Methanogenic activities of sulfide and nitric oxide amended mesophilic, methanogenic culture: Role of nitrososufides complex

Sulfide (S2−) and nitric oxide (NO) can be formed in anaerobic digester if nitrate and sulfate were presented in the influent streams. This study noted by 4,5-diaminofluorescein diacetate (DAF-2DA) staining and confocal laser scanning microscopy (CLSM) the presence of nitrososulfides (SNO) complex in the S2− + NO-amended methanogenic sludge. Kinetic analysis suggested two-step kinetics involving chemical equilibrium between S2−, NO and SNO as step 1 and the slow conversion from SNO to N2O as step 2. The SNO complex was claimed to have higher inhibition effect than S2− or NO alone on the methangenic activities. Comments were made on the role of SNO complex for the interactions between sulfur, nitrogen and carbon metabolisms in anaerobic digestion.