Microbiodegradation Of Two Aquacultural Drugs In The Sediment

1. The study of the degradation of the malachite green (MG) in the aquacultural sediment showed that the half-life of MG was from12.9days to50.34days. Leuomalachite green (LMG) was generate during the degradation. The elumination of LMG was slower than MG The decrease of initial concentration of MG and the increase of the temperature is benefit to the degradation of MG. The microbiodegradation was play an important role in the degradation, while the photodegradation was not important. The half-life of furazolidone in the sediment was33.39h.. The metabolite,3-amino-2-oxazolidone (AOZ), was detected during degradation. The half-life of AOZ was22.5days.2. Strain MJ1isolated from MG polluted fishery pond can degrada MG effectivly and was identified as Pseudomonas sp. This strain can also degrade LMG The24h and72h degradation rate of MG was8.33%and93.6%respectivly. The24h and72h degradation rate of LMG was72.9.%and84.4%respectivly. Degrdation ratio was more than90%if the initial concentration of MG was under10mg/L. The optimal degrdation temperature was30-35℃. The optimal degradation pH range was7.0-9.0. Nine main transformation products of MG degradated by strain MJ1were identified by liquid chromatography mass spectrometry. The possible metabolic pathway of degradation of MG by strain MJ1was cleavage of one benzene ring.3. Strain F1and F5isolated from furazolidone polluted fishery pond can degrade AOZ efficiantly. Degradation ratio of strain F1and F5was85.6%and89.7%respectivly. Strain F1and F5were identified as Ochrobacterum sp. and Pseudomonas aeruginosa. The optimal condition of strain F1was20-40℃and pH7.0-8.0. the optimal condition of strain F5were30-35℃and pH6.0-8.04. Strain MJ1(Pseudomonas sp.) and M3(Pantoea sp.) were immobilized by sodium alginate. Optimal immobilizing condition was:5%CaCl2,2%sodium alginate,16h calsifying time and600mg/kg bacterial biomass. Degradation ratio of strain MJ1and M3was increased after immobilization. The optimal condition of immobilzed strain MJ1was pH6.0-9.0and30-35℃, while strain M3was pH5.0-9.0and25-30℃. Mixed immobilized bacteria MJ1and M3can degrade MG in the sediment. The degaradation half-life of MG in the sediment was shortened if adding immobilized bacteria. Adding the biomass of the immobilized bacteria can increase the degradation rate and ratio. Sunlight can degrade some of MG in the sediment.5. Aute toxicity test of Daphnia magna showed that the LC50of strain MJ1and M3were both more than500mg/L. Aute toxicity test of Brachydanio rerio showed that the LC50of strain MJ1and M3were both more than500mg/L. strain MJ1and M3had no oxidative stress on Carassius auratus.