Screening And Identification Of A Microcystin-degrading Bacteria Strain And The Biodegradation Of Microcystin-LR By The Bacteria Strain

For the global pollution problem of microcystins (MCs) in recent years, the research choose Chaohu Lake where blue-green algae is more serious and frequent as research object and carry out some detailed studies. In this paper, MCs degradation bacterium is separated and identificated in the way of enrichment training based on MCs as the only carbon source. Taxonomy status of MCs degradation bacterium is determined by the morphology, physiological biochemistry experiment and16S rDNA sequence analysis to provide effective bacterium source for the cyanobacteria toxin microbial degradation of pollution control in the chaohu lake. The result indicats that the MCs degradation bacterium named M6with length of1408bp shows similarity of99%to candle shape Bacillus.In order to optimize the degradation effect of the MCs degradation bacterium, this study research the efect to degradation effect of some facts such as carbon, nitrogen source, pH value, quantity and the initial concentration of the MCs based on the MCs as the only carbon, nitrogen source. It also determines the optimal environment degradation of the reaction of degradation and the maximum efficiency. The result indicates that plus carbon source (glycerin) can largely promote the growth of the M6degrading bacteria and the degradation of efficiency and the degradation rate of MC-LR, up to66.2%. Plus plus nitrogen source (ammonium) can promote the degradation efficiency of MC-LR. When the pH value is7.0-8.0, the growth of the strains and the degradation of efficiency of MC-LR is higher. When the pH value is8.0, the degradation efficiency reachs the maximum value, up to62.0%. When inoculation amount ranges from1%-10%, the degradation rate of MC-LR grows as the degradation rate increases and the degradation of highest efficiency strains is51.3%. When initial concentration of MC-LR is between1.95to15.6, the degradation rate of MC-LR increses. When the initial concentration of MC-LR is15.6mg/L, MC-LR degradation rate is up to59.2%.This study also researches degradation mechanism of M6and positions the degradation bacterium M6degradation MC-LR. At the same time, it carry out the SDS-PAGE whole cell electrophoresis on M6before and after being inducted by MC-LR to be sure the change of the cell protein. It also investigates efect of environmental factors such as pH value, quantity and the initial concentration of the MCs on the inside the cell thick liquid enzyme degradation effect. The result shows that degradation bacterium M6degradation MC-LR of the active material is located in cells, belonging to the intracellular enzyme, based on SDS-PAGE whole cell electrophoresis, we find that at three enzymes at least joins in the MC-LR of degradation process, and these three enzymes is degradation bacterium itself, not the organization of the enzyme inducible enzyme. When the cell in thick liquid enzyme concentration reached404.9mg/L, MC-LR of initial concentration of10mg/L and pH values8.0in the system, MC-LR degradation rate reaches the highest, up to98.7%after16h. At the same time the research inducts degradation bacterium M6in different conditions, thick liquid extraction enzyme degradation and a certain amount of MC-LR preliminary understanding the environment factors on the enzyme production quantity of how much influence, we find that when have carbon source glycerin, ammonium nitrate nitrogen source, pH values8, inoculated quantity is10%and initial concentration of MC-LR is15.6mg/L, intracellular coarse extraction liquid of strains M6have larger degradation of efficiency to MC-LR. It indicates that drop solution-LR enzyme expression of MC is more in this condition.