Revealing Fungal Diversity in Mesophilic and Thermophilic Habitats of Sewage Sludge Composting by Next-Generation Sequencing

The accumulation of sewage sludge is a severe problem in many countries. Its utilization through composting has the potential to become a widely applied technology. From this perspective, our study investigated the diversity of fungi in mesophilic and thermophilic habitats when composting biosolids, cow manure and wheat straw. It was conducted using a metagenomic approach and next-generation Illumina HiSeq2000 sequencing to reveal the fungal diversity. We found significantly enhanced microbial activity in the thermophilic phase. In contrast, the activity of enzyme β-glucosidase was 29% higher in the mesophilic zone. The range of α-diversity values was more pronounced in the mesophilic habitats than in the thermophilic habitats based on diversity indices. At the class level, the mesophilic fungi were represented by Sordariomycetes—58.7%, Pezizomycetes—15.1% and Agaricomycetes—12.3%, while the most abundant thermophilic fungi found were Sordariomycetes—39.5% and Pezizomycetes—9.8%. In the further clarification of genera diversity, it is striking that at 37.2 °C, Psathyrella was the most abundant with 35.91%, followed by Chaetomidium with 20.11%. Among the thermophiles, Thielavia and Mortierella were the most common. Further research on microbial diversity changes over time is needed to manage the metabolic processes in obtaining quality soil amendment.