Combined Inhibition Of Microcystis Aeruginosa By An Algae-Lysing Bacteria-Clay Mineral System

Eutrophication of water bodies is one of the major environmental problems facing the world,especially cyanobacterial blooms caused by Microcystis aeruginosa have caused serious impacts on people’s production life,health and economic development.In this project,we adopt the microbial compound clay mineral method for the cyanobacterial bloom phenomenon,and build a composite system of algae-dissolving bacteria and minerals through laboratory simulation,so as to play the role of clay mineral carrier and"aggravator"to accelerate the settlement of algal cells in the process of algae dissolution.The system is designed to provide new ideas for the treatment of cyanobacterial water bloom.Two strains of Microcystis aeruginosa with algae lysis activity were isolated from natural water bodies,and their species were identified by 16Sr DNA as Enterobacter sp.and Acinetobacter sp.The experiments showed that the algae removal rates of Enterobacter sp.and Acinetobacter sp.were 83.3%and 76.2%respectively at 5%dosage when the initial concentration of Microcystis aeruginosa was OD_680nm=0.3（early stage of severe water bloom）.The maximum algae lysis rate of Enterobacteriaceae after 7 d at different p H treatments was 84.7%,while the algae lysis rate of Bacillus immobilis after 7 d at different p H treatments was around 72.0%.Both strains of algae lysis were mainly indirect algae lysis,supplemented by direct algae lysis.Among them,the algolytic substances secreted by Enterobacteriaceae H6 still had high algolytic activity under high temperature conditions,while the algolytic substances secreted by Bacillus immobilis D2 were more affected by high temperature.Under the condition of OD_680nm=0.1 and the settling time of 24h,among the selected clay minerals,the efficiency of bentonite in removing algal cells in the water body reached54.3%.The bentonite was mixed and cultured with algae-loving bacteria to prepare the algae-loving bacteria composite bentonite system.The algae-loving bacteria composite bentonite system in the initial algae concentration of OD_680nm=0.6,the bacterial solution injection amount of 5%,compared with the addition of only bentonite,enterobacteria,the removal rate increased by 62.5%,8.3%;compared with the addition of only bentonite,immobile bacilli,the removal rate increased by 52.4%,0.13%.Experimental results show that:the two composite systems in the better dosage of 5%,Enterobacteriaceae bentonite system better maturation time of 12h,Bacillus immobilis composite bentonite better maturation time of 24h,the initial algae concentration of OD_680nm=0.3 conditions,Enterobacteriaceae composite bentonite system and Bacillus immobilis composite bentonite system removal rate of 95.4%and 88.7%,respectively.The changes of algal cell morphology,FTIR and organic matter content in water during the process of algae lysis in the two systems were analyzed,and it was found that when the algae were co-cultured with Microcystis aeruginosa,the algal cells were wrinkled and broken,the intracellular material flowed out,the zeta potential value of the system decreased,and the stability of the system was reduced.In the process of algae lysis,the cell membrane protein and lipid composition of algae cells are destroyed,and the complete structure of algae cells is changed,thus inactivating the precipitation.In contrast,when the algae lysis complex bentonite system was co-cultured with Microcystis aeruginosa,the algal cells were folded and broken,and the broken algal cells were precipitated with the bentonite.Therefore,the composite system mainly relies on the algae lysis material secreted by the algae lysis bacteria for algae removal,and the bentonite only plays the role of a carrier and weight enhancer,which increases the concentration of local algae lysis bacteria and also plays the role of"weight enhancer"in the later stage.The bentonite only plays the role of a carrier and a weighting agent,which increases the local concentration of algae lysing bacteria and also plays the role of a"weighting agent"at a later stage to accelerate the rapid settlement of inactivated algae.This study combines algae-loving bacteria with clay minerals to achieve the goal of causing damage to Microcystis aeruginosa with rapid removal of algal cells,in order to provide a new treatment solution for cyanobacterial water bloom management.