Medium-chain carboxylates production by co-fermentation of sewage sludge and macroalgae

The co-fermentation of sewage sludge and macroalgae at different mixing ratios was performed for medium chain carboxylates (MCCs) production. The results showed that MCCs production was enhanced in co fermentation groups due to the abundant readily available organics supplied by macroalgae and the alkaline buffer capacity provided by sewage sludge. Highest MCCs concentration of 112.7 mmol C/L (25.5 mmol C/g VSadded) was obtained in the co-fermentation group with sludge/macroalgae ratio of 4:6, which was higher than MCCs produced from the mono-fermentation of sewage sludge (41.7 mmol C/L, 9.4 mmol C/g VSadded) or macroalgae (79.9 mmol C/L, 18.1 mmol C/g VSadded). Microbial analysis showed that species from genus Romboutsia, Terrisporobacter, Clostridium_sensu_stricto_12, Paraclostridium, unclassified_f_Peptostreptococcaceae and Caproiciproducens were significantly positively correlated with MCCs production. Metabolic pathways analysis demonstrated that the co-fermentation promoted the chain elongation process by stimulating the rate-limiting steps involved in the conversion of ethanol to Acetyl-CoA and circular fatty acid biosynthesis pathway.

Automated summary

The co-fermentation of sewage sludge and macroalgae can enhance the production of medium chain carboxylates (MCCs) and improve the utilization efficiency of organic matter. The highest MCCs concentration was obtained in the co-fermentation group with a sludge/macroalgae ratio of 4:6.