| With the rapid development of social economy and sharp increase of population density,more and more pollutants in water were discharged into the water,water eutrophication is getting more severe. The bloom of algae in water has brought a large amount of adverse effects to water quality,local economies and human health. Therefore,restricting the overgrowth of algae has received increasing attention. There are many limitations in the traditional methods of inhibiting algae,so the development of new products and new ideas has become an urgent need to control eutrophication problems. The inhibitory effects of microalgae from extracellular matters of beneficial bacterium in water and the current nanosized photocatalyst have provided new ideas for controlling algal blooms.Photocatalysis technology,which can effectively inhibit the growth of algae with the use of light as the energy source,has been showed to be potentially advantageous for environmental pollution prevention and a bright application future. However,common photocatalyst such as TiO2 is only activated by UV light with wavelengths below 387 nm for its band gap,which means few of the solar energy could be used for bactericide,thus limited the application of TiO2. In this study,a novel,visible light-responsive AgBiO3 algaecide was prepared and characterized,which could restrict the growth of Microcystis aeruginosa and even kill them combined with the simulated solar radiation energy. Microbiological method with extracellular matters of beneficial bacterium is characterized as safety , undestroying with ecological environment of water,in-situ remediation technology with no addition,which is a future direction of eutrophication prevention and controlling. This study find out the preliminary mechanism of inhibition of macroalgae by extracellular matters and photocatalyst and provide a scientific basis for inhibit bloom of microalgae. The main contents of this paper are as follows:（1）AgBiO3 was prepared with the ion exchange method,which was the hexagonal lattice with parameters as a= 5.641（1） and c=16.118（2） （?） and the final R factors were RWP=7.96 and RP=6.12%. SEM photograph showed AgBiO3 was mainly spherical shape with a diameter of approximately 50200 nm. There is a strong absorption in the visible region and the absorption edge is approximately 470nm,the band gap calculated is approximately 2.5eV for AgBiO3. Comparing to undoped TiO2,AgBiO3 greatly improved photocatalytic activity,decomposing methyl orange dye solutions under visible light irradiation.（2） Initial biomass density,concentration of AgBiO3,initial pH and light quality were the main factors which effect the growth inhibition of Microcystis aeruginosa. Compared with AgNO3 and NaBiO3,AgBiO3 had a stronger deleterious effect on cyanobacterium cultured in BG11with radiation of simulated natural light,while NaBiO3 was the weakest inhibitor. Morphology analysis,determination of chlorophyll a and electrolyte leaking rate revealed that AgBiO3 algaecide could damage the cyanobacterium wall and cell membrane irreversibly with their high photocatalytic activity,thus inhibited growth and proliferation of M. aeruginosa effectively.（3） Culture conditions were optimized for improved growth-inhibition of Microcystis aeruginosa exposed to AgBiO3. The optimised concentrations of medium components were as follows: ZnSO4 0.24 mg·L-1,CaCl2 125.94 mg·L-1,CuSO4 0.28 mg·L-1 and NaNO3 600 mg·L-1. The inhibition rate reached 61.86%,an increased by 44.57% over the mean value （42.79%） before optimisation。（4） In the absence of growth substrate,the mixed liquid yeast did not produce growth inhibition of algae; however,under the mixed yeast with liquid glucose added,the algae chlorophyll concentration significantly decreased and continued to maintain at a low level,meanwhile,the extracellular matters of yeast sterilized in high temperature showed a good inhibition activity of algae. It indicated that the inhibition activity of yeast is due to extracellular matters which have high thermal stability.（5） Microscope showed that the algae in the treatment sample had clear-cut contours,integrate structures and pale color compared to that in the control sample. It can be showed that active substance of the mixed yeast inhibited the growth of algae by means of destructing algal chlorophyll. By the analysis of HPLC-SEC and EEM of the samples,it is initially determined that the active substance inhibiting growth of algae is a kind of humic acid with aromatic rings which absorb ultraviolet rays strongly. By the analysis of GC/MS, active substance of mixed yeast inhibiting the growth of algae may be 2,6-Di-tert-butyl-4-methylphenol （the molecular weight of 220.35） and 2-（3H）-benzothiazole ketone （the molecular weight of 151.18）. |
