Efficient biodegradation of gibberellic acid residues by Candida tropicalis GAJ-2 and its proposed mechanism

The extensive use of gibberellic acid (GA 3 ) in agriculture leads to residues in agricultural products, raising potential human health concerns, particularly where residue limits are not established. Microbial degradation offers a promising remediation strategy, yet progress is limited by the scarcity of highly efficient degraders and an incomplete understanding of underlying mechanisms. Here, we identify a Candida tropicalis strain (GAJ-2) that achieves 83.63 % GA 3 removal within 120 h, exceeding the efficiencies reported for previously described GA 3 -degrading strains such as Aspergillus niger and Enterococcus mundtii (55.58 %–56.90 % within 5–7 days), and we further validate its residue-removal capacity in representative fruits and vegetables. Mechanistic analyses indicate that viable-cell-mediated GA 3 biotransformation by GAJ-2 mainly involves dehydroxylation, decarboxylation, and cleavage of the tetracyclic diterpenoid scaffold. These transformations are rationalized by the electronic distribution of oxygen-bearing functional groups and the electrophilic nature of C11 and adjacent positions in GA 3 . Multi-omics analyses further reveal enhanced energy metabolism and catalytic functions, together with efflux-pump regulation, and show a strong association between GA 3 catabolism and the upregulation of key enzymes ( e.g. , decarboxylases and dehydrogenases). Docking-based interaction profiling suggests that GA 3 associates with key proteins primarily through noncovalent interactions, including hydrogen bonding, van der Waals contacts, and electrostatic effects. Collectively, this work provides multi-level experimental and computational evidence supporting a plausible framework for GA 3 biodegradation by GAJ-2 and informs improved strategies for GA 3 pollution control.