Self-heating hyperthermophilic valorization of crop straw by Calditerricola sp. DKC0303: From thermotolerance mechanisms to engineering-scale biofertilizer production

Efficient conversion of crop straw into stable and agronomically valuable products is essential for improving the circular use of lignocellulosic agricultural residues. However, conventional composting is often limited by slow lignocellulose degradation and insufficient microbial activity under high-temperature conditions. In this study, Calditerricola sp. DKC0303 was used to establish a self-heating hyperthermophilic bioconversion process for crop straw valorization. At 85 °C, DKC0303 showed strong lignocellulose-degrading capacity under straw-amended conditions, with degradation efficiencies of 72.4%, 59.6%, and 31.8% for cellulose, hemicellulose, and lignin. Multi-level physiological and omics analyses indicated that its high-temperature functionality was associated with coordinated enhancement of extracellular protection, stress-response regulation, DNA repair, protein quality control, and energy metabolism. In a 12-ton composting system, DKC0303 inoculation established a hyperthermophilic phase without external heating, accelerated lignocellulosic organic matter conversion, increased humic substance formation, and improved compost maturity. The final compost reduced phytotoxicity and promoted seedling growth, increasing tomato and pepper biomass by 44.6% and 48.7%, respectively. These findings provide a basis for developing self-heating hyperthermophilic inoculation as a low-input approach for energy-efficient conversion of crop straw into mature biofertilizer.