Poly-beta-hydroxybutyrate metabolism in dynamically fed mixed microbial cultures

Area of Science:

• Environmental microbiology
• Biochemical engineering
• Wastewater treatment

Background:

• Poly-beta-hydroxybutyrate (PHB) is an energy storage compound in bacteria.
• Understanding PHB kinetics is crucial for optimizing biological nutrient removal in wastewater treatment.
• Mixed activated sludge cultures are commonly used in sequencing batch reactors (SBRs).

Purpose of the Study:

• To investigate the kinetics of PHB production and degradation in a mixed activated sludge culture.
• To determine substrate storage efficiency under dynamic feeding conditions.
• To compare experimental data with metabolic modeling predictions.

Main Methods:

• Cultivation of mixed activated sludge in a sequencing batch reactor (SBR).
• Dynamic feeding of acetate to achieve high intracellular PHB concentrations (fPHB).
• Measurement of specific PHB production and acetate uptake rates.
• Comparison with literature data and metabolic modeling equations.

Main Results:

• The ratio of specific PHB production to acetate uptake (q(feast)PHB/-q(feast)Ac) was constant under dynamic feeding (SRT > 2d).
• This ratio was 0.6 Cmol/Cmol aerobically and 0.4-0.5 Cmol/Cmol anoxically.
• PHB degradation followed first-order kinetics dependent on intracellular PHB content, independent of electron acceptor or SRT.

Conclusions:

• Kinetic descriptions for PHB production and degradation were established.
• These kinetics are applicable to dynamic fed wastewater treatment systems.
• The findings provide valuable trends for modeling PHB dynamics in biological wastewater treatment.