title: Evaluation of genetic manipulation strategies on D-lactate production by Escherichia coli.
abstract: In order to rationally manipulate the cellular metabolism of Escherichia coli for D: -lactate production, single-gene and multiple-gene deletions with mutations in acetate kinase (ackA), phosphotransacetylase (pta), phosphoenolpyruvate synthase (pps), pyruvate formate lyase (pflB), FAD-binding D-lactate dehydrogenase (dld), pyruvate oxidase (poxB), alcohol dehydrogenase (adhE), and fumarate reductase (frdA) were tested for their effects in two-phase fermentations (aerobic growth and oxygen-limited production). Lactate yield and productivity could be improved by single-gene deletions of ackA, pta, pflB, dld, poxB, and frdA in the wild type E. coli strain but were unfavorably affected by deletions of pps and adhE. However, fermentation experiments with multiple-gene mutant strains showed that deletion of pps in addition to ackA-pta deletions had no effect on lactate production, whereas the additional deletion of adhE in E. coli B0013-050 (ackA-pta pps pflB dld poxB) increased lactate yield. Deletion of all eight genes in E. coli B0013 to produce B0013-070 (ackA-pta pps pflB dld poxB adhE frdA) increased lactate yield and productivity by twofold and reduced yields of acetate, succinate, formate, and ethanol by 95, 89, 100, and 93%, respectively. When tested in a bioreactor, E. coli B0013-070 produced 125 g/l D-lactate with an increased oxygen-limited lactate productivity of 0.61 g/g h (2.1-fold greater than E. coli B0013). These kinetic properties of D-lactate production are among the highest reported and the results have revealed which genetic manipulations improved D-lactate production by E. coli.
authors.affiliation: Center for Bioresource and Bioenergy, School of Biotechnology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhou
authors.forename: Zhi-Rui
authors.initials: ZR
authors.lastname: Zuo
authors.forename: Xian-Zhong
authors.initials: XZ
authors.lastname: Chen
authors.forename: Dan-Dan
authors.initials: DD
authors.lastname: Niu
authors.forename: Kang-Ming
authors.initials: KM
authors.lastname: Tian
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Prior
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.forename: Gui-Yang
authors.initials: GY
authors.lastname: Shi
authors.forename: Suren
authors.initials: S
authors.lastname: Singh
authors.forename: Zheng-Xiang
authors.initials: ZX
authors.lastname: Wang
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics; D005285:Fermentation; D017353:Gene Deletion; D005818:Genetic Engineering; D019344:Lactic Acid / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009154:Mutation; D030781:Organisms, Genetically Modified
chemical_list: D029968:Escherichia coli Proteins; D019344:Lactic Acid