Project description:Food waste is a major source of environmental pollution, as its landfills attribute to greenhouse gas emissions. This study developed a robust upcycling bioprocess that converts food waste into lactic acid through autochthonous fermentation and further produces biodegradable polymer polyhydroxybutyrate (PHB). Food can be stored without affecting its bioconversion to lactic acid, making it feasible for industrial application. Mapping autochthonous microbiota in the food waste fermentation before and after storage revealed lactic-acid-producing microorganisms dominate during the indigenous fermentation. Furthermore, through global transcriptomic and gene set enrichment analyses, it was discovered that coupling lactic acid as carbon source with ammonium sulfate as nitrogen source in Cupriavidus necator culture upregulates pathways, including PHB biosynthesis, CO2 fixation, carbon metabolism, pyruvate metabolism, and energy metabolism compared to pairing with ammonium nitrate. There was ∼90 % PHB content in the biomass. Overall, the study provides crucial insights into establishing a bioprocess for food waste repurposing.
Project description:Manufactured nanomaterials (MNMs) are increasingly incorporated into consumer products that are disposed into sewage. In wastewater treatment, MNMs adsorb to activated sludge biomass where they may impact biological wastewater treatment performance, including nutrient removal. Here, we studied MNM effects on bacterial polyhydroxyalkanoate (PHA), specifically polyhydroxybutyrate (PHB), biosynthesis because of its importance to enhanced biological phosphorus (P) removal (EBPR). Activated sludge was sampled from an anoxic selector of a municipal wastewater treatment plant (WWTP), and PHB-containing bacteria were concentrated by density gradient centrifugation. After starvation to decrease intracellular PHB stores, bacteria were nutritionally augmented to promote PHB biosynthesis while being exposed to either MNMs (TiO2 or Ag) or to Ag salts (each at a concentration of 5 mg L-1). Cellular PHB concentration and PhyloChip community composition were analyzed. The final bacterial community composition differed from activated sludge, demonstrating that laboratory enrichment was selective. Still, PHB was synthesized to near-activated sludge levels. Ag salts altered final bacterial communities, although MNMs did not. PHB biosynthesis was diminished with Ag (salt or MNMs), indicating the potential for Ag-MNMs to physiologically impact EBPR through the effects of dissolved Ag ions on PHB producers.