Effect of moisture content on the evolution of bacterial communities and organic matter degradation during...

Composting is an excellent way to recycle biogas residues into a stable, non-toxic agricultural end product. In this study, the dynamic changes of physical-chemical parameters and bacterial community in three groups of bioaugmentation composting systems at different moisture contents (MC) of 50% (MC50), 60% (MC60) and 70% (MC70) were monitored. The differences of bacterial communities in composts with different initial MC were compared, and the interaction between biological and non-biological parameters was also explored. The results revealed that after 30 days of composting, the biogas residues compost in MC60 reached highest temperature of 64 °C, total Kjeldahl nitrogen (TKN) of 2%, seed germination index (GI) of 110%, and the longest thermophilic period duration of 5 days (55 °C). Additionally, the result of high-throughput sequencing showed that the diversity of bacterial communities in MC60 was the highest, and the abundance of Actinobacteria (16.93-52.63%), Firmicutes (8.71-56.75%), and Proteobacteria (16.88-46.95%) in all groups were the highest at phylum level. The LEfSe analysis indicated that the abundance of Ochrobactrum and Cellulomonadaceae in MC60 was significantly (p < 0.05) higher than with other treatments. Moreover, canonical correspondence analysis (CCA) indicated thermophilic period duration is significantly (p < 0.05) positively correlated with Paenibacillus. Besides, it was found the relative abundance of Nocardiopsis and Georgenia has a significant (p < 0.01) correlation with the fertilizer efficiency of compost. These results showed that controlling the initial moisture content at 60% can improve the maturity and fertilizer efficiency of compost, and enable the bacteria beneficial to composting to gain the advantage of proliferation.