Substrate preference triggers metabolic patterns of indigenous microbiome during initial composting stages.

Composting organic waste is a sustainable recycling method in agricultural systems, yet the microbial preferences for different substrates and their influence on composting efficiency remain underexplored. Here, 210 datasets of published 16S ribosomal DNA amplicon sequences from straw and manure composts worldwide were analyzed, and a database of 278 bacterial isolates was compiled. Substrate-driven microbiome variations were most prominent during the initial composting stages. Indigenous synthetic communities exhibit substrate-specific adaptations, increasing compost temperatures by 2 %-10 %, microbial abundance by 44 %-233 %, and microbial activity by 26 %-60 %. Key dissolved substrates, such as choline and succinic acid in straw compost, and phloretin and uric acid in manure compost, drive these microbial preferences. These findings highlight how substrate-specific microbiomes can be engineered to enhance microbial activity, accelerate temperature rise, and extend the thermophilic phase, providing a targeted framework to improve composting efficiency and tailor strategies to different organic waste types.