Removal Of Microcystis Aeruginosa And Microcystin-LR By White-rot Fungus Schizophyllum Commune

Eutrophication is a serious environmental problem faced by the world. A prominentproblem caused by eutrophication is the blue-green algal blooming, which can lower the usabilityof the water and cause serious ecological damage and huge economic losses. Some kinds of algacan release microcystin to the water body, microcysin-LR (MC-LR) is the most harmful species.MC-LR is also the strongest liver tumour promotor, which is a class of cyclic hepatotoxin. It ischemically stable in water and can't be effectively removed by conventional water treatmentprocesses.White-rot fungus has become a hot topic home and abroad in recent years. It has specialmetabolic type and degrade compounds extracellularly, which can degrade a variety ofrecalcitrant organic compounds. In this paper, the removal efficiency and mechanism ofMicrocystis aeruginosa and MC-LR being removed by white-rot fungus Schizophyllum commune(S. commune) were studied. The main conclusions were as follows:(1) S. commune could effectively remove Microcystis aeruginosa. The removal efficiency ofchlorophyll-a had positive correlation to S. commune dosage and reaction time, it was affectedslightly by initial pH value. Under optimal conditions, the removal efficiency of chlorophyll-acould reach about90%. Mixed microcystis could also be removed by S. commune, but theefficiency was lower.(2) S. commune could effectively degrade MC-LR. The degradation ratio of MC-LR wasgreater than80%between25~35℃and reached the maximum at30℃, yet decreased when thetemperature was higher than30℃. The degradation ratio was greater than80%between pH4.5~6.5and reached the maximum at pH4.5. Lower pH could decrease the degradation ratio ofMC-LR. In addition, the biodegradation ratio could be improved when S. commune wasinoculated into biodegradation system under stable condition after pre-incubated in liquid cultureand oxygen was purged regularly to the biodegradation system. Under such conditions, when theinitial MC-LR concentration in water was1mg/L, MC-LR was completely degraded within2days, and when the initial concentration was15mg/L, MC-LR was completely degraded within7days.(3) The white-rot fungus could produce two main types of enzymes: manganese peroxidaseand laccase. The results showed that manganese peroxidase could effectively degrade MC-LR,the process was started by hydrogen peroxide, yet laccase did not show significant degradation effect in the experiment. Compared with S. commune, enzyme had better degradation effect witha less degradation time and higher initial concentration of MC-LR.The results of this paper proved that white-rot fungus S. commune could effectively removeMicrocystis aeruginosa and MC-LR, it is a new method to remove the microcystins inwater-body and other environmental medias.