Frontiers of Chemical Science and Engineering

ISSN 2095-0179

ISSN 2095-0187(Online)

CN 11-5981/TQ

2015 Impact Factor: 1.043

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Enzyme-instructed self-assembly of peptides containing phosphoserine to form supramolecular hydrogels as potential soft biomaterials
Jie Zhou, Xuewen Du, Jiaqing Wang, Natsuko Yamagata, Bing Xu
Front. Chem. Sci. Eng.    2017, 11 (4): 509-515.
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Enzyme-instructed self-assembly (EISA) offers a facile approach to explore the supramolecular assemblies of small molecules in cellular milieu for a variety of biomedical applications. One of the commonly used enzymes is phosphatase, but the study of the substrates of phosphatases mainly focuses on the phosphotyrosine containing peptides. In this work, we examine the EISA of phosphoserine containing small peptides for the first time by designing and synthesizing a series of precursors containing only phosphoserine or both phosphoserine and phosphotyrosine. Conjugating a phosphoserine to the C-terminal of a well-established self-assembling peptide backbone, (naphthalene-2-ly)-acetyl-diphenylalanine (NapFF), affords a novel hydrogelation precursor for EISA. The incorporation of phosphotyrosine, another substrate of phosphatase, into the resulting precursor, provides one more enzymatic trigger on a single molecule, and meanwhile increases the precursors’ propensity to aggregate after being fully dephosphorylated. Exchanging the positions of phosphorylated serine and tyrosine in the peptide backbone provides insights on how the specific molecular structures influence self-assembling behaviors of small peptides and the subsequent cellular responses. Moreover, the utilization of D-amino acids largely enhances the biostability of the peptides, thus providing a unique soft material for potential biomedical applications.

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Profiling influences of gene overexpression on heterologous resveratrol production in Saccharomyces cerevisiae
Duo Liu,Bingzhi Li,Hong Liu,Xuejiao Guo,Yingjin Yuan
Front. Chem. Sci. Eng.    2017, 11 (1): 117-125.
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Metabolic engineering of heterologous resveratrol production in Saccharomyces cerevisiae faces challenges as the precursor L-tyrosine is stringently regulated by a complex biosynthetic system. We overexpressed the main gene targets in the upstream pathways to investigate their influences on the downstream resveratrol production. Single-gene overexpression and DNA assembly-directed multigene overexpression affect the production of resveratrol as well as its precursor p-coumaric acid. Finally, the collaboration of selected gene targets leads to an optimal resveratrol production of 66.14±3.74 mg·L–1, 2.27 times higher than the initial production in YPD medium (4% glucose). The newly discovered gene targets TRP1 expressing phosphoribosylanthranilate isomerase, ARO3 expressing 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase, and 4CL expressing 4-coumaryl-CoA ligase show notable positive impacts on resveratrol production in S. cerevisiae.

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A mini review: Shape memory polymers for biomedical applications
Kaojin Wang, Satu Strandman, X. X. Zhu
Front. Chem. Sci. Eng.    2017, 11 (2): 143-153.
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Shape memory polymers (SMPs) are smart materials that can change their shape in a pre-defined manner under a stimulus. The shape memory functionality has gained considerable interest for biomedical applications, which require materials that are biocompatible and sometimes biodegradable. There is a need for SMPs that are prepared from renewable sources to be used as substitutes for conventional SMPs. In this paper, advances in SMPs based on synthetic monomers and bio-compounds are discussed. Materials designed for biomedical applications are highlighted.

