title: Improving isobutanol production in metabolically engineered Escherichia coli by co-producing ethanol and modulation of pentose phosphate pathway.
abstract: Redox imbalance has been regarded as the key limitation for anaerobic isobutanol production in metabolically engineered Escherichia coli strains. In this work, the ethanol synthetic pathway was recruited to solve the NADH redundant problem while the pentose phosphate pathway was modulated to solve the NADPH deficient problem for anaerobic isobutanol production. Recruiting the ethanol synthetic pathway in strain AS108 decreased isobutanol yield from 0.66 to 0.29 mol/mol glucose. It was found that there was a negative correlation between aldehyde/alcohol dehydrogenase (AdhE) activity and isobutanol production. Decreasing AdhE activity increased isobutanol yield from 0.29 to 0.6 mol/mol. On the other hand, modulation of the glucose 6-phosphate dehydrogenase gene of the pentose phosphate pathway increased isobutanol yield from 0.29 to 0.41 mol/mol. Combination of these two strategies had a synergistic effect on improving isobutanol production. Isobutanol titer and yield of the best strain ZL021 were 53 mM and 0.74 mol/mol, which were 51 % and 12 % higher than the starting strain AS108, respectively. The total alcohol yield of strain ZL021 was 0.81 mol/mol, which was 23 % higher than strain AS108.
authors.affiliation: College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.|Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China.
authors.forename: Zichun
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.|Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China.
authors.forename: Pingping
authors.initials: P
authors.lastname: Liu
authors.affiliation: College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China.
authors.forename: Dongguang
authors.initials: D
authors.lastname: Xiao
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China. zhang_xl@tib.cas.cn.|Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China. zhang_xl@tib.cas.cn.
authors.forename: Xueli
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000440:Butanols / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D007218:Industrial Microbiology; D060847:Metabolic Engineering; D009249:NADP / Q000378:metabolism; D010427:Pentose Phosphate Pathway; D010957:Plasmids / Q000235:genetics / Q000378:metabolism
chemical_list: D000440:Butanols; D003470:Culture Media; D029968:Escherichia coli Proteins; D009249:NADP; C040507:isobutyl alcohol; D000426:Alcohol Dehydrogenase; C068383:adhE protein, E coli; D000445:Aldehyde Oxidoreductases
keywords: Co-producing; Escherichia coli; Ethanol; Isobutanol; NADPH