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Hydrolysis mechanism of carbendazim hydrolase from the strain Microbacterium ***-6F

Journal of Environmental Sciences 2017年第4期29卷 171-177页

作者： Ji Lei Shaopeng Wei Lijun Ren Shibin Hu Peng Chen Key Laboratory of Disaster Survey and Mechanism Simulation of Shaanxi Province College of Chemistry and Chemical EngineeringBaoji University of Arts and Sciences College of Resources and Environment College of Life Sciences and College of Plant ProtectionNorthwest A&F University

The carbendazim（MBC） hydrolyzing enzyme gene was cloned and heterologously expressed in Escherichia coli BL21（DE3） from a newly isolated MBC-degrading bacterium strain Microbacterium sp. strain djl-6F. high performance liquid chromatography-mass spectrometry（HPLC-MS）analysis revealed that purified MheI-6F protein catalyzes direct hydrolysis of MBC into2-aminobenzimidazole（2-AB） with a high turnover rate and moderate affinity（Kmof6.69 μmol/L and kcatof 160.88/min） without the need for any cofactors. The optimal catalytic condition of MheI-6F was identified as 45°C, pH 7.0. The enzymatic activity of MheI-6F was found to be diminished by metal ions, and strongly inhibited by sodium dodecyl sulfate（SDS）.Through generating amino acid mutations in MheI-6F, Cys16 and Cys222 were identified as the catalytic groups that are essential for the hydrolysis of MBC. This is the first report on the biodegradation of MBC at the enzymatice level.

关键词： Carbendazim Microbacterium sp.djl-6F Hydrolase MheI-6F

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Enhanced production of astaxanthin by Chromochloris zofingiensis in a microplate-based culture system under high light irradiation

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BIORESOURCE techNOLOGY 2017年第PartA期245卷 518-529页

作者： Chen, Jun-Hui Liu, Lu Wei, Dong South China Univ Technol Sch Food Sci & Engn Guangzhou 510641 Guangdong Peoples R China

The green microalga Chromochloris zofingiensis is a promising producer of natural astaxanthin. In the present study, C. zofingiensis was first cultivated in shake flasks under low light irradiation and then subjected to continuous high light irradiation, which effectively promoted astaxanthin production. In addition, a microplate-based culture system in concert with high light irradiation from blue light and white light above 150 mu mol m(-2) s(-1) was constructed and applied to improve astaxanthin production. Blue light exerted more positive influences on astaxanthin accumulation, but when the light intensity was increased to 300 mu mol m(-2) s(-1), astaxanthin biosynthesis was substantially inhibited. Conversely, in a nitrogen-deprived culture under white light, the highest astaxanthin content for C. zofingiensis, 7.1 mg/g, was obtained. The highest astaxanthin yield achieved was 38.9 mg/L in a culture with 0.1 g/L nitrate under the same culture conditions. This study demonstrates that C. zofingiensis has great potential for natural astaxanthin production.

关键词： Chromochloris zofingiensis Astaxanthin Blue light White light Microplate-based culture

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Glycidyl Fatty Acid Esters in Refined Edible Oils: A Review on Formation, Occurrence, Analysis, and Elimination Methods

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COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY 2017年第2期16卷 263-281页

作者： Cheng, Wei-wei Liu, Guo-qin Wang, Li-qing Liu, Zeng-she South China Univ Technol Sch Food Sci & Engn Guangzhou 510640 Guangdong Peoples R China Guangdong Testing Inst Prod Qual Supervis Foshan 528300 Peoples R China China Natl Qual Supervis & Testing Ctr Foods Guan Foshan 528300 Peoples R China ARS Biooils Res Unit Natl Ctr Agr Utilizat Res USDA 1815 N Univ St Peoria IL 61604 USA South China Univ Technol Guangdong Prov Key Lab Green Proc Nat Prod & Prod Guangzhou 510640 Guangdong Peoples R China