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Identification of transporter proteins for PQQ-secretion pathways by transcriptomics and proteomics analysis in Gluconobacter oxydans WSH-003
Hui Wan,Yu Xia,Jianghua Li,Zhen Kang,Jingwen Zhou
Front. Chem. Sci. Eng.    2017, 11 (1): 72-88.
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Pyrroloquinoline quinone (PQQ) plays a significant role as a redox cofactor in combination with dehydrogenases in bacteria. These dehydrogenases play key roles in the oxidation of important substrates for the biotechnology industry, such as vitamin C production. While biosynthesis of PQQ genes has been widely studied, PQQ-transport mechanisms remain unclear. Herein, we used both two-dimensional fluorescence-difference gel electrophoresis tandem mass spectrometry and RNA sequencing to investigate the effects of pqqB overexpression in an industrial strain of Gluconobacter oxydans WSH-003. We have identified 73 differentially expressed proteins and 99 differentially expressed genes, a majority of which are related to oxidation-reduction and transport processes by gene ontology analysis. We also described several putative candidate effectors that responded to increased PQQ levels resulting from pqqB overexpression. Furthermore, quantitative PCR was used to verify five putative PQQ-transport genes among different PQQ producing strains, and the results showed that ompW, B932_1930 and B932_2186 were upregulated in all conditions. Then the three genes were over-expressed in G. oxydans WSH-003 and PQQ production were detected. The results showed that extracellular PQQ of B932_1930 (a transporter) and B932_2186 (an ABC transporter permease) overexpression strains were enhanced by 1.77-fold and 1.67-fold, respectively. The results suggest that the proteins encoded by PqqB, B932_1930 and B932_2186 might enhance the PQQ secretion process.

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ZnFe2O4 deposited on BiOCl with exposed (001) and (010) facets for photocatalytic reduction of CO2 in cyclohexanol
Guixian Song, Xionggang Wu, Feng Xin, Xiaohong Yin
Front. Chem. Sci. Eng.    2017, 11 (2): 197-204.
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ZnFe2O4-BiOCl composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CO2 in cyclohexanol under ultraviolet irradiation to give cyclohexanone (CH) and cyclohexyl formate (CF). The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFe2O4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the direct-precipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed (001) facets than for the samples with more exposed (010) facets. This is due to the higher density of oxygen atoms in the exposed (001) facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the (001) facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to ·CO2. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe2O4-BiOCl composites with exposed (001) facets involves electron transfer and carbon radical formation.

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Electrochemistry during efficient copper recovery from complex electronic waste using ammonia based solutions
Zhi Sun, Hongbin Cao, Prakash Venkatesan, Wei Jin, Yanping Xiao, Jilt Sietsma, Yongxiang Yang
Front. Chem. Sci. Eng.    2017, 11 (3): 308-316.
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Leaching selectivity during metal recovery from complex electronic waste using a hydrochemical process is always one of the generic issues. It was recently improved by using ammonia-based leaching process, specifically for electronic waste enriched with copper. This research proposes electrodeposition as the subsequent approach to effectively recover copper from the solutions after selective leaching of the electronic waste and focuses on recognising the electrochemical features of copper recovery. The electrochemical reactions were investigated by considering the effects of copper concentration, scan rate and ammonium salts. The diffusion coefficient, charge transfer coefficient and heterogeneous reaction constant of the electrodeposition process were evaluated in accordance with different solution conditions. The results have shown that electrochemical recovery of copper from ammonia-based solution under the conditions of selective electronic waste treatment is charge transfer controlled and provide bases to correlate the kinetic parameters with further optimisation of the selective recovery of metals from electronic waste.

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Rhamnolipid synthesis and production with diverse resources
Qingxin Li
Front. Chem. Sci. Eng.    2017, 11 (1): 27-36.
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Rhamnolipids are one of the most effective biosurfactants that are of great interest in industrial applications such as enhancing oil recovery, health care, cosmetics, pharmaceutical processes, food processing, detergents for protein folding, and bioremediation due to their unique characteristics such as low toxicity, surface active property to reduce surface/interfacial tensions, and excellent biodegradability. The genes and metabolic pathways for rhamnolipid synthesis have been well elucidated, but its cost-effective production is still challenging. Pseudomonas aeruginosa, the most powerful rhamnolipid producer, is an opportunistic pathogen, which limits its large scale production and applications. Rhamnolipid production using engineered strains other than Pseudomonas aeruginosa such as E. coli and Pseudomonas putida has received much attention. The highest yield of rhamnolipids is achieved when oil-type carbon sources are used, but using cheaper and renewable carbon sources such as lignocellulose would be an attractive strategy to reduce the production cost of rhamnolipids for various industrial applications.

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Cell-free systems in the new age of synthetic biology
Fernando Villarreal,Cheemeng Tan
Front. Chem. Sci. Eng.    2017, 11 (1): 58-65.
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The advent of synthetic biology has ushered in new applications of cell-free transcription-translation systems. These cell-free systems are reconstituted using cellular proteins, and are amenable to modular control of their composition. Here, we discuss the historical advancement of cell-free systems, as well as their new applications in the rapid design of synthetic genetic circuits and components, directed evolution of biomolecules, diagnosis of infectious diseases, and synthesis of vaccines. Finally, we present our vision on the future direction of cell-free synthetic biology.

