Identification of 4″-isovaleryl-spiramycin III produced by Bacillus sp. fmbJ

Photocatalytic degradation efficiency of hazardous macrolide compounds using an external UV-light irradiation slurry reactor

The current work investigates the removal of two hazardous macrolide molecules, spiramycin and tylosin, by photodegradation under external UV-light irradiation conditions in a slurry photoreactor using titanium dioxide as a catalyst. The kinetics of degradation and effects of main process parameters such as catalyst dosage, initial macrolide concentration, light intensity and stirring rate on the degradation rate of pollutants have been examined in detail in order to obtain the optimum operational conditions. It was found that the process followed a pseudo first-order kinetics according to the Langmuir-Hinshelwood model. The optimum conditions for the degradation of spiramycin and tylosin were low compound concentration, 1 g L^-1 of catalyst dosage, 100 W m^-2 light intensity and 560 rpm stirring rate. Then, a maximum removal (more than 90%) was obtained after 300 min of irradiation time. Furthermore, results show that the selection of optimized operational parameters leads to satisfactory total organic carbon removal rate (up to 51%) and biochemical oxygen demand to chemical oxygen demand ratio (∼1) confirming the good potential of this technique to remove complex macrolides from aqueous solutions.

Effectively remediating spiramycin from production wastewater through hydrolyzing its functional groups using solid superacid TiO2/SO4

Breaking down the structural bonds and eliminating the functional groups are more efficient than destroying the whole molecule in antibiotic production wastewater (APW) pretreatment before further biotreatment. Two sulfated titania (TiO₂/SO₄) solid superacids, SSA1 and SSA2 were synthesized, characterized and used for hydrolytic pretreatment of spiramycin in APW. Spiramycin removal followed an order of SSA2>SSA1>TiO₂≈pH = 3>control. The hydrolytic efficiencies increased at elevated temperature from 25 °C to 65 °C. The hydrolytic kinetics followed a first-order model and SSA2 performed the fastest. The performances were positively correlated with both the total acidity determined by n-butylamine titration and the strength of acid sites measured by NH₃-temperature-programmed desorption (TPD). The residual solution for SSA2 presented the least antibacterial potency and anaerobic inhibition among all treatments. The hydrolyzed product was identified as the m/z 699.4321 fragment using UPLC-Q/TOF-MS, which was formed after losing a functional mycarose moiety from the parent molecular. The solid superacids were effective in selectively eliminating 433 mg/L of spiramycin and the antibacterial potencies of the spiramycin production wastewater, which contained very high concentrations of COD (33,000 mg/L). This hydrolytic method avoids using and handling hazardous and corrosive mineral acids on site. It is attractive as a selective catalytic pretreatment method to cleave antibiotics' functional groups and to reduce its inhibitory effects before sequential biotreatments.