Enhanced hydrogen production from formic acid by formate hydrogen lyase-overexpressing Escherichia coli strains.
ABSTRACT Genetic recombination of Escherichia coli in conjunction with process manipulation was employed to elevate the efficiency of hydrogen production in the resultant strain SR13 2 orders of magnitude above that of conventional methods. The formate hydrogen lyase (FHL)-overexpressing strain SR13 was constructed by combining FHL repressor (hycA) inactivation with FHL activator (fhlA) overexpression. Transcription of large-subunit formate dehydrogenase, fdhF, and large-subunit hydrogenase, hycE, in strain SR13 increased 6.5- and 7.0-fold, respectively, compared to the wild-type strain. On its own, this genetic modification effectively resulted in a 2.8-fold increase in hydrogen productivity of SR13 compared to the wild-type strain. Further enhancement of productivity was attained by using a novel method involving the induction of the FHL complex with high-cell-density filling of a reactor under anaerobic conditions. Continuous hydrogen production was achieved by maintaining the reactor concentration of the substrate (free formic acid) under 25 mM. An initial productivity of 23.6 g hydrogen h(-1) liter(-1) (300 liters h(-1) liter(-1) at 37 degrees C) was achieved using strain SR13 at a cell density of 93 g (dry weight) cells/liter. The hydrogen productivity reported in this work has great potential for practical application.
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ABSTRACT: Until 1972, Kawasaki disease, or acute febrile infantile mucocutaneous lymph node syndrome (MCLS), was considered in Japan to be a nonfatal disease with a favorable prognosis. Based on the findings from two autopsy cases of MCLS, we believe that sudden and unexpected death during convalescence may be due to arterial lesions, especially those involving the coronary artery, that resemble those of periarteritis nodosa. Of 29 autopsy cases of MCLS, gathered from all over Japan, all exhibited arteritis lesions (eg, aneurysm due to coronary arteritis). Such vascular pathological findings may in fact represent the same entity as infantile periarteritis nodosa. Whether infantile periarteritis nodosa can be identified with the adult type is still debatable. The particular manifestations of infantile periarteritis nodosa might be related to severe vasculitis. Autopsy cases of infantile periarteritis nodosa without MCLS manifestations are being collected and studied.Archives of pathology & laboratory medicine 03/1976; 100(2):81-6. · 2.58 Impact Factor
Article: Requirement of ArcA for redox regulation in Escherichia coli under microaerobic but not anaerobic or aerobic conditions.[show abstract] [hide abstract]
ABSTRACT: In Escherichia coli, the two-component regulatory ArcAB system functions as a major control system for the regulation of expression of genes encoding enzymes involved in both aerobic and anaerobic catabolic pathways. Previously, we have described the physiological response of wild-type E. coli to changes in oxygen availability through the complete range from anaerobiosis to full aerobiosis (S. Alexeeva, B. de Kort, G. Sawers, K. J. Hellingwerf, and M. J. Teixeira de Mattos, J. Bacteriol. 182:4934-4940, 2000, and S. Alexeeva, K. J. Hellingwerf, and M. J. Teixeira de Mattos, J. Bacteriol. 184:1402-1406, 2002). Here, we address the question of the contribution of the ArcAB-dependent transcriptional regulation to this response. Wild-type E. coli and a mutant lacking the ArcA regulator were grown in glucose-limited chemostat cultures at controlled levels of oxygen availability ranging from full aerobiosis to complete anaerobiosis. A flux analysis of the distribution of catabolic fluxes over parallel pathways was carried out, and the intracellular redox state (as reflected by the NADH/NAD ratio) was monitored for all steady states. Deletion of ArcA neither significantly altered the in vivo activity of the pyruvate dehydrogenase complex and pyruvate formate lyase nor significantly affected catabolism under fully aerobic and fully anaerobic conditions. In contrast, profound effects of the absence of ArcA were seen under conditions of oxygen-restricted growth: increased respiration, an altered electron flux distribution over the cytochrome o- and d-terminal oxidases, and a significant change in the intracellular redox state were observed. Thus, the ArcA regulator was found to exert major control on flux distribution, and it is concluded that the ArcAB system should be considered a microaerobic redox regulator.Journal of Bacteriology 02/2003; 185(1):204-9. · 3.83 Impact Factor