title: Disruption of lactate dehydrogenase and alcohol dehydrogenase for increased hydrogen production and its effect on metabolic flux in Enterobacter aerogenes.
abstract: Hydrogen production by Enterobacter aerogenes from glucose was enhanced by deleting the targeted ldhA and adh genes responsible for two NADH-consuming pathways which consume most NADH generated from glycolysis. Compared with the wild-type, the hydrogen yield of IAM1183-ΔldhA increased 1.5 fold. Metabolic flux analysis showed both IAM1183-ΔldhA and IAM1183-Δadh exhibited significant changes in flux, including enhanced flux towards the hydrogen generation. The lactate production of IAM1183-ΔldhA significantly decreased by 91.42%, while the alcohol yield of IAM1183-Δadh decreased to 30%. The mutant IAM1183-ΔldhA with better hydrogen-producing performance was selected for further investigation in a 5-L fermentor. The hydrogen production of IAM1183-ΔldhA was 2.3 times higher than the wild-type. Further results from the fermentation process showed that the pH decreased to 5.39 levels, then gradually increased to 5.96, indicating that some acidic metabolites might be degraded or uptaken by cells.
authors.affiliation: Zhejiang Province Key Laboratory of Plant Secondary Metabolism and Regulation, College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, PR China; Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China; College of Chemistry and Life Sciences, Shenyang Normal University, Shenyang 110034, PR China.
authors.forename: Hongxin
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Liyan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Chong
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China. Electronic address: xhxing@tsinghua.edu.cn.
authors.forename: Xinhui
authors.initials: X
authors.lastname: Xing
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D056804:Biofuels; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods; D003227:Conjugation, Genetic; D021902:Enterobacter aerogenes / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D006019:Glycolysis; D006859:Hydrogen / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D009154:Mutation
chemical_list: D001426:Bacterial Proteins; D056804:Biofuels; D006859:Hydrogen; D000426:Alcohol Dehydrogenase; D007770:L-Lactate Dehydrogenase
keywords: Alcohol dehydrogenase; Conjugation; Enterobacter aerogenes; Lactate dehydrogenase; Metabolic flux analysis