The Characteristics Of Microcystin-lr Degradation By Pseudomonas Putida

A strain which degraded microcystin-LR(MC-LR) was isolated from sedimentsof a bloom artificial lake in Guangdong Province, and was identified as Pseudomonasputida. To reveal the biodegradation efficiencies and mechanism, its degradationcharacteristics, changes of cellular microstructure and ions utilization were studied, toprovide a scientific basis for treatment of micro polluted source water containing MC.The degradation rate of0.5mg·L-1MC-LR degradation by P.putida could reach52.6%within10days. The optimum conditions for MC-LR degradation consisted asfollows: pH7, bacterial dosage1.0g·L-1, and culturing temperature30°C. The studyalso showed that the optimal strain age was36h and the best carbon source wasstarch and the best nitrogen source was CH3COONH4. P.putida could tolerate thetoxicity of Cu2+, although the presence of these heavy metals posed certain influenceon MC-LR degradation.The paper also studied removal of MC-LR by microbial combined with Fentonreagent. The optimal conditions of removing MC-LR by Fenton reagent alone were asfollows: the concentration of H2O2was1mmol·L-1, H2O2□Fe2+=10□1(theconcentration ratio), pH4, the initial concentration of MC-LR was0.5mg·L-1andreaction for60min. After microbial degradation, Fenton reagent was used for deeptreatment, at this point, the degradation efficiency of MC-LR was up to almost100%.Through observation of the bacterial microstructure, we found that starch indegradation system could make some mesh fabric which was like polysaccharidematerial gathering around bacteial cells. Cu2+in degradation system could makegranular material appeared in the cell surface, compared with control system, the cellsurface expressioned more smooth and the state of bacteria apperared more full. With0.5mg·L-1MC-LR, part of cells were depression and flocculent substances leakedafter three days. The presence of MC-LR promoted the anions release, and there was asignificantly positive correlation between anion concentration and degradation rate ofMC-LR at different levels.The experiment of cell surface hydrophobicity (CSH) of P.putida showed that the bacterial CSH tended to reduce over time, P.putida exhibited hydtophobic, increasedthe contact opportunities between P.putida and MC-LR, thus affected its degradationrate. The experiment of the cell membrane permeability results showed that there wascertain correlation between the degradation of MC-LR by P.putida and the cellmembrane permeability.