Periodic change in DO concentration for efficient poly-β-hydroxy-butyrate production using temperature-inducible recombinantEscherichia coli with proteome analysis

Abstract

Recombinant Escherichia coli strain harboring the λpR-pL promotor and heterologus poly-β- hydroxybutyrate (PHB) biosynthesis genes was used to investigate the effect of culture conditions on the efficient PHB production. The expression of phb genes was induced by a temperature upshift from 33°C to 38°C. The protein expression levels were measured by using two-dimensional electrophoresis, and the enzyme activities were also measured to understand the effect of culture temperature, carbon sources, and the dissolved oxygen (DO) concentration on the metabolic regulations. AcetylCoA is an important branch point for PHB production. The decrease in DO concentration lowers the citrate synthase activity, thus limit the flux toward the TCA cycle, and increase the flux for PHB production. Since NADPH is required for PHB production, the PHB production does not continue leading the overproduction of acetate and lac- tate. Based on these observations, a new operation was considered where DO concentration was changed periodically, and it was verified its usefulness for the efficient PHB production by experiments.