Model-based data evaluation of polyhydroxybutyrate producing mixed microbial cultures in aerobic sequencing batch and...

Area of Science:

• Biotechnology and biochemical engineering
• Microbial biotechnology
• Sustainable materials science

Background:

• Polyhydroxyalkanoates (PHAs) are bioplastics produced by mixed microbial cultures.
• Current two-step PHA production (enrichment in SBR, production in fed-batch) involves dynamic bioreactor systems.
• Rapid changes in substrate, PHA, and biomass concentrations complicate process characterization and rate identification.

Purpose of the Study:

• To develop and validate a structured approach for evaluating PHA production experiments in sequencing batch reactors (SBRs) and fed-batch systems.
• To improve the accuracy of biomass-specific conversion rates in dynamic microbial culture environments.
• To enable reliable comparison and characterization of PHA-producing microbial consortia.

Main Methods:

• A five-step evaluation framework was implemented: comprehensive parameter measurement (including off-gas), data correction, calculation of gas evolution rates, conversion balancing, and metabolic modeling.
• Measurements included substrate (acetate), nitrogen source (ammonia), and PHA (polyhydroxybutyrate - PHB) conversions.
• The approach was applied to numerous datasets from PHA-producing cultures.

Main Results:

• Steps 1-4 successfully generated high-quality datasets.
• Metabolic modeling (Step 5) provided accurate estimates for substrate, ammonia, and PHB conversions, adhering to material balances.
• Modeled off-gas conversions showed some deviation from measured values, potentially due to stoichiometric inaccuracies.

Conclusions:

• The developed structured approach is highly effective for evaluating dynamic SBR and fed-batch experiments in PHA production.
• It ensures data quality and enables precise determination of biomass-specific conversion rates.
• The method serves as a valuable tool for assessing and comparing PHB-producing microbial cultures.