Glycidyl fatty acid esters (GEs), one of the main contaminants in processed oils, are mainly formed during the deodorization step in the refining process of edible oils and therefore occur in almost all refined edible oils. GEs are potential carcinogens, due to the fact that they readily hydrolyze into the free form glycidol in the gastrointestinal tract, which has been found to induce tumors in various rat tissues. Furthermore, glycidol has already been identified as a possible human carcinogen'' (group 2A) by the Intl. Agency for research on Cancer (IARC). Therefore, significant effort has been devoted to inhibit and eliminate the formation of GEs. The aim of this review is to provide a comprehensive summary on the following topics: (i) GE occurrence data for different edible oils and oil-based food products, (ii) precursors of GEs, (iii) factors influencing the formation of GEs, (iv) potential reaction mechanisms involving the leaving group and reaction intermediates, and (v) analytical methods, including the indirect and direct methods. More importantly, the various elimination methods for GEs in refined edible oils are being reviewed with focus on 3 aspects: (i) inhibition and removal of reactants, (ii) modification of reactive conditions, and (iii) elimination of GE products.

关键词： elimination methods formation mechanisms glycidyl fatty acid esters heat-induced food toxicants refined edible oils

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Intensity and Compactness Enabled Saliency Estimation for Leakage Detection in Diabetic and Malarial Retinopathy

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IEEE TRANSACTIONS ON MEDICAL IMAGING 2017年第1期36卷 51-63页

作者： Zhao, Yitian Zheng, Yalin Liu, Yonghuai Yang, Jian Zhao, Yifan Chen, Duanduan Wang, Yongtian Beijing Inst Technol Sch Opt & Elect Beijing Engn Res Ctr Mixed Real & Adv Display Beijing 100081 Peoples R China Univ Liverpool Dept Eye & Vis Sci Liverpool L69 3GA Merseyside England Aberystwyth Univ Dept Comp Sci Aberystwyth SY23 3DB Dyfed Wales Cranfield Univ EPSRC Ctr Innovat Mfg Throughlife Engn Serv Cranfield MK43 0AL Beds England Beijing Inst Technol Sch Life Sci Beijing 100081 Peoples R China

Leakage in retinal angiography currently is a key feature for confirming the activities of lesions in the management of a wide range of retinal diseases, such as diabetic maculopathy and paediatric malarial retinopathy. This paper proposes a new saliency-based method for the detection of leakage in fluorescein angiography. A superpixel approach is firstly employed to divide the image into meaningful patches (or superpixels) at different levels. Two saliency cues, intensity and compactness, are then proposed for the estimation of the saliency map of each individual superpixel at each level. The saliency maps at different levels over the same cues are fused using an averaging operator. The two saliency maps over different cues are fused using a pixel-wise multiplication operator. Leaking regions are finally detected by thresholding the saliency map followed by a graph-cut segmentation. The proposed method has been validated using the only two publicly available datasets: one for malarial retinopathy and the other for diabetic retinopathy. The experimental results show that it outperforms one of the latest competitors and performs as well as a human expert for leakage detection and outperforms several state-of-the-art methods for saliency detection.

关键词： Leakage diabetic malarial retinopathy fluorescein angiogram saliency segmentation

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Determination of 15 phthalate esters in air by gas-phase and particle-phase simultaneous sampling

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Journal of Environmental Sciences 2017年第5期29卷 137-145页

作者： Chenchen Chi Meng Xia Chen Zhou Xueqing Wang Mili Weng Xueyou Shen College of Environmental & Resource Sciences Zhejiang University Hangzhou 310058 China Zhejiang National Radiation Environmental Technology Co. Ltd. Hangzhou 310011 China School of Environmental and Resource Sciences Zhejiang Agriculture and Forestry University Hangzhou 310058 China Zhejiang Provincial Key Laboratory of Organic PollutionProcess and Control Hangzhou 3100S8 China

Based on previous research, the sampling and analysis methods for phthalate esters （PAEs） were improved by increasing the sampling flow of indoor air from 1 to 4 L/min, shortening the sampling duration from 8 to 2 hr. Meanwhile, through the optimization of chromatographic conditions, the concentrations of 9 additional PAE pollutants in indoor air were measured. The optimized chromatographic conditions required a similar amount of time for analysis as before, but gave high responsivity, the capability of simultaneously distinguishing 15 kinds of PAEs, and a high level of discrimination between individual sample peaks, as well as stable peak generation. The recovery rate of all gas-phase and particle-phase samples of the 15 kinds of PAEs ranged from 91.26% to 109.42%, meeting the quantitative analysis requirements for indoor and outdoor air sampling and analysis. For the first time, investigation of the concentration levels as well as characteristics of 15 kinds of PAEs in the indoor air from four different traffic micro-environments （private vehicles, busses, taxis and subways） was carried out, along with validation of the optimized sampling and analytical method. The results show that all the 9 additional PAEs could be detected at relatively high pollution levels in the indoor air from the four traffic micro-environments. As none of the pollution levels of the 15 kinds of PAEs in the indoor air from the 4 traffic micro-environments should be neglected, it is of great significance to increase the types of PAEs able to be detected in indoor air.

