Production and Characterization of Ethanol- and Protease-Tolerant and Xylooligosaccharides-Producing Endoxylanase from Humicola sp Ly01

( 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.

Biochemical Characterization of a GDSL-Motif Esterase from Bacillus sp. K91 with a New Putative Catalytic Mechanism

( 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.

Quasi-Fixed-Frequency Hysteresis Current Tracking Control Strategy for Modular Multilevel Converters

Jun Mei,Yu Ji,Xiaozhou Du,Tian Ma,Can Huang,Qinran Hu 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

This study proposes a quasi-fixed-frequency hysteresis current tracking control strategy for modular multilevel converters (MMCs) on the basis of voltage partition principle. First, by monitoring the grid voltage and the deviation between the output and reference currents, the output voltage is determined, thus prompting the output current to quickly and efficiently track the given current. Second, the voltages of the upper/lower capacitor of the arm and the voltages between the upper and lower arms are balanced by combining these arms with virtual loop mapping and arm voltage balance control, respectively. In particular, the proposed method is designed for any level and number of sub-modules. The validity of the proposed method is verified by simulations and experimental results of a five-level MMC prototype.

Response of Saccharomyces cerevisiae to Ethanol Stress Involves Actions of Protein Asrlp

( Jun Mei Ding ),( Xiao Wei Huang ),( Na Zhao ),( Feng Gao ),( Qian Lu ),( Ke Qin Zhang ) 한국미생물 · 생명공학회 2010 Journal of microbiology and biotechnology Vol.20 No.12

During the fermentation process of Saccharomyces cerevisiae, yeast cells must rapidly respond to a wide variety of external stresses in order to survive the constantly changing environment, including ethanol stress. The accumulation of ethanol can severely inhibit cell growth activity and productivity. Thus, the response to changing ethanol concentrations is one of the most important stress reactions in S. cerevisiae and worthy of thorough investigation. Therefore, this study examined the relationship between ethanol tolerance in S. cerevisiae and a unique protein called alcohol sensitive RING/PHD finger 1 protein (Asr1p). A real-time PCR showed that upon exposure to 8% ethanol, the expression of Asr1 was continuously enhanced, reaching a peak 2 h after stimulation. This result was confirmed by monitoring the fluorescence levels using a strain with a green fluorescent protein tagged to the C-terminal of Asr1p. The fluorescent microscopy also revealed a change in the subcellular localization before and after stimulation. Furthermore, the disruption of the Asr1 gene resulted in hypersensitivity on the medium containing ethanol, when compared with the wild-type strain. Thus, when taken together, the present results suggest that Asr1 is involved in the response to ethanol stress in the yeast S. cerevisiae.

Development and Application of Distributed Multilayer On-line Monitoring System for High Voltage Vacuum Circuit Breaker

Mei Fei,Mei Jun,Zheng Jianyong,Wang Yiping 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.4

On-line monitoring system is important for high voltage vacuum circuit breakers (HVCBs) in operation condition assessment and fault diagnosis. A distributed multilayer system with client/server architecture is developed on rated voltage 10kV HVCB with spring operating mechanism. It can collect data when HVCB switches, calculate the necessary parameters, show the operation conditions and provide abundant information for fault diagnosis. Ensemble empirical mode decomposition (EEMD) is used to detect the singular point which is regarded as the contact moment. This method has been applied to on-line monitoring system successfully and its satisfactory effect has been proved through experiments. SVM and FCM are both effective methods for fault diagnosis. A combinative algorithm is designed to judge the faults of HVCB’s operating mechanism. The system"s precision and stability are confirmed by field tests.

Study of Proteolysis, Lipolysis, and Volatile Compounds of a Camembert-type Cheese Manufactured Using a Freeze-dried Tibetan Kefir Co-culture during Ripening

Jun Mei,Qizhen Guo,Yan Wu,Yunfei Li,Huaning Yu 한국식품과학회 2015 Food Science and Biotechnology Vol.24 No.2

The use of a freeze-dried Tibetan kefir coculture as a starter for production of Camembert-type cheese was investigated. Maturation of produced cheese was monitored for 35 days and the chemical composition, proteolysis, lipolysis, and volatile compounds were studied. The cheese underwent proteolysis. The content of pH 4.6- soluble nitrogen, 12% trichloroacetic acid-soluble nitrogen, and the total free amino acid content increased while the total nitrogen content decreased. Palmitic, myristic, oleic, and capric acid were the representative free fatty acids, which increased in amount during ripening. A total of 45 compounds were detected, including 16 acids, 8 ketones, 6 alcohols, 7 esters, and 8 unclassified compounds. Volatile carboxylic acids were abundant in the headspace of the cheese.

Quasi-Fixed-Frequency Hysteresis Current Tracking Control Strategy for Modular Multilevel Converters

Mei, Jun,Ji, Yu,Du, Xiaozhou,Ma, Tian,Huang, Can,Hu, Qinran The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

This study proposes a quasi-fixed-frequency hysteresis current tracking control strategy for modular multilevel converters (MMCs) on the basis of voltage partition principle. First, by monitoring the grid voltage and the deviation between the output and reference currents, the output voltage is determined, thus prompting the output current to quickly and efficiently track the given current. Second, the voltages of the upper/lower capacitor of the arm and the voltages between the upper and lower arms are balanced by combining these arms with virtual loop mapping and arm voltage balance control, respectively. In particular, the proposed method is designed for any level and number of sub-modules. The validity of the proposed method is verified by simulations and experimental results of a five-level MMC prototype.

