Enhanced hydrolysis of fermentative antibiotics in production wastewater: Hydrolysis potential prediction and engineering application

An enhanced hydrolysis process has been proposed as a promising pretreatment method for removing high concentrations of antibiotics from production wastewater. Herein, the prediction of hydrolysis efficiency and reactive moieties of 14 fermentative antibiotics belonging to six classes were investigated at 85 °C under different pH conditions. Eight antibiotics (penicillin V, erythromycin, spiramycin, streptomycin, chloramphenicol, vancomycin, bacitracin, and colistin) could be hydrolyzed at 85 °C within 1 h. A semi-empirical prediction tool using the parameterized model number 3 method was established by making correlations between the enhanced hydrolysis efficiency and ΔE (the energy gap between the lowest unoccupied and highest occupied molecular orbitals (ELUMO and EHOMO)). Good negative correlations (R2 = 0.452–0.884, p < 0.05) were obtained between △E and enhanced hydrolysis efficiency in the pH range of 3–11, and the predicted results were significantly close to their experimental values (R2 = 0.802, p < 0.01) for the training and test sets. The tool was further verified by the density functional theory calculations, and showed that the ΔE of antibiotics was one of the key factors affecting the hydrolysis efficiency. The hydrolysis moieties of streptomycin and spectinomycin were determined to be the pseudoglycosidic bonds, streptose or hemiketal structures, which were related to the active antibacterial group. The antibacterial activity of actual production wastewater could be effectively destroyed with the enhanced hydrolysis process. More importantly, a full-scale wastewater treatment plant in an oxytetracycline factory in Hebei, China has already upgraded their systems by adopting the enhanced hydrolysis pretreatment, and 99.9% oxytetracycline removal was achieved. In general, this study could provide a useful tool in establishing a sound enhanced hydrolysis pretreatment strategy for different antibiotic production wastewaters.