Time filter

Source Type

Yang F.,South China University of Technology | Yang X.,South China University of Technology | Yang X.,City University of Hong Kong | Li Z.,South China University of Technology | And 4 more authors.
Applied Microbiology and Biotechnology

Thermoanaerobacterium aotearoense P8G3#4 produced β-glucosidase (BGL) intracellularly when grown in liquid culture on cellobiose. The gene bgl, encoding β-glucosidase, was cloned and sequenced. Analysis revealed that the bgl contained an open reading frame of 1314 bp encoding a protein of 446 amino acid residues, and the product belonged to the glycoside hydrolase family 1 with the canonical glycoside hydrolase family 1 (GH1) (β/α)8 TIM barrel fold. Expression of pET-bgl together with a chaperone gene cloned in vector pGro7 in Escherichia coli dramatically enhanced the crude enzyme activity to a specific activity of 256.3 U/mg wet cells, which resulted in a 9.2-fold increase of that obtained from the expression without any chaperones. The purified BGL exhibited relatively high thermostability and pH stability with its highest activity at 60 °C and pH 6.0. In addition, the activities of BGL were remarkably stimulated by the addition of 5 mM Na+ or K+. The enzyme showed strong ability to hydrolyze cellobiose with a Km and Vmax of 25.45 mM and 740.5 U/mg, respectively. The BGL was activated by glucose at concentration varying from 50 to 250 mM and tolerant to glucose inhibition with a Ki of 800 mM glucose. The supplement of the purified BGL to the sugarcane bagasse hydrolysis mixture containing a commercial cellulase resulted in about 20 % enhancement of the released reducing sugars. These properties of the purified BGL should have important practical implication in its potential applications for better industrial production of glucose or bioethanol started from lignocellulosic biomass. © 2015, Springer-Verlag Berlin Heidelberg. Source

Lu G.-N.,South China University of Technology | Lu G.-N.,The College of New Jersey | Dang Z.,South China University of Technology | Dang Z.,Guangzhou Higher Education Mega Center | And 5 more authors.
Journal of Hazardous Materials

This paper reports a theoretical validation and proposition of the reductive dechlorination pathways for polychlorinated dibenzo-p-dioxin (PCDD) congeners. Density functional theory (DFT) calculations were carried out at the B3LYP/6-31G(d) level for all PCDDs and Mulliken atomic charges on chlorine atoms were adopted as the probe of the dechlorination reaction activity. The experimentally substantiated dechlorination pathways of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) and its daughter products in the presence of zero-valent zinc were validated and the complete pathway of dechlorination of octachlorodibenzo-p-dioxin (OCDD) was proposed. The proposed pathways were found to be consistent with anaerobic biotransformation of several PCDD congeners. Four rules of thumb arrived from this study include (1) the chlorine atoms in the longitudinal (1,4,6,9) positions are removed in preference to the chlorine atoms on lateral (2,3,7,8) positions; (2) the chlorine atom that has more neighboring chlorine atoms at ortho-, meta- and para-positions is to be eliminated; (3) reductive dechlorination prefers to take place on the benzene ring having more chlorine substitutions; and (4) a chlorine atom on the side of the longitudinal symmetry axis containing more chlorine atoms is preferentially eliminated. These rules of thumb can be conveniently used for rapidly predicting the major dechlorination pathway for a given PCDD in specific systems. © 2009 Elsevier B.V. Source

Zhang M.-S.,Sun Yat Sen University | Zhang M.-S.,Guangzhou Higher Education Mega Center | Tan H.-Z.,Sun Yat Sen University | Mao J.-F.,Shanghai JiaoTong University
IEEE Transactions on Components, Packaging and Manufacturing Technology

In this paper, a novel layer stack-up with free cavity resonance is proposed for high-performance power noise suppression. In this layer stack-up, power planes for power delivery are sandwiched by ground planes and are moved close to the component sides, so that they are separated from signal layers. Signal layers are isolated by ground planes, which provide ideal ground reference. Arrays of ground shorting vias are introduced to ac short ground reference plane pairs to remove their cavity resonances. This structure has free cavity resonance under the corner frequency of the periodic via array, and it has an excellent wideband noise suppression with starting point from dc. This stack-up not only has high-performance noise suppression, but also can significantly improve the signal integrity and reduce the electromagnetic interference of the board. Simulation and measurement are performed to verify the validity of the proposed layer stack-up. © 2014 IEEE. Source

Ou H.-S.,South China University of Technology | Wei C.-H.,South China University of Technology | Wei C.-H.,Guangzhou Higher Education Mega Center | Deng Y.,Montclair State University | And 3 more authors.
Environmental Science and Pollution Research

A novel dual coagulant system of polyaluminum chloride sulfate (PACS) and polydiallyldimethylammonium chloride (PDADMAC) was used to treat natural algae-laden water from Meiliang Gulf, Lake Taihu. PACS (Aln(OH)mCl3n-m-2k(SO4)k) has a mass ratio of 10 %, a SO4 2-/Al3 + mole ratio of 0.0664, and an OH/Al mole ratio of 2. The PDADMAC ([C8H16NCl]m) has a MW which ranges from 5 × 105 to 20 × 105 Da. The variations of contaminants in water samples during treatments were estimated in the form of principal component analysis (PCA) factor scores and conventional variables (turbidity, DOC, etc.). Parallel factor analysis determined four chromophoric dissolved organic matters (CDOM) components, and PCA identified four integrated principle factors. PCA factor 1 had significant correlations with chlorophyll-a (r = 0.718), protein-like CDOM C1 (0.689), and C2 (0.756). Factor 2 correlated with UV254 (0.672), humic-like CDOM component C3 (0.716), and C4 (0.758). Factors 3 and 4 had correlations with NH3-N (0.748) and T-P (0.769), respectively. The variations of PCA factors scores revealed that PACS contributed less aluminum dissolution than PAC to obtain equivalent removal efficiency of contaminants. This might be due to the high cationic charge and pre-hydrolyzation of PACS. Compared with PACS coagulation (20 mg L-1), the removal of PCA factors 1, 2, and 4 increased 45, 33, and 12 %, respectively, in combined PACS-PDADMAC treatment (0.8 mg L-1 + 20 mg L-1). Since PAC contained more Al (0.053 g/1 g) than PACS (0.028 g/1 g), the results indicated that PACS contributed less Al dissolution into the water to obtain equivalent removal efficiency. © 2013 Springer-Verlag Berlin Heidelberg. Source

Zhang H.L.,Guangzhou Higher Education Mega Center | Chen Y.H.,Guangzhou Higher Education Mega Center | Qi J.Y.,No.7West Street | Lin B.G.,No.7West Street | Fang J.D.,No.7West Street
Advanced Materials Research

Take the Shenzhen Nanshan Municipal solid waste incinerator(MSWI) as the object, in total 18 ambient air samples were got. The study analyzed the distribution characteristics of ambient air heavy metals (Cu, Cd, Pb, Cr) and As in the surroundings of the MSWI. The EPA Risk Assessment Guidance for Superfund(RAGS) was used to assess the exposure risk. The results demonstrated that the Pb and Cd value in the surroundings of the MSWI were in the accept level according to the Ambient Air Quality Standards(GB3095-2012); The risk assessment showed that the carcinogenic and non-carcinogenic risks via inhalation exposure in the sorrounding of the MSWI were in the accessible levels. © (2013) Trans Tech Publications, Switzerland. Source

Discover hidden collaborations