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Cell surface protein engineering for high-performance whole-cell catalysts
Hajime Nakatani,Katsutoshi Hori
Front. Chem. Sci. Eng.    2017, 11 (1): 46-57.
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Cell surface protein engineering facilitated by accumulation of information on genome and protein structure involves heterologous production and modification of cell surface proteins using genetic engineering, and is important for the development of high-performance whole-cell catalysts. In this field, cell surface display is a major technology by exposing target proteins, such as enzymes, on the cell surface using a carrier protein. The target proteins are fused to the carrier proteins that transport and tether them to the cell surface, as well as to a secretion signal. This paper reviews cell surface display systems for prokaryotic and eukaryotic cells from the perspective of carrier proteins, which determine the number of displayed molecules, and the localization, size, and direction (N- or C-terminal anchoring) of the passengers. We also discuss advanced methods for displaying multiple enzymes and a new method for the immobilization of whole-cell catalysts using adhesive surface proteins.

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Assembly of biosynthetic pathways in Saccharomyces cerevisiae using a marker recyclable integrative plasmid toolbox
Lidan Ye,Xiaomei Lv,Hongwei Yu
Front. Chem. Sci. Eng.    2017, 11 (1): 126-132.
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A robust and versatile tool for multigene pathway assembly is a key to the biosynthesis of high-value chemicals. Here we report the rapid construction of biosynthetic pathways in Saccharomyces cerevisiae using a marker recyclable integrative toolbox (pUMRI) developed in our research group, which has features of ready-to-use, convenient marker recycling, arbitrary element replacement, shuttle plasmid, auxotrophic marker independence, GAL regulation, and decentralized assembly. Functional isoprenoid biosynthesis pathways containing 4–11 genes with lengths ranging from ~10 to ~22 kb were assembled using this toolbox within 1–5 rounds of reiterative recombination. In combination with GAL-regulated metabolic engineering, high production of isoprenoids (e.g., 16.3 mg?g?1 dcw carotenoids) was achieved. These results demonstrate the wide range of application and the efficiency of the pUMRI toolbox in multigene pathway construction of S. cerevisiae.

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Catalytic oxidation of carbon monoxide, toluene, and ethyl acetate over the xPd/OMS-2 catalysts: Effect of Pd loading
Zhidan Fu, Lisha Liu, Yong Song, Qing Ye, Shuiyuan Cheng, Tianfang Kang, Hongxing Dai
Front. Chem. Sci. Eng.    2017, 11 (2): 185-196.
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The Pd catalyst supported on cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) were prepared. The effect of Pd loading on the catalytic oxidation of carbon monoxide, toluene, and ethyl acetate over xPd/OMS-2 has been investigated. The results show that the Pd loading plays an important role on the physicochemical properties of the xPd/OMS-2 catalysts which outperform the Pd-free counterpart with the 0.5Pd/OMS-2 catalyst being the best. The temperature for 50% conversion was 25, 240 and 160 °C, and the temperature for 90% conversion was 55, 285 and 200 °C for oxidation of CO, toluene, and ethyl acetate, respectively. The low-temperature reducibility and high oxygen mobility of xPd/OMS-2 are the factors contributable to the excellent catalytic performance of 0.5Pd/OMS-2.

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Aptamer-coded DNA nanoparticles for targeted doxorubicin delivery using pH-sensitive spacer
Pengwei Zhang, Junxiao Ye, Ergang Liu, Lu Sun, Jiacheng Zhang, Seung Jin Lee, Junbo Gong, Huining He, Victor C. Yang
Front. Chem. Sci. Eng.    2017, 11 (4): 529-536.
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An anticancer drug delivery system consisting of DNA nanoparticles synthesized by rolling circle amplification (RCA) was developed for prostate cancer membrane antigen (PSMA) targeted cancer therapy. The template of RCA was a DNA oligodeoxynucleotide coded with PSMA-targeted aptamer, drug-loading domain, primer binding site and pH-sensitive spacer. Anticancer drug doxorubicin, as the model drug, was loaded into the drug-loading domain (multiple GC-pair sequences) of the DNA nanoparticles by intercalation. Due to the integrated pH-sensitive spacers in the nanoparticles, in an acidic environment, the cumulative release of doxorubicin was far more than the cumulative release of the drug in the normal physiological environment. In cell uptake experiments, treated with doxorubicin loaded DNA nanoparticles, PSMA-positive C4-2 cells could take up more doxorubicin than PSMA-null PC-3 cells. The prepared DNA nanoparticles showed the potential as drug delivery system for PSMA targeting prostate cancer therapy.

