Accumulation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Azotobacter vinelandii with different 3HV fraction in shake flasks and bioreactor

In the present study, the production of poly(3-hydroxybutyrate-co-3–hydroxyvalerate) (PHBV) by Azotobacter vinelandii was evaluated in shake flasks and bioreactors, utilizing different precursors and oxygen transfer rates (OTRs). In shake flask cultures, the highest PHBV yield from sucrose (0.16 g g^–1) and 3-hydroxyvalerate (3HV) fraction in the PHA chain (27.4 mol%) were obtained with valerate (1.0 g L⁻¹). In the bioreactor, the cultures were grown under oxygen-limited conditions, and the maximum OTR (OTR_max) was varied by adjusting the agitation rate. In the cultures grown at low OTR_max (4.3 mmol L⁻¹ h⁻¹), the intracellular content of PHBV (73% w w⁻¹) was improved, whereas a maximum 3HV fraction (35 mol %) was obtained when a higher OTR_max (17.2 mmol L⁻¹ h⁻¹, to 600 rpm) was employed. The findings obtained suggest that the PHBV production and the content of 3HV incorporated into the polymer were affected by the OTR. Based on the evidence, it is possible to produce PHBV with a different composition by varying the OTR of the culture; thus, the approach in this study could be used to scale up PHBV production.