Activated carbon facilitates Saccharomyces cerevisiae colonization in an electron-donor self-sustaining chain elongation fermentation system.

Chain elongation is a promising technology for the resourceful utilization of organic waste and wastewater. Glucose and starch were used as model substrates to demonstrate that exogenous electron donors are essential for chain elongation. Glucose and starch affects caproate synthesis in the chain elongation lacking of electron donor producing microorganisms, while glucose and ethanol significantly influence the succession of microbial community. Activated carbon enhanced the colonization of Saccharomyces cerevisiae and strengthened the chain elongation process, with the relative abundance of S. cerevisiae significantly increasing by 28.3 % and 176.1 % in the presence of 5 g/L and 10 g/L of activated carbon, respectively. The reverse β-oxidation (RBO) cycle was identified as the primary metabolic pathway for caproate production. The relative abundance of genes encoding key enzymes in the RBO pathway showed increase. This study provides valuable insights into optimizing chain elongation, paving the way for sustainable and efficient organic waste valorization technologies.