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Chen J.,State Key Laboratory of Materials Oriented Chemical Engineering | Chen J.,Nanjing University of Technology | Zhang W.,State Key Laboratory of Materials Oriented Chemical Engineering | Zhang W.,Nanjing University of Technology | And 4 more authors.
Bioresource Technology | Year: 2014

A screw extrude steam explosion (SESE) apparatus was designed and introduced to pretreat corn stover continuously for its following enzymatic hydrolysis. SESE parameters temperature (100, 120, 150. °C) and residence time (1, 2, 3. min) were investigated. The enzymatic hydrolysis of corn stover pretreated by SESE and steam explosion (SE) process was carried out and analyzed systematically. A serial of analysis methods were established, and the corn stover before/after the pretreatment were characterized by scanning electron microscope (SEM), X-ray Diffraction (XRD) and Thermal Gravity/Derivative Thermal Gravity Analysis (TG/DTG). After treated by SESE pretreatment at the optimum condition (150. °C, 2. min), the pretreated corn stover exhibited highest enzymatic hydrolysis yield (89%), and rare fermentation inhibitors formed. Characterization results indicated that the highest yield could be attributed to the effective removal of lignin/hemicellulose and destruction of cellulose structure by SESE pretreatment. © 2014 Elsevier Ltd.


Ye Q.,State Key Laboratory of Materials Oriented Chemical Engineering | Ye Q.,Nanjing University of Technology | Ye Q.,National Engineering Technique Research Center for Biotechnology | Ouyang P.,State Key Laboratory of Materials Oriented Chemical Engineering | And 5 more authors.
Applied Microbiology and Biotechnology | Year: 2011

Ethyl (S)-4-chloro-3-hydroxybutanoate ester ((S)-CHBE) is a precursor of enantiopure intermediates used for the production of chiral drugs, including the cholesterol-lowering 3-hydroxy-3-methyl-glutaryl CoA reductase inhibitors (statins). The asymmetric reduction of ethyl 4-chloro-3-oxobutanoate ester (COBE) to (S)-CHBE by biocatalysis has several positive attributes, including low cost, mild reaction conditions, high yield, and a high level of enantioselectivity. During genome database mining of the yeast Pichia stipitis, our group found two novel carbonyl reductases (PsCRI and PsCRII) that have a promising future for the industrial production of (S)-CHBE with >99% enantiomeric excess. This review covers the main process of biosynthesis of (S)-CHBE: screening of microorganisms that catalyze the reduction of COBE to (S)-CHBE (I); gene cloning, expression, and characterization of carbonyl reductases for the production of (S)-CHBE in Escherichia coli (II); development of cofactor generation systems for regenerating cofactors (III); and biocatalysis of COBE to (S)-CHBE by recombinant E. coli (IV). © 2010 Springer-Verlag.


Zhang Y.,State Key Laboratory of Materials Oriented Chemical Engineering | Zhang Y.,Nanjing University of Technology | Feng X.,State Key Laboratory of Materials Oriented Chemical Engineering | Feng X.,Nanjing University of Technology | And 6 more authors.
Bioresource Technology | Year: 2010

The production of ε-PL by Kitasatospora sp. MY 5-36 through entrapment or adsorption on bagasse, synthetic sponge, macroporous silica gel, and loofah sponge was investigated in shake flask cultures, and immobilization on loofah sponge gave the highest ε-PL production. Repeated fed-batch cultures for ε-PL production were also carried out in a stirred bioreactor and final ε-PL concentrations and productivity of 34.11 g L-1 and 9.34 g L-1 d-1, respectively were achieved by cells immobilize in loofah sponge. These values exceeded those for cultures with free cells (22.53 g L-1 and 3.30 g L-1 d-1). The immobilized cells were reused five times over a period of 526 h. These results suggest that the immobilization approach is promising for industrial applications. © 2010 Elsevier Ltd. All rights reserved.


