Enhancing PHA production through metal-organic frameworks: Mechanisms involving superproton transport and bacterial metabolic pathways

The effective fermentation of organic waste for polyhydroxyalkanoate (PHA) production is crucial for waste pollution prevention and comprehensive utilization. Glycerol, a common component of organic waste and a by-product of biodiesel production, can serve as a valuable raw material for PHA synthesis. This study explored the potential of metal-organic frameworks (MOFs), specifically MOF-808, to enhance the PHA production by Cupriavidus necator (C. necator) and Bacillus cereus (B. cereus) using glycerol as the substrate. Our results demonstrated that the addition of MOF-808 significantly promoted PHA synthesis without altering the PHA composition. Notably, the proportion of PHA to cell dry weight (CDW) increased significantly (P < 0.05) in both C. necator (from 17.17% to 30.43%) and B. cereus (from 11.30% to 37.93%), with a shortened growth period observed in the latter. The enhanced superproton transport properties of MOF-808 elevated the ATP energy supply level, regulated coenzyme A metabolism, and modulated the PHA synthesis pathway in the bacterial strains. Additionally, MOF-808 improved the utilization of the PHA precursor acetyl-CoA by C. necator, and enhanced the PHA production in B. cereus by facilitating cell growth and PHA synthesis in two distinct stages. Importantly, the recovered MOF-808 structure remained stable, enabling potential recycling. This study provides compelling evidence for the enhancement of PHA production and offers valuable insights into the utilization of organic waste as a valuable resource.