Two contrary roles of Fe3O4 nanoparticles on kinetic and thermodynamic of Paclitaxel degradation by Citrobacter amalonaticus Rashtia immobilized on sodium alginate gel beads

Roles of Fe3O4 nanoparticles (NPs) on biodegradation of Paclitaxel by Citrobacter amalonaticus immobilized on alginate gel beads were investigated. Limitation in substrate diffusion is the major drawback of the cell immobilization method. To overcome this problem, bacterial cells were immobilized on the gel beads containing different concentrations (5-20 mg/mL) of Fe3O4 NPs and their Paclitaxel degrading potential at different temperatures was investigated using kinetic and thermodynamic modeling. Co-immobilization of bacterial cells with 5,10 and 20 mg/mL Fe3O4 NPs enhanced biodegradation efficiencies to 66%, 80% and 78%, respectively, compared to the NPs free immobilized cells (41.9%). The optimum concentration of Fe3O4 NPs (10 mg/mL) had both inhibitory and accelerating effects on paclitaxel degradation depending on the incubation time and temperature. Increasing dose of Fe3O4 NPs could increase paclitaxel degradation, despite increasing of thermodynamic inhibitory factors, only when longer time and higher temperature were used. Delta G values increased about 11.2 KJ/mol at all temperatures of 285, 295 and 305 K, and Delta H increased 54.4%, in comparison with the treatment without NPs. This indicates that, inclusion of Fe3O4 NPs into the immobilization gels can increase the local concentration of Paclitaxel (with -OH2+ groups) and bacterial accessibility to the substrate and thus enhance biodegradation efficiency. (C) 2017 Elsevier B.V. All rights reserved.