关键词： Air pollution Phthalate esters Traffic micro-environment Gas-phase and particle-phase Sampling and analytical method

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Automatic liver segmentation based on appearance and context information

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BIOMEDICAL ENGINEERING ONLINE 2017年第1期16卷 1-12页

作者： Zheng, Yongchang Ai, Danni Mu, Jinrong Cong, Weijian Wang, Xuan Zhao, Haitao Yang, Jian Chinese Acad Med Sci Peking Union Med Coll Peking Union Med Coll Hosp Dept Liver Surg Beijing 100730 Peoples R China Beijing Inst Technol Beijing Engn Res Ctr Mixed Real & Adv Display Sch Opt & Elect Beijing 100081 Peoples R China Chinese Acad Med Sci Peking Union Med Coll Peking Union Med Coll Hosp Dept Radiol Beijing 100730 Peoples R China

Background: Automated image segmentation has benefits for reducing clinicians' workload, quicker diagnosis, and a standardization of the diagnosis. Methods: This study proposes an automatic liver segmentation approach based on appearance and context information. The relationship between neighboring pixels in blocks is utilized to estimate appearance information, which is used for training the first classifier and obtaining the probability distribution map. The map is used for extracting context information, along with appearance features, to train the next classifier. The prior probability distribution map is achieved after iterations and refined through an improved random walk for liver segmentation without user interaction. Results: The proposed approach is evaluated using CT images with eight contemporary approaches, and it achieves the highest VOE, RVD, ASD, RMSD and MSD. It also achieves a high average score of 76 using the MICCAI-2007 Grand Challenge scoring system. Conclusions: Experimental results show that the proposed method is superior to eight other state of the art methods.

关键词： Context Feature Appearance Feature Active Shape Model Liver Segmentation Precise Segmentation

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Weakly Supervised Learning of Part Selection Model with Spatial Constraints for Fine-Grained Image Classification 31

Weakly Supervised Learning of Part Selection Model with Spat...

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31st AAAI Conference on Artificial Intelligence

作者： He, Xiangteng Peng, Yuxin Peking Univ Inst Comp Sci & Technol Beijing 100871 Peoples R China

Fine-grained image classification is challenging due to the large intra-class variance and small inter-class variance, aiming at recognizing hundreds of sub-categories belonging to the same basic-level category. Since two different sub-categories is distinguished only by the subtle differences in some specific parts, semantic part localization is crucial for fine-grained image classification. Most previous works improve the accuracy by looking for the semantic parts, but rely heavily upon the use of the object or part annotations of images whose labeling are costly. Recently, some researchers begin to focus on recognizing sub-categories via weakly supervised part detection instead of using the expensive annotations. However, these works ignore the spatial relationship between the object and its parts as well as the interaction of the parts, both of them are helpful to promote part selection. Therefore, this paper proposes a weakly supervised part selection method with spatial constraints for fine-grained image classification, which is free of using any bounding box or part annotations. We first learn a whole-object detector automatically to localize the object through jointly using saliency extraction and co-segmentation. Then two spatial constraints are proposed to select the distinguished parts. The first spatial constraint, called box constraint, defines the relationship between the object and its parts, and aims to ensure that the selected parts are definitely located in the object region, and have the largest overlap with the object region. The second spatial constraint, called parts constraint, defines the relationship of the object's parts, is to reduce the parts' overlap with each other to avoid the information redundancy and ensure the selected parts are the most distinguishing parts from other categories. Combining two spatial constraints promotes parts selection significantly as well as achieves a notable improvement on fine-grained image classification.

