Valorization of waste activated sludge for microalgae cultivation: Differential roles and mechanisms of extracellular and intracellular substances.

Intracellular substances from waste activated sludge boost Chlorella pyrenoidosa biomass to 0.37 g L^-1, while extracellular substances improve microalgal flocculation and harvesting.

• Why it matters: Efficiently utilizing waste activated sludge (WAS) can mitigate environmental risks and recover valuable resources, addressing a critical gap in sustainable waste management and bioresource production.
• What they did: The study compared crushed sludge extract, extracellular, and intracellular substances from municipal WAS, analyzing their effects on microalgae growth, biomass, and metabolite production through biochemical assays and transcriptomic analysis.
• The result: Findings demonstrate that ISS enhances biomass, ESS improves flocculation, and CCS increases metabolite yields, providing a foundation for sustainable microalgae cultivation and harvesting from WAS.