New insights into biodrying mechanism associated with tryptophan and tyrosine degradations during sewage sludge biodrying

Sewage sludge biodrying is a treatment that uses bio-heat generated from organic degradation to remove water from sewage sludge. Dewatering is still limited during biodrying, due to the presence of extracellular polymeric substances (EPS) in sludge. To study the biodrying mechanism associated with EPS compositions tryptophan and tyrosine degradations, this study investigated the microbial function in sludge biodrying material. This study conducted a taxonomic analysis of biodrying material; determined the most abundant genetic functions; analyzed the functional microorganisms involved in the degradations of tryptophan and tyrosine; and summarized the metabolic pathways. The results indicated efficient degradations of tryptophan and tyrosine were observed during the initial thermophilic phase; functional microorganisms were mainly from the phyla Firmicutes, Actinobacteria, and Proteobacteria, enriched with genes involved in amino acid transport and metabolism. These findings highlight the potentially important microorganisms and typical pathways that may help improve de-waterability during biodegradation.