A disintegrable lignin-based hydrogel enhances lignocellulose transformation and humification during cow manure–corn straw composting

A Lig-SA-CS hydrogel previously developed from DES-isolated corn-straw lignin was further evaluated in this study as a bio-based carrier for the co-encapsulation of Bacillus subtilis and Kosakonia cowanii during composting. The hydrogel showed progressive temperature-responsive structural changes, remaining relatively stable at 30–40 ℃ while undergoing swelling, structural weakening, and partial disintegration under elevated-temperature exposure. Composting results indicated that the hydrogel-encapsulated treatment (T2) maintained thermophilic conditions (>50 °C) for approximately 16 days, with the thermophilic phase ending around day 18 and exhibited greater moisture retention. Consequently, T2 reached the selected maturity-related thresholds (C/N < 15 and GI > 80%) by day 28, earlier than the free-bacteria treatment (T1, 35 days) and the control (CK, 42 days). Enhanced cellulase, LiP, MnP, and Lac activities in the T2 group were associated with improved lignocellulose transformation and increased formation of reducing sugars and polyphenols. FTIR-2D-COS analysis indicated a sequential structural evolution in T2, with lignin-derived aromatic structures responding earlier, followed by later responses of polysaccharide-related structures. Microbial community analysis identified 11 key taxa in T2, whose network positions and environmental associations suggested potential involvement in lignocellulose transformation and humification. Overall, the Lig-SA-CS-mediated bioaugmentation strategy enhanced lignocellulose transformation and humic acid formation, providing a promising material-assisted approach for the valorization of agricultural organic wastes and the production of humified compost products.