Analysis of population heterogeneity with reporter strains

(M.Sc. Manh Dat Hoang)

Population heterogeneity describes the diverse behaviour of cells of an isogenic culture in bioprocesses. This phenomenon especially arises in bioreactors of industrial scale due to the occurrence of inhomogeneity. A better understanding of the mechanisms behind the formation of population heterogeneity could support future scale-up procedures from homogeneous laboratory bioreactors to large-scale production processes.

The aim of this research project is the investigation of process conditions leading to the formation of subpopulations in a fed-batch process with E. coli converting glycerol to L-phenylalanine at laboratory scale. Gradients can be generated in laboratory scale by the application of a two-compartment reactor consisting of a stirred-tank reactor coupled to a plug flow reactor in by-pass. Thus, microorganisms can be exposed to different gradients like substrate deficiency or excess inside the plug flow reactor. 

To monitor the formation of subpopulations in bioprocesses in vivo, an L-phenylalanine producing E. coli reporter strain shall be used. For that, the expression of fluorescent proteins are coupled to specific cellular properties allowing the screening of growth rate, general stress response, oxygen availability and the product formation of single cells. The expressed fluorescence of the producing cells at different process conditions can be analyzed by flow cytometry and occurring subpopulations can be isolated and further characterized with a cell sorter.


  • Hoang MD, Polte I, Frantzmann L, von den Eichen N, Heins AL, Weuster-Botz D (2023): Impact of mixing insufficiencies on L-phenylalanine production with an Escherichia coli reporter strain in a novel two-compartment bioreactor. Microb Cell Fact 22: 153.
  • Hoang MD, Riessner S, Oropeza Vargas JE, von den Eichen N, Heins AL (2023): Influence of varying pre-culture conditions on the level of population heterogeneity in batch cultures with an Escherichia coli triple reporter strain. Microorganisms 11: 1763.
  • Hoang MD, Doan DT, Schmidt M, Kranz H, Kremling A, Heins A-L (2023): Application of an Escherichia coli triple reporter strain for at-line monitoring of single-cell physiology during L-phenylalanine production. Eng Life Sci 23: e2100162.
  • Doan DT, Hoang MD, Heins A-L, Kremling A (2022): Applications of coarse-grained models in metabolic engineering. Front Mol Biosc 9: 806213.
  • Heins A-L, Hoang MD, Weuster-Botz D (2022): Advances in automated real-time flow cytometry for monitoring of bioreactor processes. Eng Life Sci, 22: 260-278.