Screening and identification of a microcystin-degrading bacterium strain and its enzymatic degradation of microcystin-LR by intracellular extract of Bacillus cereus

Abstract:

Abstract:［Objective］To provide effective microorganisms for the treatment of water polluted by microcystins (MCs)，the strains capable of biodegrading microcystin LR(MC-LR) were isolated from the sediment of Chaohu Lake． The degradation of microcystin-LR by the intracellular extracts of the strains were studied． ［Methods］The enrichment culture using MCLR as the sole carbon source was utilized to isolate the microcystin-degrading strains． The isolated strain was identified according to the observation of morphology，the physiological and chemical tests and the analysis of 16S rRNA gene sequences． The degradation of MC-LR by the intracellular extracts was studied． ［Results］Strain M6 effectively degrading MC-LR was isolated and the strain M6 could grow utilizing MC-LR as the sole carbon source． Phylogenetic analysis based on 16S rRNA gene showed the similarity of 99% between strain M6 and Bacillus cereus． The experimental results suggest that the active substances for degrading MC-LR were the intracellular extracts which were the tissue enzymes of cells rather than induced enzymes． The degradation of MC-LR may be due to the catalytic effects of three enzymes． The degradation rate of 98.7% could be reached under the following conditions: pH 8.0，404.9mg/L of intracellular extracts，and 10 mg/L of the initial concentration of MC-LR.［Conclusion］Strain M6 which could biodegrade MC-LR efficiently was identified as Bacillus cereus． The influences of pH，the concentration of intracellular extracts and the initial concentration of MC-LR on the enzymatic reaction were obvious．