The effect of inoculum/substrate on methane production in anaerobic digestion systems promoted by trace elements
The key regulatory role of trace elements(TEs)in anaerobic digestion systems has been established,but their intrinsic effects and mechanisms have not yet been fully elucidated.This study investigates the biological effects of TEs on biogas fermentation by examining the dynamic distribution of TEs under different inoculum/substrate(I/S)conditions in an anaerobic digestion system.It aims to clarify the interaction between the chemical form of TEs and the key influencing factors and microbial communities in the anaerobic fermentation process.Results from the 10 batches of experimental anaerobic digestion of glucose showed an 80.7%enhancement in cumulative methane production with the addition of TEs at an I/S ratio of 1.5.Among the three TEs(Fe,Co and Ni)added,the different chemical forms of elemental Fe showed the strongest correlation with pH,alkalinity,volatile fatty acids and ammonia nitrogen content in anaerobic digestion.The pH value was notably correlated with the four chemical forms of Fe.When the anaerobic digestion system operates stably,the relative abundance of Methanosaeta was the highest(53.8%),while the relative abundance of Methanosarcina was the highest(34.0%)when the anaerobic digestion system operates abnormally.