Evaluation of Freeze-dried Tibetan Kefir co-culture as a Starter for Production of Bod ljong Cheese

Jun Mei,Fei Feng,Qizhen Guo,Yunfei Li,Yan Wu 한국식품과학회 2015 Food Science and Biotechnology Vol.24 No.3

The physico-chemical profile, proteolysis, flavor, and microbiological changes were investigated, and a sensory evaluation was performed for Bod ljong cheese prepared using a freeze-dried Tibetan kefir co-culture during ripening. The proteolysis level was high, the pH 4.6-soluble nitrogen, 12% trichloroacetic acid-soluble nitrogen, water soluble nitrogen, and total free amino acid contents increased, and the protein content decreased during ripening. The effect of the starter culture on production of aroma-related compounds responsible for cheese flavor was also studied using solidphase microextraction GC-MS techniques. Alcohols and esters were the most abundant volatile compounds. Microbial counts during ripening increased steadily. Lactic acid bacteria, Lactobacillus and Lactococcus, were the dominant flora during ripening. Enterococci, Enterobacteriaceae, and Salmonella sp. bacterial counts were low or zero. The cheese was subjected to sensory evaluation by a panel and compared to commercial Bod ljong-type cheese.

Retrospective Study of Gemcitabine Based Chemotherapy for Unresectable or Recurrent Esophagus Squamous Cell Carcinoma Refractory to First Line Chemotherapy

Wang, Mei,Gu, Jun,Wang, Hai-Xing,Wu, Mei-Hong,Li, Yong-Mei,Wang, Ya-Jie Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.8

Purpose: To investigate the efficacy and toxicity of a combination of gemcitabine with nedaplatin (GN) or cisplatin (GC) for patients with unresectable or recurrent esophagus squamous cell carcinoma. Methods: Gemcitabine was administered at 1 g/m2 intravenously on days 1 and 8; and nedaplatin or cisplatin were administered at 80 mg/m2 intravenously on day 1. We analyzed the response rate, overall survival time, progression-free survival time, and toxicity in 21 patients treated with GN and 27 patients treated with GC. Results: In patients treated with gemcitabine plus nedaplatin, the ORR was 47.6%, the median progression-free survival time was 4.1 months, and the median survival time was 9.3 months. In patients treated with gemcitabine plus cisplatin, the ORR was 48.2%, the median progression-free survival time was 3.9 months, and the median survival time was 9.1 months, respectively. There were no statistically significant differences in ORR, PFS and OS between the two groups. In both, the most commonly observed toxicities were thrombocytopenia and fatigue. Nausea and vomiting was more frequent in the GC group than in the GN group. Conclusion: Gemcitabine based chemotherapy was effective and tolerable for patients with unresectable or recurrent esophagus squamous cell carcinoma refractory to first line chemotherapy.

Diagnosis Value of Membrane Glycolipids Biochemistry Index in Intracranial and Gastrointestinal Tumors

Lv, Jun,Lv, Can-Qun,Mei, Ping,Qi, Shi-Mei Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.7

The diagnostic value of membrane glycolipid biochemistry index, the lipid-bound sialic acid (LSA) and total sialic acid (TSA) in cerebrospinal fluid (CSF) was evaluated in 30 intracranial and 65 gastrointestinal tumors. The plasma LSA, TSA and red cell membrane sialic acid (R-SA) in were determined according to the method of Sevenmerhulm. Our results showed that the levels of LSA and TSA in CSF of intracranial tumor patients was higher than that of normal group(p<0.01). The concentration of TSA and LSA in patients with malignant glioma was higher than that of benign meningioma patients(P<0.01). No significance was found between intracranial halmatoma patients and normal control group for levels of membrane glycolipids (p>0.05). Results also found that the plasma LSA, TSA and R-SA of gastric carcinoma were significantly higher than those of control group (p<0.05); while no significant difference was found in the plasma LSA, TSA and R-SA levels between chronic gastritis, gastrohelcoma and normal control group (p>0.05). Plasma LSA, TSA and R-SA levels of gastric carcinoma patient were significantly higher than those of chronic gastritis patients and gastrohelcoma patients(p<0.05). It was also found that plasma LSA, TSA and R-SA contents were significantly higher in large intestine carcinoma patients than in benign in stestine tumor patients (p<0.05) while no significant difference was found between intestine benign tumor and normal control group (p>0.05). The levels of LSA, TSA and R-SA were obviously higher in the patients with metastasis than in the ones without (p<0.05.) The membrane glycolipid biochemistry index LSA and TSA in CSF are sensive markers for diagnosing intracranial tumors. For gastrointestinal malignant tumors the plasma LSA TSA and red blood cell membrane SA may be considered as auxiliary indicators for diagnosis. They can be used for distinguishing benign from malignant tumors.