title: Enhanced H2 Production and Redirected Metabolic Flux via Overexpression of fhlA and pncB in Klebsiella HQ-3 Strain.
abstract: Genetic modifications are considered as one of the most important technologies for improving fermentative hydrogen yield. Herein, we overexpress fhlA and pncB genes from Klebsiella HQ-3 independently to enhance hydrogen molar yield. HQ-3-fhlA/pncB strain is developed by manipulation of pET28-Pkan/fhlA Kan(r) and pBBR1-MCS5/pncB Gm(r) as expression vectors to examine the synchronous effects of fhlA and pncB. Optimization of anaerobic batch fermentations is achieved and the maximum yield of biohydrogen (1.42 mol H2/mol of glucose) is produced in the range of pH 6.5-7.0 at 33-37 °C. Whole cell H2 yield is increased up to 40 % from HQ-3-fhlA/pncB, as compared with HQ-3-fhlA 20 % and HQ-3-pncB 12 % keeping HQ-3-C as a control. Mechanism of improved H2 yield is studied in combination with metabolic flux analysis by measuring glucose consumption and other metabolites including formate, succinate, 2,3 butanediol, lactate, acetate, ethanol, and hydrogen. The results suggest that under transient conditions, the increase in the total level of NAD by NAPRTase can enhance the rate of NADH-dependent pathways, and therefore, final distribution of metabolites is changed. Combined overexpression of fhlA and pncB eventually modifies the energy and carbon balance leading to enhanced H2 production from FHL as well as by NADH pathway.
authors.affiliation: Key Laboratory of Molecular Biophysics, the Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Jawed
authors.affiliation: Key Laboratory of Molecular Biophysics, the Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Pi
authors.affiliation: Key Laboratory of Molecular Biophysics, the Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.|College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.affiliation: Key Laboratory of Molecular Biophysics, the Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.|College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
authors.forename: Houjin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
authors.forename: Abdul
authors.initials: A
authors.lastname: Hakeem
authors.affiliation: Key Laboratory of Molecular Biophysics, the Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China. yanyunjun@hust.edu.cn.|College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China. yanyunjun@hust.edu.cn.
authors.forename: Yunjun
authors.initials: Y
authors.lastname: Yan
mesh_terms: D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007709:Klebsiella / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D006859:Hydrogen
keywords: Biohydrogen; Dark fermentation; Formate hydrogen lyase activator; Klebsiella HQ-3; Nicotinic acid phosphoribosyltransferase; Overexpression