A biologically-based regulatory method for the lignin phenol monomers to specific components and electron transfer...

The lignin was degraded into phenol and then oxidized into quinones of chemical structure of humic substances (HS) in the polyphenol pathway, and it was considered a crucial process contributing to redox capabilities of HS. However, the microbial formation and degradation of lignin phenol monomers, and their effects on the humification process remains unclear. In this study, p-hydroxybenzoic acid, syringic acid), 4-coumaric acid, and ferulic acid were found to significantly influenced the electron transfer capacity (ETC) of HS. Moreover, 4 microbial groups (Group 1, 2, 3 and 4) were identified, among with 18 microorganisms (15 bacteria and 3 fungi) were linked to lignin degradation and humic substance synthesis processes. The alteration in the HS structure indicated that the aromatic core (Groups 2 and 3) and the outer structure containing aromatic groups (Groups 1 and 2) were formed in the mesophilic and thermophilic phases, accompanied by a progressive enhancement of ETC. Subsequently, the HS formed outer layer structure carrying alkyl and carboxyl groups (Groups 1), and the ETC decreased in the mature phase. Therefore, the study proposed regulatory strategies including adjustment of organic nitrogen level, stimulation of key microbial activity, and the suppression of ongoing HS structural transformations mediated by Group 1 at different phases of composts. These strategies aim to promote the generation of crucial phenol monomers and their subsequent transformation, providing a novel approach to enhance the quality of straw compost.