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Engineering of β-carotene hydroxylase and ketolase for astaxanthin overproduction in Saccharomyces cerevisiae
Ruizhao Wang, Xiaoli Gu, Mingdong Yao, Caihui Pan, Hong Liu, Wenhai Xiao, Ying Wang, Yingjin Yuan
Front. Chem. Sci. Eng.    2017, 11 (1): 89-99.
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The conversion of β-carotene to astaxanthin is a complex pathway network, in which two steps of hydroxylation and two steps of ketolation are catalyzed by β-carotene hydroxylase (CrtZ) and β-carotene ketolase (CrtW) respectively. Here, astaxanthin biosynthesis pathway was constructed in Saccharomyces cerevisiae by introducing heterologous CrtZ and CrtW into an existing high β-carotene producing strain. Both genes crtZ and crtW were codon optimized and expressed under the control of constitutive promoters. Through combinatorial expression of CrtZ and CrtW from diverse species, nine strains in dark red were visually chosen from thirty combinations. In all the selected strains, strain SyBE_Sc118060 with CrtW from Brevundimonas vesicularis DC263 and CrtZ from Alcaligenes sp. strain PC-1 achieved the highest astaxanthin yield of 3.1 mg/g DCW. Protein phylogenetic analysis shows that the shorter evolutionary distance of CrtW is, the higher astaxanthin titer is. Further, when the promoter of crtZ in strain SyBE_Sc118060 was replaced from FBA1p to TEF1p, the astaxanthin yield was increased by 30.4% (from 3.4 to 4.5 mg/g DCW). In the meanwhile, 33.5-fold increase on crtZ transcription level and 39.1-fold enhancement on the transcriptional ratio of crtZ to crtW were observed at early exponential phase in medium with 4% (w/v) glucose. Otherwise, although the ratio of crtZ to crtW were increased at mid-, late-exponential phases in medium with 2% (w/v) glucose, the transcription level of both crtZ and crtW were actually decreased during the whole time course, consequently leading to no significant improvement on astaxanthin production. Finally, through high cell density fed-batch fermentation using a carbon source restriction strategy, the production of astaxanthin in a 5-L bioreactor reached to 81.0 mg/L, which was the highest astaxanthin titer reported in yeast. This study provides a reference to greatly enhance desired compounds accumulation by employing the key enzyme(s) in microbes.

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A comparison of the catalytic hydrogenation of 2-amylanthraquinone and 2-ethylanthraquinone over a Pd/Al 2O3 catalyst
Enxian Yuan, Xiangwei Ren, Li Wang, Wentao Zhao
Front. Chem. Sci. Eng.    2017, 11 (2): 177-184.
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The hydrogenation of 2-ethylanthraquinone (eAQ), 2-tert-amylanthraquinone (taAQ) and their mixtures with molar ratios of 1:1 and 1:2 to the corresponding hydroquinones (eAQH2 and taAQH2) were studied over a Pd/Al2O3 catalyst in a semi-batch slurry reactor at 60 °C and at 0.3 MPa. Compared to eAQ, TaAQ exhibited a significantly slower hydrogenation rate (about half) but had a higher maximum yield of H2O2 and a smaller amount of degradation products. This can be ascribed to the longer and branched side chain in taAQ, which limits its accessibility to the Pd surface and its diffusion through the pores of the catalyst. Density functional theory calculations showed that it is more difficult for taAQ to adsorb onto a Pd (111) surface than for eAQ. The hydrogenation of the eAQ/taAQ mixtures had the slowest rates, lowest H2O2yields and the highest amounts of degradation products.

