Detection and Mitigation of Nitrofuran and Chloramphenicol Residues in Mud Crab (Scylla olivacea) Aquaculture
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UNIVERSITI MALAYSIA SARAWAK
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The rapid expansion of mud crab (Scylla olivacea) aquaculture in Southeast Asia has contributed significantly to the global seafood industry but simultaneously raised critical concerns regarding food safety, public health, and environmental sustainability due to the unregulated use of banned antibiotics. Nitrofuran metabolites and chloramphenicol (CAP), recognized for their carcinogenic and genotoxic effects, continue to persist in aquaculture systems despite strict international bans and regulatory frameworks, exposing consumers to serious health risks and threatening the ecological integrity of surrounding environments. This study addresses the urgent research gap in developing sustainable mitigation strategies for antibiotic contamination in mud crab farming by simultaneously investigating the environmental distribution of residues and evaluating the novel application of probiotics to reduce them. Comprehensive sampling was conducted across commercial ponds, riverine systems, and natural mangrove habitats to identify the occurrence and bioaccumulation patterns of antibiotic residues, with water, soil, and biological samples including mud crabs, snails, and tilapia feed analyzed using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The baseline survey revealed that nitrofuran metabolites, particularly semicarbazide (SEM), reached their highest concentrations in intensive aquaculture ponds, with water and soil levels of 1.5 μg/L and 2.0 μg/kg respectively, compared to 0.1–0.3 μg/L and 0.2–0.4 μg/kg in natural mangrove habitats. Tissue-specific accumulation was evident, as crab shell tissues contained 3.51 ± 0.03 ng/g SEM, while muscle tissues showed only 0.33 ± 0.01 ng/g, suggesting exoskeletal deposition as a primary storage pathway. CAP residues, although less prevalent, were detected at 0.02 μg/kg in aquaculture water and 0.18 μg/kg in crab muscle, exceeding international trade tolerances and signaling a pressing food safety concern. To develop a residue mitigation approach, a 12-week feeding trial was conducted using Lacto-Sacc probiotics composed of Lactobacillus acidophilus, Enterococcus faecium, and Saccharomyces cerevisiae at dietary inclusion levels of 0%, 1%, and v 1.5%. The 1.5% Lacto-Sacc diet yielded remarkable outcomes by reducing SEM in crab shell tissues by 90%, from 3.51 ng/g to 0.193 ± 0.01 ng/g, while CAP residues in crab muscle declined to below detectable limits (<0.01 μg/kg). Simultaneously, probiotic supplementation improved aquaculture performance by increasing survival rates from 78.4% ± 2.3% in the control group to 93.2% ± 1.5% in the highest probiotic group, alongside significant improvements in water quality, with dissolved oxygen maintained at 7.5–8.0 mg/L and ammonia levels reduced to below 0.3 mg/L in treated ponds. These findings provide compelling evidence that probiotics not only enhance the health and survival of mud crabs but also serve as a practical, eco-friendly strategy to mitigate antibiotic residues, reducing environmental contamination and supporting compliance with international food safety standards. The environmental implications extend beyond farm-level improvements, as the adoption of probiotic-based mitigation reduces antibiotic discharge into mangrove and river ecosystems, diminishes the risk of antibiotic resistance development, and prevents the bioaccumulation of toxic residues in non-target species. The novelty of this study lies in its integration of environmental residue monitoring with a biologically driven solution, offering a scientific foundation for transitioning toward antibiotic-free, sustainable mud crab aquaculture. Furthermore, this approach aligns with global sustainability initiatives by improving consumer confidence in aquaculture products and strengthening the export competitiveness of mud crab industries in regions like Bangladesh, Malaysia, and Vietnam. In conclusion, this study establishes that dietary probiotics can serve as an effective, scalable, and environmentally responsible alternative to chemical-based disease management in mud crab aquaculture, bridging a critical research gap in residue mitigation and offering a pathway toward safer seafood production.