Microbial Ecology Mechanism For Quick Degradation Of Oxytetracycline During Chicken Feces Composting

As the additive, oxytetracycline （OTC） was increasingly used in livestock and poultry industry,OTC residues in feces may have potential hazards to agricultural ecological environments. In thepresent thesis, a high performance liquid chromatography（HPLC） method was developed fordetermination of oxytetracycline residues in chicken feces compost, the effects of C/N, initial watercontent and conditioner on degradation of OTC, parameters and microorganism diversity wereinvestigated during chicken feces composting using the method of aerobic-composting.The method for determining oxytetracycline: The feces sample were extracted by Mcllvaine buffer,and cleaned up with solid phase extraction columnella of Water Oasis HLB analysis; the cartridges weresequentially rinsed with3mL5%methanol-water; Finally, the cartridges were eluted with3ml0.01mol/l oxalic acid methanol; The mobile phase had0.01mol/l oxalic acid solution, acetonitrile,methanol （85:10:5, v/v） at a flow rate1.0ml/min. Detection was performed with an ultraviolet （UV）detector （1100, Agilent, USA） at a wavelength of355nm. The mean recoveries of oxytetracyclineranged from77.19%to84.26%and the limit of detection （LOD） was established at0.045mg·kg^-1, theHPLC method can be preferably used for measure of oxytetracycline in feces of chicken.The remove rate of oxytetracycline from chicken feces decreased with the increasingoxytetracycline concentrations in chicken feces. OTC could decrease the rising rate of compostingtemperature and make the high temperature （≥50℃） period shorter than that of the control. The strongimpacts of OTC to maturity of chicken feces composting were found when the OTC addition contentswere higher than75mg OTC kg^-1. The rate of NH+4-N to NO-3-N, and GI were much higher than0.5and80%, respectively. The main bacteria were bacillus and thermophilic at high temperaturecomposting period, the fungus were saccharomyces and aspergillus, while the cryptococcus albidus wassensitive to oxytetracycline.Effects of initial water content on oxytetracycline degradation in chick feces and the selectedparamenters were also found.The degradation rate of oxytetracycline was higher in the high watercontent was higher thanthat in low water content. The initial water content ranged from55%⁶5%could signinfacantly decrease the OTC in chick feces. The rising rate of composting temperaturedecreased with the increasing water content.Effects of C/N on the oxytetracycline degradation in chick feces and the selected parameters werealso found. The degradation rate of oxytetracycline with high C/N composting was superior to that withlow C/N. The temperature of T2（25.5） and T3（32.8） treatments was higher than T1（21.6） treatment,high C/N could significantly decrease the OTC residues and their biotoxicity in chick feces.With biochar, corn stalks, grass, wheat straw as the conditioner, we found the removal rate ofoxytetracycline was obvious except for the biochar treatment and the concentration of oxytetracyclinewas below30mg·kg^-1at the end of composting. The removal rate of wheat straw treatment was morethan80%. The GI of biochar, corn stalks, grass, wheat straw treatments were42.36%,92.16%,85.22%and90.45%, respectively. During the whole period of composting, the bacteria deversity of biochar treatment was higher than other treatments and the fungus community structure and diversity of the fourtreatments were similar.In conclusion, OTC in chicken feces can be quickly degraded with the high water content of55%⁶5%, high C/N of25.5³2.8, and with corn stalks or wheat straw as conditioners.