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Cofactor engineering in cyanobacteria to overcome imbalance between NADPH and NADH: A mini review
Jongmoon Park,Yunnam Choi
Front. Chem. Sci. Eng.    2017, 11 (1): 66-71.
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Cyanobacteria can produce useful renewable fuels and high-value chemicals using sunlight and atmospheric carbon dioxide by photosynthesis. Genetic manipulation has increased the variety of chemicals that cyanobacteria can produce. However, their uniquely abundant NADPH-pool, in other words insufficient supply of NADH, tends to limit their production yields in case of utilizing NADH-dependent enzyme, which is quite common in heterotrophic microbes. To overcome this cofactor imbalance and enhance cyanobacterial fuel and chemical production, various approaches for cofactor engineering have been employed. In this review, we focus on three approaches: (1) utilization of NADPH-dependent enzymes, (2) increasing NADH production, and (3) changing cofactor specificity of NADH-dependent enzymes from NADH to NADPH.

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Designer enzyme for green materials innovation: Lactate-polymerizing enzyme as a key catalyst
Seiichi Taguchi
Front. Chem. Sci. Eng.    2017, 11 (1): 139-142.
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Establishment of the regeneratable whole-cell catalyst platform for the?production of biobased polymeric materials is a?typical topic of synthetic biology. In this commentary, discovery story of a “lactate-polymerizing enzyme” (LPE)?and LPE-based?achievements for creating a new variety of polyesters with incorporated unnatural monomers are presented. Besides the importance of microbial platform itself is discussed referring to the “ballooning”-Escherichia coli.

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Synthetically engineered microbes reveal interesting principles of cooperation
Michael D. Dressler,Corey J. Clark,Chelsea A. Thachettu,Yasmine Zakaria,Omar Tonsi Eldakar,Robert P. Smith
Front. Chem. Sci. Eng.    2017, 11 (1): 3-14.
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Cooperation is ubiquitous in biological systems. However, if natural selection favors traits that confer an advantage to one individual over another, then helping others would be paradoxical. Nevertheless, cooperation persists and is critical in maintaining homeostasis in systems ranging from populations of bacteria to groupings of mammals. Developing an understanding of the dynamics and mechanisms by which cooperation operates is critical in understanding ecological and evolutionary relationships. Over the past decade, synthetic biology has emerged as a powerful tool to study social dynamics. By engineering rationally controlled and modulatable behavior into microbes, we have increased our overall understanding of how cooperation enhances, or conversely constrains, populations. Furthermore, it has increased our understanding of how cooperation is maintained within populations, which may provide a useful framework to influence populations by altering cooperation. As many bacterial pathogens require cooperation to infect the host and survive, the principles developed using synthetic biology offer promise of developing novel tools and strategies to treat infections, which may reduce the use of antimicrobial agents. Overall, the use of engineered cooperative microbes has allowed the field to verify existing, and develop novel, theories that may govern cooperative behaviors at all levels of biology.

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The influence of curing conditions on the mechanical properties and leaching of inorganic polymers made of fayalitic slag
Remus I. Iacobescu, Valérie Cappuyns, Tinne Geens, Lubica Kriskova, Silviana Onisei, Peter T. Jones, Yiannis Pontikes
Front. Chem. Sci. Eng.    2017, 11 (3): 317-327.
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This study reports on the impact of the curing conditions on the mechanical properties and leaching of inorganic polymer (IP) mortars made from a water quenched fayalitic slag. Three similar IP mortars were produced by mixing together slag, aggregate and activating solution, and cured in three different environments for 28 d: a) at 20 °C and relative humidity (RH) ~ 50% (T20RH50), b) at 20 °C and RH≥90% (T20RH90) and c) at 60 °C and RH ~ 20% (T60RH20). Compressive strength (EN 196-1) varied between 19 MPa (T20RH50) and 31 MPa (T20RH90). This was found to be attributed to the cracks formed upon curing. Geochemical modelling and two leaching tests were performed, the EA NEN 7375 tank test, and the BS EN 12457-1 single batch test. Results show that Cu, Ni, Pb, Zn and As leaching occurred even at high pH, which varied between 10 and 11 in the tank test’s leachates and between 12 and 12.5 in the single batch’s leachates. Leaching values obtained were below the requirements for non-shaped materials of Flemish legislation for As, Cu and Ni in the single batch test.

