Isolation And Study On Biological Characteristics Of Water Purification Bacillus And Application In Marine Culture Pond

The accumulation of organic pollutants,ammonia nitrogen and nitrite nitrogen is the main inducement factor of aquaculture water deterioration,diseases occurrence and quality decreasing with fish and shrimps.The implementation of bioremediation by beneficial microorganism has become the research and development focus at present.To screen and gain dominant Bacillus strains or their combinations which have excellent water purification effects and preparation performance is the crux to formulate efficient mieroecology Water-Purifying Products.228 Bacillus strains were isolated and purified from the marine pond sediment.Two dominant strains,Bacillus T301 and T905,were obtained through the salt tolerance, degradation of organic matter and ammonia and nitrite nitrogen screening tests.The four days ammonia degradation rate of T301 was 55.18%and 52.00%and nitrite nitrogen degradation rate was 55.95%and 51.52%separately,while,ammonia degradation rate of T905 was 35.25%and 36.53%and the nitrite nitrogen degradation rate was 72.10%and 74.17%separately,when the initial ammonia and nitrate nitrogen concentration was 20 mg/L and 40 mg/L in simulated fresh and sea aquaculture water.Based on morphological features and results of physiological and biochemical characteristics,T301 and T905 was identified as Bacillus subtilis according to The Manual of Systematic Methods of Determinative Bacterial and Bergey's Manual of Determinative Bacteriology.The results of safety tests showed that the toxicity of the two strains was actually non-toxic on mice and white-leg shrimps.The study of the biological characteristics of strains showed that the T301 and T905 strains could use glucose,starch,lactose, mannitol,sugar and other carbon sources.The organic nitrogen sources of peptone,yeast extract,beef Gaodeng were more conducive for the growth of the bacteria than inorganic nitrogen source.The results of t-tests showed that K₂HPO₄ and KH₂PO₄ had significant effects on the growth of Bacillus subtilis T301 and T905(P＜0.01)and other inorganic salt do not(P＞0.05).The suitable conditions for T301 and T905 growth were consistent with water purification.The appropriate temperature ranged from 22℃to 38℃and pH value from 6 to 8.5.The influence of salt concentration was not significant for their growth and water purification,therefore,T301 and T905 strains could be used for both fresh and sea aquaculture water purification.The results of the study that the influence of additives on the water purification effect indicated that glucose,starch,such as carbon source could improve water purification effect,which may be related to high content of organic matter and the relative lack of carbon in water,which limited the growth of the strains.The results suggested that appropriate carbon could be added to enhance the effectiveness of water purification in the practical production.Seven days later after the use of compound strains,COD degradation rate was 68.90%,ammonia degradation rate was 63.09%and nitrite nitrogen degradation rate was 72.76%in the compatibility of strains test,which showed that the use of compound strains could significantly increase the COD degradation rates and make up for the shortcomings that the low degradation rote of nitrite nitrogen of single use of T301 and the low degradation rate of ammonia with single use of T905.The match usage of the two strains could achieve complementary advantages in water purification,which was better than a single strain.The ammonia and nitrite nitrogen was in the detection limit at the fifth day and COD relative degradation rate was 64.41%at the seventh day after the application of the compound Bacillus preparation in shrimp marine culture pound.In the course of the experiments,there were smaller fluctuations with dissolved oxygen(5.01 to 5.81)and above 5 mg/L in the testing pool.pH value fluctuations were smaller(7.54 to 7.96)too. The results indicated that compound Bacillus agents could remarkably reduce pollutant concentration such as COD,ammonia and nitrite nitrogen and keep stability of dissolved oxygen and pH value.The various water quality indexes of the testing pool,which have reached good water quality index,were better than the control pool.The above experimental results showed that the compound strains,be composed of Bacillus subtilis T301 and T905,had prominent water purification function and a wide application prospect.