Rhamnolipid Modulates Microbial Interspecies Electron Transfer for Synchronous Sulfidogenesis and Acidogenesis from...

Area of Science:

• Environmental Microbiology
• Biotechnology
• Biogeochemistry

Background:

• Synchronous sulfidogenesis and acidogenesis (SSA) are vital for waste treatment and resource recovery.
• Inefficient electron transfer and metabolic imbalance hinder SSA performance, particularly with sulfate-rich mariculture solid wastes (MSW).

Purpose of the Study:

• To investigate the role and mechanism of rhamnolipid (RL) in enhancing microbial interspecies electron transfer for SSA during MSW anaerobic fermentation.
• To elucidate how RL modulates microbial communities and metabolic pathways for improved SSA.

Main Methods:

• Anaerobic fermentation of MSW with varying RL concentrations.
• Analysis of sulfide and short-chain fatty acid yields.
• Characterization of extracellular polymeric substances (EPS) electroactivity.
• Metagenomic and metatranscriptomic analyses.
• Investigation of intracellular electron transfer pathways.

Main Results:

• RL significantly improved sulfide and short-chain fatty acid yields.
• RL enhanced EPS capacitance and electroactivity, facilitating electron transfer.
• RL promoted pili formation, redox mediator secretion (flavin and cytochrome c), and intracellular electron transfer to sulfate reductase.
• Metagenomic and metatranscriptomic data confirmed microbial enrichment and upregulation of key SSA-related genes.

Conclusions:

• Rhamnolipid plays a crucial role in optimizing SSA by enhancing microbial electron transfer and metabolic balance.
• RL's mechanism involves modulating EPS properties, promoting electron shuttles, and activating intracellular pathways.
• These findings offer novel insights into biosurfactant applications for improving waste treatment and resource recovery processes.