Abstract:Objective Hyperthermophilic composting (hTC) exhibits significant advantages during organic solid waste treatment such as nitrous oxide mitigation, nitrogen retention, antibiotic resistance genes removal compared with those of conventional composting (cTC). Such advantages are closely linked with hyperthermophilic temperatures However, the reason for extremely high composting temperature remains unclear.Method Here, by using PICRUSt (physiological investigation of communities by reconstruction of unobserved states), the variations in microbial function during hTC and cTC using chicken manure were studied. The reason for the extremely high composting temperature in hTC was explored.Result Results show that the composting temperature could reach up to 80℃ and last for more than 5 days in hTC. hTC exhibited significant differences in both the composition of the microbial community and their metabolic pathways abundance during the hyperthermophilic stage. The abundances of thermogenesis related metabolic pathways (such as energy metabolism, carbohydrate metabolism) and aerobic respiration chain-related genes (such as NADH dehydrogenase gene, succinate dehydrogenase gene) were significantly increased during the hyperthermophilic stage (P < 0.05). Furthermore, the abundance of the enriched metabolic pathways and functional genes was significantly correlated with the temperature variation of hTC (P < 0.05). Random forest regression models comparing the predicted to actual composting temperatures found strong correlations in both treatments (for hTC, adjusted R2 =0.96; for cTC, adjusted R2 =0.97). The model indicated that the abundances of K03943(NADH dehydrogenase flavoprotein 2), k15862 (cytochrome c oxidase cbb3-type subunit I/II) and k05580 (NADH-quinone oxidoreductase subunit I) were the most important factors affecting the composting temperature in hTC. By comparison, the highest composting temperature of cTC was below 70℃, and the abundance of metabolic pathways and functional genes related to heat production was significantly negatively correlated with compost temperature (P < 0.05).Conclusion Our results suggest that the hTC community might metabolize organic matter more rapidly by significantly increasing the abundance of functional genes related to the aerobic respiration chain, thus increasing the rate of ATP synthesis and generating more metabolic heat.