One‐step production of 2,3‐butanediol from starch by secretory over‐expression of amylase in Klebsiella pneumoniae

BACKGROUND: 2,3‐Butanediol (2,3‐BD) is a valuable chemical that can be biosynthesized from many kinds of substrates. For commercial biological production of 2,3‐BD, it is desirable to use cheap substrate without pretreatment, such as starch. However, there have been few reports on the production of 2,3‐BD directly from starch. RESULTS: In this work, gene malS coding for α‐amylase (EC 3.2.1.1) precursor was inserted into plasmid pUC18K, and secretory over‐expression of α‐amylase was achieved by engineered Klebsiella pneumoniae. The extracellular recombinant amylase accelerated the hydrolyzation of starch, and one‐step production of 2,3‐BD from starch was carried out by engineered K. pneumoniae. A 2,3‐BD concentration of 3.8 g L^?1 and yield of 0.19 g 2,3‐BD g^?1 starch were obtained after 24 h fermentation. CONCLUSION: The one‐step production of 2,3‐BD from starch was achieved by secretory over‐expression of amylase in K. pneumoniae. This would simplify the process and reduce the production cost considerably by enabling use of starch with minimal pretreatment. Copyright © 2008 Society of Chemical Industry     

Synthesis of p‐aminophenol from the hydrogenation of nitrobenzene over metal–solid acid bifunctional catalyst

BACKGROUND: A single‐step conversion of nitrobenzene (NB) to p‐aminophenol (PAP) through catalytic hydrogenation is a widely used synthesis route for PAP. The main shortcoming of this route is the use of sulfuric acid for rearrangement of the phenylhydroxylamine (PHA) intermediate. In this paper, S₂O₈^2?/ZrO₂ (PSZ) solid acid and Pt‐S₂O₈^2?/ZrO₂ (Pt‐PSZ) bifunctional catalysts were prepared for the synthesis of PAP in non‐acid medium. RESULTS: Calcination temperature has a substantial effect on the acidity, structure and activity for PHA rearrangement of PSZ. The highest PAP yield was 33.8% over PSZ calcined at 823 K when the reaction was carried out in water at 423 K. A high PAP yield of 23.9% was achieved by a single‐step reaction of nitrobenzene over Pt‐PSZ bifunctional catalysts. CONCLUSION: PSZ solid acid exhibits high activity for PHA rearrangement. Perfect tetragonal ZrO₂ and much stronger acid sites play important roles in catalytic activity. Inhibiting the hydrogenation activity by reducing the amount of Pt loading on Pt‐PSZ can improve the competition of PHA rearrangement on acid sites with hydrogenation of PHA on metal active sites, resulting in better selectivity to PAP. Copyright © 2008 Society of Chemical Industry     

我国企业品牌弱势原因分析

我国是一个制造业大国但同时又是一个品牌弱国。我国企业由于缺少品牌优势,产品出口乃至整个国民经济都受到严重影响。我国企业缺少强势品牌的原因在于:缺乏品牌经营的环境和意识;品牌管理手段落后,缺乏战略性的品牌管理与规划;品牌价值观定位不准确,缺乏以品牌核心价值为中心的品牌识别;缺乏品牌战略管理组织与管理人才以及品牌的定期检查制度和危机处理机制。要改变这种状况,必须尽快更新观念,强化品牌基础工作,尤其是注重品牌组织管理体系的建设和专业人才的培养与引进,充分借鉴国外成功经验并结合实际不断创新。只有这样,才能提高本土品牌的影响力,逐步缩小与国外著名品牌的差距。     

宽带无线接入系统WiMAX的应用与部署

介绍了宽带无线接入系统WiMAX的关键技术，并与其他接入技术作了比较；阐述了WiMAX的主要应用、组网部署；也指出了WiMAX存在的一些主要问题。     

互联网业务流量监测技术的应用和设计

对互联网业务流量监测技术的应用及现状进行了分析，并针对NetFlow技术，对互联网业务流量监测系统建设方案设计中需要考虑的几个重要问题进行了讨论。     

秦皇岛发电有限责任公司年产2.5亿块粉煤灰烧结砖生产线项目工艺设计特点

1 项目建设的目的 秦皇岛发电有限责任公司原名秦皇岛热电厂,目前是一座装机容量100万千瓦的国有大型火力发电企业,年发电量68亿kWh.由于三期工程正在筹建,拟建2×30万kW供热发电机组.为了合理地利用三期工程排放的粉煤灰,不再新建储灰场污染环境,秦皇岛发电有限责任公司经过国内外详细考察,反复论证,认为最有效的大量利用途径之一是用其烧制粉煤灰烧结砖这种新型墙体材料.考虑到国内设备生产能力及粉煤灰掺量难以满足要求,因此,决定引进具有国际先进水平的设备.通过更换模具和改变原料配比,能生产高档清水砖、空心砖、不同规格与不同孔洞率的保温、承重与非承重砌块.     

A Customized Radiation Sensor for Ionization Collection

The measurement of absorbed doses is fundamental to radiation biology and oncology. A customized parallel plate radiation sensor was designed and fabricated as a precursor to investigating novel materials, such as carbon nanotubes, as a substitute for conventional metallic conducting plates or active volume medium. This sensor contains two thick and large-area electrodes that provide the sensor with a good signal-to-noise ratio. The 6 MV and 15 MV photon beams produced by a Varian Clinac 21 EX medical linear accelerator were used in the experiments. The linear accelerator was calibrated such that 1 monitor unit (MU) produces 1 cGy of dose in water with depth of 5 cm for a calibration geometry of source-to-axis distance equal to 100 cm and 10times10 cm² field size at the point of measurement. Ionization measurements were performed by varying the bias voltages, electrode separations, exposures, and angles of the incident beam to characterize the sensor. Signal saturation characteristics of the sensor with different electrode separations and exposures were investigated. This sensor displayed excellent linear response to exposure up to 600 MU. An analytical modeling using the pencil beam model and simulations based on device configuration were given to explain the results. In oblique incident beam experiments, the prototype sensor showed an accurate response compared to simulation results for a small field size of 1times1 cm². The sensor was tested to be suitable in the study of ionization collection efficiencies for different materials     

焦作市石灰岩开发及应用

焦作市石灰岩储量极为丰富,要把资源优势转变为经济优势,就要搞好综合开发利用,生产出科技含量高,具有市场竞争能力的新产品。本文旨在探讨石灰岩资源综合利用的新途径,为焦作矿业经济可持续发展作出新贡献,并为焦作市矿产资源规划提供科学依据。     

小麦胚的营养价值及应用开发

小麦胚是小麦籽粒的精华，本文论述了小麦胚蛋白和小麦胚芽油的营养价值、制取及其开发利用，并分析了小麦胚资源开发利用存在的问题及其途径。     

Effects and properties of poly(arylene ether benzonitrile)s of various molecular weights blended with sulfonated poly(ether ether ketone)

Poly(arylene ether benzonitrile) (PAEBN) was synthesized with 2,6‐dichlorobenzonitrile and biphenol. PAEBNs with various molecular weights (MWs), 1,640,000 and 185,000 g/mol, were synthesized by control of the stoichiometry of the monomers and were blended with sulfonated poly(ether ether ketone) (SPEEK). The effects of MW on the water uptake, swelling, methanol permeability, and proton conductivity of the SPEEK/PAEBN blend membranes were investigated. The molecular mobility of the SPEEK/PAEBN blends was also examined in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008