Particle size effects in microbial characteristics in thermophilic anaerobic digestion of cattle manure containing copper oxide

Roles of bulk-, micron-, and nano-copper oxide (CuO) on methane production, microbial diversity, functions during thermophilic anaerobic digestion (AD) were investigated in this study. Results showed that bulk-, micron-, and nano-CuO promoted methane production by 27.8%, 47.6%. and 83.1% compared to the control group, respectively. Microbial community analysis demonstrated that different particle sizes could cause various shifts on bacteria community, while had little effect on archaeal diversity. Thereinto, bacteria belonging to phylum Firmicutes and Coprothermobacterota dominated in enhanced hydrolysis process in groups with nano-CuO and bulk-CuO, respectively, while micron-CuO had stronger promotion on the abundances of hydrolytic and fermentative bacteria belonging to families Peptostreptococcaceae, Caloramatoraceae, Erysipelotrichaceae, and Clostridiaceae, than other two CuO sizes. Metabolic pathways revealed that energy-related metabolism and material transformation in bacteria were only boosted by micron-CuO, and nano-CuO and bulk-CuO were important to methanogenic activity, stimulating energy consumption and methane metabolism, respectively.

Automated summary

This study investigated the roles of different particle sizes of copper oxide (CuO) in thermophilic anaerobic digestion (AD) on methane production, microbial diversity, and functions. The results showed that bulk-, micron-, and nano-CuO had varying degrees of promotion on methane production. Microbial community analysis revealed that different particle sizes of CuO affected bacterial community composition more than archaeal diversity. Metabolic pathway analysis showed that only the micron-CuO promoted energy-related metabolism and material transformation in bacteria, while nano-CuO and bulk-CuO were important for methanogenic activity and methane metabolism, respectively.