Bacillus licheniformis accelerates humification process through enhancing shikimate pathway and lignin degradation in pilot-scale composting

Lignin degradation and shikimate pathway are important pathways for humus precursor synthesis. The effects of lignin degradation and Sap on humification process of pig manure composting with Bacillus licheniformis were discussed. The study found 35.60 % lignin degradation in experimental group (CT) versus 26.80 % in the control group (CK). The humus components showed increased heterogeneity in compost: The humus substances content increased by 8.71 % in the CK and by 20.72 % in the CT, while the humic acid content increased by 81.48 % and 170.01 % respectively in the CK and the CT. In addition, CT significantly increased the abundances of Saccharomonospora and Planifilum. Meanwhile, CT stimulated key genes of s shikimate pathway in microorganisms, enhanced the activity of AA family protease, accelerated lignin degradation and shikimate pathway, and promoted the synthesis of amino acids. The production of humus in compost was promoted by lignin-protein and Maillard pathways, which provided a theoretical basis for directed humification of compost through microbial metabolic pathways.