Polyhydroxybutyrate production from lactate using a mixed microbial culture.

Area of Science:

• Microbiology
• Biotechnology
• Environmental Science

Background:

• Poly-3-hydroxybutyrate (PHB) is a biopolymer with diverse applications.
• Enriching microbial cultures for high PHB yield is crucial for cost-effective bioproduction.
• Understanding substrate impact on microbial community structure and function is key.

Purpose of the Study:

• To investigate lactate and a lactate/acetate mixture for enriching PHB-producing mixed cultures.
• To evaluate the PHB accumulation capacity and production rates of newly enriched cultures.
• To determine the effect of different carbon sources on microbial community composition and PHB functionality.

Main Methods:

• Enrichment of mixed microbial cultures in sequencing batch reactors (SBRs) under feast-famine conditions.
• Operation of SBRs with specific cycle lengths, solids retention times (SRTs), and temperatures.
• Characterization of PHB content, production rates, and dominant microbial species in enriched cultures.

Main Results:

• A novel gammaproteobacterium-dominated culture enriched on lactate achieved over 90 wt% PHB in 6 hours, a record rate.
• A mixed culture enriched on lactate/acetate reached 84 wt% PHB in just over 8 hours.
• Predominant species included Plasticicumulans acidivorans and Thauera selenatis, with evidence of substrate specialization.

Conclusions:

• Substrate choice significantly influences the microbial composition of PHB-producing cultures.
• Despite compositional shifts, the overall functionality and efficiency of the PHB production process remained largely unaffected.
• Lactate is a highly effective substrate for enriching superior PHB-accumulating bacterial consortia.