Co-Metabolic Mechanism Analysis of Sulfidogenesis and Acidogenesis for Mariculture Solid Waste Treatment: Key Functional Microorganisms and Enzymes

Sulfidogenesis is a non-negligible process during the acidogenic fermentation of mariculture solid waste (MSW), and its interactions with acidogenesis are still unclear. To fill this gap, this study explored the co-metabolism mechanisms of acidogenesis and sulfidogenesis during the acidogenic fermentation of MSW with thermal (TH) pretreatment, alkaline fermentation (AF), and their combination (TH-AF) pretreatment. The interactions of sulfidogenesis and acidogenesis were altered by the changes in substrate availability and fermentation environment under the intervention of TH and AF pretreatments. Both acidogenesis and sulfidogenesis were boosted with TH pretreatment by supplying adequate substrates, and their competition for substrates was alleviated. Moreover, sulfidogenesis was constrained by 87.3% with TH-AF pretreatment, which reduced volatile fatty acid (VFA) consumption by sulfate reduction bacteria (SRB) and further enhanced the VFA accumulation. Notably, acidogenesis could be promoted by sulfidogenesis due to the enhancement of MSW hydrolysis and enrichment of acidogenic bacteria (Prolixibacter, Ruminococcus, etc.). Different pretreatments could redirect the metabolic pathways by changing the types of key functional microorganisms and enzymes in MSW anaerobic fermentation. Overall, this study provides useful information for developing an efficient and sustainable treatment of MSW.