Insights on anaerobic digestion foaming via association between bacterial metabolism and variations in microbiota

Abstract Background: Foaming in anaerobic digesters is considered a global concern due to significant impacts on process efficiency and operational costs. Although the importance of the organic loading rate on anaerobic foaming is now widely recognized, little is known about the key bacteria among the hundreds of species inducing foaming, especially the metabolite-microbiota correlation that influences foaming in anaerobic digesters.Results: Here, we show that the organic loading rate promotes foaming and decreases the performances of bench-scale batch digesters. Metabolomics analysis revealed distinct changes in the metabolic phenotype, including mainly short-chain fatty acids and amino acids, decreasing the surface tension and inducing foaming. Furthermore, the correlation analysis revealed that Clostridium clusters were the main microbes contributing to these metabolite foaming incidents.Conclusions: We provide the foaming microbes and metabolites in anaerobic digestion. Our findings elucidate the complex formation of foaming in anaerobic digestion and provide an effective early-warning for the control of foaming in full-scale digesters.