Ketoprofen Tolerance and Removal by Rhodococcus spp

Bacteria of the genus Rhodococcus are degraders of various ecotoxicants, including pharmaceuticals, yet their activity against ketoprofen-a non-steroidal anti-inflammatory drug (NSAID) frequently detected in aquatic environments-remains poorly explored. To address this gap, we assessed the tolerance and removal of ketoprofen across Rhodococcus strains from the Regional Specialised Collection of Alkanotrophic Microorganisms (official acronym IEGM, WFCC number 285). All 175 strains tolerated ketoprofen at minimum inhibitory concentrations far above reported environmental levels. Two particularly resilient strains, R. erythropolis IEGM 712 and R. qingshengii IEGM 746, sustained growth in ketoprofen-supplemented medium. Transmission electron microscopy (TEM) examinations showed that most cells preserved structural integrity and morphology, while energy dispersive X-ray spectroscopy and elemental mapping showed maintenance of K+ homeostasis. Over 14 days of cultivation in the mineral medium with n-hexadecane, these two strains removed 40-58% of ketoprofen. Exposure to ketoprofen altered cellular morphometry and surface charge (ζ-potential) and led to the formation of by-products with a predicted lower ecotoxicity than the parent compound. These findings underscore the potential of Rhodococcus strains for the bioremediation of ketoprofen.