Effects of microbial inoculum on microbial community and enzyme activity involved in nitrogen-sulfur metabolism during sewage sludge composting

The purpose of this study was to access the effects of thermotolerant nitrifying microorganisms and sulfur-oxidizing bacteria on microbial community and enzyme activity involved in nitrogen‑sulfur metabolism during laboratory-scale sewage sludge (SS) composting，and to do a microbial-environmental factor association analysis to promote composting key species for nitrogen‑sulfur transformation in the body. The microbial community structure and the activities variation of six key enzyme involved were detected. The microbial inocula added had little impact on the diversity of the microbial community but changed its succession direction, and the abundance of Actinobacteria was decreased obviously of inoculation treatment (TR). The three dominant genera and indicator species in TR were significantly correlated with the conversion of nitrogen and sulfur. The addition of microbial inocula promoted the conversion of nitrogen and sulfur in SS compost, and increased the activities of the key enzymes and the microbial genera involved in nitrogen‑sulfur conversion. In other words, the nitrification and sulfur oxidation were enhanced simultaneously in the later stage of composting in TR.