Efficient allelochemical removal from continuous capsicum cultivation using horseradish peroxidase–loaded biochar

Abstract Secretion and long-term accumulation of phenolic acid allelopathic substances are critical factors decreasing yield in continuous capsicum cropping systems. However, there are limited effective technologies and methods for removing these substances. In this study, biochar (BC) with ultrahigh specific surface area and pore volume was prepared via K 2 CO 3 etching, called carbonate-modified biochar (CBC). Then, it was loaded with horseradish peroxidase (HRP) under glutaraldehyde crosslinking conditions to form HRP–CBC. The maximum loading capacity of HRP reached 311.46 U g −1 . Under various factors, the degradation efficiency of allelopathic substances such as ferulic acid followed the order HRP–CBC > HRP–BC > HRP, indicating that the combination of alkaline etching and enzyme immobilization enhances ferulic acid degradation. At a HRP–CBC dose of 2 U mL −1 and pH 7, the degradation of 20 mg L −1 ferulic acid was achieved within 6 h. Furthermore, this method demonstrated excellent degradation performance against multiple phenolic acid compounds responsible for yield reduction in continuous chili pepper cropping systems. HRP–CBC exhibited superior stability, enhanced stress resistance, and broad application potential. The inhibitory effect of ferulic acid on chili seed germination disappeared after degradation by immobilized HRP. Liquid chromatography–mass spectrometry and ecotoxicity analyses confirmed that HRP–CBC degraded ferulic acid into less toxic small organic molecules through a free radical-mediated mechanism. Therefore, a modified biochar immobilized with HRP offers a promising strategy for removing phenolic acid allelopathic substances from continuous cropping systems. Graphical Abstract