Pretreatment of spiramycin fermentation residue by thermally activated peroxydisulfate for improving biodegradability: Insights into matrix disintegration and antibiotics degradation

Abstract

Spiramycin fermentation residue (SFR) can be managed to recycle organic substances through bioprocesses. However, its rigid matrix structure and high residual antibiotic of spiramycin (SPM) are not conducive to the high efficiency of bioprocesses. The pretreatment of SFR by thermally activated peroxydisulfate (TAP) was first employed for improving its biodegradability by matrix structure disintegration and residual SPM degradation. The results demonstrated that the SFR were efficiently disintegrated to smaller particles. The effective destruction of SFR matrix structure was predicted by the release of carbohydrates and proteins, and was intuitively confirmed by scanning electron microscopy (SEM). The production of dissolved organic matters was clearly enhanced by TAP treatment, but the increment decreased with the increase of PDS dosage due to the mineralization of radicals. The degradation of SPM fitted to first-order kinetics model, and its degradation rate was promoted by increasing PDS dosage, increasing activation temperature and decreasing pH. The degradation pathway of SPM was mainly the separation of sugar groups (mycarose, mycaminose and forosamine) from the lactone ring, and the final oxidation product of SPM that have been identified was predicted to be harmless. The efficient and powerful TAP might be a suitable pretreatment approach for improving the biodegradability of SFR.