title: Novel redox potential-based screening strategy for rapid isolation of Klebsiella pneumoniae mutants with enhanced 1,3-propanediol-producing capability.
abstract: This report describes a novel redox potential (oxidoreduction potential [ORP])-based screening strategy for the isolation of mutants of Klebsiella pneumoniae which have an increased ability to produce 1,3-propanediol (1,3-PD). This method can be described as follows: first, to determine an ORP range which is preferred for the wild-type strain to grow and to produce 1,3-PD; second, to subject a chemically mutagenized culture to a reduced ORP level which is deleterious for the wild-type strain. Colonies that showed high specific growth rates at deleterious ORP levels were selected, and their abilities to produce 1,3-PD were investigated. In an ORP-based screening experiment where the ORP was controlled at -280 mV, 4 out of 11 isolated strains were recognized as positive mutant strains. A mutant which is capable of producing higher concentrations of 1,3-PD was subjected to fed-batch fermentations for further characterization. Its preferred ORP level (-280 mV) was significantly lower than that of its parent (-190 mV). The highest 1,3-PD concentration of the mutant was 915 mmol liter(-1), which was 63.1% higher than that of the parent. Metabolic-flux analysis suggested that the intracellular reductive branch of the mutant was strengthened, which improved 1,3-PD biosynthesis. The procedure and results presented here provide a novel method of screening for strains with improved product formation.
authors.affiliation: Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Chenyu
authors.initials: C
authors.lastname: Du
authors.forename: Yanping
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yin
authors.initials: Y
authors.lastname: Li
authors.forename: Zhu'an
authors.initials: Z
authors.lastname: Cao
mesh_terms: D000693:Anaerobiosis; D007711:Klebsiella pneumoniae / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D008660:Metabolism / Q000235:genetics; D009154:Mutation; D009243:NAD / Q000032:analysis; D010084:Oxidation-Reduction; D011409:Propylene Glycols / Q000378:metabolism*
chemical_list: D011409:Propylene Glycols; D009243:NAD; C041787:1,3-propanediol