Mo L.,Nanjing University of Technology | Mo L.,Jiangsu National Synergetic Innovation Center for Advanced Materials | Zhang F.,Nanjing University of Technology | Deng M.,Nanjing University of Technology | And 2 more authors.
Cement and Concrete Research | Year: 2016

Calcium carbonate binders were prepared via carbonating the paste specimens cast with steel slag alone or the steel slag blends incorporating 20% of Portland cement (PC) under CO2 curing (0.1 MPa gas pressure) for up to 14 d. The carbonate products, mechanical strengths, and microstructures were quantitatively investigated. Results showed that, after accelerated carbonation, the compressive strengths of both steel slag pastes and slag-PC pastes were increased remarkably, being 44.1 and 72.0 MPa respectively after 14 d of CO2 curing. The longer carbonation duration, the greater quantity of calcium carbonates formed and hence the higher compressive strength gained. The mechanical strength augments were mainly attributed to the formation of calcium carbonate, which caused microstructure densification associated with reducing pore size and pore volume in the carbonated pastes. In addition, the aggregated calcium carbonates exhibited good micromechanical properties with a mean nanoindentation modulus of 38.9 GPa and a mean hardness of 1.79 GPa. © 2016 Elsevier Ltd


Feng X.,State Key Laboratory of Materials Oriented Chemical Engineering | Feng X.,Nanjing University of Technology | Chen F.,State Key Laboratory of Materials Oriented Chemical Engineering | Chen F.,Nanjing University of Technology | And 9 more authors.
Bioresource Technology | Year: 2011

Propionic acid production by Propionibacterium freudenreichii from molasses and waste propionibacterium cells was studied in plant fibrous-bed bioreactor (PFB). With non-treated molasses as carbon source, 12.69±0.40gl-1 of propionic acid was attained at 120h in free-cell fermentation, whereas the PFB fermentation yielded 41.22±2.06gl-1 at 120h and faster cells growth was observed. In order to optimize the fermentation outcomes, fed-batch fermentation was performed with hydrolyzed molasses in PFB, giving 91.89±4.59gl-1 of propionic acid at 254h. Further studies were carried out using hydrolyzed waste propionibacterium cells as substitute nitrogen source, resulting in a propionic acid concentration of 79.81±3.99gl-1 at 302h. The present study suggests that the low-cost molasses and waste propionibacterium cells can be utilized for the green and economical production of propionic acid by P. freudenreichii. © 2011 Elsevier Ltd.


Xu Z.,State Key Laboratory of Materials Oriented Chemical Engineering | Xu Z.,Nanjing University of Technology | Li S.,State Key Laboratory of Materials Oriented Chemical Engineering | Li S.,Nanjing University of Technology | And 6 more authors.
Applied Microbiology and Biotechnology | Year: 2014

L-Arabinose isomerase (AI), a key enzyme in the microbial pentose phosphate pathway, has been regarded as an important biological catalyst in rare sugar production. This enzyme could isomerize L-arabinose into L-ribulose, as well as D-galactose into D-tagatose. Both the two monosaccharides show excellent commercial values in food and pharmaceutical industries. With the identification of novel AI family members, some of them have exhibited remarkable potential in industrial applications. The biological production processes for D-tagatose and L-ribose (or L-ribulose) using AI have been developed and improved in recent years. Meanwhile, protein engineering techniques involving rational design has effectively enhanced the catalytic properties of various AIs. Moreover, the crystal structure of AI has been disclosed, which sheds light on the understanding of AI structure and catalytic mechanism at molecular levels. This article reports recent developments in (i) novel AI screening, (ii) AI-mediated rare sugar production processes, (iii) molecular modification of AI, and (iv) structural biology study of AI. Based on previous reports, an analysis of the future development has also been initiated. © 2014, Springer-Verlag Berlin Heidelberg.


Zhou P.,State Key Laboratory of Materials Oriented Chemical Engineering | Zhou P.,Nanjing University of Technology | Li S.,State Key Laboratory of Materials Oriented Chemical Engineering | Li S.,Nanjing University of Technology | And 5 more authors.
Enzyme and Microbial Technology | Year: 2012

The biotransformation of d-arabitol into xylitol was investigated with focus on the conversion of d-xylulose into xylitol. This critical conversion was accomplished using Escherichia coli to co-express a xylitol dehydrogenase gene from Gluconobacter oxydans and a cofactor regeneration enzyme gene which was a glucose dehydrogenase gene from Bacillus subtilis for system 1 and an alcohol dehydrogenase gene from G. oxydans for system 2. Both systems efficiently converted d-xylulose into xylitol without the addition of expensive NADH. Approximately 26.91g/L xylitol was obtained from around 30g/L d-xylulose within system 1 (E. coli Rosetta/Duet-xdh-gdh), with a 92% conversion yield, somewhat higher than that of system 2 (E. coli Rosetta/Duet-xdh-adh, 24.9g/L, 85.2%). The xylitol yields for both systems were more than 3-fold higher compared to that of the G. oxydans NH-10 cells (7.32g/L). The total turnover number (TTN), defined as the number of moles of xylitol formed per mole of NAD +, was 32,100 for system 1 and 17,600 for system 2. Compared with that of G. oxydans NH-10, the TTN increased by 21-fold for system 1 and 11-fold for system 2, hence, the co-expression systems greatly enhanced the NADH supply for the conversion, benefiting the practical synthesis of xylitol. © 2012 Elsevier Inc.


