Findings in lignin-acclimated composting: microbial shifts enhance humification

The aim of domesticated composting with regular straw replenishment is to obtain an efficient microbial agent to overcome the limitation posed by refractory lignin on straw resource utilization. However, it remains unclear whether a highly efficient lignin-degrading microbe would still contribute to lignin humification. Therefore, A 125-day domesticated composting experiment was conducted to explore the metabolic preferences of microorganisms at different stages. Results showed that humification in lignin-domesticated composting was primarily driven by humic acids (HA). Compared with fungi, bacterial community diversity was higher, and bacteria accounted for 93.45 % of core microbial metabolic functions, indicating a higher metabolic conversion potential. Furthermore, bacteria represented over 81.82 % of humification-related core microorganisms, demonstrating their dominant role in HA formation. Moreover, the microbial metabolic preferences indicated that microorganisms mainly carried out degradation pathways and gradually shifted towards humification as domestication progressed. This reflected the metabolic transformation of microorganisms in lignin-domesticated composting, which was not dominated by degradation alone. This study elucidated lignin-acclimated composting impacts on humus formation and microbial dynamics.