z. mobilis strain that could tolerate higher furfural. The best strain, Z. mobilis ZMF3-3, has showed 94.84 % theoretical ethanol yield under 3-g/l furfural stress condition, and the theoretical ethanol yield of ZM4 is only 9.89 %. Our study also demonstrated that ALE method might also be used as a powerful metabolic engineering tool for metabolic engineering in Z. mobilis. Furthermore, the two best strains could be used as novel host for further metabolic engineering in cellulosic ethanol or future biorefinery. Importantly, the two strains may also be used as novel-tolerant model organisms for the genetic mechanism on the “omics” level, which will provide some useful information for inverse metabolic engineering. © 2015, Springer-Verlag Berlin Heidelberg. Source

Zhu N.-M.,Biogas Institute of Ministry of Agriculture | Zhu N.-M.,Key Laboratory of Development and Application of Rural Renewable Energy | Chen M.,Southwest University of Science and Technology | Guo X.-J.,Biogas Institute of Ministry of Agriculture | And 3 more authors.
Journal of Hazardous Materials

In recent years, a potential controversy has arisen that whether the metal speciation in solid matrix determined its electrokinetic (EK) removal efficiency or by contrast. In present study, Cu and Zn in anaerobic digestate were selected as candidates to investigate the relation between the species of metal and EK treatment. The obtained results show that the removal efficiency for each fraction decreased in the order as follows: exchangeable ≥ bound to carbonates > bound to Fe-Mn oxides > bound to organic matters » residual. For both Cu and Zn, their total removal performance was dependent on their dominant fraction in the digestate. A constant pH maintenance around the digestate via circulation of acid electrolyte is an optional operation because a strong acid atmosphere (pH < 2) around the digestate can be formed automatically as EK time elapses. Despite that many reactions occurred during EK process, the species distribution of Cu and Zn in the digestate determined their total EK removal efficiency essentially. © 2014 Elsevier B.V. Source

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