%A Halmschlag,Birthe
%A Putri,Sastia P.
%A Fukusaki,Eiichiro
%A Blank,Lars M.
%D 2020
%J Frontiers in Bioengineering and Biotechnology
%C
%F
%G English
%K biopolymer,Bacillus subtilis,natto,Metabolomics,natural product
%Q
%R 10.3389/fbioe.2020.00038
%W
%L
%M
%P
%7
%8 2020-January-30
%9 Original Research
%#
%! Metabolic impact of γ-PGA production
%*
%<
%T Identification of Key Metabolites in Poly-γ-Glutamic Acid Production by Tuning γ-PGA Synthetase Expression
%U https://www.frontiersin.org/articles/10.3389/fbioe.2020.00038
%V 8
%0 JOURNAL ARTICLE
%@ 2296-4185
%X Poly-γ-glutamic acid (γ-PGA) production is commonly achieved using glycerol, citrate, and L-glutamic acid as substrates. The constitutive expression of the γ-PGA synthetase enabled γ-PGA production with Bacillus subtilis from glucose only. The precursors for γ-PGA synthesis, D- and L-glutamate, are ubiquitous metabolites. Hence, the metabolic flux toward γ-PGA directly depends on the concentration and activity of the synthetase and thereby on its expression. To identify pathway bottlenecks and important metabolites that are highly correlated with γ-PGA production from glucose, we engineered B. subtilis strains with varying γ-PGA synthesis rates. To alter the rate of γ-PGA synthesis, the expression level was controlled by two approaches: (1) Using promoter variants from the constitutive promoter Pveg and (2) Varying induction strength of the xylose inducible promoter Pxyl. The variation in the metabolism caused by γ-PGA production was investigated using metabolome analysis. The xylose-induction strategy revealed that the γ-PGA production rate increased the total fluxes through metabolism indicating a driven by demand adaption of the metabolism. Metabolic bottlenecks during γ-PGA from glucose were identified by generation of a model that correlates γ-PGA production rate with intracellular metabolite levels. The generated model indicates the correlation of certain metabolites such as phosphoenolpyruvate with γ-PGA production. The identified metabolites are targets for strain improvement to achieve high level γ-PGA production from glucose.