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A conceptual methodology for simultaneous optimization of water and heat with non-isothermal mixing
Yanlong Hou, Wanni Xie, Zhenya Duan, Jingtao Wang
Front. Chem. Sci. Eng.    2017, 11 (2): 154-165.
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A new conceptual methodology is proposed to simultaneously integrate water allocation and energy networks with non-isothermal mixing. This method employs a simultaneous model and includes two design steps. In the first step, the water allocation network (WAN), which could achieve the targets of saving water and energy, is obtained by taking account the temperature factor into the design procedure. The optimized targets of both freshwater and energy are reached at this step which ensures this approach is a simultaneous one. In the second step, based on the obtained WAN, the whole water allocation and heat exchange network (WAHEN) is combined with the non-isothermal mixing to reduce the number of heat exchangers. The thus obtained WAHEN can achieve three optimization targets (minimization of water, energy and the number of heat exchangers). Furthermore, the effectivity of our method has been demonstrated by solving two literature examples.

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Solvates and polymorphs of clindamycin phosphate: Structural, thermal stability and moisture stability studies
Junbo Gong, Dejiang Zhang, Yuanyuan Ran, Keke Zhang, Shichao Du
Front. Chem. Sci. Eng.    2017, 11 (2): 220-230.
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Clindamycin phosphate (CP), an antibacterial agent, has been reported to form several solid-state forms. The crystal structures of two CP solvates, a dimethyl sulfoxide (DMSO) solvate and a methanol/water solvate (solvate V), have been determined by single crystal X-ray diffraction. The properties and transformations of these forms were characterized by powder X-ray diffraction, Single-crystal X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, hot-stage microscopy, and dynamic vapor sorption. Very different hydrogen bonding networks exist among the host-host and host-solvent molecules in the two crystal structures, resulting in different moisture stabilities. The thermal stabilities of the two solvates upon heating and desolvation were also studied. When the temperature was above the boiling point of methanol, solvate V converted to a polymorphic phase after a one step desolvation process, whereas the desolvation temperature of the DMSO solvate was below the boiling point of DMSO. At the relative humidity above 43%, the DMSO solvate transformed to a hydrate at 25 °C. In contrast, solvate V did not transform at any of the humidities studied.

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Genome reprogramming for synthetic biology
Kylie Standage-Beier,Xiao Wang
Front. Chem. Sci. Eng.    2017, 11 (1): 37-45.
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The ability to go from a digitized DNA sequence to a predictable biological function is central to synthetic biology. Genome engineering tools facilitate rewriting and implementation of engineered DNA sequences. Recent development of new programmable tools to reengineer genomes has spurred myriad advances in synthetic biology. Tools such as clustered regularly interspace short palindromic repeats enable RNA-guided rational redesign of organisms and implementation of synthetic gene systems. New directed evolution methods generate organisms with radically restructured genomes. These restructured organisms have useful new phenotypes for biotechnology, such as bacteriophage resistance and increased genetic stability. Advanced DNA synthesis and assembly methods have also enabled the construction of fully synthetic organisms, such as J. Craig Venter Institute (JCVI)-syn 3.0. Here we summarize the recent advances in programmable genome engineering tools.

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Surface modification of broom sorghum-based activated carbon via functionalization with triethylenetetramine and urea for CO2capture enhancement
Elaheh Mehrvarz, Ali A. Ghoreyshi, Mohsen Jahanshahi
Front. Chem. Sci. Eng.    2017, 11 (2): 252-265.
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A new type of activated carbon (AC) was synthesized using broom sorghum stalk as a low cost carbon source through chemical activation with H3PO4 and KOH. The AC obtained by KOH had the largest BET surface area of 1619 m2·g−1 and the highest micropore volume of 0.671 cm3·g−1. CO2 adsorption was enhanced by functionalizing the AC with two different amines: triethylenetetramine (TETA) and urea. The structure of the prepared ACs was characterized by Brunauer-Emmett-Teller method, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and acid-base Boehm titration analyses. The adsorption behavior of CO2 onto raw and amine-functionalized ACs was investigated in the temperature range of 288–308 K and pressures up to 25 bar. The amount of CO2 uptake at 298 K and 1 bar achieved by AC-TETA and AC-urea was 3.22 and 2.33 mmol·g−1which shows a 92% and 40% improvement compared to pristine AC (1.66 mmol·g−1), respectively. Among different model isotherms used to describe the adsorption equilibria, Sips isotherm presented a perfect fit in all cases. Gas adsorption kinetic study revealed a fast kinetics of CO2adsorption onto the ACs. The evaluation of the isosteric heat of adsorption demonstrated the exothermic nature of the CO2 adsorption onto unmodified and modified samples.

