Synergistic humification in straw composting driven by lytic polysaccharide monooxygenase: Insights into enzymatic...

Agricultural lignocellulosic waste, especially cereal straw, presents significant environmental and management challenges worldwide. Although aerobic composting provides a sustainable way to recover value, its effectiveness is limited by the resistant nature of lignocellulose. This study explains how the addition of lytic polysaccharide monooxygenase (LPMO) enhances the synergistic humification process during straw composting. Compared with the control, the inclusion of LPMO accelerates the breakdown of cellulose, hemicellulose, and lignin, increasing their breakdown by 1.69 %, 3.95 %, and 1.31 %, respectively. It also alters the microbial community, boosting key groups such as Streptomyces, Devosia, Colletotrichum, and Coniochaeta. At the functional gene level, LPMO increases pathways for carbon synthesis and decreases carbon release. Meanwhile, genes involved in ammonification, nitrification, and assimilatory nitrate reduction (ANRA) become more abundant, while denitrification genes shift, with nirK increasing and nosZ decreasing. This LPMO-driven change in functional genes ultimately helps retain carbon and nitrogen. As a result, LPMO yields higher levels of humic acids (HA) and better humification metrics, as indicated by excitation-emission matrix (EEM) spectroscopy, suggesting more mature humic substances. These findings show that LPMO promotes humification by improving substrate accessibility, shaping microbial communities, and enhancing carbon and nitrogen processes, highlighting its potential to efficiently turn waste into high-quality compost.