Removal Of Microcystin By A Strain Of Algae-lysing Bacteria And Its Degradation Characteristics

In recent years, with the fast increase of population and development of economy, eutrophication and harmful algae blooms have become increasingly severe in our country. Algal cells in eutrophic water body like Microcystis aeruginosa can produce microcystins, and therefore impact aquatic organisms and human health. Therefore, people pay more and more attention to microcystins in natural waters degrade. Using microorganism in the water to remove the algae and degrade the toxins in the algae bloom water is characteristic of safety, effectiveness, specific functionalities and no secondary pollution. As the fact of that the physical and chemical method of removing the algae can not achieve the ideal effect. Contemporary removed algae and algae toxins by the algae-lysing bacteria has become a research hotspot. In this paper, a strain of algae-lysing bacteria numbered SW3 was isolated from algae bloom water body. And the algae and algae toxins in water could be removed effectively by the algae-lysing bacteria SW3.In this paper, the Microcystis aeruginosa and its algal toxin MC-LR are mainresearch objects. We make a preliminary study on the algicidal effect of the algae-lysing bacteria SW3. Degradation characteristics of algal toxin MC-LR by algae-lysing bacteria SW3 was systemically studied.In addition, the algae-lysing bacteria SW3 was identified at the molecular level by the sequence analysis of 16S rDNA.Three strains of algae-lysing bacteria were isolated from algae bloom water body had good algae-lysing effects, and the three strains were numbered as SW1, SW2 and SW3 respectively. The degradation effect of the three algae-lysing bacteria on algal toxin MC-LR are studied preliminary. Among the three strains of algae-lysing bacteria, the SW3 had the best removal effect. Then we studied the degradation characteristics of SW3 to algal toxin MC-LR deeply.The biodegradation characteristics of SW3 against MC-LR showed that the bacterial cell and MC-LR concentrations had a deep influence on removing effects of MC-LR. The greater the initial bacterial cell density, the higher the removal rate of MC-LR. When the same initial concentration of algae-lysing bacteria SW3 were added to water samples of different concentration of MC-LR respectively, the results showed that the degradation rate of MC-LR was the highest as the initial MC-LR density was about 4.67mg/L. The initial concentration of MC-LR is too high or too low will both decrease the removal rate of MC-LR. The environmental factors such as temperature and pH can influence the degradation effects of MC-LR by algae-lysing bacteria SW3. The removal rate of MC-LR by SW3 increased while the environmental temperature increased. The removal effects of MC-LR were mensurated at four different temperatures (20℃、25℃、30℃and 35℃), and the degradation rate of MC-LR from high to low were as follows:30℃>35℃>25℃>20℃. It was suitable for algae-lysing bacteria SW3 to growth and reproduction at the temperature of 30℃～35℃. And the enzyme activity was improved at about 30℃. Both of the factors above could improve the degradation rate of MC-LR. In this paper, five different pH gradients were set up to mensurate the effect of pH on MC-LR removal rate. The pH gradients were 6.5,7.0,7.5,8.0 and 9.0. The results showed that algae-lysing bacteria SW3 had a higher degradation of MC-LR in a neutral or slightly alkaline environment. And the removal effects were pH7.5>pH7.0>pH8.0>pH6.5>pH9.0.The algae-lysing bacteria SW3 was identified by the sequence analysis of 16S rDNA. The DNA sequence was taken similarity analysis with the obtained sequences in GenBank. Then took the phylogenetic analysis. The result showed that the strain SW3 shared 99% sequence homology with one strain of Lysinibacillus. According to the result, the algae-lysing bacteria SW3 belonged to Lysinibacillus.