Diclofenac Removal by Actinobacterial Strains and Ecotoxicological Responses

Diclofenac (DCF) is a widely detected pharmaceutical whose persistence and biologically active transformation products raise environmental concern. This study evaluated DCF tolerance and removal by actinobacterial strains and integrated chemical performance with plant- and earthworm-based ecotoxicological responses. Phenotypic screening at 1, 5, and 10 g L−1 DCF revealed strain- and concentration-dependent responses in growth, sporulation, and pigment production, with Streptomyces sp. E5N50 and Streptomyces sp. Z2 selected for further study. In liquid assays, after 5 days of incubation, only low biomass production was observed when 50 mg L−1 DCF was supplied without glucose, relative to glucose-containing controls. E5N50 showed modest DCF removal (approximately 23–26%), while Z2 achieved 90.8% in glucose-supplemented medium and about 70% when glucose and ammonium were supplied. A seven-day time-course study with Streptomyces sp. Z2 showed that DCF removal continued after biomass had reached its maximum, suggesting that the process was not exclusively growth-associated. Ecotoxicological responses were organism- and endpoint-dependent. The glucose + DCF + Z2 treatment, associated with the highest DCF removal, significantly increased tomato radicle elongation, whereas glucose + ammonium + DCF + Z2 produced the most favorable Eisenia fetida response, with significantly reduced body-mass loss and increased coelomocyte abundance despite the lower DCF removal removalobserved in this treatment. Overall, Z2 exhibited potential for DCF removal under defined laboratory liquid-culture conditions, and the combined chemical and biological assessment highlighted that parent-compound removal and ecotoxicological improvement provide complementary measures of remediation performance.