Isolation And Screening Of A Strain Of Photosynthetic Bacteria And Its Application In Water Purification Of Shrimp Culture System

Photonsynthetic Bacteria(PSB)are the earliest known prokaryote with the original photonsynthetic system.Because they have both anabolism and catabolism,they distribute widely in various natural environments.Photonsynthetic Bacteria can effectively use small molecules of fatty acids and alcohols in the environment.They can also have a good degradation effect on ammonia nitrogen,nitrite and hydrogen sulfide in water,so they are widely used in the treatment of high concentration organic wastewater and purification of aquaculture water.In addition,photosynthetic bacteria are rich in nutrients such as vitamin B12,biotin,coenzyme Q,carotenoids and lysine,which can be added to the feeds to increase the production of livestocks.Thus,they also have broad applications in food and pharmaceutical fields.In the field of new energy,photosynthetic bacteria have the advantages of high hydrogen production rate,high purity and high energy utilization ratio.They can generate new energy while treating wastewater,and realize wastewater resource utilization.In this study,a photosynthetic bacteria was isolated and screened from the marine environment.Using analysis of the 16 S rDNA of the strain was identified as Ectothiorhodospira magna.The effects of temperature,salinity,and carbon source on the conversion of ammonia,nitrite and nitrate were studied.The application of photosynthetic bacteria combined with other microbial preparations in the water culture of Penaeus vannamei is also investigated.The conclusion are summarized below:1.The effects of five carbon sources such as sodium acetate,sodium succinate,sodium propionate,sodium pyruvate and sodium malate on the removal of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen by photosynthetic bacteria were compared.The results show that sodium acetate has the best removal effect as an external carbon source.And the conversion ability of inorganic nitrogen is positively correlated with the concentration of sodium acetate.Under the condition of initial addition of 40 mM/L sodium acetate,the ammonia nitrogen removal rate of to 20 mM/L on 7days was 81.83%.While 72 mM/L sodium acetate was added,and the removal rate of 8 mM/L sodium nitrite on 7 days was 46.21%.While 2mM/L sodium acetate was added,and the removal rate to 8mM/L nitrate on 7 days was 89.70%.Under the condition of coexistence of three kinds of inorganic nitrogen,the conversion ability of photosynthetic bacteria to inorganic nitrogen is affected by the concentration of sodium acetate.The higher the concentration of sodium acetate,the faster the conversion efficiency of photosynthetic bacteria,and the photosynthetic bacteria will preferentially remove ammonia nitrogen in water.2.The photosynthetic bacteria have obvious ammoniation effect on the organic nitrogen dissolved in the water from the shrimp feed,and the concentration of ammonia nitrogen formed by ammoxidation in the water body is reduced to less than 1 mg/L within 7 days by virtue of their own ability to remove and convert ammonia nitrogen.The nitrite converted from the ammonia nitrogen can also be removed and transformed into other froms.However,the ability of the photosynthetic bacteria to remove the converted nitrite is relatively weak.In the application,it is better to use a probiotic agent with strong nitrite removal ability.3.Three sets of biofilm systems were constructed by adding photosynthetic bacteria + Bacillus subtilis + nitrifying bacteria and photosynthetic bacteria + nitrifying bacteria,respectively,using polyester fiber balls and ceramsite as artificial carrier materials.The use of triple probiotics and the use of polyester fiber balls as artificial carriers allows faster construction of nitration systems and higher removal rates.The method of increasing ammonia nitrogen load was used to increase the nitrification capacity of the biofilm system.Under the ammonia nitrogen load of 9 mg/L,the ammonia nitrogen removal rate at 24 h was 35.39%.4.The photosynthetic bacteria are added to the biofilm system to have a good inhibitory effect on vibrios.In the biofilm system using and the photosynthetic bacteria,nitrifying bacteria,Bacillus subtilis as triple probiotic bacteria agent,and the polyester fiber ball as the artificial carrier the maximum number of vibrios in the culture stage was 50 CFU/mL.