title: Inactivation of aldehyde dehydrogenase: a key factor for engineering 1,3-propanediol production by Klebsiella pneumoniae.
abstract: Production of 1,3-propanediol (1,3-PD) from glycerol by Klebsiella pneumoniae is restrained by ethanol formation. The first step in the formation of ethanol from acetyl-CoA is catalyzed by aldehyde dehydrogenase (ALDH), an enzyme that competes with 1,3-PD oxidoreductase for the cofactor NADH. This study aimed to improve the production of 1,3-PD by engineering the ethanol formation pathway. An inactivation mutation of the aldA gene encoding ALDH in K. pneumoniae YMU2 was generated by insertion of a tetracycline resistance marker. Inactivation of ALDH resulted in a nearly abolished ethanol formation but a significantly improved 1,3-PD production. Metabolic flux analysis revealed that a pronounced redistribution of intracellular metabolic flux occurred. The final titer, the productivity of 1,3-PD and the yield of 1,3-PD relative to glycerol of the mutant strain reached 927.6 mmol L(-1), 14.05 mmol L(-1)h(-1) and 0.699 mol mol(-1), respectively, which were much higher than those of the parent strain. In addition, the specific 1,3-PD-producing capability (1,3-PD produced per gram of cells) of the mutant strain was 2-fold that of the parent strain due to a lower growth yield of the mutant. By increasing NADH availability, this study demonstrates an important metabolic engineering approach to improve the efficiency of oxidoreduction-coupled bioprocesses.
authors.affiliation: Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yin
authors.initials: Y
authors.lastname: Li
authors.forename: Chenyu
authors.initials: C
authors.lastname: Du
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.forename: Zhu'an
authors.initials: Z
authors.lastname: Cao
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics*; D019149:Bioreactors; D053898:Biosynthetic Pathways; D001709:Biotechnology / Q000379:methods*; D017931:DNA Primers; D000431:Ethanol / Q000378:metabolism; D020868:Gene Silencing; D005818:Genetic Engineering / Q000379:methods*; D005990:Glycerol / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009243:NAD / Q000378:metabolism; D011409:Propylene Glycols / Q000378:metabolism*; D013753:Tetracycline Resistance / Q000235:genetics
chemical_list: D017931:DNA Primers; D011409:Propylene Glycols; D009243:NAD; D000431:Ethanol; C041787:1,3-propanediol; D000444:Aldehyde Dehydrogenase; D005990:Glycerol