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Functional ferritin nanoparticles for biomedical applications
Zhantong Wang, Haiyan Gao, Yang Zhang, Gang Liu, Gang Niu, Xiaoyuan Chen
Front. Chem. Sci. Eng.    2017, 11 (4): 633-646.
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Ferritin, a major iron storage protein with a hollow interior cavity, has been reported recently to play many important roles in biomedical and bioengineering applications. Owing to the unique architecture and surface properties, ferritin nanoparticles offer favorable characteristics and can be either genetically or chemically modified to impart functionalities to their surfaces, and therapeutics or probes can be encapsulated in their interiors by controlled and reversible assembly/disassembly. There has been an outburst of interest regarding the employment of functional ferritin nanoparticles in nanomedicine. This review will highlight the recent advances in ferritin nanoparticles for drug delivery, bioassay, and molecular imaging with a particular focus on their biomedical applications.

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The effect of doping and steam treatment on the catalytic activities of nano-scale H-ZSM-5 in the methanol to gasoline reaction
Baodong Song, Yongqiang Li, Gang Cao, Zhenhai Sun, Xu Han
Front. Chem. Sci. Eng.    2017, 11 (4): 564-574.
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In the transformation of methanol to gasoline (MTG), the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treated nano-scale H-ZSM-5 (NHZ5) catalysts impregnated with Ag(I), Zn(II) or P(V) have been investigated in a continuous flow fixed bed reactor. The NH3-TPD results showed that after impregnation, the Ag/NHZ5, Zn/NHZ5 and P/NHZ5 catalysts contained comparatively more strong, medium-strong and weak acid sites, respectively. Treatment with steam decreased the number of acid sites in all the catalysts, but the pore volumes in the catalysts were larger which improved carbon deposition resistance resulting in prolonged lifetimes. After 6 h of MTG reaction, the selectivity to gasoline for the steam-treated catalysts, AgH2O/NHZ5, ZnH2O/NHZ5 and PH2O/NHZ5 were 70.5, 68.4 and 68.7 wt-%, respectively, whereas their respective aromatic contents in the produced gasoline were 61.9, 55.4 and 39.0 wt-%. Thus PH2O/NHZ5 is the most promising catalyst for MTG applications which can meet the China IV gasoline standard that the amount of aromatics in gasoline should be less than 48 wt-%.

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Collaborations of China with the world in Synbio
Front. Chem. Sci. Eng.    2017, 11 (1): 1-2.
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Metal salts with highly electronegative cations as efficient catalysts for the liquid-phase nitration of benzene by NO2 to nitrobenzene
Shenghui Zhou, Kuiyi You, Zhengming Yi, Pingle Liu, Hean Luo
Front. Chem. Sci. Eng.    2017, 11 (2): 205-210.
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Metal salts with highly electronegative cations have been used to effectively catalyze the liquid-phase nitration of benzene by NO2 to nitrobenzene under solvent-free conditions. Several salts including FeCl3, ZrCl4, AlCl3, CuCl2, NiCl2, ZnCl2, MnCl2, Fe(NO3)3·9H2O, Bi(NO3)3·5H2O, Zr(NO3)4·5H2O, Cu(NO3)2·6H2O, Ni(NO3)2·6H2O, Zn(NO3)2·6H2O, Fe2(SO4)3, and CuSO4 were examined and anhydrous FeCl3 exhibited the best catalytic performance under the optimal reaction conditions. The benzene conversion and selectivity to nitrobenzene were both over 99%. In addition, it was determined that the metal counterion and the presence of water hydrates in the salt affects the catalytic activity. This method is simple and efficient and may have potential industrial application prospects.

