Screening And Characterization Of Fosfomycin-degrading Bacterial Strains

Fosfomycin (FOM) is a broad-spectrum antibiotic which has been widely used in clinic. It has bactericidal activity against various gram-positive and distinct gram-negative bacteria by irreversibly blocking bacterial cell wall synthesis. A large amount of pharmaceutical wastewater is produced in the manufacturing of FOM. The FOM pharmaceutical wastewater contains lots of pollutants, which make the wastewater to be complex, toxic and refractory. The physical-chemical wastewater treatment technologies were difficult to be adopted because of the high costs. However there are some problems with biological treatment because of the low treatment efficiency which can’t meet the discharge standard. Thus, how to improve the FOM pharmaceutical wastewater treatment efficiency become a burning question and has the urgent practical significance.In this study, to improve the FOM treatment efficiency by biological system, the FOM degrading bacteria were isolated and the characteristics were studied. The mixture of FOM degrading bacteria was bioaugmented into the biological FOM treatment system and removal efficiency was studied.A rapid and accurate ion chromatography (IC) method for fosfomycin determination in pharmaceutical industrial wastewater was developed. The separation of the fosfomycin was obtained by using a Dionex column. The suppressor was ASRS300with electric conductance. The leachate was30mmol KOH and the current was75mA. The applied flowrate was1mL/min. The typical retention time for fosfomycin was3.847±0.2min. The recoveries of fosfomycin from industrial pharmaceutical wastewater ranged from75%to91%, with a relative standard deviation (RSD) from1%to3%.Activated sludge was acclimated to FOM and the acclimated activated sludge was a high efficiency flora for degrading FOM and200mg/L FOM could be completely degraded in12hours. The removal efficiency of FOM was higher than that of TOC. The concentration of PO43-increase dgradually with pH decreasing which showed that C-P bond of FOM maybe cleave and a kind of phosphoric acid could be generated during degradation. The kinetics of FOM biodegradation was also studied by batch tests. The results showed that there was no obvious difference between the kinetic equations in a range of pH6-8and the highest degradation rate was got when the temperature was30℃. The results showed that the degradation of FOM could be simulated by first-order dynamics model and Haldane Model. In Haldane equation, the maximum degradation rate, the saturation constant and the inhibition constant were41mg/g/h,556mg/L,298mg/L, respectively. The activated sludge also had a higher treatment efficiency for the fosfomycin industrial pharmaceutical wastewater than that of un-activated sludge. The diversities acclimated activated sludge system was monitored by PCR-DGGE. The results showed there were5predominated species in the system, two of which may be related with the FOM degradation.Three degradation strains named F1, F2, F3with FOM as the sole source of carbon were domesticated and isolated from activated sludge using streak plate method. The conventional analysis and16SrDNA identification showed that one strain was Flectobacillus sp. and the other two were Burkholderiaceae. F3has a higher degradation rate than F1, F2in the tested condition and the optimal growth and degradation conditions of F3are:inoculated with20%bacteria, temperature of20℃, pH of5.0and shaker rotary speed of150r/min.The activated sludge was bioaugmented into hydrolysis-biological contact oxidation system to treat fosfomycin pharmaceutical wastewater. The system had a higher and stable COD removal rate than conventional activated sludge system. However, the phosphorus removal efficiency by the bioaugmented system needed a further study. The changes of microbial community structure characteristics were monitored preliminary by PCR-DGGE. The diversity of the bioaugmented activated sludge gradually improved, which played an important role to keep the stability of the system. And the bioaugmented sludge system similarity with the original sludge increased which showed that the advantage bacteria in raw sludge still occupyed an important position.