Contribution of sulfur-containing precursors to release of hydrogen sulfide in sludge composting.

Hydrogen sulfide (H 2 S) production during composting can impact the environment and human health. Especially during the thermophilic phase, H 2 S is discharged in large quantities. However, in sludge composting, the contributions of different sulfur-containing precursors to H 2 S fluxes, key functional microorganisms, and key environmental parameters for reducing H 2 S flux remain unclear. Analysis of cysteine (Cys), methionine (Met), and sulfate (SO 4 2−) concentrations, multiple stepwise regression analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis of metagenomes showed that Cys was the main contributor to the production of H 2 S and that Met was among the main sources during the first three days of composting, while the SO 4 2− contribution to H 2 S was negligible. Fifteen functional genera involved in the conversion of precursors to H 2 S were identified by co-occurrence network analysis. Only Bacillus showed high temperature resistance (>50 °C) and the ability to reduce H 2 S. Redundancy analysis showed that total carbon (64.0 %) and pH (23.3 %) had significant effects on functional bacteria. H 2 S had a quadratic relationship with sulfur-containing precursors. All microbial network sulfur-containing precursors metabolism modules showed a highly significant relationship with Cys. [Display omitted] • Cysteine was the main contributor to H 2 S release during sludge composting. • Met was one of the main sources during first three days of composting. • SO 4 2− contribution to H 2 S was negligible. • Bacillus was the only thermotolerant core bacteria that can reduce H 2 S to cysteine. • Total carbon (TC) (64.0 %) and pH (23.3 %) significantly affect functional bacteria. [ABSTRACT FROM AUTHOR]