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Towards Cr(VI)-free anodization of aluminum alloys for aerospace adhesive bonding applications: A review
Shoshan T. Abrahami, John M. M. de Kok, Herman Terryn, Johannes M. C. Mol
Front. Chem. Sci. Eng.    2017, 11 (3): 465-482.
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For more than six decades, chromic acid anodizing (CAA) has been the central process in the surface pre-treatment of aluminum for adhesively bonded aircraft structures. Unfortunately, this electrolyte contains hexavalent chromium (Cr(VI)), a compound known for its toxicity and carcinogenic properties. To comply with the new strict international regulations, the Cr(VI)-era will soon have to come to an end. Anodizing aluminum in acid electrolytes produces a self-ordered porous oxide layer. Although different acids can be used to create this type of structure, the excellent adhesion and corrosion resistance that is currently achieved by the complete Cr(VI)-based process is not easily matched. This paper provides a critical overview and appraisal of proposed alternatives to CAA, including combinations of multiple anodizing steps, pre- and post anodizing treatments. The work is presented in terms of the modifications to the oxide properties, such as morphological features (e.g., pore size, barrier layer thickness) and surface chemistry, in order to evaluate the link between fundamental principles of adhesion and bond performance.

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Cited: Crossref(1) WebOfScience(2)
Recent advances in SERS detection of perchlorate
Jumin Hao, Xiaoguang Meng
Front. Chem. Sci. Eng.    2017, 11 (3): 448-464.
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Perchlorate has recently emerged as a widespread environmental contaminant of healthy concern. Development of novel detection methods for perchlorate with the potential for field use has been an urgent need. The investigation has shown that surface-enhanced Raman scattering (SERS) technique has great potential to become a practical analysis tool for the rapid screening and routine monitoring of perchlorate in the field, particularly when coupled with portable/handheld Raman spectrometers. In this review article, we summarize progress made in SERS analysis of perchlorate in water and other media with an emphasis on the development of SERS substrates for perchlorate detection. The potential of this technique for fast screening and field testing of perchlorate-contaminated environmental samples is discussed. The challenges and possible solutions are also addressed, aiming to provide a better understanding on the development directions in the research field.

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Cited: WebOfScience(1)
Construction, characterization and application of a genome-wide promoter library in Saccharomyces cerevisiae
Ting Yuan, Yakun Guo, Junkai Dong, Tianyi Li, Tong Zhou, Kaiwen Sun, Mei Zhang, Qingyu Wu, Zhen Xie, Yizhi Cai, Limin Cao, Junbiao Dai
Front. Chem. Sci. Eng.    2017, 11 (1): 107-116.
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Promoters are critical elements to control gene expression but could behave differently under various growth conditions. Here we report the construction of a genome-wide promoter library, in which each native promoter in Saccharomyces cerevisiae was cloned upstream of a yellow fluorescent protein (YFP) reporter gene. Nine libraries were arbitrarily defined and assembled in bacteria. The resulting pools of promoters could be prepared and transformed into a yeast strain either as centromeric plasmids or integrated into a genomic locus upon enzymatic treatment. Using fluorescence activated cell sorting, we classified the yeast strains based on YFP fluorescence intensity and arbitrarily divided the entire library into 12 bins, representing weak to strong promoters. Several strong promoters were identified from the most active bins and their activities were assayed under different growth conditions. Finally, these promoters were applied to drive the expression of genes in xylose utilization to improve fermentation efficiency. Together, this library could provide a quick solution to identify and utilize desired promoters under user-defined growth conditions.

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The preparation and performance of lignin-based activated carbon fiber adsorbents for treating gaseous streams
Min Song, Wei Zhang, Yongsheng Chen, Jinming Luo, John C. Crittenden
Front. Chem. Sci. Eng.    2017, 11 (3): 328-337.
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Two types of lignin-based carbon fibers were prepared by electrospinning method. The first was activated with Fe3O4 (LCF-Fe), and the second was not activated with Fe3O4 (LCF). Gas phase adsorption isotherms for toluene on LCF-Fe and LCF were studied. The gas phase adsorption isotherm for 0% RH showed LCF-Fe have about 439 mg/g adsorption capacity which was close to that of commercially available activated carbon (500 mg/g). The Dubinin-Radushkevich equation described the isotherm data very well. Competitive adsorption isotherms between water vapor and toluene were measured for their RH from 0 to 80%. The effect of humidity on toluene gas-phase adsorption was predicted by using the Okazaki et al. model. In addition, a constant pattern homogeneous surface diffusion model (CPHSDM) was used to predict the toluene breakthrough curve of continuous flow-packed columns containing LCF-Fe, and its capacity was 412 mg/g. Our study, which included material characterization, adsorption isotherms, kinetics, the impact of humidity and fixed bed performance modeling, demonstrated the suitability of lignin-based carbon fiber for volatile organic compound removal from gas streams.

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