Efficiency Of Thermally Activated Peroxydisulfate Combined With Aerobic Composting For Spiramycin Fermentation Residue Treatment And Safety Analysis Of Organic Fertilizer

Antibiotic fermentation residues is the solid and semi-solid precipitation discharged during antibiotic production.It is rich in organic matters and other nutrients,but contains a small amount of antibiotic residue.However,the residual antibiotics will lead to potential bacterial resistance risks.In this paper,spiramycin fermentation residue is taken as the research object.Based on the properties of spiramycin and its fermentation residue,thermally activated peroxydisulfate（PDS）is used to explore spiramycin degradation mechanism and spiramycin fermentation residue disintegration efficiency,the thermally activated PDS pretreatment effect on aerobic composting efficiency for spiramycin fermentation residue,and further carry out the safety analysis of organic fertilizer for spiramycin fermentation residue compost in order to provide technical support for the safe utilization of spiramycin fermentation residue.Because the residual spiramycin in fermentation residue can not achieve the efficient biodegradation after aerobic composting,the degradation influence factors and mechanism of spiramycin in water were studied by thermally activated PDS.The results showed that spiramycin degradation could be improved by increasing the PDS concentration and reaction temperature and decreasing the initial p H.The spiramycin degradation conformed to the pseudo-first-order kinetic,and the apparent activation energy was 83.3 k J/mol.The ESR spectroscopy and radical analysis indicated that SO₄^·-and·OH were the main active species.According to the analysis of spiramycin degradation products by HPLC-QTOF/MS,the main degradation path of spiramycin was that each sugar group gradually fell off from the lactone ring.The spiramycin degradation products were demonstrated to no longer have antibacterial activity by Vibrio fischeri.Based on the degradation analysis of spiramycin by thermally activated PDS in water,the thermally activated PDS treatment for spiramycin fermentation residue were studied.The results showed that the degradation rate of spiramycin increased by 2.83 times when the activation temperature increased from 50℃to 90℃.The parameters of thermally activated PDS treatment for spiramycin fermantation residue were determined as follows:the dosage of PDS was 20 g/kg,the initial p H value was 4,the activation temperature was 90℃,and the spiramycin could be completely degraded after 120 min of treatment.The spiramycin fermentation residue could be significantly disintegrated by thermally activated PDS pretreatment which was proved by SEM and particle size analysis.The pretreatment contributed to the dissolution of organic substances such as proteins and polysacharides,and accumulation of inorganic nitrogen.In order to improve the aerobic composting efficiency of spiramycin fermentation residue,intermittent aeration was used to ensure aerobic conditions,wheat straw was used to adjust the C/N ratio and permeability of the compost substrate,and compound microbial agents were inoculated to enrich the compost microbial diversity.The aerobic composting process parameters for spiramycin fermentation residue were determined by composting process research as follows:the intermittent aeration rate was 0.5 L/（min kg）（aeration program:30 min aeration,60 min stop）,and the mass ratio of spiramycin fermentation residue and wheat straw was 1:1（C/N was about 21.5）,the addition amount of compound microbial agents was 2‰,and the composting treatment reached a stable state of maturity for 28 days.The effect of thermally activated PDS pretreatment on the physicochemical properties,gas emissions and compost maturity during composting of spiramycin fermentation residue were investigated.After the spiramycin fermentation residue was pretreated to completely remove spiramycin residues,the composting peak temperature increased by 3.2℃,the cumulative release of NH₃ and CO₂ increased by 6.98%and 12.9%,respectively,and the cumulative release of CH₄ and N₂O decreased by 34.0%and 5.27%,respectively.3D-EEM fluorescence spectra and UV spectra,humic acid/fulvic acid and ammonium nitrogen/nitrate nitrogen analysis during composting showed that the pretreatment improved compost maturity by increasing the content of humic acid and nitrate nitrogen in the compost.Based on the degradation of spiramycin,bacterial community succession and changes in antibiotic resistance genes（ARGs）and mobile genetic factors（MGEs）during the aerobic composting process of spiramycin fermentation residue,the control and mechanism of ARGs in the composting process were studied.The results indicated that the bacterial community diversity was increased by pretreatment during composting.The pretreatment was beneficial to the proliferation of Bacteroidetes,but inhibited the growth of Actinobacteria.The total relative abundance of ARGs and MGEs decreased by 29.1%and 30.3%,respectively,after42-day composting of the pretreated spiramycin fermentation residue.The interaction between environmental factors,bacterial communities and MGEs had a greater impact on the changes of ARGs than individual effects.The main reason for the reduction of ARGs by pretreatment was that the changes in compost physicochemical properties caused by pretreatment affect bacterial community succession and reduce the abundance of MGEs,resulting in a reduction in the proportion of ARGs hosts and the probability of horizontal transfer.The application safety of organic fertilizer for spiramycin fermentation residue compost were intensive studied through the residual spiramycin degradation,bacterial community succession,soil enzyme activity,ARGs and MGEs changes.The results indicated that all indicators of organic fertilizer of spiramycin fermentation residue compost meet the requirements of"Organic Fertilizer"（NY/T 525-2021）.The organic fertilizer of spiramycin fermentation residue compost improved the diversity of soil bacterial community and soil enzyme activity,and increased the relative abundance of Actinobacteria,Acidobacteria,Gemmatimonadetes and Chloroflexi,but reduce the relative abundance of Proteobacteria and Bacteroidetes.Compared with the untreated raw spiramycin fermentation residue,the relative abundance of ARGs decreased by 198 times after 60 days of compost fertilization.After treating spiramycin fermentation residue with thermally activated PDS combined with aerobic composting,the risk of soil exposure to antibiotics in the application process was completely avoided,and the soil ARGs level was significantly reduced,so the safety of organic fertilizer for spiramycin fermentation residue compost was effectively improved.