关键词： Image classification

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78th Society of Exploration Geophysicists International Exposition and Annual Meeting, SEG 2008

作者： Huang, Xinwu Zhao, Bing Li, Teng School of Engineering and Technology China Univ. of Geosciences Beijing China

ISBN: (纸本)9781605607856

In the physical insight, the data-consistence-based time-space convolution method for multiples' generation and prediction was discussed. The predicted multiples can be matched to multiples in original data by a linear (least-squares) inversion process, and then be subtracted from original data. The surface-related multiple-attenuation can be implemented in an iterative adaptive procedure and can be made very efficient. The iterative multiple suppression process are illustrated with a field data example. Comparing with other de-multiple methods, the results show that the process is very effective and stable, attenuating the multiple energy while keeping the primary events not damaged. Copyright © (2008) by the Society of Exploration Geophysicists All rights reserved.

关键词： Iterative methods

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Chitosan degradation products facilitate peripheral nerve regeneration by improving macrophage-constructed microenvironments

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BIOMATERIALS 2017年第0期134卷 64-77页

作者： Zhao, Yahong Wang, Yongjun Gong, Jiahuan Yang, Liu Niu, Changmei Ni, Xuejun Wang, Yaling Peng, Su Gu, Xiaosong Sun, Cheng Yang, Yumin Nantong Univ Key Lab Neuroregenerat Nantong 226007 Peoples R China Coinnovat Ctr Neuroregenerat Nantong 226007 Jiangsu Peoples R China Nantong Univ Dept Neurosurg Affiliated Hosp Nantong 226007 Peoples R China Nantong Univ Med Sch Nantong 226007 Peoples R China Nantong Univ Dept Ultrasound Affiliated Hosp Nantong 226007 Peoples R China

Chitosan-based artificial nerve grafts have been widely employed to repair peripheral nerve defects. Our previous study has shown that chitosan constructed nerve graft not only provides suitable scaffolds for nerve regeneration, its degradation products, chitooligosaccharides (COS), also promote nerve repair. However, the involved mechanisms are still not fully elucidated. In the present study, we observed that pro-inflammatory cytokines, as well as macrophage infiltration, were transiently up-regulated in the injured sciatic nerves which were bridged with silicon tubes filled with COS. Based upon transcriptome analysis, the axis of miR-327/CCL2 in Schwann cells (SCs) was identified as a potential target of COS. The following experiments have confirmed that COS stimulate CCL2 expression by down-regulating miR-327 in SCs. Consequently, the resulting CCL2 induces macrophage migration at injury sites to re-construct microenvironments and thus facilitates nerve regeneration. Collectively, our data provide a theoretical basis for the clinical application of chitosan-based grafts in peripheral nerve regeneration. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Chitooligosaccharides Peripheral nerve regeneration Schwann cells Chemokines Microenvironments

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Molecular characterization of CO₂ sequestration and assimilation in microalgae and its biotechnological applications

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BIORESOURCE techNOLOGY 2017年第Part2期244卷 1207-1215页

作者： Zhu, Baojun Chen, Gu Cao, Xupeng Wei, Dong South China Univ Technol Sch Food Sci & Engn Wushan Rd 381 Guangzhou 510641 Guangdong Peoples R China Chinese Acad Sci Dalian Inst Chem Phys Marine Bioengn Grp Dalian 116023 Peoples R China

Microalgae are renewable feedstock for sustainable biofuel production, cell factory for valuable chemicals and promising in alleviation of greenhouse gas CO2. However, the carbon assimilation capacity is still the bottleneck for higher productivity. Molecular characterization of CO2 sequestration and assimilation in microalgae has advanced in the past few years and are reviewed here. In some cyanobacteria, genes for 2-oxoglytarate dehydrogenase was replaced by four alternative mechanisms to fulfill TCA cycle. In green algae Coccomyxa subellipsoidea C-169, alternative carbon assimilation pathway was upregulated under high CO2 conditions. These advances thus provide new insights and new targets for accelerating CO2 sequestration rate and enhancing bioproduct synthesis in microalgae. When integrated with conventional parameter optimization, molecular approach for microalgae modification targeting at different levels is promising in generating value-added chemicals from green algae and cyanobacteria efficiently in the near future. (c) 2017 Elsevier Ltd. All rights reserved.

关键词： Microalgae Molecular characterization CO2 assimilation Genetic modification Lipid synthesis

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