Efficient remediation of meropenem using Bacillus tropicus EMB20 β-lactamase immobilized on magnetic nanoparticles

Reducing antibiotic pollution in the environment in essential to preserve the effectiveness of the available antibiotics. In the present study, β-lactamase from Bacillus tropicus EMB20 was immobilized onto magnetic nanoparticles (Fe₃O₄) through covalent coupling method. The nanoconjugate was structurally characterized using SEM, FTIR, UV-spectrometry, and XRD diffraction analyses. The prepared enzyme nanoconjugate was thereafter used for remediation of meropenem (Mer) and showed complete removal of 10 mgL^-1 Mer within 3 h of treatment. Moreover, the immobilized enzyme was successfully recovered and reused for up to 5 cycles with 57% removal efficiency. The immobilized preparation was also observed to be effective in the removal of higher Mer concentrations of 25 and 50 mgL^-1 with 79% and 75% removal efficiency, respectively. The major hydrolyzed product of Mer was found to be opened-lactam ring structure with m/z 402.16. The hydrolyzed product(s) were observed to be non-toxic as revealed through microbial MTT, confocal microscopy, and growth studies. Under the mixed conditions of 50 mgL^-1 ampicillin (Amp), 10 mgL^-1 amoxicillin (Amox) and, Mer, the nanoconjugate showed simultaneous complete removal of Amp and Mer, while 49% Amox removal was detected after 3 h of treatment. Moreover, the nanoconjugates also showed concomitant complete removal of antibiotic mixture with in 2 h from aquaculture wastewater. Overall, the study comes out with an efficient approach for remediation of β-lactam antibiotics from contaminated systems.