Bioaugmentation with Bacillus thermoamylovorans under hydrogen peroxide supplementation for enhanced straw compost humification during thermophilic phase.

Straw, a recalcitrant lignocellulosic feedstock for composting, exhibits poor biodegradability, while effective strategies for enhancing microbial degradation and humification remain limited. This study aimed to investigate the effects of Bacillus thermoamylovorans bioaugmentation under hydrogen peroxide (H2O2) supplementation during the thermophilic phase on organic matter degradation, humus formation, and microbial community succession during composting. A comparison of three composting treatments [control (CK), H2O2 addition (T1), and H2O2 addition combined with bioaugmentation (T2)] showed that T2 accelerated temperature elevation and prolonged the thermophilic phase. Cumulative measured H2O2 equivalents during days 4-8 were 40.44 % and 12.15 % higher in T2 than in CK and T1, respectively. At the end of composting, T2 enhanced lignocellulose degradation, with dissolved organic carbon increasing by 76.61 % compared with CK . Enhanced humification in T2 resulted in 24.79 % and 32.49 % increases in humus and humic acid content, respectively, compared with CK. High-throughput sequencing and network analysis revealed that bioaugmentation under H2O2 supplementation selectively enriched thermophilic Bacillota, with Bacillus abundance being 32.27 % higher than that in T1 during the early thermophilic stage and threefold higher during the late thermophilic stage. Key thermophilic taxa within Bacillota showed positive associations with H2O2, temperature, and humus formation. PICRUSt2 prediction further revealed enrichment of amino sugar and nucleotide sugar metabolism, ascorbate and aldarate metabolism, and inositol phosphate metabolism during the early thermophilic stage, together with increased potentials for superoxide dismutase-, respiratory chain-, and oxidase-associated functions, suggesting enhanced carbon turnover and redox regulation. These findings suggest that exploiting the intrinsic H2O2-producing potential of an inoculated thermophilic strain under H2O2 supplementation may serve as a targeted bioaugmentation strategy for enhancing straw compost humification.