Electrical conductances of dilute aqueous solutions of β-lactam antibiotics of the penicillin group in the 278.15K to 313.15K temperature range. Sodium salts of oxacillin, cloxacillin, dicloxacillin and nafcillin

Quantum chemical prediction of effects of temperature on hydrolysis rate of penicillin under weakly acidic condition

Temperature and pH are important factors affecting the hydrolysis of β-lactam antibiotics in water environments. However, the determination of hydrolysis kinetics and pathways is experimentally challenging, particularly in low temperature aqueous solutions because of time and cost constraints. In this study, an equation was employed to correct the Gibbs energy calculated in aqueous solutions by density functional theory methods to predict the effect of temperature on the hydrolysis kinetics and pathways of penicillin G. The results indicate that the most likely hydrolysis mechanism involves the opening of the β-lactam ring of anionic penicillin G protonated at the β-lactam oxygen atom with the participation of the carboxyl group and a water molecule. The results also suggest that the carboxyl group of β-lactam antibiotics was crucial for the hydrogen transfer. The predicted rate constants were of the same order of magnitude as the experimental values obtained under comparable pH and temperature conditions. Therefore, the quantum chemical methodology described herein can be potentially employed to determine pH- and temperature-based two-dimensional hydrolysis rate models, which can enable the prediction of the β-lactam antibiotics persistence in frigid waters.

Elimination of Isoxazolyl-Penicillins antibiotics in waters by the ligninolytic native Colombian strain Leptosphaerulina sp. considerations on biodegradation process and antimicrobial activity removal

In this work, Leptosphaerulina sp. (a Colombian native fungus) significantly removed three Isoxazolyl-Penicillin antibiotics (IP): oxacillin (OXA, 16000 μg L^-1), cloxacillin (CLX, 17500 μg L^-1) and dicloxacillin (DCX, 19000 μg L^-1) from water. The biological treatment was performed at pH 5.6, 28 °C, and 160 rpm for 15 days. The biotransformation process and lack of toxicity of the final solutions (antibacterial activity (AA) and cytotoxicity) were tested. The role of enzymes in IP removal was analysed through in vitro studies with enzymatic extracts (crude and pre-purified) from Leptosphaerulina sp., commercial enzymes and enzymatic inhibitors. Furthermore, the applicability of mycoremediation process to a complex matrix (simulated hospital wastewater) was evaluated. IP were considerably abated by the fungus, OXA was the fastest degraded (day 6), followed by CLX (day 7) and DCX (day 8). Antibiotics biodegradation was associated to laccase and versatile peroxidase action. Assays using commercial enzymes (i.e. laccase from Trametes versicolor and horseradish peroxidase) and inhibitors (EDTA, NaCl, sodium acetate, manganese (II) ions) confirmed the significant role of enzymatic transformation. Whereas, biomass sorption was not an important process in the antibiotics elimination. Evaluation of AA against Staphylococcus aureus ATCC 6538 revealed that Leptosphaerulina sp. also eliminated the AA. In addition, the cytotoxicity assay (MTT) on the HepG2 cell line demonstrated that the IP final solutions were non-toxic. Finally, Leptosphaerulina sp. eliminated OXA and its AA from synthetic hospital wastewater at 6 days. All these results evidenced the potential of Leptosphaerulina sp. mycoremediation as a novel environmentally friendly process for the removal of IP from aqueous systems.