Short-term aerobic pretreatment of swine manure enhances short-chain fatty acid production in anaerobic fermentation: performance and mechanisms.

Facing the dual challenges of swine manure pollution control and carbon resource recovery under intensive farming conditions, conventional anaerobic fermentation technologies are limited in their application for high-value conversion due to low hydrolysis efficiency and high operational costs. To address these limitations, this study proposed a self-heating strategy using short-term aerobic pretreatment, aiming to optimize substrate pretreatment and enhance the synthesis of short-chain fatty acids during subsequent acidogenic fermentation. The results demonstrated that this pretreatment approach rapidly activates aerobic microbial metabolism and significantly improves the substrate's overall properties, as reflected by a decreased pH and increased conductivity, moisture content, total protein, and total organic carbon, and effectively promotes the solubilization and hydrolysis of organic matter, thereby increasing the bioavailability of substrates for anaerobic fermentation. Microbial community analysis further revealed that the pretreatment process selectively enriched hydrolytic-acidogenic bacteria, including Clostridium, Bacillus, Paenibacillus, and Streptomyces, while synergistically enhancing the activities of key metabolic enzymes such as cellulase, protease, and acetate kinase. These effects systematically strengthened the metabolic pathways from substrate degradation to acid synthesis. As a result, the short‑term aerobic pretreatment achieved a significant improvement in SCFAs production and energy efficiency. Specifically, the total SCFAs yield increased by 21.31% ± 4.23%, while energy consumption declined by 94.48% ± 1.48%. In addition, the unit acid production cost amounted to merely 4.37% ± 0.15% of that required for the conventional low‑temperature thermal treatment. Moreover, it significantly reduced the abundance of high-risk antibiotic resistance genes in fermentation residues, highlighting its environmental benefits. This study elucidates the synergistic mechanism of short-term aerobic pretreatment across "substrate-microorganism-enzyme" dimensions, confirming it as an efficient, economical, and sustainable pretreatment technology for swine manure resource recovery.