Effects of rhamnolipid and Tween-80 on cellulase activities and metabolic functions of the bacterial community during chicken manure composting

Metabolism by microorganisms is the basis of composting. In this study, the dynamic changes in the enzyme activity levels, bacterial community structure, and metabolism functions were investigated during chicken manure composting with an added bio-surfactant (rhamnolipid) or chemical surfactant (Tween-80). The results showed that rhamnolipid and Tween-80 improved the quality of the finished compost in terms of the C/N ratio, water-soluble carbon content, germination index, E4/E6 ratio, and the cellulase activity, especially with Tween-80. Furthermore, the bacterial communities were determined by high-throughput sequencing, and their metabolism functions were evaluated using the PICRUSt and Biolog methods. Tween-80 greatly influenced the bacterial community structure, where it enhanced the abundances of bacteria that degrade cellulose and lignin (e.g., members of the order Bacillales) and the capacities for carbohydrate and amino acid metabolism. Network analysis also showed that the order Bacillales was closely related to the metabolism of characteristic carbon sources, especially carbohydrates.