Phosphate-inducible poly-hydroxy butyrate production dynamics in CO2 supplemented upscaled cultivation of engineered Phaeodactylum tricornutum

Abstract Diatoms such as Phaeodactylum tricornutum are emerging sustainable alternatives to traditional eukaryotic microbial cell factories. In order facilitate a viable process for production of heterologous metabolites, rational genetic design specifically tailored metabolic requirements well optimised culture conditions required. this study we investigated the effect constitutive and inducible expression poly-3-hydroxybutyrate (PHB) pathway in P. using non-integrative episomes 3 different configurations. Constitutive led downregulation at least one individual gene out three ( phaA , phaB phaC ) was outperformed by expression. To further asses optimise dynamics PHB accumulation driven alkaline phosphatase 1 promoter, upscaled lab-scale bioreactors tested supplemented CO 2 on biomass accumulation. While ambient cultivation resulted maximum yield 2.3% dry weight (CDW) day 11, under elevated concentrations peaked 1.7% CDW 8, coincident with titres 27.9 mg L −1 that were approximately threefold higher than . With other more valuable bio-products mind, these results highlight importance substrate availability supply additional reduction equivalents boost relieve potential enzymatic bottlenecks improved product