A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temp...A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen（DO） on cold active lipase production by batch culture of metagenomic library recombinant clone（CAPL3） from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 ℃ for the first 15 h, and then switched to30 ℃. The cold active lipase activity and productivity reached 315.2 U·ml^-1and 8.08 U·ml^-1·h^-1, respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30℃. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34℃, 30% during 0–15 h;30 ℃, 30% during 15–18 h, and 30 ℃, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml^-1at 39 h, which was 28.8% higher than that achieved without temperature and DO control（275.3 U·ml^-1）.展开更多
WC powders were uniformly coated by Ni nanoparticles through a combined chemical co-precipitation and subsequent high temperature hydrogen reduction strategy(abbreviated as CM-WCN),and then were consolidated by vacuum...WC powders were uniformly coated by Ni nanoparticles through a combined chemical co-precipitation and subsequent high temperature hydrogen reduction strategy(abbreviated as CM-WCN),and then were consolidated by vacuum sintering at 1450°C for 1 h to obtain WC−Ni cemented carbides.The microstructure and properties of the as-consolidated CM-WCN were investigated.The average grain size of WC in the consolidated CM-WCN was calculated to be in the range of 3.0−3.8μm and only few pores were observed.A relative density of 99.6%,hardness of HRA 86.5 and bending strength of 1860 MPa were obtained for the CM-WCN−10wt.%Ni,and the highest impact toughness of 6.17 J/cm^(2 )was obtained for the CM-WCN−12wt.%Ni,surpassing those of the hand mixed WC−Ni(HM-WCN)cemented carbides examined in this study and the other similar materials in the literature.CM-WCN cemented carbides possess excellent mechanical properties,due to their highly uniform structure and low porosity that could be ascribed to the intergranular-dominated fracture mode accompanied by a large number of plastic deformation tears of the bonding phase.In addition,the corrosion resistance of CM-WCN was superior to that of HM-WCN at the Ni content of 6−12 wt.%.展开更多
基金Supported by the Hi-Tech Research and Development Program of China(863 program of China2012AA092103)China Ocean Mineral Resources R&D Association(DY125-15-T-06)
文摘A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen（DO） on cold active lipase production by batch culture of metagenomic library recombinant clone（CAPL3） from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 ℃ for the first 15 h, and then switched to30 ℃. The cold active lipase activity and productivity reached 315.2 U·ml^-1and 8.08 U·ml^-1·h^-1, respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30℃. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34℃, 30% during 0–15 h;30 ℃, 30% during 15–18 h, and 30 ℃, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml^-1at 39 h, which was 28.8% higher than that achieved without temperature and DO control（275.3 U·ml^-1）.
基金the financial supports from the National Natural Science Foundation of China (Nos. 51778213, 52078189)the Fundamental Research Funds for the Central Universities, China (No. B200202073)。
文摘WC powders were uniformly coated by Ni nanoparticles through a combined chemical co-precipitation and subsequent high temperature hydrogen reduction strategy(abbreviated as CM-WCN),and then were consolidated by vacuum sintering at 1450°C for 1 h to obtain WC−Ni cemented carbides.The microstructure and properties of the as-consolidated CM-WCN were investigated.The average grain size of WC in the consolidated CM-WCN was calculated to be in the range of 3.0−3.8μm and only few pores were observed.A relative density of 99.6%,hardness of HRA 86.5 and bending strength of 1860 MPa were obtained for the CM-WCN−10wt.%Ni,and the highest impact toughness of 6.17 J/cm^(2 )was obtained for the CM-WCN−12wt.%Ni,surpassing those of the hand mixed WC−Ni(HM-WCN)cemented carbides examined in this study and the other similar materials in the literature.CM-WCN cemented carbides possess excellent mechanical properties,due to their highly uniform structure and low porosity that could be ascribed to the intergranular-dominated fracture mode accompanied by a large number of plastic deformation tears of the bonding phase.In addition,the corrosion resistance of CM-WCN was superior to that of HM-WCN at the Ni content of 6−12 wt.%.
