دانلود رایگان مقاله آنالیز فرآیند مبتنی بر مدل تولید هتروتروف-اتوتروف پلی

Abstract

Heterotrophic-autotrophic poly(3-hydroxybutyrate) (PHB) production is a promising process to produce bioplastics from CO2, which is more sustainable and safe compared to completely heterotrophic or completely autotrophic alternatives, respectively. In this study, pure culture heterotrophic-autotrophic PHB production was described through a mathematical model, which was validated on experimental datasets obtained with different organic substrates and applying different switching points from growth phase to PHB production phase. The mathematical model provided an accurate prediction of the dynamic behaviour of heterotrophic biomass growth and autotrophic PHB production. The model was subsequently applied for scenario analysis, to determine the optimal operation conditions in terms of O2 and NH4+-N concentrations in the fermentation medium. The optimal scenario for maximal PHB production was 0.224 mg/L oxygen concentration at ammonium-nitrogen (NH4+-N) free condition.

4. Conclusions

• Heterotrophic-autotrophic PHB production was described based on existing models for heterotrophic–heterotrophic PHB production and autotrophic–autotrophic PHB production, and applying parameter values previously obtained for these cases. The simulation results matched experimental data very well, without the need for additional model calibration except for the maximum PHB to residual cell ratio. • Both the type of organic substrate used in growth phase and the duration of heterotrophic growth phase negatively affect the autotrophic PHB production capacity (maximum PHB to residual cell ratio) in the heterotrophic-autotrophic PHB production process. Further research is recommended to establish correlations in this respect. • While it is generally known that oxygen stress conditions stimulate PHB production, too low O2 concentrations may have an adverse effect because of oxygen limitation. The optimal O2 concentration for PHB production was determined as 0.224 mg/L. Above this value, PHB production was restricted due to inhibition. • The optimal NH4 +-N concentration for biomass growth was 0.60-0.70 g/L NH4 +-N, while PHB production was maximal under NH4 +-N free condition.