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Metabolic engineering of Escherichia coli for the production of putrescine: A four carbon diamine
Qian, Zhi-Gang,Xia, Xiao-Xia,Lee, Sang Yup Wiley Subscription Services, Inc., A Wiley Company 2009 Biotechnology and bioengineering Vol.104 No.4
<P>A four carbon linear chain diamine, putrescine (1,4-diaminobutane), is an important platform chemical having a wide range of applications in chemical industry. Biotechnological production of putrescine from renewable feedstock is a promising alternative to the chemical synthesis that originates from non-renewable petroleum. Here we report development of a metabolically engineered strain of Escherichia coli that produces putrescine at high titer in glucose mineral salts medium. First, a base strain was constructed by inactivating the putrescine degradation and utilization pathways, and deleting the ornithine carbamoyltransferase chain I gene argI to make more precursors available for putrescine synthesis. Next, ornithine decarboxylase, which converts ornithine to putrescine, was amplified by a combination of plasmid-based and chromosome-based overexpression of the coding genes under the strong tac or trc promoter. Furthermore, the ornithine biosynthetic genes (argC-E) were overexpressed from the trc promoter, which replaced the native promoter in the genome, to increase the ornithine pool. Finally, strain performance was further improved by the deletion of the stress responsive RNA polymerase sigma factor RpoS, a well-known global transcription regulator that controls the expression of ca. 10% of the E. coli genes. The final engineered E. coli strain was able to produce 1.68 g L<SUP>−1</SUP> of putrescine with a yield of 0.168 g g<SUP>−1</SUP> glucose. Furthermore, high cell density cultivation allowed production of 24.2 g L<SUP>−1</SUP> of putrescine with a productivity of 0.75 g L<SUP>−1</SUP> h<SUP>−1</SUP>. The strategy reported here should be useful for the bio-based production of putrescine from renewable resources, and also for the development of strains capable of producing other diamines, which are important as nitrogen-containing platform chemicals. Biotechnol. Bioeng. 2009; 104: 651–662 © 2009 Wiley Periodicals, Inc.</P>
Qian, Zhi‐,Gang,Xia, Xiao‐,Xia,Lee, Sang Yup Wiley Subscription Services, Inc., A Wiley Company 2011 Biotechnology and bioengineering Vol.108 No.1
<P><B>Abstract</B></P><P>A five carbon linear chain diamine, cadaverine (1,5‐diaminopentane), is an important platform chemical having many applications in chemical industry. Bio‐based production of cadaverine from renewable feedstock is a promising and sustainable alternative to the petroleum‐based chemical synthesis. Here, we report development of a metabolically engineered strain of <I>Escherichia coli</I> that overproduces cadaverine in glucose mineral salts medium. First, cadaverine degradation and utilization pathways were inactivated. Next, <SMALL>L</SMALL>‐lysine decarboxylase, which converts <SMALL>L</SMALL>‐lysine directly to cadaverine, was amplified by plasmid‐based overexpression of the <I>cadA</I> gene under the strong <I>tac</I> promoter. Furthermore, the <SMALL>L</SMALL>‐lysine biosynthetic pool was increased by the overexpression of the <I>dapA</I> gene encoding dihydrodipicolinate synthase through the replacement of the native promoter with the strong <I>trc</I> promoter in the genome. The final engineered strain was able to produce 9.61 g L<SUP>−1</SUP> of cadaverine with a productivity of 0.32 g L<SUP>−1</SUP> h<SUP>−1</SUP> by fed‐batch cultivation. The strategy reported here should be useful for the bio‐based production of cadaverine from renewable resources. Biotechnol. Bioeng. 2011; 108:93–103. © 2010 Wiley Periodicals, Inc.</P>
Zhi-gang Min,Chen Niu,Qiu-li Zhang,Ming Zhang,Yu-cheng Qian 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.5
Objective: To identify the optimal factors in diffusion tensor imaging for predicting corticospinal tract (CST) injury caused by brain tumors. Materials and Methods: This prospective study included 33 patients with motor weakness and 64 patients with normal motor function. The movement of the CST, minimum distance between the CST and the tumor, and relative fractional anisotropy (rFA) of the CST on diffusion tensor imaging, were compared between patients with motor weakness and normal function. Logistic regression analysis was used to obtain the optimal factor predicting motor weakness. Results: In patients with motor weakness, the displacement (8.44 ± 6.64 mm) of the CST (p = 0.009), minimum distance (3.98 ± 7.49 mm) between the CST and tumor (p < 0.001), and rFA (0.83 ± 0.11) of the CST (p < 0.001) were significantly different from those of the normal group (4.64 ± 6.65 mm, 14.87 ± 12.04 mm, and 0.98 ± 0.05, respectively) (p = 0.009, p < 0.001, and p < 0.001). The frequencies of patients with the CST passing through the tumor (6%, p = 0.002), CST close to the tumor (23%, p < 0.001), CST close to a malignant tumor (high grade glioma, metastasis, or lymphoma) (19%, p < 0.001), and CST passing through infiltrating edema (19%, p < 0.001) in the motor weakness group, were significantly different from those of the patients with normal motor function (0, 8, 1, and 10%, respectively). Logistic regression analysis showed that decreased rFA and CST close to a malignant tumor were effective variables related to motor weakness. Conclusion: Decreased fractional anisotropy, combined with closeness of a malignant tumor to the CST, is the optimal factor in predicting CST injury caused by a brain tumor.
Research on the Oxidation-Protective Coatings for Carbon/Carbon Composites
Li, He-Jun,Fu, Qian-Gang,Huang, Jian-Feng,Zeng, Xie-Rong,Li, Ke-Zhi Korean Carbon Society 2005 Carbon Letters Vol.6 No.2
Anti-oxidation coatings are the key technique for carbon/carbon (C/C) composites used as the thermal structural materials. The microstructure and oxidation behavior of several kinds of high-performance ceramic coatings for C/C composites prepared in Northwestern Polytechnical University were introduced in this paper. It showed that the ceramic coatings such as SiC, Si-$MoSi_2$, SiC-$MoSi_2$, $Al_2O_3$-mullite-SiC and SiC/yttrium silicate/glass coatings possessed excellent oxidation resistance at high temperatures, and some of these coatings were characterized with excellent thermal shock resistance. The SiC-$MoSi_2$ coating system has the best oxidation protective property, which can effectively protect C/C composites from oxidation up to 1973 K. In addition, the protection and failure reasons of some coatings at high temperature were also provided.