Enrichment of PHA-producing bacteria under continuous substrate supply

Area of Science:

• Microbiology
• Biotechnology
• Environmental Science

Background:

• Polyhydroxyalkanoate (PHA) bioplastics are biodegradable polymers produced by microorganisms.
• Traditional enrichment of PHA-producing bacteria relies on a feast-famine substrate supply strategy.
• Optimizing microbial communities for efficient PHA accumulation is crucial for sustainable bioplastic production.

Purpose of the Study:

• To investigate the effect of continuous substrate feeding versus pulsed feeding on PHA-producing microbial community enrichment.
• To compare PHA production rates and storage capacities under different feeding regimes.
• To identify the key factors driving the enrichment of high-performance PHA producers.

Main Methods:

• Two sequencing batch reactors (SBRs) were operated with different acetate feeding strategies.
• Reactor 1: Continuous substrate (acetate) dosing.
• Reactor 2: Half acetate dosed at the start of the cycle, half continuously.

Main Results:

• Continuous feeding in Reactor 1 enriched Zoogloea sp., resulting in 53 wt.% PHA accumulation but with lower production rates and storage capacity.
• A mixed feeding strategy (Reactor 2) enriched Plasticicumulans acidivorans, achieving 85 wt.% PHA accumulation.
• The presence of a distinct feast phase was critical for enriching superior PHA-producing bacteria.

Conclusions:

• Periodic substrate excess (feast phase) is essential for enriching bacteria with high PHA-producing capacity.
• Continuous substrate feeding alone is insufficient for enriching top-tier PHA producers.
• The famine phase is not a prerequisite for enriching efficient PHA-accumulating microbial communities.