Genetic and nutrient modulation of acetyl-CoA levels in Synechocystis for n-butanol production

Microb Cell Fact. 2015 Oct 16;14:167. doi: 10.1186/s12934-015-0355-9.

Abstract

Background: There is a strong interest in using photosynthetic cyanobacteria as production hosts for biofuels and chemicals. Recent work has shown the benefit of pathway engineering, enzyme tolerance, and co-factor usage for improving yields of fermentation products.

Results: An n-butanol pathway was inserted into a Synechocystis mutant deficient in polyhydroxybutyrate synthesis. We found that nitrogen starvation increased specific butanol productivity up to threefold, but cessation of cell growth limited total n-butanol titers. Metabolite profiling showed that acetyl-CoA increased twofold during nitrogen starvation. Introduction of a phosphoketolase increased acetyl-CoA levels sixfold at nitrogen replete conditions and increased butanol titers from 22 to 37 mg/L at day 8. Flux balance analysis of photoautotrophic metabolism showed that a Calvin-Benson-Bassham-Phosphoketolase pathway had higher theoretical butanol productivity than CBB-Embden-Meyerhof-Parnas and a reduced butanol ATP demand.

Conclusion: These results demonstrate that phosphoketolase overexpression and modulation of nitrogen levels are two attractive routes toward increased production of acetyl-CoA derived products in cyanobacteria and could be implemented with complementary metabolic engineering strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Butanol / chemistry
  • 1-Butanol / metabolism*
  • Acetyl Coenzyme A / metabolism*
  • Adenosine Triphosphate / metabolism
  • Aldehyde-Lyases / genetics
  • Aldehyde-Lyases / metabolism
  • Biomass
  • Metabolic Engineering
  • Metabolome
  • NAD / chemistry
  • NAD / metabolism
  • Nitrogen / metabolism
  • Synechocystis / metabolism*

Substances

  • NAD
  • Acetyl Coenzyme A
  • Adenosine Triphosphate
  • 1-Butanol
  • Aldehyde-Lyases
  • phosphoketolase
  • Nitrogen