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Glycerol steam reforming over Ni/γ-Al2O3 catalysts modified by metal oxides
Cheng-Hua Xu,Zun-Yu Huang,Chuan-Qi Liu,Hui-Wen Xiao,Jun Chen,Yong-Xiang Zhang,Ya-Cong Lei 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.3
The metal oxides modified Ni/γ-Al2O3 catalysts for glycerol steam reforming were prepared by impregnation. Characterization results of fresh catalysts indicated that the molybdates modification abated the acidity and the stronger metal-support interaction of Ni/γ-Al2O3 catalysts, leading to a stable catalytic activity. Especially, NiMoLa-CaMg/γ-Al2O3 (NiMoLa/CMA) catalyst exhibited no deactivation along with glycerol complete conversion to stable gaseous products containing 69% H2, 20% CO and 10% CO2 during time-on-stream of 42 h. TPO of spent Ni/γ-Al2O3catalysts modified by different components showed that the carbon deposit on acidic sites and NiAl2O4 species led to catalysts deactivation. A lower reforming temperature and a higher LHSV and glycerol content were helpful to the production of syngas from GSR over NiMoLa/CMA; the reverse conditions would improve the formation of H2.
( Jun Pei Zhou ),( Qian Wu ),( Rui Zhang ),( Yu Ying Yang ),( Xiang Hua Tang ),( Jun Jun Li ),( Jun Mei Ding ),( Yan Yan Dong ),( Zun Xi Huang ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.6
This paper reports the production and characterization of crude xylanase from the newly isolated Humicola sp. Ly01. The highest (41.8 U/ml) production of the crude xylanase was obtained under the optimized conditions (w/v): 0.5% wheat bran, 0.2% KH2PO4, and 0.5% peptone; initial pH 7.0; incubation time 72 h; 30℃; and 150 rpm. A considerable amount of the crude xylanase was induced using hulless barley bran or soybean meal as the carbon source, but a small amount of the enzyme was produced when supplementary urea was used as the nitrogen source to wheat bran. The crude xylanase showed apparent optimal cellulase-free xylanase activity at 60℃ and pH 6.0, more than 71.8% of the maximum xylanase activity in 3.0-30.0% (v/v) ethanol and more than 82.3% of the initial xylanase activity after incubation in 3.0-30.0% (v/v) ethanol at 30℃ for 2 h. The crude xylanase was moderately resistant to both acid and neutral protease digestion, and released 7.9 and 10.9 μmol/ml reducing sugar from xylan in the simulated gastric and intestinal fluids, respectively. The xylooligosaccharides were the main products of the hydrolysis of xylan by the crude xylanase. These properties suggested the potential of the crude enzyme for being applied in the animal feed industry, xylooligosaccharides production, and high-alcohol conditions such as ethanol production and brewing.
( Jun Mei Ding ),( Ting Ting Yu ),( Lian Ming Liang ),( Zhen Rong Xie ),( Yun Juan Yang ),( Jun Pei Zhou ),( Bo Xu ),( Jun Jun Li ),( Zun Xi Huang ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.11
The esterase gene Est8 from the thermophilic bacterium Bacillus sp. K91 was cloned and expressed in Escherichia coli. The monomeric enzyme exhibited a theoretical molecular mass of 24.5 kDa and an optimal activity around 50°C at pH 9.0. A model of Est8 was constructed using a hypothetical YxiM precursor structure (2O14_A) from Bacillus subtilis as template. The structure showed an α/β-hydrolase fold and indicated the presence of a typical catalytic triad consisting of Ser-11, Asp-182, and His-185, which were investigated by site directed replacements coupled with kinetic characterization. Asp-182 and His-185 residues were more critical than the Ser-11 residue in the catalytic activity of Est8. A comparison of the amino acid sequence showed that Est8 could be grouped into the GDSL family and further classified as an SGNH hydrolase. Est8 is a new member of the SGNH hydrolase subfamily and may employ a different catalytic mechanism.
( Bo Xu ),( Li Ming Dai ),( Jun Jun Li ),( Meng Deng ),( Hua Biao Miao ),( Jun Pei Zhou ),( Yue Lin Mu ),( Qian Wu ),( Xiang Hua Tang ),( Yun Juan Yang ),( Jun Mei Ding ),( Nan Yu Han ),( Zun Xi Huang 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.1
Xylanases sourced from different bacteria have significantly different enzymatic properties. Therefore, studying xylanases from different bacteria is important to their applications in different fields. A potential xylanase degradation gene in Massilia was recently discovered through genomic sequencing. However, its xylanase activity remains unexplored. This paper is the first to report a xylanase (XynRBM26) belonging to the glycosyl hydrolase family (GH10) from the genus Massilia. The gene encodes a 383-residue polypeptide (XynRBM26) with the highest identity of 62% with the endoxylanase from uncultured bacterium BLR13. The XynRBM26 expressed in Escherichia coli BL21 is a monomer with a molecular mass of 45.0 kDa. According to enzymatic characteristic analysis, pH 5.5 is the most appropriate for XynRBM26, which could maintain more than 90% activity between pH 5.0 and 8.0. Moreover, XynRBM26 is stable at 37°C and could maintain at least 96% activity after being placed at 37°C for 1 h. This paper is the first to report that GH10 xylanase in an animal gastrointestinal tract (GIT) has salt tolerance, which could maintain 86% activity in 5 M NaCl. Under the optimum conditions, Km, Vmax, and kcat of XynRBM26 to beechwood xylan are 9.49 mg/ml, 65.79 μmol/min/mg, and 47.34 /sec, respectively. Considering that XynRBM26 comes from an animal GIT, this xylanase has potential application in feedstuff. Moreover, XynRBM26 is applicable to high-salt food and seafood processing, as well as other high-salt environmental biotechnological fields, because of its high catalytic activity in high-concentration NaCl.