Zhang D.,State Key Laboratory of Materials Oriented Chemical Engineering | Zhang D.,Nanjing University of Technology | Feng X.,State Key Laboratory of Materials Oriented Chemical Engineering | Feng X.,Nanjing University of Technology | And 6 more authors.
Bioresource Technology | Year: 2012

The production of poly(γ-glutamic acid) by Bacillus subtilis NX-2 from cane molasses and monosodium glutamate waste liquor (MGWL) was studied for the first time in this work. When batch fermentation was carried out with untreated molasses, 33.6±0.37gL -1 PGA was obtained with a productivity of 0.46±0.006gL -1h -1. In order to minimize the substrate inhibition, fed-batch fermentation was performed with untreated or hydrolyzed molasses in 7.5L bioreactor, giving 50.2±0.53 and 51.1±0.51gL -1 of PGA at 96h, respectively. Further studies were carried out by using MGWL as another carbon source, resulting in a PGA concentration of 52.1±0.52gL -1 with a productivity of 0.54±0.003gL -1h -1. These results suggest that the low-cost cane molasses and MGWL can be used for the environmental-friendly and economical production of PGA by B. subtilis NX-2. © 2012 Elsevier Ltd.


Yang J.,Key Laboratory of Mesoscopic Chemistry | Zhou Y.,Key Laboratory of Mesoscopic Chemistry | Yang J.Y.,Key Laboratory of Mesoscopic Chemistry | Lin W.G.,Key Laboratory of Mesoscopic Chemistry | And 4 more authors.
Journal of Physical Chemistry C | Year: 2010

The activity of zeolite MCM-22 in trapping nitrosamines, a class of well-known carcinogenic environmental pollutants, is reported in this article for the first time. MCM-22 possesses a set of unique porous structures and morphologies, making it possible to trap both volatile nitrosamines and bulky tobacco specific nitrosamines. Liquid adsorption and instantaneous gaseous adsorption methods have been employed to study the impact of morphology on MCM-22's ability in adsorbing nitrosamines in both gaseous and liquid media. As-synthesized MCM-22 was subjected to different treatments to induce morphological changes. SEM revealed a special rose-like appearance. The effects of these morphological modifications on MCM-22's adsorption capacities was studied and compared to NaY and NaZSM-5. The results obtained seem to suggest that enhanced collision probability between adsorbate and adsorbent may have an important role to play for MCM-22. Furthermore, the treatments created mesopores in MCM-22 that enhance mass transport within its hierarchical structure. © 2010 American Chemical Society.


Yan N.,State Key Laboratory of Materials Oriented Chemical Engineering | Wang Y.,State Key Laboratory of Materials Oriented Chemical Engineering
Journal of Polymer Science, Part B: Polymer Physics | Year: 2016

Swelling of block copolymers by selective solvents has emerged as an extremely simple and efficient process to produce nanoporous materials with well-controlled porosities. However, the role of the swelling agents in this pore-making process remains to be elucidated. Here we investigate the evolution of morphology, thickness, and surface chemistry of thin films of polystyrene-block-poly (2-vinyl pyridine) (PS-b-P2VP) soaked in a series of alcohols with changing carbon atoms and hydroxyl groups in their molecules. It is found that, in addition to a strong affinity to the dispersed P2VP microdomains, the swelling agents should also have a moderate swelling effect to PS to allow appropriate plastic deformation of the PS matrix. Monohydric alcohols with longer aliphatic chains exhibit stronger ability to induce the pore formation and a remarkable increase in film thickness is associated with the pore formation. High-carbon alcohols including n-propanol, n-butanol, and n-hexanol produce cylindrical micelles upon prolonged exposure for their strong affinity toward the PS matrix. In contrast, methanol and polyhydric alcohols including glycol and glycerol show very limited effect to swell the copolymer films as their affinity to the PS matrix is low; however, they also evidently induce the surface segregation of P2VP blocks. © 2016 Wiley Periodicals, Inc.

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