Alkali-thermal humification treatment for simultaneous plant-growth-promoting compounds production and antibiotic removal from lincomycin fermentation residues

Fermentation-based antibiotic production results in the generation of nutrient-rich antibiotic mycelial residues with significant recycling potential. However, the high concentration of residual antibiotics restricts their application in high-value contexts. This study employs an alkali-thermal humification treatment (AHT) to safely manage lincomycin mycelial residues (LMRs) and assesses the feasibility of the resulting LMRs liquid as organic fertilizer. The removal efficiency for lincomycin attains 98.38 % at 200 °C under AHT. Density functional theory calculations combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) reveal that hydrothermal degradation of lincomycin occurs through processes such as hydrolyzation, N-demethylation, hydroxylation, and desulfurization. Post AHT, the LMRs liquid contains substantial quantities of amino acids (2.9 g/L) and humic acid (17.29 g/L) at 200 °C. Molecular networking identifies fatty acids and indole derivatives as plant-growth-promoting compounds in LMRs liquid, rendering it an appealing option for organic fertilization. Furthermore, a new pathway termed "Radicals-based polymerization" is proposed, which augments humic acid yield and organic stabilization. This study provides valuable insights into the comprehensive removal of antibiotics while concurrently recovering plant-growth-promoting compounds from antibiotic mycelial residues through the application of the AHT process.