The exponential growth in fisheries has led to a concurrent surge in global fish production, reaching approximately 178 million tonnes by the year 2020. This increase in fish production, however, results in huge quantities of fish waste being generated throughout the processing stages, raising serious concerns related to its disposal. Estimates suggest that 27% of globally produced fish is lost as bio-waste during processing, which can result in adverse environmental effects if not managed scientifically.
Among the various forms of fish waste, fish scales constitute a substantial portion but have received limited attention in terms of valorization and management strategies. Despite being biodegradable, fish scales exhibit recalcitrance to enzymatic degradation due to their rigid structural and chemical properties, posing obstacles to their efficient disposal. In this context, a study was carried out to seek an eco-friendly yet simple method for managing fish scale bio-waste using bacteria. T he presence of scale-degrading bacteria in the marine and terrestrial environment was investigated, which yielded a total of 83 bacterial isolates, with 19 isolates from seawater and 13 from fish scale and soil samples exhibiting gelatinase activity. Notably, 13 seawater isolates and 11 isolates from fish scale and soil samples demonstrated promising fish scale-degrading capabilities. Three isolates among them displayed efficient scale degradation across media containing varying concentrations of peptone.
Furthermore, t wo isolates of Lysinibacillus fusiformis (KT02 and KT05) were examined for their efficacy in degrading scales from mixed carp and pink perch. Both strains efficiently degraded the fish scales within five days, with KT02 demonstrating superior degradation capability. The b iochemical analyses of the fish scales before and after degradation by Lysinibacillus fusiformis KT02 revealed significant differences (p < 0.05) in protein and ash contents, indicating successful degradation. Furthermore, changes in amino acid, mineral, and fatty acid compositions underscore the transformative potential of bacterial remediation in converting fish scale waste into useful bioactive compounds. These results highlight the promising role of bacterial remediation in mitigating the environmental impact of fish scale biowaste. The efficient degradation of fish scales by Lysinibacillus fusiformis isolates shows potential of this approach for sustainable waste management in the fisheries industry . Thus, bacterial s cale degradation holds promise for yielding valuable bioactive compounds, eventually contributing to circular economy strategies. Future research endeavours should focus on elucidating the mechanisms of scale hydrolysis , optimizing bacterial degradation processes, and studying bioactivities of scale degradation products to understand their potential biomedical applications in order to maximize resource utilization and minimize environmental pollution.