Metabolism of sucrose in a non-fermentative Escherichia coli under oxygen limitation

Metabolism of sucrose in a non-fermentative Escherichia coli under oxygen limitation

Olavarria, Karel (TU Delft OLD BT/Cell Systems Engineering)
Fina, Albert (Student TU Delft)
Velasco Alvarez, M.I. (TU Delft OLD BT/Cell Systems Engineering)
van Loosdrecht, Mark C.M. (TU Delft BT/Environmental Biotechnology)
Wahl, S.A. (TU Delft OLD BT/Cell Systems Engineering)

2019

Biotechnological industry strives to develop anaerobic bioprocesses fueled by abundant and cheap carbon sources, like sucrose. However, oxygen-limiting conditions often lead to by-product formation and reduced ATP yields. While by-product formation is typically decreased by gene deletion, the breakdown of oligosaccharides with inorganic phosphate instead of water could increment the ATP yield. To observe the effect of oxygen limitation during sucrose consumption, a non-fermentative Escherichia coli K-12 strain was transformed with genes enabling sucrose assimilation. It was observed that the combined deletion of the genes adhE, adhP, mhpF, ldhA, and pta abolished the anaerobic growth using sucrose. Therefore, the biomass-specific conversion rates were obtained using oxygen-limited continuous cultures. Strains performing the breakdown of the sucrose by hydrolysis (SUC-HYD) or phosphorolysis (SUC-PHOSP) were studied in such conditions. An experimentally validated in silico model, modified to account for plasmid and protein burdens, was employed to calculate carbon and electron consistent conversion rates. In both strains, the biomass yields were lower than expected and, strikingly, SUC-PHOSP showed a yield lower than SUC-HYD. Flux balance analyses indicated a significant increase in the non-growth-associated ATP expenses by comparison with the growth on glucose. The observed fructose-1,6-biphosphatase and phosphoglucomutase activities, as well as the concentrations of glycogen, suggest the operation of ATP futile cycles triggered by a combination of the oxygen limitation and the metabolites released during the sucrose breakdown.

Carbon storage regulator A
Data reconciliation
Flux balance analysis
Plasmid burden
Sucrose phosphorolysis

http://resolver.tudelft.nl/uuid:76f4478b-3f30-44a7-8321-581b16ea1a5d

https://doi.org/10.1007/s00253-019-09909-6

0175-7598

Applied Microbiology and Biotechnology, 103 (15), 6245-6256

Institutional Repository

journal article

© 2019 Karel Olavarria, Albert Fina, M.I. Velasco Alvarez, Mark C.M. van Loosdrecht, S.A. Wahl